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Top 10 Indianapolis 500 Driver Peeves

10. Radio loses FM signal in fourth turn.

9. You crash going 200 mph and you end up in a Marv Albert blooper reel.

8. Suction cup Garfield blocks view of track.

7. Going fast is scary!

6. Having to take a leak with 100 laps left.

5. Forgetting to remove "the Club" before the race starts.

4. When the tape player eats your "Chorus Line" cassette before you've even gone 50 laps.

3. People who pronounce it "Grand Prix."

2. When wife says you lack viscosity.

1. Potholes.

Top 10 Indianapolis 500 Pit Crew Pet Peeves

10. Drivers who want a free NFL mug with every fill-up.

9. Being played in the movies by Jim Nabors.

8. Racers in such a hurry to get out of pit they run over your origami birds.

7. For the rest of your life, any time you're in a car that gets a flat, everyone just assumes that you should fix it.

6. They keep blacking out the good parts of the Rob Lowe video.

5. It's hard to pick up chicks while reeking of methane.

4. The way those suction-cup Garfield dolls fall off at 230 miles per hour.

3. Joke T-shirts that say "Pit Crew Guys Do It in Seven Seconds".

2. Really big dogs who get themselves booked on TV shows and then don't show up.

1. Those pansies at Jiffy-Lube.

Top 10 Perks of Winning the Indianapolis 500

10. Getting showered with 10W-40 in victory lane celebration.

9. Honorary New York City taxi license.

8. Right to represent Earth in Pan-Galactic Monster Truck Rally.

7. Invitation to start Mr. Gotti's car for him.

6. Good chance of meeting Kamaar the Magician backstage at Letterman show.

5. Don't have to shut off lights and lock up speedway like guy who finishes last.

4. Get to throw one free punch at Mr. Goodwrench.

3. Offers of employment from Domino's Pizza.

2. Trophy, bouquet of roses, and a big, wet kiss from Jim Nabors.

1. All the Valvoline a guy can drink.

Auto Parts

Auto parts are components of automobiles. They mainly are, in alphabetic order (only car specific articles or articles with car section):

Air filters

Automotive air filter clogged with dust and debris.An air filter is a device which removes contaminants, often solid particulates such as dust, pollen, mold, and bacteria from air. Air filters are used in application where air quality is important, notably in building ventilation systems and in engines, such as internal combustion engines, gas compressors, diving air compressors, gas turbines and others.

Some buildings, as well as aircraft and other man-made environments (e.g., satellites and space shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method uses fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favor. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid-dynamics of the air-compressor part of the Gas Turbines.

Air filter Air Condition/Heater Filter

Air filter Changing Air Filters

Energy Star advises air filters be checked every month, especially during heavy use months (winter and summer). If the filter looks dirty after a month, it should be changed. The air filter should be changed at least every 3 months. A dirty filter will slow down air flow and make the system work harder and use more energy to warm or cool. Improper air flow can cause air conditioning components to freeze. A clean filter will also prevent dust and dirt from building up in the system which can lead to expensive maintenance and/or early system failure.

Air filter Climate control air filters

There are four main types of mechanical air filter media: paper, foam, synthetics, and cotton.

Air filters are found in most all forced-air heating, ventilation, and air conditioning systems. The efficacy of the air filters in such systems significantly affects the Indoor Air Quality. The United States Department of Energy advises that "Air Filtration should have a Minimum Efficiency Reporting Value (MERV) of 13 as determined by ASHRAE 5.2.2-1999." There are a variety of different types of HVAC filters available. Many are inexpensive and not very efficient. Some options are panel, pleated, electrostatic, HEPA, electronic and media. ASHRAE recommends (MERV 6 or higher) air filters to lower the amounts of pollen, mold and dust that reaches the wet evaporator coils in air conditioning systems. Wet coils contaminated with high levels of pollen and dust can allow mold colonies to grow.

Polyester and/or glass fibres are commonly used to make web formations used for air filtration. Both materials have high temperature ratings of at least 120°C (250°F), and are widely used in commercial, industrial and residential applications. Polyester and glass fibres can be blended with cotton or other fibres to produce a wide range of performance characteristics. In some cases Polypropylene, which has a lower temperature tolerance, is used to enhance chemical resistance. Tiny synthetic fibres known as microfibres are used in many types of HEPA (High Efficiency Particulate Air) filters.

Many in-duct filters for home forced air heating and air conditioning systems are made from plain, loosely-spun fiberglass. These filters are inexpensive, disposable, and come in various densities and sizes. Less-dense filters allow for higher airflow, but do not remove as much dust. Higher density filters remove more particles, but are more expensive and offer more resistance to the air. They also become more quickly "loaded" with contaminants and dust.

Automotive cabin air filters

The cabin air filter is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the combustion air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes. Being a relatively recent addition to automobile equipment, this filter is often overlooked and clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream.

Internal combustion air filters

The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.

Most modern, fuel-injected vehicles use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with a large pipe.

Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually a few inches high and between 6 and 16 inches in diameter. This is positioned above the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid.

Paper Air filter

Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The "paper" term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief amongst tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt.

Foam Air filter

Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered.

Cotton Air filter

Cotton gauze is employed in a small number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters.

Oil Bath Air filter

An oil bath air cleaner consists of a round base bowl containing a pool of oil, and a round insert which is filled with fibre, mesh, foam, or another coarse filter media. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the base bowl. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the base bowl, down through the gap between the outer wall of the insert and the inner wall of the base bowl, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles are trapped by the filtration media in the insert, which is wetted by oil droplets aspirated thereinto by normal airflow.

Oil bath air cleaners were very widely used in automotive and small-engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size, without loss of filtration efficacy or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.

Automobile self starter

1920's era self-starter.An automobile self-starter (commonly "starter motor" or simply "starter") is an electric motor that initiates piston motion in a car's internal combustion engine before it can power itself.

Automobile self starter History

Both Otto cycle and Diesel cycle internal-combustion engines require the pistons to be moving before the ignition phase of the cycle. This means that the engine must be set in motion by an external force before it can power itself. Originally, a hand crank was used to start engines, but it was inconvenient and rather hard work to crank the engine up to speed. It was also highly dangerous.

Even though cranks had an overrun mechanism to prevent it, when the engine started, the crank could begin to spin along with the crankshaft. Additionally, care had to be taken to retard the spark in order to prevent backfiring: with wrong settings, the engine could kick back (run in reverse), pulling the crank with it, because the overrun safety mechanism works in one direction only.

Although users were advised to cup their fingers under the crank and pull up, it felt natural for operators to grasp the handle with the fingers on one side, the thumb on the other. Even a simple backfire could result in a broken thumb; it was possible to end up with a broken wrist, or worse. Moreover, increasingly larger engines with higher compression ratios made hand cranking a more physically demanding endeavor.

While the need was fairly obvious as early as 1899, Clyde J. Coleman applied for U.S. Patent 745,157 for an electric automobile self-starter inventing one that actually worked waited until 1911 when Charles F. Kettering of Dayton Electric Laboratories (DELCO) invented and filed for U.S. Patent 1,150,523 for the first useful electric starter. The starters were first installed by Cadillac on production models in 1912. These starters also worked as generators once the engine was running, a concept that is now being revived in hybrid vehicles. By 1920, most manufacturers included self-starters.

Automobile self starter Electric starter

The modern starter motor is either a permanent-magnet or a series- or series-parallel wound direct current electric motor with a solenoid switch (similar to a relay) mounted on it. When current from the starting battery is applied to the solenoid, usually through a key-operated switch, it pushes out the drive pinion on the starter driveshaft and meshes the pinion with the ring gear on the flywheel of the engine.

The solenoid also closes high-current contacts for the starter motor, which begins to turn. Once the engine starts, the key-operated switch is opened, a spring in the solenoid assembly pulls the pinion gear away from the ring gear, and the starter motor stops. The starter's pinion is clutched to its driveshaft through an overrunning sprag clutch which permits the pinion to transmit drive in only one direction. In this manner, drive is transmitted through the pinion to the flywheel ring gear, but if the pinion remains engaged (as for example because the operator fails to release the key as soon as the engine starts), the pinion will spin independently of its driveshaft. This prevents the engine driving the starter, for such backdrive would cause the starter to spin so fast as to fly apart.

This overrunning-clutch pinion arrangement was phased into use beginning in the early 1960s; prior to that time, a Bendix drive was used. The Bendix system places the starter drive pinion on a helically-cut driveshaft. When the starter motor begins turning, the inertia of the drive pinion assembly causes it to ride forward on the helix and thus engage with the ring gear. When the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative speed of the starter, at which point the drive pinion is forced back down the helical shaft and thus out of mesh with the ring gear.

An intermediate development between the Bendix drive developed in the 1930s and the overrunning-clutch designs introduced in the 1960s was the Bendix Folo-Thru drive. The standard Bendix drive would disengage from the ring gear as soon as the engine fired, even if it did not continue to run. The Folo-Thru drive contains a latching mechanism and a set of flyweights in the body of the drive unit. When the starter motor begins turning and the drive unit is forced forward on the helical shaft by inertia, it is latched into the engaged position. Only once the drive unit is spun at a speed higher than that attained by the starter motor itself (i.e., it is backdriven by the running engine) will the flyweights pull radially outward, releasing the latch and permitting the overdriven drive unit to be spun out of engagement. In this manner, unwanted starter disengagement is avoided prior to a successful engine start.

Automobile self starter Gear-reduction starters

Chrysler Corporation contributed materially to the modern development of the starter motor. In 1962, Chrysler introduced a starter incorporating a geartrain between the motor and the driveshaft. Rolls Royce had introduced a conceptually similar starter in 1946, but Chrysler's was the first volume-production unit. The motor shaft has integrally-cut gear teeth forming a drive gear which mesh with a larger adjacent driven gear to provide a gear reduction ratio of 3.75:1. This permits the use of a higher-speed, lower-current, lighter and more compact motor assembly while increasing cranking torque. Variants of this starter design were used on most vehicles produced by Chrysler Corporation from 1962 through 1987. The Chrysler starter made a unique, readily identifiable sound when cranking the engine.

Hear a Chrysler gear-reduction starter at work

Problems listening to the file? See media help.

This starter formed the design basis for the offset gear reduction starters now employed by about half the vehicles on the road, and the conceptual basis for virtually all of them. Many Japanese automakers phased in gear reduction starters in the 1970's and 1980's. Light aircraft engines also made extensive use of this kind of starter, because its light weight offered an advantage. Those starters not employing offset geartrains like the Chrysler unit generally employ planetary epicyclic geartrains instead. Direct-drive starters are almost entirely obsolete due to their larger size, heavier weight and higher current requirements. Ford also issued a nonstandard starter, a direct-drive "movable pole shoe" design that provided cost reduction rather than electrical or mechanical benefits. This type of starter eliminated the solenoid, replacing it with a movable pole shoe and a separate starter relay. The Ford starter operated as follows:

The operator closed the key-operated starting switch.

A small electric current flowed through the starter relay coil, closing the contacts and sending a large current to the starter motor assembly.

One of the pole shoes, hinged at the front, linked to the starter drive, and spring-loaded away from its normal operating position, swung into position. This moved a pinion gear to engage the flywheel ring gear, and simultaneously closed a pair of heavy-duty contacts supplying current to the starter motor winding. The starter motor cranked the engine until it started. An overrunning clutch in the pinion gear uncoupled the gear from the ring gear.

The operator released the key-operated starting switch, cutting power to the starter motor assembly. A spring retracted the pole shoe, and with it, the pinion gear.

This starter was used on Ford vehicles from 1975 through 1990, when a gear-reduction unit conceptually similar to the Chrysler unit replaced it.

Automobile self starter Pneumatic starter

Some gas turbine engines and Diesel engines, particularly on trucks, use a pneumatic self-starter. The system consists of a geared turbine, an air compressor and a pressure tank. Compressed air released from the tank is used to spin the turbine, and through a set of reduction gears, engages the ring gear on the flywheel, much like an electric starter would. The engine, once running, powers the compressor to recharge the tank.

Another method, for large diesel engines, uses additional valves in cylinder heads. Compressed air is let in the cylinders so that its pressure pushes pistons down when appropriate; at the upward piston movement, air is discharged through normal exhaust valves.

Since large trucks typically use air brakes, the system does double duty, supplying compressed air to the brake system. Pneumatic starters have the advantages of delivering high torque, mechanical simplicity and reliability. They eliminate the need for oversized, heavy storage batteries in prime mover electrical systems.

Automobile self starter Auxiliary starter engine

A large, high power Diesel engine, such as those used in off-road heavy equipment, may have a small gasoline-powered engine attached to the side as a starter.

These were also sometimes called pony engines. On some applications, they shared the same cooling system and oil supply. As the pony engine warmed up, it circulated warm coolant and warm oil in the diesel engine. In addition to making it easier to crank, it improved the service life.

Automobile self starter Static-start engine

Another way to provide for shutting off a car's engine when it is stopped, then immediately restarting it when it's time to go, is by employing a static-start engine. Such an engine requires no starter motor, but employs sensors to determine the exact position of each piston, then precisely timing the injection and ignition of fuel to turn over the engine.

Bell housing

The bell housing is part of the transmission system on a gasoline (also known as petrol) or diesel powered vehicle. It is bolted to the engine block and contains the flywheel and the torque converter or clutch of the transmission. The starter motor is usually mounted here engaging with a ring gear on the flywheel. On the opposite end to the engine is usually bolted the gearbox.

The above is the normal arrangement for an in line transmission system for a conventional rear wheel drive or all wheel drive vehicle. The arrangement for a transverse mounted engine and transmission for a front wheel drive vehicle has the gear box and differential below the engine and consequently the bell housing is a simple cover for the flywheel.

A bare Buick, Olds, Pontiac pattern bellhousing viewed from the engine endBell housings take their name from their shape rather than their function. To the technically literate they are better-known as clutch housings or torque converter housings, depending on what they actually house.

Brakes

Disc brake on a motorcycle.A brake is a device for slowing or stopping the motion of a machine or vehicle, or alternatively a device to restrain it from starting to move again. The kinetic energy lost by the moving part is usually translated to heat by friction. Alternatively, in regenerative braking, much of the energy is recovered and stored in a flywheel, capacitor or turned into alternating current by an alternator, then rectified and stored in a battery for later use.

Note that kinetic energy increases with the square of the velocity (E = ½m·v2 relationship). This means that if the speed of a vehicle doubles, it has four times as much energy. The brakes must therefore dissipate four times as much energy to stop it and consequently the braking distance is four times as long.

Brakes of some description are fitted to most wheeled vehicles, including automobiles of all kinds, trucks, trains, motorcycles, and bicycles. Baggage carts and shopping carts may have them for use on a moving ramp.

Some aeroplanes are fitted with wheel brakes on the undercarriage. Some aircraft also feature air brakes designed to slow them down in flight. Notable examples include gliders and some WWII-era fighter aircraft. These allow the aircraft to maintain a safe speed in a steep descent. The Saab B 17 dive bomber used the deployed undercarriage as an air brake.

Deceleration and avoiding acceleration when going downhill can also be achieved by using a low gear; see engine braking.

Friction brakes on cars store the heat in the rotating part (drum brake or disc brake) during the brake application and release it to the air gradually.

Brake Effects on noise pollution

The action of braking for motor vehicles produces recognizable sound level emissions, varying with the specific tire types and with the roadway surface type produces considerable effect upon sound levels or noise pollution emanating from moving vehicles. There is a considerable range in acoustical intensities produced depending upon the specific tire tread design and the rapidity of deceleration required to slow the vehicle.

Bucket seat

Bucket seats in a 1968 Saab Sonett mk2 V4.A bucket seat is a seat contoured to hold one person, distinct from bench seats which are flat platforms designed to seat multiple people. Bucket seats are standard in fast cars to keep riders in place when making sharp or quick turns.

The term appears to come from the French word, baquet, meaning "cockpit". Bucket seats resemble seats that were used in the cockpits of early aircraft, and are still used today in single-pilot aircraft.

Racing vehicles usually have only one bucket seat. Vehicles sold to the general public often have two bucket seats in the front compartment, and may contain more in a rear compartment. Commercial aircraft now have bucket seats for all passengers.

Automobile bucket seats first came into use after World War II on European small cars, due to:

their relatively small size compared to a bench seat; and lack of seating room for a middle passenger, due to the presence of a floor-mounted shifter and parking brake lever. The bucket seat trend was especially apparent in sporty cars, particularly two-seater sports cars, most of which were manufactured in European nations.

For decades, American cars were typically equipped with bench seats, which permitted three-passenger seating. The advent of compact cars and specialty vehicles such as the Ford Thunderbird in the late 1950s and early 1960s, and sporty versions of both standard-sized and compact cars, accelerated the bucket-seat trend in domestic cars around 1960.

By 1962, more than a million U.S. built cars were factory equipped with bucket seats, which were then further popularized with the advent of sporty compact cars, often dubbed "ponycars", such as the Ford Mustang.

In later decades, as U.S. cars were designed smaller in order to meet increasingly stringent fuel economy standards as well as intense competition from imported cars (particularly Japanese models), bucket seats became more common in domestic cars with each passing year. The once-standard bench seat is now generally relegated to a few larger sedans and pickup trucks.

Bumpers

The bumper of a BMW M5, highlighted in redA bumper is a part of an automobile designed to allow one vehicle to impact with another and to withstand that collision without severe damage to the vehicle's frame. Brush guards, push bars, etc. were added "after-market" to bumpers of automobiles, pickups, trucks, and utility vehicles since at least the 1920s to provide additional protection to the vehicle. While bumpers were originally made of heavy steel, in later years they have been constructed of rubber, plastic, or painted light metal leaving them susceptible to damage from even minimal contact. For the most part, these vehicles cannot push, or be pushed by, another vehicle. An entire after-market industry has developed which now produces various guards to protect these vulnerable modern bumpers.

The fun of bumping one car into another led to the creation of bumper cars at amusement parks and carnivals. These small cars are designed to fit one or at most two people and crashed into each other consistently.

Bumper History

Early bumpers were little more than a strap or flat iron. They later swelled out to chromed bumpers, especially in the 1960s. In the early 1970s self repairing bumpers were introduced and after a while they became mandatory (thus killing the Opel GT). Towards the end of the 1980s self repairing bumpers went out of style and were replaced with fibreglass "bumpers" that cracked at impact.

Bumper Reliability

Bumper laws had been rolled back in 1982, reducing the reliability of bumpers in newer cars to sustain damage. Minor collisions may already ruin the aesthetic appearance (paint and finish) of bumpers, and cracked bumpers can only be replaced entirely, resulting in hefty repair costs even for minor collisions.

Bumper Legal issues

In many jurisdictions, bumpers are legally required on all vehicles for safety reasons. The height and placement of bumpers may be legally specified as well, to ensure that when vehicles of different heights are in an accident, that the smaller vehicle will not slide under the larger vehicle, particularly in collisions with semi-trailer trucks.

Buzzers

Electronic symbol for a buzzer

Metal disk with piezoelectric disk attached, as found in a buzzerFor the woodworking machine, see jointer. A buzzer or beeper is a signaling device, usually electronic, typically used in automobiles, household appliances such as a microwave oven, or game shows.

It most commonly consists of a number of switches or sensors connected to a control unit that determines if and which button was pushed or a preset time has lapsed, and usually illuminates a light on the appropriate button or control panel, and sounds a warning in the form of a continuous or intermittent buzzing or beeping sound. Initially this device was based on an electromechanical system which was identical to an electric bell without the metal gong (which makes the ringing noise). Often these units were anchored to a wall or ceiling and used the ceiling or wall as a sounding board. Another implementation with some AC-connected devices was to implement a circuit to make the AC current into a noise loud enough to drive a loudspeaker and hook this circuit up to a cheap 8-ohm speaker. Nowadays, it is more popular to use a ceramic-based piezoelectric sounder like a Sonalert which makes a high-pitched tone. Usually these were hooked up to "driver" circuits which varied the pitch of the sound or pulsed the sound on and off.

In game shows it is also known as a "lockout system," because when one person signals ("buzzes in"), all others are locked out from signalling. Several game shows have large buzzer buttons which are identified as "plungers".

The word "buzzer" comes from the rasping noise that buzzers made when they were electromechanical devices, operated from stepped-down AC line voltage at 50 or 60 cycles. Other sounds commonly used to indicate that a button has been pressed are a ring or a beep.

Some systems, such as the one used on Jeopardy!, make no noise at all, instead using light. Another example is the buzzer at the end of each stage in Sasuke, Kunoichi, and Viking. These buzzers do not make a sound or turn on a light; instead, they stop a nearby digital clock, briefly fire two smoke cannons on each side of the stage exit, and open the exit. However, at the end of the Heartbreaker in Viking, the buzzer is replaced with a sword that, when removed, causes two contacts to touch, closing the circuit and causing the latter two actions above to occur.

Nowadays some people use the word "buzzer" as to describe a person who's able to create a big buzz around a brand, an event or a company.

Car battery

Lead-acid car batteryA car battery is a type of rechargeable battery that supplies electric energy to an automobile. Usually this refers to a SLI battery (Starting - Lighting - Ignition) to power the starter motor, the lights, and the ignition system of a vehicle’s engine. This also may describe a traction battery used for the main power source of an electric vehicle.

Automotive starter batteries (usually of lead-acid type) provide a nominal 12-volt potential difference by connecting six galvanic cells in series. Since the cells naturally produce about 2.1 V, the actual voltage is roughly 12.6 V. Lead-acid batteries are made up of plates of lead and lead oxide, which are submerged into an electrolyte solution of 35% sulfuric acid and 65% water. This causes a chemical reaction that releases electrons, allowing them to flow through conductors to produce electricity. As the battery discharges, the acid of the electrolyte reacts with the materials of the plates, changing their surface to lead sulphate. When the battery is recharged, the chemical reaction is reversed: the lead sulphate reforms into lead oxide and lead. With the plates restored to their original condition, the process may now be repeated.

Car battery Types

Lead-acid batteries have different uses. Several elements are alloyed with the lead such as calcium, cadmium or strontium to change density, hardness, or porosity of the plates and to make the plates easier to manufacture.

The starting (cranking) or shallow cycle type is designed to deliver quick bursts of energy, usually to start an engine. They usually have a greater plate count in order to have a larger surface area that provides high electric current for short period of time. Once the engine is started, they are continuously recharged. See Jump start (vehicle). The deep cycle (or motive) type is designed to continuously provide power for long periods of time (for example in a trolling motor for a small boat, a golf cart or other battery electric vehicle). They can also be used to store energy from a photovoltaic array or a small wind turbine. They usually have thicker plates in order to have a greater capacity and survive a higher number of charge/discharge cycles. See battery pack.

Some batteries are claimed by their manufacturers to be dual purpose (starting and deep cycling).

Car battery Use and maintenance

Car battery Fluid level

Formerly car batteries using lead-antimony plates would require regular top-up to replace water lost due to electrolysis on each charging cycle. By changing the alloying element, more recent designs have lower water loss unless overcharged. Modern car batteries have low maintenance requirements, and may not provide caps for addition of water to the cells. If the battery has easily detachable caps then a top up may be required from time to time. Prolonged overcharging or charging at excessively high voltage causes some of the water in the electrolyte to be broken up into hydrogen and oxygen gases, which escape from the cells. If the electrolyte liquid level drops too low, the plates are exposed to air, lose capacity and are damaged. The cells can be topped up with distilled or deionised water just above the visible plates. The sulphuric acid in the battery normally does not require replacement since it is not consumed even on overcharging.

Impurities in the water will reduce the life and performance of the battery. Manufacturers usually recommend use of demineralized or distilled water since even potable tap water can contain high levels of minerals.

Car battery Charge and discharge

In normal automotive service the vehicle's engine-driven alternator powers the vehicle's electrical systems and restores charge used from the battery during engine cranking. When installing a new battery or recharging a battery that has been accidentally discharged completely, one of several different methods can be used to charge it. The most gentle of these is called trickle charging. Other methods include slow-charging and quick-charging, the latter being the harshest.

In emergencies a battery can be jump started, by the battery of another vehicle or by a hand portable battery booster.

Car battery Changing a battery

In most modern automobiles, the grounding is provided by connecting the body of the car to the negative electrode of the battery, a system called 'negative ground'. In the past some cars had 'positive ground'. Such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge.

The recommended practice when removing a car battery is to disconnect the ground connection first and then other terminal. This ensures that a short circuit will not occur by a wrench touching grounded engine parts while disconnecting the other terminal. Similarly, the ground should be connected last when installing a battery.

Care should be taken when first filling the battery with acid, as acids are highly corrosive and can damage eyes, skin and mucous membranes. A 1994 study by the National Highway Traffic Safety Association estimated that in 1994 more than 2000 people were injured in the United States while working with automobile batteries.

Car battery Freshness

Because of "sulfation" (see lead-acid battery), lead-acid batteries stored with electrolyte slowly deteriorate. Car batteries should be installed within one year of manufacture. In the United States, the manufacturing date is printed on a sticker. The date can be written in plain text or using an alphanumerical code. The first character is a letter that specifies the month (A for January, B for February and so on). The letter "I" is skipped due to its potential to be mistaken for the number 1. The second character is a single digit that indicates the year of manufacturing (for example, 6 for 2006).

Car battery Corrosion

Corrosion at the battery terminals can prevent a car from starting. To prevent corrosion, during regular battery service the terminals may be cleaned with a wire brush and corrosion products washed away with water. When the battery terminals are re-assembled, they are coated with vaseline/petrolium jelly (grease is not desired) to reduce the rate of corrosion accumulation.

Car battery Battery defects

Common battery faults include:

Shorted cell due to failure of the separator between the positive and negative plates

Broken internal connections due to corrosion

Broken plates due to vibration and corrosion

Low electrolyte

Cracked or broken case

Broken terminals

Sulfation after prolonged disuse.

In addition, the primary wear-out mechanism is the shedding of active material from the battery plates, which accumulates at the bottom of the cells and which may eventually short-circuit the plates.

Early automotive batteries could sometimes be repaired by dismantling and replacing damaged separators, plates, intercell connectors, and other repairs. Modern battery cases do not facilitate such repairs; an internal fault generally requires replacement of the entire unit.

Car battery Exploding batteries

Any lead-acid battery system when overcharged will produce hydrogen gas. If the rate of overcharge is small, the vents of each cell allow the dissipation of the gas. However, on severe overcharge or if ventilation is inadequate, a flammable concentration of hydrogen may remain in the cell or in the battery enclosure. Any spark can cause an explosion, which will damage the battery and its surroundings and which will disperse acid into the surroundings. Car batteries should always be handled with proper protective equipment (goggles, overalls, gloves).

Car battery Terms and ratings

Ampere-hours (A·h) is the product of the time that a battery can deliver a certain amount of current (in hours) times that current (in amps), for a particular discharge period. This is one indication of the total amount of charge a battery is able to store and deliver at its rated voltage. This rating is rarely stated for automotive batteries.

Cranking amps (CA), also sometimes referred to as marine cranking amps (MCA), is the amount of current a battery can provide at 32°F (0°C). The rating is defined as the number of amperes a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery).

Cold cranking amps (CCA) is the amount of current a battery can provide at 0°F (-18°C). The rating is defined as the amperage a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures.

Hot cranking amps (HCA) is the amount of current a battery can provide at 80°F (26.7°C). The rating is defined as the amperage a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery).

Reserve capacity minutes (RCM), also referred to as reserve capacity (RC), is a battery's ability to sustain a minimum stated electrical load; it is defined as the time (in minutes) that a lead-acid battery at 80°F (27°C) will continuously deliver 25 amperes before its voltage drops below 10.5 volts.

Battery Council International group size (BCI) specifies a battery's physical dimensions, such as length, width, and height. These groups determined are by the Battery Council International organization.

Peukert's Law expresses the fact that the capacity available from a battery varies according to how rapidly it is discharged. A battery discharged at high rate will give fewer amperehours than one discharged more slowly.

The hydrometer measures the density, and therefore indirectly the amount of sulfuric acid in the electrolyte. A low reading means that sulfate is bound to the battery plates and that the battery is discharged. Upon recharge of the battery, the sulfate returns to the electrolyte.

The open circuit voltage, measured when the engine is off. It can be approximately related to the charge of the battery by: Open Circuit Voltage (12V) Open Circuit Voltage (6V) Approximate charge Relative acid density Open circuit voltage is also affected by temperature, and the specific gravity of the electrolyte at full charge.

Car battery Lead-acid

The following is common for lead-acid batteries:

Quiescent (open-circuit) voltage at full

charge: 12.6 V

Unloading-end: 11.8 V

Charge with 13.2-14.4 V

Gassing voltage: 14.4 V

Continuous-preservation charge with max. 13.2 V

After full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V. The energy to weight ratio, or specific energy, is in the range of 30 Wh/kg (108 kJ/kg).

Car battery Formats

Lead-acid battery The most commonly used battery for SLI applications. It has a low specific energy, but is cheaper than high-performance battery types.

Car battery Future Trends

Due to the increase of electric power payloads in today’s automobile, a 42 V power system has been considered and is being developed to replace the existing 14 V power system. (14 V and 42 V refer to the alternator charging voltage). See for example Modeling of 36 V Lead Acid Battery for the 42 V Automotive System Simulation. For 42 V systems, 18 cell lead acid battery with a nominal 36 V is proposed.

Car Catalytic converters

Catalytic converter on a Saab 9-5.A catalytic converter (colloquially, "cat" or "catcon") is a device used to reduce the toxicity of emissions from an internal combustion engine. First widely introduced on series-production automobiles in the US market for the 1975 model year to comply with tightening EPA regulations on auto exhaust, catalytic converters are still most commonly used in motor vehicle exhaust systems. Catalytic converters are also used on generator sets, forklifts, mining equipment, trucks, buses, trains, and other engine-equipped machines. A catalytic converter provides an environment for a chemical reaction wherein toxic combustion by-products are converted to less-toxic substances.

Car Catalytic converter Functions

Car Catalytic converter Three-way catalytic converters

A three-way catalytic converter has three simultaneous tasks:

Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx ? xO2 + N2

Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 ? 2CO2

Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 ? 2xCO2 + yH2O These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This is between 14.8 and 14.9 parts air to 1 part fuel, by weight, for gasoline (the ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels). When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation. If an engine could be operated with infinitesimally small oscillations about the stoichiometric point for the fuel used, it is theoretically possible to reach 100% conversion efficiencies.

Since 1981, three-way catalytic converters have been at the heart of vehicle emission control systems in North American roadgoing vehicles, and have been used on "large spark ignition" (LSI) engines since 2001 in California, and from 2004 in the other 49 states. LSI engines are used in forklifts, aerial boom lifts, ice resurfacing machines and construction equipment. The converters used in those types of machines are three-way types, and are designed to reduce combined NOx+HC emissions from 12 gram/BHP-hour to 3 gram/BHP-hour or less, as mandated by the United States Environmental Protection Agency's (EPA) 2004 regulations.

A further drop to 2 gram/BHP-hour of NOx+HC emissions is mandated in 2007 (note: NOx is the industry standard short form for nitric oxide (NO) and nitrogen dioxide (NO2) both of which are smog precursors. HC is the industry short form for hydrocarbons). The EPA intends to introduce emissions rules for stationary spark ignition engines, to take effect in January 2008.

Car Catalytic converter Two-way catalytic converters

A two-way catalytic converter has two simultaneous tasks:

Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 ? 2CO2

Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 ? 2xCO2 + yH2O

This type of catalytic converter is widely used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. They were also used on spark ignition (gasoline) engines in USA market automobiles up until 1981, when they were replaced by three-way converters due to regulatory changes requiring reductions on NOx emissions.

Reduction of the NOx emissions requires an additional step. Platinum catalysis can be used. Instead of catalysis, a true reactant diesel fuel or ammonia pyrolyzed in situ from urea can be used to reduce the NOx into nitrogen.

Curiously, the regulations regarding hydrocarbons vary according to the engine regulated, as well as the jurisdiction. In some cases, "non-methane hydrocarbons" are regulated, while in other cases, "total hydrocarbons" are regulated. Technology for one application (to meet a non-methane hydrocarbon standard) may not be suitable for use in an application that has to meet a total hydrocarbon standard. Methane is not toxic, but is more difficult to break down in a catalytic converter, so in effect a "non-methane hydrocarbon" standard can be considered to be looser. Since methane is a greenhouse gas, interest is rising in how to eliminate emissions of it.

Car Catalytic converter Catalyst poisoning and deactivation

Catalytic converters become ineffective in the presence of lead due to catalyst poisoning. Therefore, vehicles equipped with catalytic converters must only be run on unleaded gasoline, and it is this fact, as much as concerns about the possibly harmful effects of lead emissions, which caused the end of pump-available leaded gasoline in countries where catalytic converters have been in common use for many years. Leaded "race only" fuel is still used for non-catalyst vehicles in some countries. Catalyst poisoning occurs when a substance in the engine exhaust coats the surface of the catalyst, preventing further exhaust access to the catalytic materials. Poisoning can sometimes be reversed by running the engine under a very heavy load for an extended period of time to raise exhaust gas temperature, which may cause liquefaction or sublimation of the catalyst poison. Common catalyst poisons are lead, sulfur, zinc, manganese, silicon and phosphorus.

Zinc, phosphorus and sulfur originate from lubricant antiwear additives such as ZDDP; sulfur and manganese primarily originate from fuel impurities or from additives such as Methylcyclopentadienyl Manganese Tricarbonyl (MMT), respectively. Silicon poisoning in automotive applications is the result of engine damage, such as a faulty cylinder head gasket or cracked casting, admitting silicate-containing coolant into the combustion chamber. In stationary engines silicon poisoning is more often caused by the use of methane landfill gas as a fuel.

Removal of sulfur from a catalyst surface by running heated exhaust gases over the catalyst surface is often successful; however, removal of lead deposits in this manner is usually not possible because of lead's high boiling point. In particularly bad cases of catalyst poisoning by lead, the catalytic converter can actually become completely plugged with lead residue.

A variety of conditions may cause the catalyst to overheat (heat deactivation) and potentially to melt down. Some factors that can cause this are:

lubricating oil in the exhaust system (caused by engine wear, or by damaged rings or valves) an engine misfire or ignition failure (causing unburnt fuel to enter the exhaust) a cracked exhaust valve (again, causing unburnt fuel in the exhaust)

Overly rich fuel mixtures are not usually a problem - there is too little unused oxygen for the exothermic reaction to be large enough to cause damage. A slightly leaner than stoichiometric mix is far more dangerous, as the oxygen level is elevated, allowing a very large exotherm, and many engine manufacturers design "rich excursions" as a catalyst protection measure in the engine control software. In the early days of catalyst-equipped cars, (primarily in the USA) before the advent of sophisticated engine management systems, it was necessary for fuel/air mixtures to be significantly richer than had hitherto been the case to allow the catalyst to work effectively. This contributed to the very poor fuel consumption figures achieved by such cars.

Engine misfires can overheat and destroy the converter as the excessive amounts of unburned fuel are broken down within it, especially when the engine is under heavy loads. Vehicles equipped with OBD-II diagnostic systems are designed to alert the driver of a misfire condition, along with other malfunctions, using the Malfunction Indicator Lamp or "Check Engine" light. If the misfire and engine load can produce heating severe enough to cause catalyst damage, the MIL will flash until the misfire or engine load is reduced.

Car Catalytic converter Technical details

The core, or substrate. In modern catalytic converters, this is most often a ceramic honeycomb, however stainless steel foil honeycombs are also used. The purpose of the core is to "support the catalyst" and therefore it is often called a "catalyst support". The ceramic substrate was invented by Rodney Bagley, Irwin Lachman and Ronald Lewis at Corning Glass for which they were inducted into the National Inventors Hall of Fame in 2002. The washcoat. In an effort to make converters more efficient, a washcoat is utilized, most often a mixture of silica and alumina. The washcoat, when added to the core, forms a rough, irregular surface which has a far greater surface area than the flat core surfaces, which is desirable to give the converter core a larger surface area, and therefore more places for active precious metal sites. The catalyst is added to the washcoat (in suspension) before application to the core. The catalyst itself is most often a precious metal. Platinum is the most active catalyst and is widely used. However, it is not suitable for all applications because of unwanted additional reactions and/or cost. Palladium and rhodium are two other precious metals that are used. Platinum and rhodium are used as a reduction catalyst, while platinum and palladium are used as an oxidization catalyst. Cerium, iron, manganese and nickel are also used, though each has its own limitations. Nickel is not legal for use in the European Union (due to reaction with carbon monoxide). While copper can be used, its use is illegal in North America due to the formation of dioxin.

Car Catalytic converter Conventional spark ignition engines

Catalytic converters are used on spark ignition (gasoline; liquified petroleum gas (LPG); flexible fuel vehicles burning varying blends of E85 and gasoline; compressed natural gas (CNG)) engines; and compression ignition (diesel) engines.

For spark ignition engines, the most commonly used catalytic converter is the three-way converter which converts the three main pollutants of concern CO, HC, and NOx to less-toxic substances. The control of NOx involves a reduction process that releases oxygen and the control of CO and HC involves an oxidation process that consumes oxygen. Therefore, a 3-way converter contains two catalyst-coated stages: The first catalyst stage encountered by the exhaust is for reduction of NOx, which produces oxygen employed by the second stage to oxidize CO and HC. 3-way converters work most efficiently with exhaust from engines operated on a stoichiometric air-fuel mixture. Generally, such engines are equipped with closed-loop feedback fuel mixture control employing one or more oxygen (lambda) sensors. While a 3-way catalyst can be used in an open-loop system, NOx reduction efficiency is low. Since NOx emissions are now regulated throughout the world, open-loop fuel systems are obsolete in many jurisdictions. Closed-loop maintenance of the stoichiometric air-fuel ratio is most often attained by means of an engine management system with computer-controlled fuel injection, though early in the deployment of 3-way converters, carburetors equipped for feedback mixture control were used during the transition to fuel injection. Within a narrow ratio band surrounding stoichiometry, conversion of all three pollutants is very complete, sometimes approaching 100%. However, outside of that band, conversion efficiency falls off very rapidly. Two-way (or oxidation) converters act only to control CO and HC, and have therefore been abandoned on conventional spark ignition engines in most jurisdictions due to an inability to control NOx.

A three-way catalyst reduces emissions of CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides) simultaneously when the oxygen level of the exhaust gas stream is below 1.0%, though performance is best at below 0.5% O2. Unwanted reactions, such as the formation of H2S (hydrogen sulfide) and NH3 (ammonia), can occur in the three-way catalyst. Formation of each can be limited by modifications to the washcoat and precious metals used. It is, however, difficult to eliminate these side products entirely.

For example, when control of H2S (hydrogen sulfide) emissions is desired, nickel or manganese is added to the washcoat - both substances act to block the adsorption of sulfur by the washcoat. H2S is formed when the washcoat has adsorbed sulfur during a low temperature part of the operating cycle, which is then released during the high temperature part of the cycle and the sulfur combines with HC. For "lean burn" spark ignition engines (e.g. compressed natural gas, or compressed natural gas with diesel fuel pilot injection), an oxidation catalyst is used in the same manner as in a compression ignition engine.

Recently, many systems have used a pre-catalyst in the system to reduce startup emissions and burn off hydrocarbons from the extra-rich mixture used in a cold engine. Upstream and downstream parts are now often separated in the system to provide an optimum temperature and space for extra oxygen sensors. The converter needs to be placed close enough to the engine to quickly reach operating temperature but far enough away to avoid heat damage.

Many three-way catalytic converters utilize an air injection tube between the first (NOx reduction) and second (HC and CO oxidation) biscuits of the converter. This tube is fed by either an air pump or by an aspirator. The injected air provides oxygen for the catalyst's oxidizing reaction. These systems also sometimes include an upstream air injector to admit oxygen to the exhaust system before it reaches the catalytic converter. This precleans the extra-rich exhaust from a cold engine, and helps bring the catalytic converter quickly up to operating temperature.

Most newer systems do not employ air injection. Instead, they provide a constantly varying mixture that quickly and continually cycles between lean and rich to keep the first catalyst (NOx reduction) from becoming oxygen loaded, and to keep the second catalyst (CO oxidization) sufficiently oxygen-saturated. They also utilize several oxygen sensors to monitor the exhaust, at least one before the catalytic converter for each bank of cylinders, and one after the converter. Some systems contain the reduction and oxidation functions separately rather than in a common housing.

Car Catalytic converter Diesel engines

For compression ignition (i.e., Diesel) engines, the most commonly used catalytic converter is the diesel oxidation catalyst. The catalyst uses excess O2 (oxygen) in the exhaust gas stream to oxidize CO (Carbon Monoxide) to CO2 (Carbon Dioxide) and HC (hydrocarbons) to H2O (water) and CO2. These converters often reach 90% effectiveness, virtually eliminating diesel odor and helping to reduce visible particulates (soot), however they are incapable of reducing NOx as chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream would react first.

To reduce NOx on a compression ignition engine it is necessary to change the exhaust gas - two main technologies are used for this - selective catalytic reduction (SCR) and NOx (NOx) traps (or NOx Adsorbers).

Another issue for diesel engines is particulate (soot). This can be controlled by a soot trap or diesel particulate filter (DPF), as catalytic converters are unable to affect elemental carbon (however they will remove up to 90% of the soluble organic fraction). A clogging soot filter creates a lot of back pressure decreasing engine performance. However, once clogged, the filter goes through a regeneration cycle where diesel fuel is injected directly into the exhaust stream and the soot is burned off. After the soot has been burned off the regeneration cycle stops and injection of diesel fuel stops. This regeneration cycle should not affect performance of the engine.

All major diesel engine manufacturers in the USA (Ford, Caterpillar, Cummins, Volvo, MMC) starting January 1, 2007 are required to have a catalytic converter and a soot filter inline, as per new EPA legislation. http://www.epa.gov/otaq/highway-diesel/regs/2007-heavy-duty-highway.htm

Car Catalytic converter Oxygen storage in three-way converters

In order to oxidize CO and HC, the catalytic converter also has the capability of storing the oxygen from the exhaust gas stream, usually when the air fuel ratio goes lean. When insufficient oxygen is available from the exhaust stream the stored oxygen is released and consumed. This happens either when oxygen derived from NOx reduction is unavailable or certain maneuvers such as hard acceleration enrich the mixture beyond the ability of the converter to compensate.

Note that diesel catalysts do not use this feature as there is sufficient O2 in the exhaust gas stream to handle the CO & HC reductions needed.

Car Catalytic converter Regulations

Emissions regulations vary considerably from jurisdiction to jurisdiction, as do what engines are regulated. In North America any spark ignition engine of over 19 kW (25 hp) power output built later than January 1, 2004 probably has a three-way catalytic converter installed. In Japan a similar set of regulations came into effect January 1, 2007, while the European Union has not yet enacted analogous regulations. Most automobile spark ignition engines in North America have been fitted with catalytic converters since the mid-1970s and the technology used in non-automotive applications is generally based on automotive technology.

Diesel engine regulations are similarly varied, with some jurisdictions focusing on NOx (Nitric Oxide and Nitrogen Dioxide) emissions and others focusing on particulate (soot) emissions. This can cause problems for the engine manufacturers as it may not be economical to design an engine to meet two sets of regulations.

An important issue is that fuel quality varies widely from place to place, even within jurisdictions, as do the regulations covering fuel quality. In North America, Europe, Japan, and Hong Kong both gasoline and diesel fuel are highly regulated and there are campaigns under way to regulate CNG and LPG as well. In most of Asia and Africa this is not true - in some places sulfur content of the fuel can reach 20,000 parts per million (2%). Any sulfur in the fuel may be oxidized to SO2 (sulfur dioxide) or even SO3 (sulfur trioxide) in the combustion chamber. If sulfur passes over a catalyst it may be further oxidized in the catalyst, i.e. (SO2 may be further oxidized to SO3). Sulfur oxides are precursors to sulfuric acid, a major component of acid rain. While it is possible to add substances like vanadium to the catalyst wash coat to combat sulfur oxide formation, this will reduce the effectiveness of the catalyst the best solution is further refinement of the fuel at the refinery to remove the sulfur. Regulations in Japan, Europe and by 2007 North America tightly restrict the amount of sulfur permitted in motor fuels. However, the expense is such that this is not practical in many developing countries. As a result cities in these countries with high levels of vehicular traffic suffer damage to buildings due to acid rain eating away the stone/woodwork, and acid rain has deleterious effects on the local ecosystem.

Car Catalytic converter Regulatory agencies

The agencies charged with regulating engine emissions vary from jurisdiction to jurisdiction, even in the same country. For example, in the United States, overall responsibility belongs to the United States Environmental Protection Agency (EPA), but due to special requirements of the State of California, emissions in California are regulated by the Air Resources Board. In Texas, the Texas Railroad Commission is responsible for regulating emissions from LPG fueled rich burn engines (but not gasoline fueled rich burn engines).

California Air Resources Board - California, United States (most sources)

Environment Canada - Canada (most sources)

Environmental Protection Agency - United States (most sources)

Texas Railroad Commission - Texas, United States (LPG fueled engines only)

Transport Canada - Canada (trains and ships)

Car Catalytic converter Criticisms

Car Catalytic converter Environmental impact

Catalytic converters have proven to be reliable devices and have been successful in reducing noxious tailpipe emissions. However, they may have some adverse environmental impacts in use:

The requirement for a rich burn engine to run at the stoichiometric point means it uses more fuel than a "lean burn" engine running at a mixture of 20:1 or less. This increases the amount of fossil fuel consumed and the carbon dioxide emissions of the vehicle. However, NOx control on lean burn engines is problematic at best, and many lean burn engine manufacturers are considering rich burn variations.

The manufacturing of catalytic converters requires palladium and/or platinum; a portion of the world supply of these precious metals is produced near the Russian city of Norilsk, with significant negative environmental effects.

Car Catalytic converter theft

Due to the use of precious metals including platinum worth up to $1,200 an ounce; palladium at up to $320 an ounce; and rhodium at up to $6,400 an ounce, catalytic converters are a target for thieves. The problem is especially common among late-model Toyota trucks and SUVs, due to their high ground clearance and easily-removed bolt-on catalytic converters. Welded-in converters are also at risk of theft from SUVs and trucks, as they can be removed within five minutes by means of a battery powered reciprocating saw. The value of precious metals in a single converter is low, seldom over $50 per converter at 2007 prices. UK prices fluctuate between £35-$70 and £45-$90 for genuine converters and approx £8-£16 for non genuine converters being bought as scrap metal.

Car Catalytic converter Diagnostics

Various jurisdictions now legislate on-board diagnostics to monitor the effectiveness of the emissions control system, including the catalytic converter and such diagnostics are often included in aftermarket retrofit kits as a matter of course, even if legislation does not directly require them.

On-board diagnostics take several forms, depending upon the legislation and the type of emissions control product being monitored, the three main types are:

temperature

oxygen

NOx

Car Catalytic converter Temperature sensors

Temperature sensors are used for two purposes. The first is as a warning system, typically on obsolete 2-Way catalytic converters such as are still sometimes used on LPG forklifts. The function of the sensor is to warn of temperature excursions above the safe operating temperature of 750°Celsius of the two-way catalytic converter. Note that modern catalytic converters are not as susceptible to temperature damage with many modern three-way platinum based converters able to handle temperatures of 900°C sustained. Temperature sensors are also used to monitor catalyst functioning - usually two sensors will be fitted, with one before the catalyst and one after to monitor the temperature rise over the catalytic converter core. For every 1% of CO in the exhaust gas stream the exhaust gas temperature will rise by 100°C.

Car Catalytic converter Oxygen sensors

The Oxygen sensor or "lambda sensor" is the basis of the closed loop control system on a spark ignited rich burn engine, however it is also used for diagnostics. Oxygen sensors only work when at operating temperature, when they output a voltage based on the O2 level in the exhaust gas to the computer. Typically a single wire oxygen sensor will take 3-5 minutes to reach operating temperature. The more expensive heated sensors (3 to 5 wires) can reach operating temperature in 1 minute.

The simplest sort of diagnostic an oxygen sensor can perform is related to the closed loop control system. If the system makes a change to the air-fuel ratio based on oxygen sensor readings, and the readings do not change, the sensor will light an indicator on the instrument panel warning the operator that there is a problem with the vehicle. There is a delay before this happens - usually five minutes of engine operation. Most systems do not store the state, so turning off the engine and turning it back on will reset the system, and if the error is transient the light will not come back on. However, if the problem is recurring, the light will come on as soon as the sensor reaches operating temperature and a manufacturer-defined driving pattern known as a drive-trace is completed. Until this procedure has finished, the diagnostic computer will set a parameter called a readiness monitor to "unready". The readiness monitor system was implemented in order to ensure that diagnostic computers would not falsely report working emissions systems in vehicles whose computer's error memory had recently been cleared. Such diagnostics have been factory fitted to automobiles since 1985 in North America and factory fitted to off-road spark ignition engines since 2004.

The second sort of diagnostic is more complex and is a result of the California OBD-II rule (though temperature sensors are sometimes used for this). In vehicles with OBD-II, a second oxygen sensor is fitted after the catalytic converter to monitor the O2 levels. The on-board computer makes comparisons between the readings of the two sensors. If both sensors give the same output, the catalytic converter is non-functioning, and must be replaced. It will also spot less serious damage to a catalytic converter, such as the use of leaded racing fuel in an on-road vehicle.

Car Catalytic converter NOx sensors

NOx sensors are extremely expensive and are generally only used when a compression ignition engine is fitted with a selective catalytic reduction converter, or a NOx adsorber catalyst in a feedback system. When fitted to an SCR system, there may be one or two sensors. When one sensor is fitted it will be pre-catalyst, when two are fitted the second one is post catalyst. They are utilized for the same reasons and in the same manner as an oxygen sensor - the only difference is the substance being monitored.

Car door

A car door is generally an opening to enter to the car (or their compartments or partition), often equipped with a hinged or sliding panel which can be moved to leave the opening accessible, or to close it more or less securely.

Car door Brakes

Car doors generally include a three-stage door brake.

Car door Parts

Car glass

Door handles

Door switch (simple on/off mechanism ; when the car door is open, the switch is off).

Running board

Passenger side dash mounted storage box.

Car door Situations

Front door

Rear door

Trunk or boot

Car door Types

Manual Electric (power opening and closing).

Car door Number of doors

Cars are usually sold as "three-door" or "five-door" models. In these cases, the number includes the trunk or boot door, so a three-door car has two front doors plus the trunk, and a five-door car has two front doors, two rear doors and the trunk.

Car door Being doored

Cyclists refer to colliding with an open car door as "being doored". This usually happens when the cyclist is biking alongside a row of parallel-parked cars, and a driver suddenly opens his or her door immediately in front of the cyclist.

Clutches

Clutch Flywheel

Clutch for a drive shaft: The clutch disc (center) spins with the flywheel (left). To disengage, the lever is pulled (black arrow), causing a white pressure plate (right) to disengage the green clutch disc from turning the drive shaft, which turns within the thrust-bearing ring of the lever. At rest, all 3 rings connect, with no gaps.

Single, dry, clutch friction disc. The splined hub is attached to the disc with springs to damp chatter.A clutch is a mechanism for transmitting rotation, which can be engaged and disengaged. Clutches are useful in devices that have two rotating shafts. In these devices, one shaft is typically driven by a motor or pulley, and the other shaft drives another device. In a drill, for instance, one shaft is driven by a motor, and the other drives a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.

Vehicle clutches

There are many different vehicle clutch designs but most are based on one or more friction discs, pressed tightly together or against a flywheel using springs. The friction material varies in composition depending on whether the clutch is dry or wet, and on other considerations. Friction discs once contained asbestos, but this has been largely eliminated. Clutches found in heavy duty applications such as trucks and competition cars use ceramic clutches that have a greatly increased friction coefficient, however these have a "grabby" action and are unsuitable for road cars. The spring pressure is released when the clutch pedal is depressed thus either pushing or pulling the diaphragm of the pressure plate, depending on type, and the friction plate is released and allowed to rotate freely.

When engaging the clutch, the engine speed may need to be increased from idle, using the manual throttle, so that the engine does not stall (although in most cars, especially diesels, there is enough power at idling speed that the car can move. This requires fine control of the clutch). However, raising the engine speed too high while engaging the clutch will cause excessive clutch plate wear. Engaging the clutch abruptly when the engine is turning at high speed causes a harsh, jerky start. This kind of start is desired in drag racing and other competitions, however.

Wet and dry clutches

A 'wet clutch' is immersed in a cooling lubricating fluid, which also keeps the surfaces clean and gives smoother performance and longer life. Wet clutches, however, tend to lose some energy to the liquid. A 'dry clutch', as the name implies, is not bathed in fluid. Since the surfaces of a wet clutch can be slippery (as with a motorcycle clutch bathed in engine oil), stacking multiple clutch disks can compensate for slippage.

Clutch operation in automobiles

In a car the clutch is operated by the left-most pedal using hydraulics or a cable connection from the pedal to the clutch mechanism. Even though the clutch may physically be located very close to the pedal, such remote means of actuation are necessary to eliminate the effect of slight engine movement, engine mountings being flexible by design. With a rigid mechanical linkage, smooth engagement would be near-impossible, because engine movement inevitably occurs as the drive is "taken up". No pressure on the pedal means that the clutch plates are engaged (driving), while depressing the pedal disengages the clutch plates, allowing the driver to shift gears or coast.

A manual transmission contains cogs for selecting gears. These cogs have matching teeth, called dog teeth, which means that the rotation speeds of the two parts have to match for engagement. This speed matching is achieved by a secondary clutch called a synchronizer, a device that uses frictional contact to bring the two parts to the same speed, and a locking mechanism called a blocker ring to prevent engagement of the teeth (full movement of the shift lever into gear) until the speeds are synchronized.

Non-powertrain clutches in automobiles

There are other clutches found in a car. For example, a belt-driven engine cooling fan may have a clutch that is heat-activated. The driving and driven elements are separated by a silicone-based fluid. When the temperature is low, the fluid is thin and so the clutch slips. When the temperature is high, the fluid thickens, causing the fan to spin. There are also electronically engaged clutches (such as for anAir conditioning compressor) that use magnetic force to lock the pulley and compressor together.

Clutch operation in motorcycles

On most motorcycles, the clutch is operated by the clutch lever, located on the left handlebar. No pressure on the lever means that the clutch plates are engaged (driving), while pulling the lever back towards the rider will disengage the clutch plates, allowing the rider to shift gears. Motorcycle clutches are usually made up of a stack of alternating plain steel and friction plates. One type of plate has lugs on its inner diameter that key it to the engine crankshaft, while the other type of plate has lugs on its outer diameter that key it to a basket that turns the transmission input shaft. The plates are forced together by a set of coil springs when the clutch is engaged. Racing motorcycles often use slipper clutches to eliminate the effects of engine braking.

Centrifugal clutches

Cylinder heads

A 302/5.0L Ford cylinder head.In an internal combustion engine, the cylinder head sits atop the cylinders and consists of a platform containing part of the combustion chamber and the location of the valves and spark plugs. In a flathead engine, the mechanical parts of the valve train are all contained within the block, and the head is essentially a flat plate of metal bolted to the top of the cylinder bank with a head gasket in between; this simplicity leads to ease of manufacture and repair, and accounts for the flathead engine's early success in production automobiles and continued success in small engines, such as lawnmowers. This design, however, requires the incoming air to flow through a convoluted path, which limits the ability of the engine to perform at higher rpm, leading to the adoption of the overhead valve head design.

In the overhead valve head, the top half of the cylinder head contains the camshaft in an overhead cam engine, or another mechanism (such as rocker arms and pushrods) to transfer rotational mechanics from the crankshaft to linear mechanics to operate the valves (pushrod engines perform this conversion at the camshaft lower in the engine and use a rod to push a rocker arm that acts on the valve). Internally the cylinder head has passages called ports for the fuel/air mixture to travel to the inlet valves from the intake manifold, for exhaust gases to travel from the exhaust valves to the exhaust manifold, and for antifreeze to cool the head and engine.

The number of cylinder heads in an engine is a function of the engine configuration. A straight engine has only one cylinder head. A V engine usually has two cylinder heads, one at each end of the V, although Volkswagen, for instance, produces a V6 called the VR6, where the angle between the cylinder banks is so narrow that it utilizes a single head. A boxer engine has two heads.

The cylinder head is key to the performance of the internal combustion engine, as the shape of the combustion chamber, inlet passages and ports (and to a lesser extent the exhaust) determines a major portion of the volumetric efficiency and compression ratio of the engine.

Dashboards

The dashboard of a modern car, a Bentley Continental GTCA dashboard, dash, and sometimes fascia (chiefly in British English) is a control panel located under the windshield of an automobile. It contains instrumentation and controls pertaining to operation of the vehicle.

Originally, a dashboard was the upturned screen of wood or leather placed on the front of a horse-drawn carriage, sleigh or other vehicle that protected the driver from mud, debris, water and snow thrown up by the horse's hooves.

Dashboard Types of dashboards

Lawn mowers, farm tractors, and earlier automobiles sometimes have little more than a steering wheel and some form of ignition or power switch.

Custom-built racing cars often simply have a piece of sheet metal that forms the dashboard. Whenever a new gauge needs to be added, a hole is drilled in the appropriate location. Open wheeled racing cars often have no space for a dashboard, so the instrument cluster is integrated into the center of the steering wheel.

Motorcycles and mopeds have a compressed version of car dashboards, but nevertheless larger machines sometimes have enough room for items such as audio equipment and GPS navigation.

Dashboard Dashboard and centre console layout

Increasingly, manufacturers are experimenting with moving all display portions to the center console. Various arguments are put forward for this, including cost savings when constructing both left- and right-hand-drive versions.

Dashboard Padded dashboards and safety

Padded dashboards were advocated in the 1940s by car safety pioneer Claire L. Straith.

Under the aegis of a safety program initiated by Robert McNamara (see The Fog of War documentary), padded "safety" dashboards were introduced in 1956 by Ford under the name "Safeguard". Consumers showed little interest.

One of the safety enhancements of the 1970s was the widespread adoption of padded dashboards. The padding is commonly polyurethane foam, while the surface is commonly either polyvinyl chloride (PVC) or leather in the case of luxury models.

In the 1990s, airbags became a common fitment on dashboards, and are mandatory in some countries.

Dashboard Dashboard items

Dashboard instruments displaying various car and engine conditionsItems located on the dashboard first included the steering wheel and the instrument cluster. The instrument cluster pictured to the right conatins gauges such as a speedometer, tachometer, odometer, fuel gauge, and indicators such as a gear shift position, seat belt warning light, and engine malfunction light. Later came heating and ventilation controls and vents, lighting controls, and audio equipment. In more modern cars, automotive navigation systems are mounted in the dashboard.

Dashboard Audio equipment

The first audio component other than a radio was a monophonic phonograph option on some Chrysler cars well before the cassette or eight-track tape players, which could only be operated when the car was stopped. Graphic equalizers and controls for increased bass came next, and finally CD players.

The audio system controls (such as radio and CD player) may also be on the dashboard, although volume and tuning, for example, may be controlled from a stalk beside the steering wheel.

The top of a dashboard may contain speakers for an audio system, and vents for the heating and air conditioning system. A glovebox is often found on the passenger side, and sometimes on both sides.

Dashboard Fashion in instrumentation

In the 1940s through the 1960s, American car manufacturers and their imitators designed unusually-shaped instruments on a dashboard laden with chrome and transparent plastic, which could be less readable but was often thought to be more stylish. Sunlight could cause a bright glare on the chrome, particularly for a convertible.

With the coming of the LED in consumer electronics, some manufacturers used instruments with digital readouts to make their cars appear more up to date, but this has faded from practise. Some cars use a head-up display to project the speed of the car onto the windscreen in imitation of fighter aircraft, but in a far less complex display.

Differential (mechanical device)

Input torque is applied to the ring gear, which turns the entire carrier (all blue), providing torque to both side gears (red and yellow), which in turn may drive the left and right wheels. If the resistance at both wheels is equal, the planet gear (green) does not rotate, and both wheels turn at the same rate.

If the left side gear (red) encounters resistance, the planet gear (green) rotates about the left side gear, in turn applying extra rotation to the right side gear (yellow).

In an automobile and other wheeled vehicles, a differential is a device, usually consisting of gears, that allows each of the driving wheels to rotate at different speeds, while supplying equal torque to each of them. In automotive applications it is sometimes referred to as a "pumpkin".

Differential Purpose

A vehicle's wheels rotate at different speeds, especially when turning corners. The differential is designed to drive a pair of wheels with equal force, while allowing them to rotate at different speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism. When cornering, the inner wheel travels a shorter distance than the outer wheel, resulting in the inner wheel spinning and/or the outer wheel dragging. This results in difficult and unpredictable handling, damage to tires and roads and strain on, and possible failure of the entire drive train.

Differential History

There are many claims to the invention of the differential gear, but it is likely that it was known, at least in some places, in ancient times. Here are some of the milestones in the history of this device.

1050 BC-771 BC: The Book of Song claimed the South Pointing Chariot, which uses a differential gear, was invented during the Western Zhou Dynasty.

150 BC - 100 BC - The Antikythera mechanism, discovered on an ancient shipwreck near the Greek island of Antikythera, employed a differential gear.

227 - 239 AD - Despite doubts from fellow ministers at court, Ma Jun from the Kingdom of Wei in China invents the first historically verifiable South Pointing Chariot, which provided cardinal direction as a non-magnetic, mechanized compass.

658, 666 AD - two Chinese Buddhist monks and engineers create South Pointing Chariots for Emperor Tenji of Japan.

1027, 1107 AD - Documented Chinese reproductions of the South Pointing Chariot by Yan Su and then Wu Deren, which described in detail the mechanical functions and gear ratios of the device much more so than earlier Chinese records.

1720 - Joseph Williamson uses a differential gear in a clock.

1810 - Rudolph Ackermann of Germany invents a four-wheel steering system for carriages, which some later writers mistakenly report as a differential.

1827 - modern automotive differential patented by watchmaker Onésiphore Pecqueur (1792-1852) of the Conservatoire des Arts et

Métiers in France for use on a steam car. Sources: Britannica Online.

1832 - Richard Roberts of England patents 'gear of compensation', a differential for road locomotives.

1876 - James Starley of Coventry invents chain-drive differential for use on bicycles; invention later used on automobiles by Karl Benz.

1897 - first use of differential on an Australian steam car by David Shearer.

1913 - Packard introduces the spiral-gear differential, which cuts gear noise.

1926 - Packard introduces the hypoid differential, which enables the propeller shaft and its hump in the interior of the car to be lowered.

Differential Functional description

The differential on the rear axle of a carThe following description of a differential applies to a "traditional" rear-wheel-drive car or truck: Power is supplied from the engine, via the gearbox, to a driveshaft (British term: propeller shaft), which runs to the rear axle. A pinion gear at the end of the propeller shaft is encased within the differential itself, and it engages with the large ring gear (British term: crownwheel), shown in the diagrams. The ring gear is attached to a carrier, which holds a set of small planetary gears. The three planetary gears are set up in such a way that the two outer gears (the side gears) can rotate in opposite directions relative to each other. The pair of side gears drive the axle shafts to each of the wheels. The entire carrier rotates in the same direction as the ring gear, but within that motion, the side gears can counter-rotate relative to each other.

Thus, for example, if the car is making a turn to the right, the main ring gear may make 10 full revolutions, and during that time, the left wheel will speed up because it has further to travel, and the right wheel will slow down correspondingly, as it has less distance to travel. The side gears will turn in opposite directions relative to each other by, say, 2 full turns each (4 full turns with regard to each other), resulting in the left wheel making 12 revolutions, and the right wheel making 8 revolutions.

When the vehicle is travelling in a straight line, there will be no movement of the planetary system of gears other than the minute movements necessary to compensate for slight differences in wheel diameter, undulations in the road (which make for a longer or shorter wheel path), etc.

Differential Loss of traction

One undesirable side effect of a differential is that it can reduce overall torque - the rotational force which propels the vehicle. The amount of torque required to propel the vehicle at any given moment depends on the load at that instant - how heavy the vehicle is, how much drag and friction there is, the gradient of the road, the vehicle's momentum and so on. For the purpose of this article, we will refer to this amount of torque as the "threshold torque".

The torque on each wheel is a result of the engine and transmission applying torsion, a twisting force, against the resistance of the traction at that wheel. Unless the load is exceptionally high, the engine and transmission can usually supply as much torque as necessary, so the limiting factor is usually the traction under each wheel. It is therefore convenient to define traction as the amount of torque that can be generated between the tire and the ground before the wheel starts to slip. If the total traction under all the driven wheels exceeds the threshold torque, the vehicle will be driven forward; if not, then one or more wheels will simply spin.

To illustrate how a differential can limit overall torque, imagine a simple rear-wheel-drive vehicle, with one rear wheel on asphalt with good grip, and the other on a patch of slippery ice. With the load, gradient, etc., the vehicle requires, say, 2000 Nm of torque to move forward (i.e. the threshold torque). Let us further assume that the non-spinning traction on the ice equates to 400 Nm, and the asphalt to 3000 Nm.

If the two wheels were driven without a differential, each wheel would push against the ground as hard as possible. The wheel on ice would quickly reach the limit of traction (400 Nm), but would be unable to spin because the other wheel has good traction. The traction of the asphalt plus the small extra traction from the ice exceeds the threshold requirement, so the vehicle will be propelled forward.

With a differential, however, as soon as the "ice wheel" reaches 400 Nm, it will start to spin, and then develop less traction~300Nm. The planetary gears inside the differential carrier will start to rotate because the "asphalt wheel" encounters greater resistance. Instead of driving the asphalt wheel with more force, the differential will allow the ice wheel to spin faster, and the asphalt wheel to remain stationary, compensating for extra speed of the spinning ice wheel. The torque on both wheels will be the same - limited to the lesser traction of 300 Nm each. Since 600 Nm is less than the required threshold of 2000 Nm, the vehicle will not be able to move.

Note that an observer will simply see one stationary wheel and one spinning wheel. It will not be obvious that both wheels are generating the same torque (i.e. both wheels are in fact pushing equally, despite the difference in rotational speed). This has led to a widely held misconception that a vehicle with a differential is really only "one-wheel-drive". In fact, a normal differential always provides equal torque to both driven wheels (unless it is a locking, torque-biasing, or limited slip type).

Differential Traction-adding devices

There are various devices for getting more traction from vehicles with differentials.

ARB, Air Locking DifferentialOne solution is the limited slip differential (LSD), the most well-known of which is the clutch-type LSD. With this differential, the side gears are coupled to the carrier via a stack of clutch plates which limits the speed difference between the two wheels.

A locking differential employs a mechanism for allowing the planetary gears to be locked relative to each other, causing both wheels to turn at the same speed regardless of which has more traction; this is equivalent to removing the differential entirely.

The torsen differential keeps sending some torque to the wheel with more resistance

Electronic traction control systems usually use the ABS system to detect a spinning wheel and apply the brake to it. This progressively raises the reaction torque at that wheel, and the differential compensates by transmitting more torque through the other wheel - the one with better traction.

A viscous coupling unit replaces the differential entirely. It works on the principle of allowing the two output shafts to counter-rotate relative to each other within a viscous fluid. The fluid allows slow relative movements of the shafts, such as those caused by cornering, but will strongly resist high-speed movements, such as those caused by a single wheel spinning.

A four-wheel-drive vehicle will have at least two differentials (one for each pair of wheels) and possibly a center differential to apportion power between the front and rear axles. Vehicles without a center differential should not be driven on dry, paved roads in four wheel drive mode, as small differences in rotational speed between the front and rear wheels cause a torque to be applied across the transmission. This phenomenon is known as "wind-up" and can cause damage to the transmission. On loose surfaces these differences are absorbed by the slippage on the road surface.

The NP242 is an example of a transfer case that acts as a center differential allowing the drive shafts to spin at different speeds. This permits the four-wheel-drive vehicle to drive on paved surfaces without experiencing "wind-up".

Differential Non-automotive applications

Reconstructed 19th century carding mill differentialA differential gear train can also be used to give the difference between two input axles. Mills often used such gears to apply torque in the required axis.

The oldest known example of a differential was once thought to be in the Antikythera mechanism. It was supposed to have used such a train to produce the difference between two inputs, one input related to the position of the sun on the zodiac, and the other input related to the position of the moon on the zodiac; the output of the differential gave a quantity related to the moon's phase. It has now been proven that the assumption of the existence of a differential gearing arrangement was incorrect.

In the first half of the twentieth century, mechanical analog computers, called differential analyzers, were constructed that used differential gear trains to perform addition and subtraction.

Differential Active differentials

A relatively new technology is the electronically-controlled active differential. A computer uses inputs from multiple sensors, including yaw rate, steering angle, and lateral acceleration and adjusts the distribution of torque to compensate for undesirable handling behaviors like understeer. Active differentials used to play a large role in the World Rally Championship, but in the 2006 season the FIA has limited the use of active differentials only to those drivers who have not competed in the World Rally Championship in the last five years.

Fully integrated active differentials are used on the Ferrari F430 and on the rear wheels in the Acura RL.

The second constraint of the differential is passive it is actuated by the friction kinematics chain through the ground. The difference in torque on the tires (caused by turns or bumpy ground) drives the second degree of freedom, (overcoming the torque of inner friction) to equalise the driving torque on the tires. The sensitivity of the differential depends on the inner friction through the second degree of freedom. All of the differentials (so called active and passive) use clutches and brakes for restricting the second degree of freedom, so all suffer from the same disadvantage decreased sensitivity to a dynamically changing environment. The sensitivity of the computer controlled differential is also limited by the time delay caused by sensors and the response time of the actuators.

Driveshafts

Driveshafts are carriers of torque: they are subject to torsion and shear stress, which represents the difference between the input force and the load. They thus need to be strong enough to bear the stress, without imposing too great an additional inertia by virtue of the weight of the shaft.

Driveshaft Automotive driveshafts

Driveshaft Vehicles

Most automobiles today use rigid driveshafts to deliver power from a transmission to the wheels. A pair of short driveshafts is commonly used to send power from a central differential, transmission, or transaxle to the wheels.

In front-engined, rear-drive vehicles, a longer driveshaft is also required to send power the length of the vehicle. Two forms dominate: The torque tube with a single universal joint and the Hotchkiss drive with two or more joints. This system became known as Système Panhard after the automobile company, Panhard et Levassor patented it.

Early automobiles often used chain drive or belt drive mechanisms rather than a driveshaft. Some used electrical generators and motors to transmit power to the wheels.

In British English, the term "driveshaft" is restricted to a transverse shaft which transmits power to the wheels, especially the front wheels. A driveshaft connecting the gearbox to a rear differential is called a propeller shaft (or more commonly a "prop-shaft") and a driveshaft connecting a rear differential to a rear wheel is usually called a halfshaft. The name derives from the fact that two such shafts are required to form one rear axle.

There are different types of driveshafts in Automotive Industry:

1 piece driveshaft

2 piece driveshaft

Driveshaft Slip in Tube driveshaft

The Slip in Tube Driveshaft is the new type which also helps in Crash Energy Management. It can be compressed in case of crash.

It is also known as a collapsible driveshaft.

Driveshaft Driveshaft for Research and Development (R&D)

The automotive industry also uses driveshafts at testing plants. At an engine test stand a drive shaft is used to transfer a certain speed / torque from the combustion engine to a dynamometer. A "shaft guard" is used at a shaft connection to protect against contact with the drive shaft and for detection of a shaft failure. At a transmission test stand a drive shaft connects the prime mover with the transmission.

Driveshaft Motorcycle driveshafts

Driveshafts have been used on motorcycles almost as long as there have been motorcycles. As an alternative to chain and belt drives, driveshafts offer relatively maintenance-free operation and long life. A disadvantage of shaft drive on a motorcycle is that gearing is needed to turn the power 90° from the shaft to the rear wheel, losing some power in the process. On the other hand, it is easier to protect the shaft linkages and drive gears from dust, sand and mud.

The best known motorcycle manufacturer to use shaft drive for a long time since 1923 is BMW. Among contemporary manufacturers, Moto Guzzi is also well-known for its shaft drive motorcycles. The British company, Triumph and all four Japanese brands, Honda, Suzuki, Kawasaki and Yamaha, have produced shaft drive motorcycles.

The first use of a driveshaft on an off-road motorcycle was in the Tote Gote Nova series. It used a straight shaft powering a worm gear which then turned a gear. The outer casing was aluminum, and was supported by two rubber bushings. The engine faced forward in the frame.

Motorcycle engines positioned such that the crankshaft is longitudinal and parallel to the frame are often used for shaft driven motorcycles. The requires only one 90° turn in power transmission, rather than two. Moto Guzzi, BMW, Triumph, and Honda use this engine layout.

Motorcycles with shaft drive are subject to shaft effect where the chassis climbs when power is applied. This is counteracted with systems such as BMW's Paralever, Moto Guzzi's CARC and Kawasaki's Tetralever.

Driveshaft Marine driveshafts

On a power-driven ship, the driveshaft, or propeller shaft, usually connects the transmission inside the vessel directly to the propeller, passing through a stuffing box or other seal at the point it exits the hull.

As the rotating propeller pushes the vessel forward, the marine driveshaft is also subject to compression, and when going reverse, to tension.

Cardan shafts are also often used in marine applications between the transmission and either a propeller gearbox or waterjet.

Driveshaft Driveshafts in Bicycles

A shaft-driven bicycle.The driveshaft has served as an alternative to a chain-drive in bicycles for the past century, although never becoming very popular. A shaft-driven bicycle is described as "acatane". When used on a bicycle, a driveshaft has several advantages and disadvantages:

Driveshaft Advantages

Drive system is less likely to become jammed or broken, a common problem with chain-driven bicycles The use of a gear system creates a smoother and more consistent pedalling motion

The rider cannot become dirtied from chain grease or injured by the chain from "Chain bite", which occurs when clothing or even a body part catches between the chain and a sprocket

Lower maintenance than a chain system when the driveshaft is enclosed in a tube, the common convention

More consistent performance. Dynamic Bicycles claims that a driveshaft bicycle consistently delivers 94% efficiency, whereas a chain-driven bike can deliver anywhere from 75-97% efficiency based on condition.

Greater clearance: with the absence of a derailleur or other low-hanging machinery, the bicycle has nearly twice the ground clearance

Driveshaft Disadvantages

A driveshaft system weighs more than a chain system, usually 1-2 pounds heavier

At optimum upkeep, a chain delivers greater efficiency

Many of the advantages claimed by driveshaft's proponents can be achieved on a chain-driven bicycle, such as covering the chain and gears with a metal or plastic cover

Use of lightweight derailleur gears with a high number of ratios is impossible, although hub gears can be used

Wheel removal can be complicated in some designs (as it is for some chain-driven bicycles with hub gears).

Engine control units

An engine control unit (ECU) is an electronic control unit which controls various aspects of an internal combustion engine's operation. The simplest ECUs control only the quantity of fuel injected into each cylinder each engine cycle. More advanced ECUs found on most modern cars also control the ignition timing, variable valve timing (VVT), the level of boost maintained by the turbocharger (in turbocharged cars), and control other peripherals.

E11: An aftermarket ECUECUs determine the quantity of fuel, ignition timing and other parameters by monitoring the engine through sensors. These can include, MAP sensor, throttle position sensor, air temperature sensor, oxygen sensor and many others. Often this is done using a control loop (such as a PID controller).

Before ECUs most engine parameters were fixed. The quantity of fuel per cylinder per engine cycle was determined by a carburetor or injector pump.

Engine control unit ECU operation

Engine control unit Control of fuel injection

For an engine with fuel injection, an ECU will determine the quantity of fuel to inject based on a number of parameters. If the throttle pedal is pressed further down, this will open the throttle body and allow more air to be pulled into the engine. The ECU will inject more fuel according to how much air is passing into the engine. If the engine has not warmed up yet, more fuel will be injected (causing the engine to run slightly 'rich' until the engine warms up).

Engine control unit Control of ignition timing

A spark ignition engine requires a spark to initiate combustion in the combustion chamber. An ECU can adjust the exact timing of the spark (called ignition timing) to provide better power and economy. If the ECU detects knock, a condition which is potentially destructive to engines, and "judges" it to be the result of the ignition timing being too early in the compression stroke, it will delay (retard) the timing of the spark to prevent this.

A second, more common source, cause, of knock/ping is operating the engine in too low of an RPM range for the "work" requirement of the moment. In this case the knock/ping results from the piston not being able to move downward as fast as the flame front is expanding.

But this latter mostly applies only to manual transmission equipped vehicles. The ECU controlling an automatic transmission would simply downshift the transmission were this the cause of knock/ping.

Engine control unit Control of variable valve timing

Some engines have Variable Valve Timing. In such an engine, the ECU controls the time in the engine cycle at which the valves open. The valves are usually opened later at higher speed than at lower speed. This can optimise the flow of air into the cylinder, increasing power and economy.

Engine control unit Control of starting

A relatively recent application of engine control is the use of precisely timed injection and ignition to start an engine without the use of a starter motor. Such a static-start engine would provide the efficiency and pollution-reductiton improvements of a mild hybrid-electric drive, but without the expense and complexity of an oversized starter motor.

Engine control unit Programmable ECUs

A special category of ECUs are those which are programmable. These units do not have a fixed behavior, but can be reprogrammed by the user.

Programmable ECUs are required where significant aftermarket modifications have been made to a vehicle's engine. Examples include adding or changing of a turbocharger, adding or changing of an intercooler, changing of the exhaust system, and conversion to run on alternative fuel. As a consequence of these changes, the old ECU may not provide appropriate control for the new configuration. In these situations, a programmable ECU can be wired in. These can be programmed/mapped with a laptop connected using a serial or USB cable, while the engine is running.

The programmable ECU may control the amount of fuel to be injected into each cylinder. This varies depending on the engine's RPM and the position of the gas pedal (or the manifold air pressure). The engine tuner can adjust this by bringing up a spreadsheet-like page on the laptop where each cell represents an intersection between a specific RPM value and a gas pedal position (or the throttle position, as it is called). In this cell a number corresponding to the amount of fuel to be injected is entered.

By modifying these values while monitoring the exhausts using a wide band lambda probe to see if the engine runs rich or lean, the tuner can find the optimal amount of fuel to inject to the engine at every different combination of RPM and throttle position. This process is often carried out at a dynamometer, giving the tuner a controlled environment to work in.

Other parameters that are often mappable are:

Ignition: Defines when the spark plug should fire for a cylinder.

Rev limit: Defines the maximum RPM that the engine is allowed to rev to. After this fuel and/or ignition is cut.

Water temperature correction: Allows for additional fuel to be added when the engine is cold (choke).

Transient fueling: Tells the ECU to add a specific amount of fuel when throttle is applied.

Low fuel pressure modifier: Tells the ECU to increase the injector fire time to compensate for a loss of fuel pressure.

Closed loop lambda: Lets the ECU monitor a permanently installed lambda probe and modify the fueling to achieve stoichiometric (ideal) combustion.

Some of the more advanced race ECUs include functionality such as launch control, limiting the power of the engine in first gear to avoid burnouts. Other examples of advanced functions are:

Waste gate control: Sets up the behavior of a turbo waste gate, controlling boost. Banked injection: Sets up the behavior of double injectors per cylinder, used to get a finer fuel injection control and atomization over a wide RPM range.

Variable cam timing: Tells the ECU how to control variable intake and exhaust cams. Gear control: Tells the ECU to cut ignition during (sequential gearbox) upshifts or blip the throttle during downshifts.

A race ECU is often equipped with a data logger recording all sensors for later analysis using special software in a PC. This can be useful to track down engine stalls, misfires or other undesired behaviors during a race by downloading the log data and looking for anomalies after the event. The data logger usually has a capacity between 0.5 and 16 Mbytes.

In order to communicate with the driver, a race ECU can often be connected to a "data stack", which is a simple dash board presenting the driver with the current RPM, speed and other basic engine data. These race stacks, which are almost always digital, talk to the ECU using one of several proprietary protocols running over RS232, CANbus.

Engine control unit ECU flashing

Example reflash tuning softwareMany recent (around 1996 or newer) cars use OBD-II ECUs that are sometimes capable of having their programming changed through the OBD port.

Automotive enthusiasts with modern cars take advantage of this technology when tuning their engines. Rather than use an entire new engine management system, one can use the appropriate software to adjust the factory equipped computer. By doing so, it is possible to retain all stock functions and wiring while using a custom tuned program. This should not be confused with "chip tuning", where the owner has ECU ROM physically replaced with a different one -- no hardware modification is (usually) involved with flashing ECUs, although special equipment is required.

Factory engine management systems often have similar controls as aftermarket units intended for racing, such as 3-dimensional timing and fuel control maps. They generally do not have the ability to control extra ancillary devices, such as variable valve timing if the factory vehicle was a fixed geometry camshaft or boost control if the factory car was not turbocharged.

Engine control unit History

Engine control unit Hybrid digital designs

A hybrid digital design was popular in the mid-'80s. This used analogue techniques to measure and process input parameters from the engine, then used a look-up table stored in a digital ROM chip to yield precomputed output values. Later systems compute these outputs dynamically. The ROM type of system is amenable to tuning if one knows the system well. The disadvantage of such systems is that the precomputed values are only optimal for an idealised, new engine. As the engine wears, the system is less able to compensate than a CPU based system.

Sophisticated engine management systems receive inputs from other sources, and control other parts of the engine; for instance, some variable valve timing systems are electronically controlled, and turbocharger wastegates can also be managed. They also may communicate with transmission control units or directly interface electronically-controlled automatic transmissions, traction control systems, and the like. The Controller Area Network or CAN bus automotive network is often used to achieve communication between these devices.

Engine control unit Modern ECUs

Modern ECUs use a microprocessor which can process the inputs from the engine sensors in real time. An electronic control unit contains the hardware and software (firmware). The hardware consists of electronic components on a printed circuit board (PCB). The main component on this circuit board is a microcontroller chip (CPU). The software is stored in the microcontroller or other chips on the PCB, typically in EPROMs or flash memory so the CPU can be re-programmed by uploading updated code. This is also referred to as an (electronic) Engine Management System (EMS).

Engine control unit Other applications

Such systems are used for many internal combustion engines in other applications. In aeronautical applications, the systems are known as "FADECs" (Full Authority Digital Engine Controls). This kind of electronic control is less common in piston-engined aeroplanes than in automobiles, because of the large costs of certifying parts for aviation use, relatively small demand, and the consequent stagnation of technological innovation in this market. Also, a carburated engine with magneto ignition and a gravity feed fuel system does not require any electrical power to run, which is a safety bonus.

Engine control unit ECU failures

As usually occurs with a technology shift, computer-controlled engine management has replaced old failure modes with new ones. With advanced age, a failing ECU can cause seemingly random starting and driveability faults. For example, a vehicle may refuse to start when cranked with the starter motor, but may respond easily to a push start. Failing electrolytic capacitors in the ECU no longer smooth the power supply to the microprocessor, and the varying load on the starter motor causes sufficient line voltage fluctuation that the computer reboots repeatedly while attempting to start the engine. An industry has evolved to refurbish ECUs with this and other types of failures related to age and use.

Exhaust systems

Exhaust pipe of a carAn exhaust system is usually tubing used to guide waste exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system design, the exhaust gas may flow through one or more of:

Exhaust system Cylinder head and exhaust manifold

A turbocharger to increase engine power.

A catalytic converter to reduce air pollution.

A muffler (North America) / silencer (Europe), to reduce noise.

Exhaust system Design criteria

An exhaust pipe must be carefully designed to carry toxic and/or noxious gases away from the users of the machine. Indoor generators and furnaces can quickly fill an enclosed space with carbon monoxide or other poisonous exhaust gases if they are not properly vented to the outdoors. Also, the gases from most types of machine are very hot; the pipe must be heat-resistant, and it must not pass through or near anything which can burn or can be damaged by heat. A chimney serves as an exhaust pipe in a stationary structure.

Exhaust system Motorcycles

In most motorcycles all or most of the exhaust system is visible and may be chrome plated as a display feature.

On a two-cylinder motorcycle, "siamese exhaust pipes" are where both cylinders blow into the same exhaust pipe. This usage is derived from "Siamese twin".

Exhaust system Trucks

In many trucks / lorries all or most of the exhaust system is visible. Often in such trucks the silencer is surrounded by a perforated metal sheath to avoid people getting burnt touching the hot silencer. This sheath may be chrome plated as a display feature. Part of the pipe between the engine and the silencer is often flexible metal industrial ducting, as in the image in the "Terminology".

Exhaust system Two-stroke engines

In a two-stroke engine, such as that used on dirt bikes, a bulge in the exhaust pipe known as an expansion chamber uses the pressure of the exhaust to create a pump that squeezes more air and fuel into the cylinder during the intake stroke. This provides greater power and fuel efficiency.

Exhaust system Ship's or large boat's onboard engine

With a ship's or large boat's onboard below-decks diesel engine:-

Lagging the exhaust pipe stops it from overheating the engine room where people must work to service the engine. Feeding water into the exhaust pipe cools the exhaust gas and thus lessens the back-pressure at the engine's cylinders' exhaust ports and thus helps the cylinders to empty quicker.

Exhaust system Outboard motors

In outboard motors the exhaust system is usually a vertical passage through the engine structure and to reduce out-of-water noise blows out underwater, sometimes through the middle of the propeller.

Exhaust system Terminology

Exhaust system Manifold or header

In most production engines, the manifold is an assembly designed to collect the exhaust gas from two or more cylinders into one pipe. Manifolds are often made of cast iron in stock production cars, and may have material-saving design features such as to use the least metal, to occupy the least space necessary, or have the lowest production cost. These design restrictions often result in a design that is cost effective but that does not do the most efficient job of venting the gases from the engine. Inefficiencies generally occur due to the nature of the combustion engine and its cylinders. Since cylinders fire at different times, exhaust leaves them at different times, and pressure waves from gas emerging from one cylinder might not be completely vacated through the exhaust system when another comes. This creates a back pressure and restriction in the engine's exhaust system that can restrict the engine's true performance possibilities.

A header (sometimes called extractor in Australia) is another name for a manifold, specifically a manifold designed for performance. During design, engineers create a manifold without regard to weight or cost but instead for optimal flow of the exhaust gases. This design results in a header that is more efficient at scavenging the exhaust from the cylinders. Headers are generally circular steel tubing with bends and folds calculated to make the paths from each cylinder's exhaust port to the common outlet all equal length, and joined at narrow angles to encourage pressure waves to flow through the outlet, and not back towards other cylinders. In a set of tuned headers the pipe lengths are carefully calculated to enhance exhaust flow in a particular engine revolutions per minute range.

Headers are generally made by aftermarket automotive companies, but sometimes can be bought from the high-performance parts department at car dealerships. Generally, most car performance enthusiasts buy aftermarket headers made by companies solely focused on producing reliable, cost-effective well-designed headers specifically for their car. Headers can also be custom designed by a custom shop. Due to the advanced materials that some aftermarket headers are made of, this can be expensive. Luckily, an exhaust system can be custom built for any car, and generally is not specific to the car's motor or design except for needing to properly connect solidly to the engine. This is usually accomplished by correct sizing in the design stage, and selecting a proper gasket type and size for the engine.

Exhaust system Header-back

Header-back (or header back) is to the part of the exhaust system from the outlet of the header to the final vent to open air everything from the header back. Header-back systems are generally produced as aftermarket performance systems for cars without turbochargers.

Exhaust system Turbo-back

Turbo-back (or turbo back) is to the part of the exhaust system from the outlet of a turbocharger to the final vent to open air. Turbo-back systems are generally produced as aftermarket performance systems for cars with turbochargers. Some turbo-back (and header-back) systems replace stock catalytic converters with others having less flow restriction.

Exhaust system With or without catalytic converter

Some systems (including in former time all systems) (sometimes nowadays called catless or no kitty) eliminate the catalytic converter, which may or may not be legal depending on place and whether the car will be driven on public roads.

Exhaust system Cat-back

Cat-back (also cat back and catback, and more recently axle back) refers to the portion of the exhaust system from the outlet of the catalytic converter to the final vent to open air. This generally includes the pipe from the converter to the muffler, the muffler, and the final length of pipe to open air.

Cat-back exhaust systems are a very popular aftermarket performance enhancement. They generally use larger diameter pipe than the stock system. Good systems will have mandrel-bent turns that allow the exhaust gas to exit with as little back pressure as possible. The mufflers included in these kits are often glasspacks, again to reduce back pressure. If the system is engineered more for show than functionality, it may be tuned to enhance the lower sounds that are lacking from high-RPM low-displacement engines.

Exhaust system Tailpipe and tip

Dual exhaust pipes attached to a car's mufflerWith trucks, sometimes the silencer is crossways under the front of the cab and its tailpipe blows sideways to the offside (right in UK, left in USA).

The end of the final length of exhaust pipe where it vents to open air, generally the only visible part, often ends with just a straight or angled cut, but may include a fancy tip. The tip is usually chromed, and is often of larger pipe than the rest of the exhaust system. This produces a final reduction in pressure, as well as prevents rusting of the tips, and can be used to enhance the appearance of the car. These are the least expensive parts of the system.

When a bus, truck or tractor or excavator has a vertical exhaust pipe (called stacks or pipes behind the cab), sometimes the end is curved, or has a hinged cover flap which the gas flow blows out of the way, to try to avoid foreign objects (including droppings from a bird perching on the exhaust pipe when the vehicle is not being used) getting inside the exhaust pipe.

In some trucks, when the silencer is front-to-back under the chassis, the end of the tailpipe turns 90° and blows downwards. That avoids anyone working by the truck when stationary from getting a directed blast of the exhaust gas, but often raises dust when the truck is driving on a dry dusty unmade surface such as on a building site.

Exhaust system Lake pipes

Also known as side pipes, lake pipes are exhaust pipes, normally brightly chromed, which exit the front wheelarch of a car and then pass down the sill/rocker panel, finally opening sideways in front of the rear wheel. They are sometimes seen on custom cars and hot rods.

Fuel injection

Fuel injection is a means of metering fuel into an internal combustion engine. In modern automotive applications, fuel metering is one of several functions performed by an "engine management system".

A fuel injection system is designed and calibrated specifically for the type(s) of fuel it will handle: gasoline (petrol), Autogas (LPG, also known as propane), ethanol, methanol, methane (natural gas), hydrogen or diesel. The majority of fuel injection systems are for gasoline or diesel applications. With the advent of electronic fuel injection, the diesel and gasoline hardware has become quite similar. EFI's programmable firmware has permitted common hardware to be used with multiple different fuels. For gasoline engines, carburetors were the predominant method to meter fuel before the widespread use of fuel injection. However, a wide variety of injection systems have existed since the earliest usage of the internal combustion engine.

The primary functional difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on the vacuum created by intake air rushing through it to add the fuel to the airstream.

The fuel injector is only a nozzle and a valve: the power to inject the fuel comes from farther back in the fuel supply, from a pump or a pressure container.

Fuel injection Objectives

The functional objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system will be optimized. There are several competing objectives such as:

power output

fuel efficiency

emissions performance

ability to accommodate alternative fuels

durability

reliability

driveability and smooth operation

initial cost

maintenance cost

diagnostic capability

range of environmental operation

Certain combinations of these goals are conflicting, and it is impractical for a single engine control system to fully optimize all criteria simultaneously. In practice, automotive engineers strive to best satisfy a customer's needs competitively. The modern digital electronic fuel injection system is far more capable at optimizing these competing objectives than a carburetor.

Fuel injection Benefits

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Fuel injection Engine operation

Operational benefits to the driver of a fuel-injected car include smoother and more dependable engine response during quick throttle transitions, easier and more dependable engine starting, better operation at extremely high or low ambient temperatures, reduced maintenance intervals, and increased fuel efficiency.

An engine's air/fuel ratio must be accurately controlled under all operating conditions to achieve the desired engine performance, emissions, driveability, and fuel economy. Modern electronic fuel-injection systems meter fuel very accurately and precisely, and use closed loop fuel-injection quantity-control based on feedback from an oxygen sensor (or "O2 sensor"). This enables fuel-injected engines to produce less air pollutants than comparable carbureted engines. Properly-designed fuel injection systems can react rapidly to changing inputs such as sudden throttle movements, and will control the amount of fuel injected to match the engine's needs across a wide range of operating conditions such as engine load, ambient air temperature, engine temperature, fuel octane level, and altitude (i.e., barometric pressure).

Fuel injection Emissions, efficiency, and power

A multipoint fuel injection system generally delivers a more accurate and equal mass of fuel to each cylinder than can a carburetor, thus improving the cylinder-to-cylinder distribution. Exhaust emissions are cleaner because the more precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine, and because exhaust cleanup devices such as the catalytic converter can be optimized to operate more efficiently since the exhaust is of consistent and predictable composition.

Fuel injection generally increases engine fuel efficiency. With the improved cylinder-to-cylinder fuel distribution, less fuel is needed for the same power output. When cylinder-to-cylinder distribution is less than ideal, as is always the case to some degree with a carburetor or throttle body fuel injection, some cylinders receive excess fuel as a side effect of ensuring that all cylinders receive sufficient fuel. Power output is asymmetrical with respect to air/fuel ratio; burning extra fuel in the rich cylinders does not reduce power nearly as quickly as burning too little fuel in the lean cylinders. However, rich-running cylinders are undesirable from the standpoint of exhaust emissions, fuel efficiency, engine wear, and engine oil contamination. Deviations from perfect air/fuel distribution, however subtle, affect the emissions, by not letting the combustion events be at the chemically ideal (stoichiometric) air/fuel ratio. Grosser distribution problems eventually begin to reduce efficiency, and the grossest distribution issues finally affect power. Increasingly poorer air/fuel distribution affects emissions, efficiency, and power, in that order. By optimizing the homogeneity of cylinder-to-cylinder mixture distribution, all the cylinders approach their maximum power potential and the engine's overall power output improves.

A fuel-injected engine often produces more power than an equivalent carbureted engine. Fuel injection alone does not necessarily increase an engine's maximum potential output, for increased airflow is needed to burn more fuel to generate more heat to generate more output. The combustion process converts the fuel's chemical energy into heat energy, whether the fuel is supplied by fuel injectors or a carburetor. However, airflow is often improved with fuel injection, the components of which allow more design freedom to improve the air's path into the engine. In contrast, a carburetor's mounting options are limited because it is larger, it must be carefully oriented with respect to gravity, and it must be equidistant from each of the engine's cylinders to the maximum practicable degree. These design constraints generally compromise airflow into the engine. Furthermore, a carburetor relies on a restrictive venturi to create a local air pressure difference, which forces the fuel into the air stream. The flow loss caused by the venturi, however, is small compared to other flow losses in the induction system. In a well-designed carburetor induction system, the venturi is not a significant airflow restriction. Aside from airflow considerations, fuel injection offers a more homogeneous air/fuel mixture due to better atomization of the fuel entering the cylinders.

Fuel injection History and development

Frederick William Lanchester joined the Forward Gas Engine Company Birmingham, England in 1889. He carried out what were possibly the earliest experiments with fuel injection. In 1896 E.J. Pennington had detailed a crude form of fuel injection in the patent for his motorcycle (U.S. patent 574262).

Fuel injection has been used commercially in diesel engines since the mid-1920s. Because of its greater immunity to wildly changing g-forces on the engine, the concept was adapted for use in petrol-powered aircraft during World War II, and direct injection was employed in some notable designs like the Daimler-Benz DB 603, the BMW 801, the Shvetsov ASh-82FN (M-82FN) and later versions of the Wright R-3350 used in the B-29 Superfortress.

One of the first commercial gasoline injection systems was a mechanical system developed by Bosch and introduced in 1955 on the Mercedes-Benz 300SL. This system used a normal fuel pump, to provide fuel to a mechanically driven injection pump, which had separate plungers per injector to deliver a very high injection pressure. A variant of this system, also by Bosch, was later used by Porsche from 1969 until 1973 on the 911 production range. Porsche continued using it on its racing cars into the late seventies and early eighties, and cars like the Porsche 906, 908, 910, 917 (in its regular normally aspirated or 5.5 Liter/1500 HP Turbocharged form), and 935 all used Bosch or Kugelfischer built variants of injection. It was also used by the BMW 2000 Ti. Due to the high pressure, the fuel atomisation was exceptional; resulting in good power, throttle response and the pump design offered good reliability. It did have drawbacks as the fuel economy and emission results were terribly inefficient compared to more modern injection setups such as electronic injection, or even the Jetronic systems that went in production in the early seventies.

In 1957, Chevrolet introduced a mechanical fuel injection option, made by General Motors' Rochester Products division, for its 283 V8 engine. This system directed the inducted engine air across a "spoon shaped" plunger that moved in proportion to the air volume. The plunger connected to the fuel metering system which mechanically dispensed fuel to the cylinders via distribution tubes. This system was not a "pulse" or intermittent injection, but rather a constant flow system, metering fuel to all cylinders simultaneously from a central "spider" of injection lines. The fuel meter adjusted the amount of flow according to engine speed and load, and included a fuel reservoir, which was similar to a carburetor's float chamber. With its own high-pressure fuel pump driven by a cable from the distributor to the fuel meter, the system supplied the necessary pressure for injection. However, this was "port" injection, in which the injectors are located in the intake manifold, very near the intake valve. (Direct fuel injection is a fairly recent innovation for automobile engines.) The highest performance version of the fuel injected engine was rated at 283 hp (211 kW) from 283 in³ (4.6 L), though it really produced about 290 hp. This made it among the early production engines in history to exceed 1 hp/in³ (45.5 kW/L), after Chrysler's Hemi engine and a number of others.

During the 1960s, other mechanical injection systems such as Hilborn were occasionally used on modified American V8 engines in various racing applications such as drag racing, oval racing, and road racing. These racing-derived systems were not suitable for everyday street use, having no provisions for low speed metering or even starting (fuel had to be squirted into the injector tubes while cranking the engine in order to start it). However they were a favorite in the aforementioned competition trials in which, essentially wide-open throttle operation was prevalent.

The first commercial electronic fuel injection (EFI) system was Electrojector, developed by the Bendix Corporation and was to be offered by American Motors (AMC) in 1957. A special muscle car model, the Rambler Rebel, showcased AMC's new 327 cu in (5.4 L) engine. The Electrojector was an option and rated at 288 hp (215 kW). The Rebel Owners Manual described the design and operation of the new system. Initial press information about the Bendix system in December 1956 was followed in March 1957 by a price bulletin that pegged the option at US$395, but due to supplier difficulties, fuel-injected Rebels would only be available after June 15. This was to have been the first production EFI engine, but Electrojector's teething problems meant only pre-production cars were so equipped and none were made available to the public. The EFI system in the Rambler was a far more-advanced setup than the mechanical types then appearing on the market and the engines ran fine in warm weather, but suffered hard starting in cooler temperatures.

Chrysler offered Electrojector on specific high performance 1958 models...the 300D, the D500, and the DeSoto Adventurer, arguably the first series-production cars equipped with a throttle body EFI system, but the early electronic components were not equal to the rigors of underhood service, and were too slow to keep up with the demands of "on the fly" engine control. Most vehicles originally so equipped were field-retrofitted with 4-barrel carburetors. The Electrojector patents were subsequently sold to Bosch.

Bosch developed an electronic fuel injection system, called D-Jetronic (D for Druck, the German word for pressure), which was first used on the VW 1600TL in 1967. This was a speed/density system, using engine speed and intake manifold air density to calculate "air mass" flow rate and thus fuel requirements. The system used all analog, discrete electronics, and an electro-mechanical pressure sensor. The sensor was susceptible to vibration and dirt. This system was adopted by VW, Mercedes-Benz, Porsche, Citroën, Saab, and Volvo. Lucas licensed the system for production with Jaguar.

Bosch superseded the D-Jetronic system with the K-Jetronic and L-Jetronic systems for 1974, though some cars (such as the Volvo 164) continued using D-Jetronic for the following several years, and General Motors installed a very close copy of D-Jetronic on Cadillacs starting in 1977. L-Jetronic first appeared on the 1974 Porsche 914, and uses a mechanical airflow meter (L for Luft, German for air) that produces a signal that is proportional to "air volume". This approach required additional sensors to measure the barometer and temperature, to ultimately calculate "air mass". L-Jetronic was widely adopted on European cars of that period, and a few Japanese models a short time later.

In 1982, Bosch introduced a sensor that directly measures the air mass flow into the engine, on their L-Jetronic system. Bosch called this LH-Jetronic (L for Luftmasse, or air, and H for Hitzdraht, or hot-wire). The mass air sensor utilizes a heated platinum wire placed in the incoming air flow. The rate of the wire's cooling is proportional to the air mass flowing across the wire. Since the hot wire sensor directly measures air mass, the need for additional temperature and pressure sensors is eliminated. The LH-Jetronic system was also the first fully digital EFI system, which is now the standard approach. The advent of the digital microprocessor permitted the integration of all powertrain sub-systems into a single control module.

Fuel injection Supersession of carburetors

Throughout the 1950s and 1960s, various federal, state and local governments conducted studies into the numerous sources of air pollution. These studies ultimately attributed a significant portion of air pollution to the automobile, and concluded air pollution is not bounded by local political boundaries. At that time, such minimal emission control regulations as existed were promulgated at the municipal or, occasionally, the state level. The ineffective local regulations were gradually supplanted by more comprehensive state and federal regulations. By 1967 the state of California (Governor Reagan), created the California Air Resources Board, and in 1970, the U.S. Environmental Protection Agency was formed. Both agencies now create and enforce emission regulations for automobiles, as well as for many other sources. Similar agencies and regulations were contemporaneously developed and implemented in Europe, Australia, and Japan.

The ultimate combustion goal is to match each molecule of fuel with a corresponding number of molecules of oxygen so that neither has any molecules remaining after combustion in the engine and catalytic converter. Such a balanced condition is known as stoichiometry. Extensive carburetor modifications and complexities were needed to approach stoichiometric engine operation in order to comply with increasingly-strict US exhaust emission regulations of the 1970s and 1980s. This increase in complexity gradually eroded and then reversed the simplicity, cost, and packaging advantages carburetors had traditionally offered.

Fuel injection appeared first as novelty equipment on American-made cars in the late 1950s, such as the 1958 Chrysler products equipped with Bendix' ElectroJector, and 1957-1965 Rochester fuel injected Chevrolet Corvettes. About a decade later, more practical fuel injection systems were introduced in European-made cars. As emission regulations progressively tightened worldwide, generally led by the US state of California's especially stringent rules, automakers had to improve the precision and accuracy with which fuel was metered to the engine. Catalytic converters also became practically universal equipment.

There are three primary types of toxic emissions from an internal combustion engine: Carbon Monoxide (CO), unburnt hydrocarbons (HC), and oxides of nitrogen (NOx). CO and HC result from incomplete combustion of fuel due to insufficient oxygen in the combustion chamber. NOx, in contrast, results from excessive oxygen in the combustion chamber. The opposite causes of these pollutants makes it difficult to control all three simultaneously. Once the permissible emission levels dropped below a certain point, catalytic treatment of these three main pollutants became necessary. This required a particularly large increase in fuel metering accuracy and precision, for simultaneous catalysis of all three pollutants requires that the fuel/air ratio be held within a very narrow range of stoichiometry. The open loop fuel injection systems had already improved cylinder-to-cylinder fuel distribution and engine operation over a wide temperature range, but did not offer sufficient fuel/air ratio control to enable effective exhaust catalysis. Closed loop fuel injection systems improved the air/fuel ratio control with an exhaust gas oxygen sensor. The O2 sensor is mounted in the exhaust system upstream of the catalytic converter, and enables the engine management computer to determine and adjust the air/fuel ratio precisely and quickly.

Fuel injection was phased in through the latter '70s and '80s at an accelerating rate, with the US and German markets leading and the UK and Commonwealth markets lagging somewhat, and since the early 1990s, almost all gasoline passenger cars sold in first world markets like the United States, Europe, Japan, and Australia have come equipped with electronic fuel injection (EFI). Many motorcycles still utilize carbureted engines, though all current high-performance designs have switched to EFI.

Fuel injection systems have evolved significantly since the mid 1980s. Current systems provide an accurate, reliable and cost-effective method of metering fuel and providing maximum engine efficiency with clean exhaust emissions, which is why EFI systems have replaced carburetors in the marketplace. EFI is becoming more reliable and less expensive through widespread usage. At the same time, carburetors are becoming less available, and more expensive. Even marine applications are adopting EFI as reliability improves. Virtually all internal combustion engines, including motorcycles, off-road vehicles, and outdoor power equipment, may eventually use some form of fuel injection.

It should be noted that carburetion remains a less costly alternative where strict emission regulations and advanced vehicle diagnostic and repair infrastructure do not exist, as in developing countries. Fuel injection is gradually replacing carburetors in these nations too as they adopt emission regulations conceptually similar to those in force in Europe, Japan, Australia and North America.

Fuel injection Basic function

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The process of determining the amount of fuel, and its delivery into the engine, are known as fuel metering. Early injection systems used mechanical methods to meter fuel (non electronic, or mechanical fuel injection). Modern systems are nearly all electronic, and use an electronic solenoid (the injector) to inject the fuel. An electronic engine control unit calculates the mass of fuel to inject.

Modern fuel injection schemes follow much the same setup. There is a mass airflow sensor or manifold absolute pressure sensor at the intake, typically mounted either in the air tube feeding from the air filter box to the throttle body, or mounted directly to the throttle body itself. The mass airflow sensor does exactly what its name implies; it senses the mass of the air that flows past it, giving the computer an accurate idea of how much air is entering the engine. The next component in line is the Throttle Body. The throttle body has a throttle position sensor mounted onto it, typically on the butterfly valve of the throttle body. The throttle position sensor (TPS) reports to the computer the position of the throttle butterfly valve, which the ECM uses to calculate the load upon the engine. The fuel system consists of a fuel pump (typically mounted in-tank), a fuel pressure regulator, fuel lines (composed of either high strength plastic, metal, or reinforced rubber), a fuel rail that the injectors connect to, and the fuel injector(s). There is a coolant temperature sensor that reports the engine temperature to the ECM, which the engine uses to calculate the proper fuel ratio required. In sequential fuel injection systems there is a camshaft position sensor, which the ECM uses to determine which fuel injector to fire. The last component is the oxygen sensor. After the vehicle has warmed up, it uses the signal from the oxygen sensor to perform fine tuning of the fuel trim.

The fuel injector acts as the fuel-dispensing nozzle. It injects liquid fuel directly into the engine's air stream. In almost all cases this requires an external pump. The pump and injector are only two of several components in a complete fuel injection system.

In contrast to an EFI system, a carburetor directs the induction air through a venturi, which generates a minute difference in air pressure. The minute air pressure differences both emulsify (premix fuel with air) the fuel, and then acts as the force to push the mixture from the carburetor nozzle into the induction air stream. As more air enters the engine, a greater pressure difference is generated, and more fuel is metered into the engine. A carburetor is a self-contained fuel metering system, and is cost competitive when compared to a complete EFI system.

An EFI system requires several peripheral components in addition to the injector(s), in order to duplicate all the functions of a carburetor. A point worth noting during times of fuel metering repair is that early EFI systems are prone to diagnostic ambiguity. A single carburetor replacement can accomplish what might require numerous repair attempts to identify which one of the several EFI system components is malfunctioning. Newer EFI systems since the advent of OBD II diagnostic systems, can be very easy to diagnose due to the increased ability to monitor the realtime data streams from the individual sensors. This gives the diagnosing technician realtime feedback as to the cause of the drivability concern, and can dramatically shorten the number of diagnostic steps required to ascertain the cause of failure, something which isn't as simple to do with a carburetor. On the other hand, EFI systems require little regular maintenance; a carburetor typically requires seasonal and/or altitude adjustments.

Fuel injection Detailed function

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Note: These examples specifically apply to a modern EFI gasoline engine. Parallels to fuels other than gasoline can be made, but only conceptually.

Fuel injection Typical EFI components

Fuel Pressure Regulator

ECM - Engine Control Module; includes a digital computer and circuitry to communicate with sensors and control outputs.

Wiring Harness

Various Sensors (Some of the sensors required are listed here.)

Crank/Cam Position: Hall effect sensor

Airflow: MAF sensor, sometimes this is inferred with a MAP sensor

Exhaust Gas Oxygen: Oxygen sensor, EGO sensor, UEGO sensor

Fuel injection Functional description

Central to an EFI system is a computer called the Engine Control Unit (ECU), which monitors engine operating parameters via various sensors. The ECU interprets these parameters in order to calculate the appropriate amount of fuel to be injected, among other tasks, and controls engine operation by manipulating fuel and/or air flow as well as other variables. The optimum amount of injected fuel depends on conditions such as engine and ambient temperatures, engine speed and workload, and exhaust gas composition.

The electronic fuel injector is normally closed, and opens to inject pressurised fuel as long as electricity is applied to the injector's solenoid coil. The duration of this operation, called pulse width, is proportional to the amount of fuel desired. The electric pulse may be applied in closely-controlled sequence with the valve events on each individual cylinder (in a sequential fuel injection system), or in groups of less than the total number of injectors (in a batch fire system).

Since the nature of fuel injection dispenses fuel in discrete amounts, and since the nature of the 4-stroke-cycle engine has discrete induction (air-intake) events, the ECU calculates fuel in discrete amounts. In a sequential system, the injected fuel mass is tailored for each individual induction event. Every induction event, of every cylinder, of the entire engine, is a separate fuel mass calculation, and each injector receives a unique pulse width based on that cylinder's fuel requirements.

It is necessary to know the mass of air the engine "breathes" during each induction event. This is proportional to the intake manifold's air pressure/temperature, which is proportional to throttle position. The amount of air inducted in each intake event is known as "air-charge", and this can be determined using several methods. (See MAF sensor, and MAP sensor.)

The three elemental ingredients for combustion are fuel, air and ignition. However, complete combustion can only occur if the air and fuel is present in the exact stoichiometric ratio, which allows all the carbon and hydrogen from the fuel to combine with all the oxygen in the air, with no undesirable polluting leftovers. Oxygen sensors monitor the amount of oxygen in the exhaust, and the ECU uses this information to adjust the air-to-fuel ratio in real-time.

To achieve stoichiometry, the air mass flow into the engine is measured and multiplied by the stoichiometric air/fuel ratio 14.64:1 (by weight) for gasoline. The required fuel mass that must be injected into the engine is then translated to the required pulse width for the fuel injector. The stoichiometric ratio changes as a function of the fuel; diesel, gasoline, ethanol, methanol, propane, methane (natural gas), or hydrogen.

Deviations from stoichiometry are required during non-standard operating conditions such as heavy load, or cold operation, in which case, the mixture ratio can range from 10:1 to 18:1 (for gasoline).

Pulse width is inversely related to pressure difference across the injector inlet and outlet. For example, if the fuel line pressure increases (injector inlet), or the manifold pressure decreases (injector outlet), a smaller pulse width will admit the same fuel. Fuel injectors are available in various sizes and spray characteristics as well. Compensation for these and many other factors are programmed into the ECU's software.

Fuel pumps

"Fuel pump" should not be confused with gas pump, a device that dispenses gasoline into an automobile.

A fuel pump is a frequently (but not always) essential component on a car or other internal combustion engined device. Many engines (older motorcycle engines in particular) do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank through a line or hose to the engine. But in non-gravity feed designs, fuel has to be pumped from the fuel tank to the engine and delivered under low pressure to the carburetor or under high pressure to the fuel injection system. Often, carbureted engines use low pressure mechanical pumps that are mounted outside the fuel tank, whereas fuel injected engines often use electric fuel pumps that are mounted inside the fuel tank (and some fuel injected engines have two fuel pumps: one low pressure/high volume supply pump in the tank and one high pressure/low volume pump on or near the engine).

Fuel pump Mechanical pump

Mechanical fuel pump, fitted to cylinder headPrior to the widespread adoption of electronic fuel injection, most carburated automobile engines used mechanical fuel pumps to transfer fuel from the fuel tank into the fuel bowls of the carburetor. Most mechanical fuel pumps are diaphragm pumps, which are a type of positive displacement pump. Diaphragm pumps contain a pump chamber whose volume is increased or decreased by the flexing of a flexible diaphragm, similar to the action of a piston pump. A check valve is located at both the inlet and outlet ports of the pump chamber to force the fuel to flow in one direction only. Specific designs vary, but in the most common configuration, these pumps are typically bolted onto the engine block or head, and the engine's camshaft has an extra eccentric lobe that operates a lever on the pump, either directly or via a pushrod, by pulling the diaphragm to bottom dead center. In doing so, the volume inside the pump chamber increased, causing fuel to be drawn into the pump from the tank. The return motion of the diaphragm to top dead center is accomplished by a diaphragm spring, during which the fuel in the pump chamber is squeezed through the outlet port and into the carburetor. The pressure at which the fuel is expelled from the pump is thus limited (and therefore regulated) by the force applied by the diaphragm spring.

The carburetor typically contains a float bowl into which the expelled fuel is pumped. When the fuel level in the float bowl exceeds a certain level, the inlet valve to the carburetor will close, preventing the fuel pump from pumping more fuel into the carburetor. At this point, any remaining fuel inside the pump chamber is trapped, unable to exit through the inlet port or outlet port. The diaphragm will continue to allow pressure to the diaphragm, and during the subsequent rotation, the eccentric will pull the diaphragm back to bottom dead center, where it will remain until the inlet valve to the carburetor reopens.

Because one side of the pump diaphram contains fuel under pressure and the other side is connected to the crankcase of the engine, if the diaphram splits (a common failure), it can leak fuel into the crankcase.

The pump creates negative pressure to draw the fuel through the lines. However, the low pressure between the pump and the fuel tank, in combination with heat from the engine and/or hot weather, can cause the fuel to vaporize in the supply line. This results in fuel starvation as the fuel pump, designed to pump liquid, not vapor, is unable to suck more fuel to the engine, causing the engine to stall. This condition is different from vapor lock, where high engine heat on the pressured side of the pump (between the pump and the carburetor) boils the fuel in the lines, also starving the engine of enough fuel to run. Mechanical automotive fuel pumps generally do not generate much more than 10-15 psi, which is more than enough for most carburetors.

Fuel pump Decline of mechanical pumps

As engines moved away from carburetors and towards fuel injection, mechanical fuel pumps were replaced with electric fuel pumps, because fuel injection systems operate more efficiently at higher fuel pressures (40-60psi) than mechanical pumps can generate. Electric fuel pumps are generally located in the fuel tank, in order to use the fuel in the tank to cool the pump and to ensure a steady supply of fuel.

Another benefit of an in-tank mounted fuel pump is that a suction pump at the engine could suck in air through a (difficult to diagnose) faulty hose connections, while a leaking connection in a pressure line will show itself immediately. A potential hazard of a tank-mounted fuel pump is that all of the fuel lines are under high pressure, from the tank to the engine. Any leak will be easily detected, but is also hazardous.

Electric fuel pumps will run whenever they are switched on, which can lead to extremely dangerous situations if there is a leak due to mechanical fault or an accident. Mechanical fuel pumps are much safer, due to their lower operating pressures and because they 'turn off' when the engine stops running.

Fuel pump Electric pump

Electric fuel pump

A piston metering pump f.e. gasoline- or additiv metering pumpNowadays, the fuel pump is located inside of the fuel tank and is usually electric. The pump creates positive pressure in the fuel lines, pushing the gasoline to the engine. The higher gasoline pressure raises the boiling point. Placing the pump in the tank puts the component least likely to handle gasoline vapor well (the pump itself) farthest from the engine, submersed in cool liquid. Another benefit to placing the pump inside the tank is that it is less likely to start a fire. Though electrical components (such as a fuel pump) can spark and ignite fuel vapors, liquid fuel will not explode (see explosive limit) and therefore submerging the pump in the tank is one of the safest places to put it. In most cars, the fuel pump delivers a constant flow of gasoline to the engine; fuel not used is returned to the tank. This further reduces the chance of the fuel boiling, since it is never kept close to the hot engine for too long.

The electric fuel pump is generally on whenever the car's ignition switch is in the "on" position. The metering of the fuel into the engine is performed by the fuel-injection or carburetor systems.

The ignition switch does not carry the power to the fuel pump, instead it activates a relay which will handle the higher current load. It is common for the fuel pump relay to become oxidized and cease functioning; this is much more common than the actual fuel pump failing. Modern engines utilize solid-state control which allows the fuel pressure to be controlled via pulse-width modulation of the pump voltage. This increases the life of the pump, allows a smaller and lighter device to be used, and reduces electrical load and thereby fuel consumption.

Some cars with an electronic control unit have safety logic that will shut the electric fuel pump off even if the ignition is "on" if there is no oil pressure, either due to engine bearing damage or a non stalled engine, e.g. in a car accident. In case of an accident this will also prevent fuel leaking from any ruptured fuel line. Other cars have an additional roll over valve, that will shut off the fuel pump in case the car rolls over. Some FORD cars also have a fuel cut off switch that will simply shut power down to the electric fuel pump relay in the case of a collision.

The fuel sending unit assembly is the combination of the electric fuel pump, filter, and the electronic device used to measure the amount of fuel in the tank via a float attached to a sensor with sends data to the dash mounted fuel gauge.

Fuel tanks

A fuel tank is the part of an engine system in which the fuel is stored and released into the engine. Fuel tanks range in size and complexity from the small plastic tank of a butane lighter to the multi-chambered cryogenic Space Shuttle external tank.

Large fuel tanks in an oil refineryTypically, a fuel tank must allow:

Filling (the fuel tank must be filled in a secure way)

Storage of fuel (the system must contain a given quantity of fuel and must avoid leakage and limit evaporative emissions)

Gauging (the remaining quantity of fuel in the tank must be measured or evaluated)

Venting (if over-pressure is not allowed, the fuel vapors must be managed through valves)

Feeding of the engine (through a pump)

Fuel tank Automotive

For each new vehicle a specific fuel system has to be developed, as they must optimize the empty space left by the car architecture.

Moreover, for one car model, different versions of fuel system architectures have to be developed with more or less components, depending on the type of the car, the type of fuel (gasoline or diesel), nozzle models and the region where the car will be circulating.

Plastic High density polyethylene (HDPE) fuel tanks produced through blow moulding. This technology is increasingly used as it now shows its capacity to obtain very low emissions of fuel (see Partial zero-emissions vehicle). HDPE can also allow for complex shapes to be formed, this means the tank to be mounted directly over the rear axle, saving space and improving crash safety. Initially there were concerns over the low fracture toughness of HDPE, when compared to steel or aluminium.

Metal (steel or aluminium) fuel tanks obtained by welding of stamped sheets. Although this technology is very good in limiting fuel emissions, it tends to be less competitive and thus less on the market.

Fuel tank Central locking

Cars generally include a fuel tank filler flap (also called fuel filler cap) integrated in central locking.

Fuel tank Remote opening

Modern cars includes remote opening of the fuel tank fuel filler flap using an electric motor. Some expensive cars even have fuel tanks that cannot be opened by hand or by any way from the outside of the car.

Fuel tank Reserve tank

Sometimes called the reserve tank, a light on the instrument panel of autos typically illuminates when the fuel level dips below a certain point in the tank. There is no current standard, although some efforts are made to collect this data for all automobiles.

Fuel tank Racing fuel cells

A racing fuel cell is a fuel container that differs from an ordinary fuel tank in the following ways: It has a flexible inner liner to minimize the potential for punctures in the event of a collision or other mishap resulting in serious damage to the vehicle. It is insulated with a mesh-like structure inside the tank to minimize sloshing of fuel during competition that may otherwise cause inadequate fuel (fuel starvation) delivery to the motor under competition conditions.

Fuel tank Aircraft

Aircraft typically use three types of fuel tanks: integral, rigid removable, and bladder.

Integral tanks are areas inside the aircraft structure that have been sealed to allow fuel storage. An example of this type is the "wet wing" commonly used in larger aircraft. Since these tanks are part of the aircraft structure, they cannot be removed for service or inspection. Inspection panels must be provided to allow internal inspection, repair, and overall servicing of the tank. Most large transport aircraft use this system, storing fuel in the wings and/or tail of the airplane.

Rigid removable tanks are installed in a compartment designed to accommodate the tank. They are typically of metal construction, and may be removed for inspection, replacement, or repair. The aircraft does not rely on the tank for structural integrity. These tanks are commonly found in smaller general aviation aircraft, such as the Cessna 172.

Bladder tanks are reinforced rubberized bags installed in a section of aircraft structure designed to accommodate the weight of the fuel. The bladder is rolled up and installed into the compartment through the fuel filler neck or access panel, and is secured by means of metal buttons or snaps inside the compartment. Many high-performance light aircraft and some smaller turboprops use bladder tanks.

Fuel tanks have also been implicated in aviation disasters. For example, the official explanation for the explosion and subsequent crash of TWA Flight 800 is that an explosive fuel/air mixture was created in one of the aircraft's fuel tanks. Faulty wiring then provided an ignition source within the tank, destroying the airliner. While the accuracy of the official findings is still questioned in this case, similar explosions have occurred in other aircraft. It is possible to reduce the chance of fuel tank explosions by a fuel tank inerting system.

Fuel tank Water Supply

Water supply systems can have primary or backup power supplied by diesel-fueled generators fed by a small "day tank" and a much larger bulk storage fuel tank.

Fuel tank Safety

The proper design and construction of a fuel tank plays a major role in the safety of the system of which the tank is a part.

In automotive applications, improper placement of the fuel tank has led to increased probability of fire in collisions. Circa 1990, General Motors faced over a hundred lawsuits related to fires allegedly caused by GM's decision to place the fuel tanks in its pickup trucks outside the protection of the vehicle's frame. Ford's Ford Pinto also sparked controversy for putting the gas tank in a poorly reinforced area which can cause deadly fires and explosions if the car got into a rear end collision, costing Ford $125 million. In 1993, as one of these lawsuits resulted in a US$101 million judgement against GM (later overturned), the television show

Dateline NBC created its own controversy by staging an example of the failures. When it was discovered that Dateline's consultants had rigged the truck with incendiary devices in order to guarantee a fire, GM filed a defamation suit, and several NBC employees were fired.

Grilles

BMW's distinctive kidney-shaped grille on an E34 M5 Audi's "single frame" grille, here on a second generation TTGrille is also the name of a German self-propelled artillery vehicle. For the cooking equipment, see grill.

In automotive engineering, a grille is an opening in the bodywork of a vehicle to allow air to enter. Most vehicles feature a grille at the front of the vehicle to allow air to flow over the radiator and cool the engine compartment. Other common grille locations include below the front bumper, in front of the wheels (to cool the brakes), in the cowl for cabin ventilation, or on the rear deck lid (in rear engine vehicles).

Some cars have what appear to be tiny grilles which are not positioned to duct air through the radiator. These are horn grilles, which enable the sound of the horn to be clearly heard forward.

The grille is often a distinctive styling element, and many marques use it as their primary brand identifier. For example, Jeep has trademarked its seven-bar grille style. Rolls-Royce is famous for arranging its grille bars by hand to ensure that they appear perfectly vertical. Other makers known for their grille styling include Bugatti's horse-collar, BMW's split kidney, Rover's chrome "teeth", Dodge's cross bar, Alfa Romeo's 6-bar shield, Volvo's slash bar, Audi's relatively new, so-called single-frame grille, and an eggrate grill on late-generation Plymouths. The unusual 1971 Plymouth Barracuda grille is known as a cheesegrater. Ford's three-bar grille, introducted on the 2006 Fusion has become distinctive as well.

The contrary styling pattern also occurs. Starting from the late 1930s, Cadillac would alternate its pattern from horizontal bars to various patterns of crosshatching as a simple way of making the car look new from year to year, for this make did not have a standard grille form. Sometimes there is a sort of fashion trend in grille bars. For example, in the early years after World War II, many American car makers generally switched to fewer and thicker grille bars.

A billet grille is an aftermarket part that is used to enhance the style or function of the original OEM grille. They are generally made from billet, solid bar stock aircraft grade aluminum or stainless steel, although some are CNC Machined from one solid sheet of aluminum.

Customizers would alter the grille as a matter of course in personalizing their car, taking the grille bar from another make, for example. Even sheet metal with patterned holes for ventilation grating sold to homeowners for repair has been found filling the grille opening of custom cars.

Grille HVAC

In HVAC Room air distribution, a grille, specifically spelled with the ending e, is a class of air terminals. Most HVAC grilles are used as return or exhaust air inlets to ducts, but some are used as supply air outlets. Diffusers and nozzles, are, for example, used as supply air outlets too. Registers are a type of HVAC grille that also incorporates an air damper.

Grille History

Grilles on automobiles have taken on different designs through the years. This feature first appeared on automobiles in 1903. Several years later, the arch-shaped design became common and became the standard design on automobile grilles for many years.

In the 1930s and 1940s, automobile manufacturers became creative with their grille designs. Some these designs were bell-shaped (Buick, Chevrolet, and Pontiac), split and slightly folded (Silver Arrow, Mercury, 1946 Oldsmobile), cross-shaped (pre-war Studebaker Champion models, 1941 Cadillac, 1942 Ford), while some including Packard, Rolls-Royce, and MG-TC models still followed the older arch-shaped design.

Grilles took on a new look after World War II. Following the introduction of the 1947 Buick, Studebaker, and Kaiser, grilles became shorter and wider to accommodate for the change in design.

Headlights

A headlamp can also be mounted on a bicycle (with a battery or small electrical generator), and most other vehicles from airplanes to trains tend to have headlamps of their own. Single small headlamps may also be mounted on a helmet or attached to a strap around the head designed to be worn in situations where light is required but both hands are needed, for example in subterranean mines or for spelunking in caves.

Headlamp History of automotive headlamps

Headlamp Mechanics

The earliest headlamps were fueled by acetylene or oil and were introduced by drivers in the late 1880s. Acetylene was popular because the flame was resistant to wind and rain. The first electric headlamps were introduced in 1898 on the Columbia Electric Car from the Electric Vehicle Company of Hartford, Connecticut, but they were optional. Two factors limited the widespread use of electric headlamps: the short life of filaments in the harsh automotive environment (especially vibration), and the difficulty of producing dynamos small enough to be engine driven, yet powerful enough to produce sufficient current. "Prest-O-Lite" acetylene lights were offered by a number of manufacturers as standard equipment for 1904, and Peerless made electrical headlamps standard in 1908. In 1912, Cadillac integrated their vehicle's Delco electrical ignition and lighting system, creating the modern vehicle electrical system.

"Dipping" (low beam) headlamps were introduced in 1915 by the Guide Lamp Company, but the 1917 Cadillac system was much more useful as it allowed the light to be dipped with a lever inside the car rather than requiring the driver to stop and get out. The 1924 Bilux bulb was the first modern unit, having the light for both low (dipped) and high (main) beams of a headlamp emitting from a single bulb. A similar design was introduced the next year by Guide Lamp called the "Duplo". In 1927, the foot-operated dimmer was introduced and would become standard for much of the century. The last vehicle with a foot-operated dimmer was the 1991 Ford F-Series. Foglamps were new for 1938 Cadillacs, and that company's 1954 "Autronic Eye" system automated the switch between high and low beams.

The standardized 7 inch (178 mm) round sealed beam headlamp was introduced in 1940, and was soon required for all vehicles sold in the United States. Britain, Australia and other Commonwealth countries, as well as Japan, also made extensive use of sealed beams, but they were never widely accepted in Europe, leading to different front-end designs for each side of the Atlantic for decades.

The first halogen headlamp for vehicle use was introduced in 1962 by a consortium of European bulb and headlamp makers. Halogen technology is considered a technological advance because it makes incandescent filaments much more efficient and can produce more light than was available from non-halogen filaments at the same power consumption. These were prohibited in the United States where non-halogen sealed beam lamps were required until 1978. From 1978 to 1983, all halogen headlamps in the U.S. were sealed beams with halogen bulbs inside; these "halogen sealed beams" remained available after composite headlamps returned to the U.S. in 1983, this time with halogen bulbs.

High-intensity discharge systems were introduced in 1991's BMW 7-series. European and Japanese markets rapidly came to prefer HID headlamps, which have as much as 50% market share in those markets, but the technology was slow to be adopted in North America. 1996's Lincoln Mark VIII was an early American effort at HIDs; it was also the first and only car with DC HIDs.

Headlamp Design & Style

Beyond the engineering, performance and regulatory-compliance aspects of headlamps, there is the consideration of the various ways they are designed and arranged on a motor vehicle. Early headlamps were always round, because that is the easiest shape in which to manufacture a parabolic reflector.

Headlamp styling outside of the United States, pre-1983

European-market aerodynamic glass-covered steering headlamps retrofitted on a US-market 1968+ Citroen DSThere was no requirement in Europe for headlamps of standardised size or shape. Automakers were free to design their lamps to whatever shapes and sizes they wished, as long as the lamps met the engineering and performance requirements contained in the applicable European safety standards. That design freedom permitted the development of rectangular headlamps, first used in 1961. Developed by Cibié for the Citroën Ami 6 and by Hella for the German Ford Taunus, they were prohibited in the United States where round lamps were required until 1975. Another early headlamp styling idea involved conventional round lamps faired into the car's bodywork with aerodynamic glass covers, such as those on the 1961 Jaguar E-Type.

Headlamp styling in the United States, 1940-1983

In 1940, the US government mandated a system of two 7 in. (178 mm) round sealed beam headlamps on all vehicles. Headlamp styling in the United States virtually ceased for many decades after this event.

A system of four round lamps, rather than two one high/low and one high-beam 5¾ in. (146 mm) sealed beam on each side were introduced in 1952 when the Prevost Car company included them in its Citaden bus model. Cadillac, Chrysler and Nash placed them in some of their car models in states that permitted the new system for the 1957 model year, and other American marques followed suit when all states permitted quad lamps in 1958. These lamps had some photometric advantages, but the primary advantage was the styling novelty permitted by the use of two small rather than one large lamp per side of the vehicle. The freedom was not absolute, however; auto stylists such as Virgil Exner carried out design studies with the low beams in their conventional outboard location, and the high beams vertically stacked at the centerline of the car. No such designs reached volume production. Most cars had their headlights in pairs side by side on each side of the car; some models of Oldsmobile had a parking light in the middle of each pair.

Also popular was an arrangement in which the two headlamps on each side were stacked, low beams above high beams. Nash used this arrangement in the 1957 model year. Pontiac used this design starting in the 1963 model year; American Motors, Ford, Cadillac and Chrysler followed two years later. Also in the 1965 model year, the Buick Riviera had concealable stacked headlamps. The Mercedes-Benz W100, W108, W111, and W112 models sold in America used this arrangement because their home-market composite lamps were illegal in the US. The British firm Alvis and the French firm FACEL also used this setup for some of their cars, as did Nissan in Japan.

In the late 1950s and early 1960s, Lincoln, Buick, and Chrysler arranged the headlamps diagonally by placing the low-beam lamps outboard and above the high-beam lamps. Certain British cars used a less extreme diagonal arrangement, with the inboard high-beam lamps placed only slightly lower than the outboard low-beam units. The 1965 Gordon-Keeble, Triumph Vitesse and Bentley S3 Continental used such an arrangement. (source: World Car Catalog)

When Federal Motor Vehicle Safety Standard 108 was amended in the early 1970s to permit rectangular headlamps, these were placed in horizontally-arrayed or vertically-stacked pairs. By 1979, the majority of new cars in the US market were equipped with rectangular lamps. Again, the U.S. permitted only two standardized sizes of rectangular sealed-beam lamp: A system of two 200 mm x 142 mm (7½ in. x 5½ in.) high/low beam units corresponding to the existing 7" round format, or a system of four 165 mm x 100 mm (6½ in. x 4 in.) units, two high/low and two high-beam, corresponding to the existing 5¾ inch (146 mm) round format.

In 1968 the U.S. DOT prohibited any decorative or protective element in front of the headlamps whenever the headlamps are switched on. Glass-covered headlamps, used on e.g. the Jaguar E-Type, the pre-1968 VW Beetle, the Porsche 356, the Citroën DS and Ferrari Daytona were no longer permitted, and vehicles had to be imported with uncovered headlamps for the US market, further altering the look of European models sold in the United States. This change meant that vehicles designed for good aerodynamic performance could not achieve it for the US market.

International headlamp styling, 1983 to present

In 1983, the 44-year-old US headlamp regulations were amended to allow replaceable-bulb, nonstandard-shape, architectural headlamps with aerodynamic lenses. The first U.S.-market car since 1939 with composite headlamps was the 1984 Lincoln Mark VII. These composite headlamps, when new to the U.S. market, were commonly referred to as "Euro" headlamps, since aerodynamic headlamps were already common in Europe. Though conceptually similar to European headlamps with nonstandardized shape and replaceable-bulb construction, these headlamps conform to the SAE headlamp design standards contained in U.S. Federal Motor Vehicle Safety Standard 108, and not to the internationalized European safety standards used worldwide outside North America. Nevertheless, this significant change to US regulations largely united the formerly disparate paths of headlamp styling within and outside the North American market.

In the late 1990s, headlamps with round styling themes returned to popularity on new cars. These are generally not the discrete self-contained round lamps as found on older cars (certain Jaguars excepted), but rather involve circular or oval optical elements within an architecturally-shaped housing assembly.

Hidden headlamps

Pop up headlamps on a Mazda 323FHidden headlamps were introduced in 1936, on the Cord 810. They were mounted in the front fenders, which were smooth until the lights were cranked out, each with its own small dash-mounted crank. They aided aerodynamics when the headlamps were not in use, and were among the Cord's signature design features.

Many notable cars used this feature, but no current volume-produced car models use hidden headlamps, largely because they are expensive to construct. The system requires one or more vacuum-operated servos and reservoirs, with associated plumbing and linkage, or electric lift motors, geartrains and linkages of sufficient robustness and precision to raise the lamps to an exact position each time to assure correct beam aim despite ice, snow and age. Some early hidden headlamps, such as those on the Saab Sonett III, used a lever-operated mechanical linkage to raise the headlamps into position. Current market demands place a premium on vehicles' aerodynamic performance with lamps off and on, further reducing the attractiveness of pop-up headlamps. In addition, recent ECE Regulations contain stringent standards regarding protuberances on car bodies, in an effort to minimize injury to pedestrians struck by cars.

Some hidden headlamps themselves do not move, but rather are covered when not in use by panels designed to blend in with the front styling of the car. When the lamps are switched on, the covers are swung out of the way, usually downward or upward and into the space within the fender above or below the headlamps, as for example on the 1992 Jaguar XJ220. Actuation of the cover door mechanism may be by means of vacuum pots, as on numerous Ford large and sporty vehicles of the late 1960s through early 1980s such as the 1967-1969 Mercury Cougar, or by means of an electric motor as on various Chrysler products of the middle 1960s through late 1970s such as the 1966-1967 Dodge Charger.

Headlamp Regulations and requirements

Headlamp Functions and fitment

Modern headlamps are electrically operated, positioned in pairs, one or two on each side of the front of a vehicle. A headlamp system is required to produce a low and a high beam, which may be achieved either by an individual lamp for each function or by a single multifunction lamp. High beams (called "main beams" or "full beams" or "driving beams" in some countries) cast most of their light straight ahead, maximizing seeing distance, but producing too much glare for safe use when other vehicles are present on the road. Because there is no especial control of upward light, high beams also cause backdazzle from fog, rain and snow due to the retroflection of the water droplets. Low beams (called "dipped beams" in some countries) have stricter control of upward light, and direct most of their light downward and either rightward (in right-traffic countries) or leftward (in left-traffic countries), to provide safe forward visibility without excessive glare or backdazzle.

Some countries require automobiles to be equipped with automatic daytime running lamps (DRL), which are intended to increase the conspicuity of vehicles in motion during the daytime. DRL may consist of the manual or automatic illumination of the low beams at full or reduced intensity, or the high beams at reduced intensity, or may not involve the headlamps at all. Countries requiring DRL include Canada, Iceland, Hungary, Poland, and most Scandinavian countries.

Headlamp Traffic handedness

Most low-beam headlamps are specifically designed for use on one side of the road or the other. Headlamps for use in LH-traffic countries have low-beam headlamps that "dip to the left", i.e., the light is distributed with a downward/leftward bias to show the driver the road and signs ahead without blinding oncoming traffic. Headlamps for RH-traffic countries have low beams that "dip to the right", with most of their light directed downward/rightward. Within Europe, when driving a vehicle with RH-traffic headlamps in a LH-traffic country or vice versa for a limited time (as for example on vacation or in transit), it is a legal requirement to adjust the headlamps temporarily so that the wrong-side hot spot of the beam does not dazzle oncoming drivers. This may be achieved by adhering blackout strips or plastic prismatic lenses to a designated part of the lens, but some varieties of the projector-type headlamp can be made to produce a proper LH- or RH-traffic beam by shifting a lever or other movable element in or on the lamp assembly.

Because wrong-side-of-road headlamps blind oncoming drivers and do not adequately light the driver's way, and blackout strips and adhesive prismatic lenses reduce the safety performance of the headlamps, most countries require all vehicles registered or used on a permanent or semipermanent basis within the country to be equipped with headlamps designed for the correct traffic-handedness. North American vehicle owners sometimes privately import and install Japanese-market (JDM) headlamps on their car in the mistaken belief that the beam performance will be better, when in fact such misapplication is quite hazardous.

Headlamp Construction, performance, and aim

There are two different beam pattern and headlamp construction standards in use in the world: The ECE standard, which is allowed or required in virtually all industrialized countries except the United States, and the SAE standard that is mandatory only in the US. Japan formerly had bespoke lighting regulations similar to the US standards, but for the left side of the road. However, Japan now adheres to the ECE standard. The differences between the SAE and ECE headlamp standards are primarily in the amount of glare permitted towards other drivers on low beam (SAE permits much more glare), the minimum amount of light required to be thrown straight down the road (SAE requires more), and the specific locations within the beam at which minimum and maximum light levels are specified.

ECE low beams are characterized by a distinct horizontal "cutoff" line at the top of the beam. Below the line is bright, and above is dark. On the side of the beam facing away from oncoming traffic (right in right-traffic countries, left in left-traffic countries), this cutoff sweeps or steps upward to direct light to road signs and pedestrians. SAE low beams may or may not have a cutoff, and if a cutoff is present, it may be of two different general types: VOL, which is conceptually similar to the ECE beam in that the cutoff is located at the top of the left side of the beam and aimed slightly below horizontal, or VOR, which has the cutoff at the top of the right side of the beam and aimed at the horizon.

Proponents of each headlamp system decry the other as inadequate and unsafe: U.S. proponents of the SAE system claim that the ECE low beam cutoff gives short seeing distances and inadequate illumination for overhead road signs, while international proponents of the ECE system claim that the SAE system produces too much glare. Comparative studies have repeatedly shown that there is little or no overall safety benefit to either SAE or ECE beams; the two systems' acceptance and rejection by various countries is based primarily on inertial and philosophical grounds.

In North America, the design, performance and installation of all motor vehicle lighting devices are regulated by Federal and Canada Motor Vehicle Safety Standard 108, which incorporates SAE technical standards. Elsewhere in the world, ECE internationalised regulations are in force either by reference or by incorporation in individual countries' vehicular codes.

US laws required sealed beam headlamps on all vehicles between 1940 and 1983, and other countries such as Japan, United Kingdom and Australia also made extensive use of sealed beams. In most other countries, and in the US since 1984, replaceable-bulb headlamps predominate.

Headlamps on new vehicles must produce white light, according to both ECE and SAE standards. Previous ECE regulations also permitted selective yellow light, and from 1936 until 1993 this was required on all vehicles registered in France.

Headlamps must be kept in proper alignment (or "aim"). Regulations for aim vary from country to country and from beam specification to beam specification. US SAE headlamps are aimed without regard to headlamp mounting height. This gives vehicles with high-mounted headlamps a seeing distance advantage, at the cost of increased glare to drivers in lower vehicles. ECE headlamps' aim angle is linked to headlamp mounting height. This gives all vehicles roughly equal seeing distance and all drivers roughly equal glare.

Headlamp Optical systems

Headlamp Reflector lamps

Headlamp Lens optics

Lens optics, side view. Light is dispersed vertically (shown) and laterally (not shown). Lens optics, sealed beam example. The fresnel patches disperse the light in a precisely defined way.

A light source (filament or arc) is placed at or near the focus of a reflector, which may be parabolic or of non-parabolic complex shape. Fresnel and prism optics moulded into the headlamp lens then shift parts of the light laterally and vertically to provide the required light distribution pattern. The lens may use both refraction and TIR to achieve the desired results. Most sealed-beam headlamps have lens optics.

Headlamp Reflector optics

Starting in the 1980s, CAD technology allowed the development of reflector headlamps with nonparabolic, complex-shape reflectors. First made by Valeo under their Cibie brand, these headlamps would revolutionize automobile design. The 1987 Dodge Monaco/Eagle Premier was the first U.S.-market car with complex-reflector headlamps, while the 1990 Honda Accord was the first U.S.-market car with such headlamps employing a completely clear, nonfaceted front lens.

The optics to distribute the light in the desired pattern are designed into the reflector itself, with such a unit being known as an "optic reflector". Depending on the development tools and techniques in use, the reflector may be engineered from the start as a bespoke shape, or it may start as a parabola standing in for the size and shape of the completed package. In the latter case, the entire surface area is modified so as to produce individual segments of specifically calculated, complex contours. The precise shape of each segment is designed such that their cumulative effect produces the required light distribution pattern.

Optic reflectors are commonly made of compression-moulded or injection molded plastic, though glass and metal optic reflectors also exist. The reflective surface is vapor deposited aluminum with a clear overcoating to prevent the extremely thin aluminum from oxidizing. Extremely tight tolerances must be adhered to in the design, tooling and production of complex-reflector headlamps.

Dual-beam reflector headlamps

Night driving has long been dangerous due to the glare of headlights from oncoming traffic which temporarily blinds drivers approaching from the opposite direction. Therefore, headlamps that satisfactorily illuminate the road ahead of the automobile without causing this effect have long been sought. The first attempts to address this problem involved resistance-type dimming circuits, which decreased the brightness of the headlamps when meeting another car. This gave way to mechanical tilting reflectors and later to double-filament bulbs with a high and a low beam. Automatic headlamp dimmers were also introduced.

In a two-filament headlamp, there can only be one filament exactly at the focal point of the reflector. There are two primary means of producing two different beams from a two-filament bulb in a single reflector.

Headlamp American system

One filament is located at the focal point of the reflector. The other filament is shifted axially and radially away from the focal point. In most 2-filament sealed beams and in 2-filament replaceable bulbs type 9004, 9007 and H13, the high beam filament is at the focal point and the low beam filament is off focus. For use in right-traffic countries, the low beam filament is positioned slightly upward, forward and leftward of the focal point, so that when it is energized, the light beam is widened and shifted slightly downward and rightward of the headlamp's axis. Transverse-filament bulbs such as 9004 can only be used with the filaments horizontal, but axial-filament bulbs can be rotated or "clocked" by the headlamp designer so as to optimize the beam pattern or to effect the traffic-handedness of the low beam. The latter is accomplished by clocking the low-beam filament in an upward-forward-leftward position to produce a right-traffic low beam, or in an upward-forward-rightward position to produce a left-traffic low beam.

The opposite tactic has also been employed in certain 2-filament sealed beams: placing the low beam filament at the focal point to maximize light collection by the reflector, and positioning the high beam filament slightly rearward-rightward-downward of the focal point. The relative directional shift between the two beams is the same with either technique in a right-traffic country, the low beam is slightly downward-rightward and the high beam is slightly upward-leftward, relative to one another but the lens optics must be matched to the filament placements selected.

Headlamp European system

The traditional European method of achieving low and high beam from a single bulb involves two filaments along the axis of the reflector. The high beam filament is on the focal point, while the low beam filament is approximately 1 cm forward of the focal point and 3 mm above the axis. Below the low beam filament is a cup-shaped shield (called a "Graves Shield") spanning an arc of 165°. When the low beam filament is illuminated, this shield casts a shadow on the corresponding lower area of the reflector, blocking downward light rays that would otherwise strike the reflector and be cast above the horizon. The bulb is rotated (or "clocked") within the headlamp to position the Graves Shield so as to allow light to strike a 15° wedge of the lower half of the reflector. This is used to create the upsweep or upstep characteristic of ECE low beam light distributions. The bulb's rotative position within the reflector depends on the type of beam pattern to be produced and the traffic directionality of the market for which the headlamp is intended.

This system was first used with the Bilux/Duplo bulb of 1954, and later with the halogen H4 bulb of 1971. In 1992, U.S. regulations were amended to permit the use of H4-style bulbs. Named HB2 or 9003, for the U.S. market, and with very slightly different production tolerances stipulated, these bulbs are physically and electrically interchangeable with H4 bulbs. Similar optical techniques are used, but with different reflector and/or lens optics to create a U.S. beam pattern rather than a European one.

Each system has its advantages and disadvantages. The American system historically permitted a greater overall amount of light within the low beam, since the entire reflector and lens area is used, but at the same time, the American system has traditionally offered much less control over upward light that causes glare, and for that reason has been largely rejected outside the U.S. In addition, the American system makes it difficult to create markedly different low and high beam light distributions; the high beam is usually simply a rough copy of the low beam, shifted slightly upward and leftward. The European system traditionally produced low beams containing less overall light, because only 60% of the reflector's surface area is used to create the low beam. However, low beam focus and glare control are easier to achieve. In addition, the lower 40% of the reflector and lens are reserved for high beam formation, which facilitates the optimization of both low and high beams.

Headlamp Recent developments

Complex-reflector technology in combination with new bulb designs such as H13 is enabling the creation of European-type low and high beam patterns without the use of a Graves Shield, while the 1992 US approval of the H4 bulb has made traditionally European 60% / 40% optical area divisions for low and high beam common in the US. Therefore, the difference in active optical area and overall beam light content no longer necessarily exists between US and ECE beams. Dual-beam HID headlamps employing reflector technology have been made using adaptations of both techniques.

Headlamp Projector (polyellipsoidal) lamps

In this system a filament is located at one focus of an ellipsoidal reflector and has a condenser lens at the front of the lamp. A shade is located at the image plane, between the reflector and lens, and the projection of the top edge of this shade provides the low-beam cutoff. The shape of the shade edge, and its exact position in the optical system, determines the shape and sharpness of the cutoff. The shade may have a solenoid actuated pivot to provide both low and high beam, or it may be stationary in which case separate high-beam lamps are required. The condenser lens may have slight fresnels or other surface treatments to reduce cutoff sharpness. Recent condenser lenses incorporate optical features specifically designed to direct some light upward towards the locations of retroreflective overhead road signs.

Hella introduced its "projector beam" optics for acetylene headlamps in 1911, but following the electrification of vehicle lighting, this optical technology wasn't used for many decades. The first modern polyellipsoidal automotive lamp was the Super-Lite, an auxiliary headlamp produced in a joint venture between Chrysler Corporation and Sylvania and optionally installed in 1969 and 1970 full-size Dodge automobiles. It used an 85 watt transverse-filament tungsten-halogen bulb and was intended as a mid-beam, to extend the reach of the low beams during turnpike travel when low beams alone were inadequate but high beams would produce excessive glare.

Projector main headlamps first appeared in 1981 on the Audi Quartz, the Audi Quattro-based concept car designed by Pininfarina for Geneva Auto Salon. Developed more or less simultaneously in Germany by Hella and in France by Cibié, the projector low beam permitted accurate beam focus and a much smaller-diameter optical package, though a much deeper one, for any given beam output. The version of the 1986 BMW 7 Series sold outside North America was the first volume-production auto to use polyellipsoidal low beam headlamps.

Headlamp Light sources

Headlamp Tungsten light sources

The first electric headlamp light source was the tungsten filament, operating in a vacuum or inert-gas atmosphere inside the headlamp bulb or sealed beam. Compared to newer-technology light sources, tungsten filaments give off small amounts of light relative to the power they consume. Also, during normal operation of such lamps, tungsten boils off the surface of the filament and condenses on the bulb glass, blackening it. This reduces the light output of the filament and blocks some of the light that would pass through an unblackened bulb glass. For these reasons, plain tungsten filaments are all but obsolete in automotive headlamp service.

Headlamp Tungsten-halogen light sources

Halogen technology (also "quartz-halogen", "quartz-iodine", "iodine", "iode") makes tungsten filaments more efficacious producers of light more lumens out per watt in and Europeans chose to use this extra efficacy to provide drivers with more light than was available from nonhalogen filaments at the same power consumption. Unlike the European approach which emphasized increased light output, most U.S. low beam halogens were low current versions of their nonhalogen counterparts, producing the same amount of light with less power. A slight theoretical fuel economy benefit and reduced vehicle construction cost through reduced wire and switch ratings were the claimed benefits. There was an improvement in seeing distance with U.S. halogen high beams, which were permitted for the first time to produce 150,000 candelas (cd) per vehicle, double the nonhalogen limit of 75,000 cd but still well shy of the international European limit of 225,000 cd. After replaceable halogen bulbs were permitted in U.S. headlamps in 1983, development of U.S. bulbs continued to favour long bulb life and low power consumption, while European designs continued to prioritize optical precision and maximum output.

The first halogen bulb for vehicle use, the H1, was introduced in 1962 by a consortium of European bulb and headlamp makers. This bulb has a single axial filament that consumes 55 watts at 12.0 volts, and produces 1550 lumens ±15% when operated at 13.2 V. H2 (55 W @ 12.0 V, 1820 lm @ 13.2 V) followed in 1964, and the transverse-filament H3 (55 W @ 12.0 V, 1450 lm ±15%) in 1966. H1 still sees wide use in low beams, high beams and auxiliary foglamp and driving lamps, as does H3. The H2 does not see wide use any more because it requires an intricate bulb holder interface to the lamp, has a short life and is difficult to handle. For those reasons, H2 was withdrawn from ECE Regulation 37 for use in new lamp designs (though H2 bulbs are still manufactured for replacement purposes in existing lamps). The use of H1 and H3 bulbs was legalized in the United States in 1997. More recent single filament bulb designs include the H7 (55 W @ 12.0 V, 1500 lm ±10% @ 13.2 V), H8 (35 W @ 12.0 V, 800 lm ±15% @ 13.2 V), H9 (65 W @ 12.0 V, 2100 lm ±10% @ 13.2 V), and H11 (55 W @ 12.0 V, 1350 lm ±10% @ 13.2 V). 24-volt versions of many bulb types are available for use in trucks, buses, and other commercial and military vehicles.

The first dual-filament halogen bulb (to produce a low and a high beam with only one bulb), the H4, was released in 1971. The U.S. prohibited halogen headlamps until 1978, when halogen sealed beams were released. To this day, the H4 is still not legal for automotive use in the United States. Instead, the Americans created their own very similar standard (HB2/9003). The primary differences are that the HB2 sets more strict requirements on filament positioning, and that the HB2 are required to meet the lower maximum output standards set forth by the United States government.

The first U.S. halogen headlamp bulb, introduced in 1983, was the 9004/HB1. It is a 12.8-volt, transverse dual-filament design that produces 700 lumens on low beam and 1200 lumens on high beam. The 9004 is rated for 65 watts (high beam) and 45 watts (low beam) at 12.8 volts. Other U.S. approved halogen bulbs include the 9005/HB3 (65 W, 12.8 V), 9006/HB4 (55 W, 12.8 V), and 9007/HB5 (65/55 watts, 12.8 V).

Headlamp Halogen Infrared Reflective light sources

A further development of the tungsten-halogen bulb has a dichroic coating that passes visible light and reflects infrared radiation. The glass in such a bulb is spherical, rather than tubular. The reflected infrared radiation strikes the filament located at the centre of the sphere, heating the filament to a degree greater than occurs by passing an electric current through the filament. The filament thus superheated emits more light, without an increase in power consumption or a decrease in lifespan.

Headlamp HID light sources (Xenon and Bi-Xenon)

Xenon projector low beam headlamp illuminated on a Saab 9-5.HID stands for high-intensity discharge, the technical term for the electric arc that produces the light. Automotive HID lamps are commonly called 'xenon headlamps', although they are actually metal halide lamps that contain xenon gas. The xenon gas allows the lamps to produce minimally adequate amounts of light immediately upon startup and speed the warmup time. If argon were used instead, as is commonly done in street and other stationary metal halide lamp applications, it would take several minutes for the lamps to reach their full output. HID headlamps use a small, purpose-designed burner which produces more light than ordinary tungsten and tungsten-halogen bulbs. The light from HID headlamps has a distinct bluish tint when compared with tungsten-filament headlamps. The high intensity of the arc comes from metallic salts that are vapourised within the arc chamber.

HID headlamp bulbs produce between 2,800 and 3,500 lumens from between 35 and 38 watts of electrical power, while halogen filament headlamp bulbs produce between 700 and 2,100 lumens from between 40 and 72 watts at 12.8 V. Because of the increased amounts of light available from HID bulbs, HID headlamps producing a given beam pattern can be made smaller than halogen headlamps producing a comparable beam pattern. Alternatively, the larger size can be retained, in which case the Xenon headlamp can produce a more robust beam pattern.

HID headlamp bulbs do not run on low-voltage DC current, so they require a ballast with either an internal or external ignitor. The ballast controls the current to the bulb. When the headlamps are switched on, the ignitor provides rapidly pulsed current at several thousand volts to initiate the arc between the electrodes within the bulb. Once the arc is started, its heat begins to vapourise the metallic salts within the arc chamber, and the ballast gradually transitions from startup operation to arc-maintenance operation. Once the arc is completely stabilised, the ballast provides 85 V in conventional D1 and D2 systems, or 42 V with Mercury-free D3 and D4 systems.

The correlated color temperature of HID headlamp bulbs, at between 4100 K and 4400 K, is often described in marketing literature as being closer to the 6500 K of sunlight compared with tungsten-halogen bulbs at 3000 K to 3550 K. Nevertheless, HID headlamps' light output is not similar to daylight. The spectral power distribution (SPD) of an automotive HID headlamp is discontinuous, while the SPD of a filament lamp, like that of the sun, is a continuous curve. Moreover, the color rendering index (CRI) of tungsten-halogen headlamps (=0.98) is much closer than that of HID headlamps (~0.75) to standardised sunlight (1.00). Studies have shown no significant safety effect of this degree of CRI variation in headlighting.

The arc within an HID headlamp bulb generates considerable short-wave ultraviolet (UV) light, but none of it escapes the bulb. A UV-absorbing hard glass shield is incorporated around the bulb's arc tube. This is important to prevent degradation of UV-sensitive components and materials in headlamps, such as polycarbonate lenses and reflector hardcoats. The lamps do emit considerable near-UV light.

European vehicles equipped with HID headlamps are required by ECE regulation 48 also to be equipped with headlamp lens cleaning systems and automatic beam levelling control. Both of these measures are intended to reduce the tendency for high-output headlamps to cause high levels of glare to other road users.

HID headlamp bulb types D1R, D1S, D2R, D2S and 9500 contain the toxic heavy metal mercury. The disposal of mercury-containing vehicle parts is increasingly regulated throughout the world, for example under US EPA regulations. Newer HID bulb designs D3R, D3S, D4R, and D4S contain no mercury, but are not electrically or physically compatible with headlamps designed for previous bulb types.

The arc light source in an HID headlamp is fundamentally different from the filament light source used in tungsten/halogen headlamps. For that reason, HID-specific optics are used to collect and distribute the light. Installing HID bulbs in headlamps designed to take filament bulbs results in improperly-focused beam patterns and excessive glare, and is therefore illegal in almost all countries.

Headlamp LED light sources

Automotive headlamp applications using LEDs have been undergoing very active development since 2004. The first series-production LED headlamps are factory-installed on the 2008 Lexus LS 600h / LS 600h L (low beam, front position light and sidemarker only; high beam and turnsignal are filament based. The headlamp is supplied by Koito), and on the version of the 2008 Audi R8 sports car sold outside North America supplied by Automotive Lighting. Present designs give performance between halogen and HID headlamps, with system power consumption slightly higher than halogen headlamps. These lamps currently require large packaging and a large number of the most powerful LED emitters available. As LED technology continues to evolve, the performance of LED headlamps is predicted to improve to approach, meet, and perhaps one day surpass that of HID headlamps.

The limiting factors with LED headlamps presently include high system expense, regulatory delays and uncertainty, glare concerns related to the output spectrum of white LEDs, and logistical issues created by LED operating characteristics. LEDs are commonly considered to be low-heat devices due to the public's familiarity with small, low-output LEDs used for electronic control panels and other applications requiring only modest amounts of light. However, LEDs actually produce a significant amount of heat per unit of light output. Rather than being emitted together with the light as is the case with conventional light sources, an LED's heat is produced at the rear of the emitters. The cumulative heat of numerous high-output LED emitters operating for prolonged periods poses thermal-management challenges for plastic headlamp housings. In addition, this heat buildup materially reduces the light output of the emitters themselves. LEDs are quite temperature sensitive, with many types producing at 30 °C (85 °F) only 60% of the rated light output they produce at an emitter junction temperature 16 °C (60 °F). Prolonged operation above the maximum junction temperature will permanently degrade the LED emitter and ultimately shorten the device's life. The need to keep LED junction temperates low at high power levels always requires additional thermal management measures such as heatsinks and exhaust fans which are typically quite expensive.

Additional facets of the thermal issues with LED headlamps reveal themselves in cold ambient temperatures. Many types of LEDs produce at -12 °C (10 °F) up to 160% of their 16 °C (60 °F) rated output. The temperature-dependency of LED's light output creates serious challenges for the engineering and regulation of automotive lighting devices, which are in some cases required to produce intensities within a range smaller than the variation in LED output with temperatures normally experienced in automotive service.

Cold weather also brings another thermal-management conundrum: Not only must heat be removed from the rear of the headlamp so that the housing does not deform or melt and the emitters' output does not drop excessively, but heat must in addition be effectively applied to the front lenses of the lamps which are not heated by the cold light beam produced by LEDs to provide rapid and complete thawing of snow and ice accumulation.

LEDs are increasingly being adopted for signalling functions such as parking lamps, brake lamps and turn signals as well as Daytime Running Lamps, as in those applications they offer significant advantages over filament bulbs with fewer engineering challenges than headlamps pose.

Dynamic Headlight Beam Control

Headlamp Levelling Control

In 1954, Cibié introduced an automatic headlamp leveling system linked to the vehicle's suspension system to keep the headlamps correctly aimed regardless of vehicle load. The first vehicle to be so equipped was the Panhard Dyna Z. Beginning in the 1970s, Germany and some other European countries began requiring remote-control headlamp levelling systems that permit the driver to lower the lamps' aim by means of a dashboard control lever or knob if the rear of the vehicle is weighted down with passengers or cargo, which would tend to raise the lamps' aim angle and create glare. Such systems typically use stepper motors at the headlamp and a rotary switch on the dash marked "0", "1", "2", "3" for different beam heights, "0" being the "normal" (and highest) position for when the car is lightly loaded. Internationalized ECE Regulation 48, in force in most of the world outside North America, currently requires such systems on all vehicles. The regulation stipulates a more stringent version of this antiglare measure for vehicles equipped with headlamp bulbs producing more than 2,000 lumens, such as Xenon headlamps; such vehicles must be equipped with headlamp self-levelling systems that sense the vehicle's degree of squat due to cargo load and road inclination, and automatically adjust the headlamps' vertical aim to keep the beam correctly oriented without any action required by the driver.

Headlamp Directional headlamp

1928 Willys-Knight 70A Touring. Notice the directional headlight in the middle. Directional (steering) headlamps on a Citroën DS - the driver can see his way through curves.These provide improved lighting for cornering. Some automobiles have their headlamps connected to the steering mechanism so the lights will follow the movement of the front wheels. Czech Tatra and 1920s Cadillacs were early implementer of such a technique, producing in the 1930s a vehicle with a central directional headlamp. The American 1948 Tucker Sedan was likewise equipped with a third central headlamp connected mechanically to the steering system. The 1967 French Citroën DS and 1970 Citroën SM were equipped with an elaborate dynamic headlamp positioning system that adjusted the headlamps' horizontal and vertical positioning in response to inputs from the vehicle's steering and suspension systems, though US regulations required this system to be deleted from those models when sold in the USA.

Headlamp Advanced Front-lighting System (AFS)

There has been a recent resurgence in interest in the idea of moving or optimizing the headlight beam in response not only to vehicular steering and suspension dynamics, but also to ambient weather and visibility conditions, vehicle speed, and road curvature and contour. A task force composed primarily of European automakers, lighting companies and regulators began working to develop design and performance specifications for what is known as Advanced Front-lighting Systems, commonly "AFS". Manufacturers such as Audi and Lexus have released vehicles equipped with AFS since 2002. Rather than the mechanical linkages employed in earlier directional-headlamp systems, AFS relies on electronic sensors, transducers and actuators. Other AFS techniques include special auxiliary optical systems within a vehicle's headlamp housings. These auxiliary systems may be switched on and off as the vehicle and operating conditions call for light or darkness at the angles covered by the beam the auxiliary optics produce. Development is underway of AFS systems that use GPS signals to anticipate changes in road curvature.

Headlamp Care

Headlamps require very little care. Sealed beam headlamps are modular. When the filament burns out, the entire module is replaced. Most 1985 and later-model vehicles in North America use headlamp lens-reflector assemblies that are considered a part of the car, and just the bulb is replaced if it fails. Manufacturers vary the means by which the bulb is accessed and replaced.

Headlamp aim must be properly checked and adjusted on a regular, periodic basis. Misaimed lamps are dangerous and ineffective.

Over time, the front lens can deteriorate. It can become pitted due to abrasion of road sand and pebbles. It can become cracked, admitting water into the headlamp.

"Plastic" (polycarbonate) can become cloudy and discolored, turning yellowish. This is due to oxidation of the painted-on lens hardcoat by ultraviolet light from the sun and the headlamp bulbs. If it is minor, it can be polished out using a reputable brand of a car polish that is intended for restoring the shine to chalked paint. In more advanced stages, the deterioration extends through the actual plastic material, rendering the headlamp useless and necessitating complete replacement. Sanding or aggressively polishing the lenses can buy a small amount of time, but doing so removes the protective coating from the lens, which when so stripped will deteriorate faster and more severely.

The reflector, made out of extremely thin vaporized aluminum deposited on a metal, glass or plastic base, can become oxidized or burnt and lose its specular reflective properties. This can happen if water enters the headlamp, if bulbs of higher wattage than specified are used, or simply with age and use. If the reflector when viewed by itself is not mirror-perfect, the headlamp should be replaced, for reflectors cannot effectively be restored.

Headlamp Lens cleaners

RX350Dirt buildup on headlamp lenses increases glare to other road users, even at levels too low to reduce seeing performance significantly for the driver. Therefore, headlamp lens cleaners are required by ECE

Regulation 48 on vehicles equipped with low-beam headlamps using light sources that have a reference luminous flux of 2,000 lumens or more. This includes all HID headlamps and some high-power halogen units. Some cars have lens cleaners fitted as standard or available as optional equipment even where the headlamp specifications and/or prevailing technical regulations do not require them. North

America, for example, does not use ECE regulations, and FMVSS 108 does not require lens cleaners on any headlamps, though they are permitted. Lens cleaning systems come in two main varieties: a small motor-driven wiper blade or brush conceptually similar to those used on the windshield of the car, or a fixed or pop-up high-pressure sprayer which cleans the lenses with a spray of windshield washer fluid.

Kingpins

The kingpin is the main pivot in the steering mechanism of a car or other vehicle. Originally this was literally a steel pin on which the moveable, steerable wheel was mounted to the suspension. In newer designs, it may not be an actual pin but the axis around which the steered wheels pivot. It is usually made of metal.

There is a urban legend that Henry Ford once commissioned a survey of all scrap yards in America to see what parts on his Model T were holding up best against wear. When the results came back, it was determined that the part which rarely or never broke was the kingpin. He reduced the quality of this to meet all other parts, and thus he conserved money for the company.

The nipple at the front of a semi-trailer to connect to a fifth wheel coupling is also known as a king pin.

Mufflers

Muffler and exhaust pipe on a Ducati 695A muffler (or silencer in British English) is a device for reducing the amount of noise emitted by a machine. On internal combustion engines, the engine exhaust blows out through the muffler. The internal combustion engine muffler or silencer was developed in parallel with the firearm suppressor by Hiram Percy Maxim.

Muffler Description

Mufflers are typically installed along the exhaust pipe as part of the exhaust system of an internal combustion engine (of a vehicle, or stationary) to reduce its exhaust noise. The muffler accomplishes this with a resonating chamber, which is specifically tuned to cause destructive interference, where opposite sound waves cancel each other out.

Catalytic converters also often have a muffling effect.

Muffler Advantages

Mufflers that reduced backpressure relative to earlier models became increasingly available in the late 20th century, and resulted in increased engine efficiency, performance, power output, and simultaneously decreased overall wear and tear on the engines' components, as well as sound to levels in compliance with the law.

Types and positions of mufflers

With cars, lengthwise underneath, blowing backwards at the rear.

With large diesel-powered trucks:-

Mounted vertically behind the cab Crosswise under the front of the cab, blowing sideways.

With motorcycles

Sometimes nowadays, under the seat blowing backwards from under the back of the seat. Motorcycle enthusiasts sometimes use the term "raygun," or "pea-shooter" for the old shape of motorcycle exhaust silencer/muffler with a long straight cylindrical barrel that merged roundedly at each end into the pipe, as in this image and this image.

Odometers

A mechanical odometer with trip meter belowAn odometer (often known colloquially as a mileometer or milometer) is a device used for indicating distance traveled by an automobile or other vehicle. It may be electronic or mechanical. The word derives from the Greek words hodós, meaning 'path' or 'way', and métron, 'measure' (an older name for this device is hodometer).

Odometer Synopsis

Odometer rolloverMechanical odometers usually appear as a row of wheels with an edge of each wheel exposed to the driver. There are digits written on the edges of these wheels. A mask obscures these wheels from view, except for one row of digits which can be seen through a window in the mask.

An odometer is a device that stores the mileage(distance driven).

On older cars, odometers could only indicate up to a value of 99,999. At 100,000, the odometer would restart from zero. This is known as odometer rollover. Newer cars usually have odometers that can indicate up to a value of 999,999.

A common form of fraud is to tamper with the reading on an odometer, this is often referred to as 'clocking'. This is done to make a car appear to have been driven less than it really has been, and thus increase its apparent market value. Many new cars sold today use digital odometers that store the mileage in the vehicle's engine control module making it difficult (but not impossible) to manipulate the mileage electronically. With mechanical odometers, the speedometer can be removed from the car dash board and the digits wound back, or the drive cable can be disconnected and connected to another odometer/speedometer pair while on the road.

Most cars also include a trip meter, also referred to as a trip odometer. Unlike the odometer, a trip meter is designed to be reset at any desired point in a journey, making it possible to record the distance travelled in any particular journey or part of a journey. It was traditionally a purely mechanical device but, in most modern vehicles, it is now electronic. Most trip meters will show a maximum value of 999.9.

Odometer History

A Smiths speedometer from the 1920s showing odometer and trip meter. An electronic odometer with digital displayFor a detailed list of the recorded distances by Alexander's bematists, see Bematist.

Odometer Western world

Possibly the first evidence for the use of an odometer can be found in the works of Pliny (NH 6. 61-62) and Strabo (11.8.9). Both authors list the distances of routes traveled by Alexander the Great (r. 336-323 BC) as measured by his bematists Diognetus and Baeton. However, the high precision of the bematists's measurements rather indicates the use of a mechanical device. For example, the section between the cities Hecatompylos and Alexandria Areion, which later became a part of the silk road, was given by Alexander's bematists as 529 English miles long, that is with a deviation of 0.4% from the actual distance (531 English miles). From the nine surviving bematists' measurements in Pliny's Naturalis Historia eight show a deviation of less than 5% from the actual distance. Three of them even less than 1%. Since these minor discrepancies can be adequately explained by slight changes in the tracks of roads during the last 2300 years, the overall accuracy of the measurements implies that the bematists already must have used a sophisticated device for measuring distances, although there is no direct mentioning of such a device.

An odometer for measuring distance was first described by Vitruvius around 27 and 23 BC. The actual invention may have been by Archimedes of Syracuse during the First Punic War. Hero of Alexandria describes a similar device in chapter 34 of his Dioptra. The machine was also used in the time of Roman Emperor Commodus (c. 192 AD), although after this point in time there seems to be a gap between its use in Roman times and that of the 15th century in Western Europe.

The odometer of Vitruvius was based on chariot wheels of 4 feet (1.2 m) diameter turning 400 times in one Roman mile (about 1400 m). For each revolution a pin on the axle engaged a 400 tooth cogwheel thus turning it one complete revolution per mile. This engaged another gear with holes along the circumference, where pebbles (calculus) were located, that were to drop one by one into a box. The distance travelled would thus be given simply by counting the number of pebbles. Whether this instrument was ever built at the time is disputed. Leonardo da Vinci tried to build it according to the description but failed. Later, Ben Franklin invented his own version. Benjamin Franklin invented a simple odometer when he was going on trips in carriages. He wanted to know how far he was going, and the speed he was travelling.

Odometer China

The odometer was also later invented in ancient China, possibly by the profuse inventor and early scientist Zhang Heng (78-139 AD) of the Han Dynasty (202 BC-220 AD). Zhang Heng is often accredited with the invention of the first odometer device in China, an achievement alongside earlier contemporaries Archimedes and Heron of Alexandria from the Hellenized West. By the 3rd century (during the Three Kingdoms Period), the Chinese had termed the device as the 'jì li gu che', or 'li-recording drum carriage' (Note: the modern measurement of li = 500 m/1640 ft). Chinese texts of the 3rd century tell of the mechanical carriage's functions, and as one li is traversed, a mechanical-driven wooden figure strikes a drum, and when ten li is traversed, another wooden figure would strike a gong or a bell with its mechanical-operated arm.

The odometer was combined with the South Pointing Chariot (replica seen above) as early as the 9th century during the Tang Dynasty, and also in other models of the 11th and 12th centuries during the Song Dynasty.Despite its association with Zhang Heng or even the later Ma Jun, there is evidence to suggest that the invention of the odometer was a gradual process in Han Dynasty China that centered around the huang men court people (ie. eunuchs, palace officials, attendants and familiars, actors, acrobats, etc.) that would follow the musical procession of the royal 'drum-chariot'. The historian Joseph Needham asserts that it is no surprise this social group would have been responsible for such a device, since there is already other evidence of their craftsmenship with mechanical toys and such to delight the emperor and the court. There is speculation that some time in the 1st century BC (during the Western Han Dynasty), the beating of drums and gongs were mechanically-driven by working automatically off the rotation of the road-wheels. This might have actually been the design of one Loxia Hong (c. 110 BC), yet by 125 AD the mechanical odometer carriage in China was already known (depicted in a mural of the Xiao Tang Shan Tomb).

The odomoter was used also in subsequent periods of Chinese history. In the historical text of the Jin Shu (635 AD), the oldest part of the compiled text, the book known as the Cui Bao (c. 300 AD), recorded the use of the odometer, providing description (and interestingly enough attributing it to the Western Han era, from 202 BC-9 AD). The passage in the Jin Shu expanded upon this, explaining that it took a similar form to the mechanical device of the South Pointing Chariot invented by Ma Jun. As recorded in the Song Shi of the Song Dynasty (960-1279 AD), the odometer and South Pointing Chariot were combined into one wheeled device by engineers of the 9th century, 11th century, and 12th century (refer to South Pointing Chariot). The Sun Tzu Suan Ching (Master Sun's Mathematical Manual), dated from the 3rd century to 5th century, presented a mathematical problem for students involving the odometer. It involved a given distance between two cities, the small distance needed for one rotation of the carriage's wheel, and the posed question of how many rotations the wheels would have in all if the carriage was to travel between point A and B.

Odometer In full description

The historical text of the Song Shi (1345 AD), recording the people and events of the Chinese Song Dynasty (960-1279), also mentioned the odometer used in that period. However, unlike written sources of earlier periods, it provided a much more thoroughly detailed description of the device that harkens back to its ancient form (Wade-Giles spelling):

The odometer. The mile-measuring carriage is painted red, with pictures of flowers and birds on the four sides, and constructed in two storeys, handsomely adorned with carvings. At the completion of every li, the wooden figure of a man in the lower storey strikes a drum; at the completion of every ten li, the wooden figure in the upper storey strikes a bell. The carriage-pole ends in a phoenix-head, and the carriage is drawn by four horses. The escort was formerly of 18 men, but in the 4th year of the Yung-Hsi reign-period (987 AD) the emperor Thai Tsung increased it to 30. In the 5th year of the Thien-Sheng reign-period (1027 AD) the Chief Chamberlain Lu Tao-lung presented specifications for the construction of odometers as follows:

What follows is a long dissertation made by the Chief Chamberlain Lu Daolong on the ranging measurements and sizes of wheels and gears, along with a concluding description at the end of how the device ultimately functions:

The vehicle should have a single pole and two wheels. On the body are two storeys, each containing a carved wooden figure holding a drumstick. The road-wheels are each 6 ft in diameter, and 18 ft in circumference, one evolution covering 3 paces. According to ancient standards the pace was equal to 6 ft and 300 paces to a li; but now the li is reckoned as 360 paces of 5 ft each.

Note: the measurement of the Chinese-mile unit, the li, was changed over time, as the li in Song times differed from the length of a li in Han times.

The vehicle wheel (li lun) is attached to the left road-wheel; it has a diameter of 1.38 ft with a circumference of 4.14 ft, and has 18 cogs (chhih) 2.3 inches apart. There is also a lower horizontal wheel (hsia phing lun), of diameter 4.14 ft and circumference 12.42 ft, with 54 cogs, the same distance apart as those on the vertical wheel (2.3 inches). (This engages with the former.)

Upon a vertical shaft turning with this wheel, there is fixed a bronze "turning-like-the-wind wheel" (hsuan feng lun) which has (only) 3 cogs, the distance between these being 1.2 inches. (This turns the following one.) In the middle is a horizontal wheel, 4 ft in diameter, and 12 ft circumference, with 100 cogs, the distance between these cogs being the same as on the "turning-like-the-wind wheel" (1.2 inches).

Next, there is fixed (on the same shaft) a small horizontal wheel (hsiao phing lun) 3.3 inches in diameter and 1 ft in circumference, having 10 cogs 1.5 inches apart. (Engaging with this) there is an upper horizontal wheel (shang phing lun) having a diameter of 3.3 ft and a circumference of 10 ft, with 100 cogs, the same distance apart as those of the small horizontal wheel (1.5 inches).

When the middle horizontal wheel has made 1 revolution, the carriage will have gone 1 li and the wooden figure in the lower story will strike the drum. When the upper horizontal wheel has made 1 revolution, the carriage will have gone 10 li and the figure in the upper storey will strike the bell. The number of wheels used, great and small, is 8 inches in all, with a total of 285 teeth. Thus the motion is transmitted as if by the links of a chain, the "dog-teeth" mutually engaging with each other, so that by due revolution everything comes back to its original starting point (ti hsiang kou so, chhuan ya hsiang chih, chou erh fu shih).

Odometer Modern History

In modern times, Andre Sleeswyk was able to make a working model of an odometer using gears similar to the Antikythera mechanism as opposed to the traditional cogwheel.

The odometer as used in modern systems, where a separate gear controls each digit, was invented by William Clayton with help from Orson Pratt. Clayton, a Mormon Pioneer, developed the odometer (dubbed the "roadometer") to keep track of wheel revolutions on the pioneer wagons. The odometer had at least two gears, including one which turned every quarter-mile and one which turned every ten miles.

Odometer Law

The resale value of a vehicle is often strongly influenced by the number of miles or kilometres a passenger vehicle has on the odometer, yet odometers are inherently insecure because they are under the control of their owners. Many jurisdictions have chosen to enact laws which penalize people who are found to commit odometer fraud. In the US (and many other countries), vehicle maintenance workers are also required to keep records of the odometer any time a vehicle is serviced. Companies such as Carfax then use this data to help potential car buyers detect whether odometer rollback has occurred.

Odometer Sport

Odometers feature in some sports, both amateur and professional. Odometers designed for cycling help cyclists to determine distance cycled and often other information. (See cyclocomputer) Professional rally cars are usually equipped with a purpose-built odometer with an adjustable factor. This factor determines the number of wheel rotations in, say, one kilometre or one mile. Amateur rally cars are often also equipped with purpose-built adjustable odometers for regularity rallying.

Filter (oil)

'Cartridge' oil filter for use on a 2006 Volvo S40An oil filter is a device used to decontaminate oil that contains suspended impurities. A major application is in forming part of the lubrication system of engines in which filters are typically detachable units due to the need for regular service or replacement. The filtration of oil in engines is essential for enhancing longevity and performance.

Oil Filters in automobiles

Early automobile engines did not use any form of oil filtration. For this reason, along with the generally low standard of lubricating-oil refinement in the era, very frequent oil changes, of the order of every 500-1000 miles (800-1600 km) were often specified. The first oil filters were simple, generally consisting of a screen placed at the oil pump intake.

In 1923, Ernest Sweetland invented the original Purolator which is considered to be the first modern oil filter, featuring a more elaborate design as well as placement between the pump and the lubrication galleries of the engine. Although oil filter technology progressed over the years, as much as 90% of the oil bypassed the filter. The first 'full-flow' oil filter, introduced in 1943, was able to filter all of the oil emerging from the pump.

In 1954, WIX created the easily detachable 'spin-on' filter design which subsequently became a standard design. This type of filter is now used almost exclusively in modern passenger cars and in recent years, has gained use in heavy-duty vehicles. Oil quality and filtering capabilities have now advanced so far that some manufacturers such as Mobil sell engine oils and filters that claim to have up to a 15,000 mile change interval.

Types of oil filter

Mechanical

Mechanical designs employ a filtration element made up of layers of media, such as paper, to arrest various types of suspended contaminants. As material builds up on the filtration media, the efficiency of the filter is reduced and oil-flow is restricted. This requires the periodic replacement, or cleaning, of the filter or its media.

Bypass filters only act upon a portion of the engine oil flow, typically less than 10%, whereas those that filter the whole stream are known as full-flow filters. In some engine designs, a primary full-flow filter is accompanied by a secondary bypass filter, with the latter filtering particles too small for the primary. This dual-filter design can increase the time between subsequent servicing of the lubrication system.

Many full-flow mechanical filters incorporate an integrated pressure relief valve to allow a bypass mode. If the filtration element becomes completely clogged, this valve allows oil to bypass the filter, protecting the engine from oil starvation. The valve may also open in very cold conditions if a high viscosity oil is used.

There are two main designs for road-vehicle engines:

Cartridge filters have a housing that is bolted to the engine and a removable cartridge contains the filtration element. The advantage of only having to remove the filtration element is that the seal between the engine block and filter is not disturbed.

Spin-on filters attach directly to the side of the engine block by a threaded fitting. The main advantage is that used filters are easily removed and the whole thing is typically disposed of, but care must be taken not to over-tighten the new filter.

Cartridge filters are seen in several European and Asian car designs, whereas North American engine manufacturers generally favor the spin-on filter. Current examples of engine manufacturers that use cartridge filters include Mercedes-Benz, BMW, Volvo, Toyota (V6), Volkswagen, and Hyundai (V6). Ford's North American-market diesel V8 uses cartridge filters also. GM switched to using spin-on filters exclusively in 1960 for the North American market. However, GM has moved some of its engine designs such as the Ecotec family of 4 cylinder engines back to the cartridge type. Ease of recycling, minimization of waste, and reduction in trapped motor oil inside a disposed filter are often given as the reason for companies reverting to cartridge designs instead of spin-on filters.

Many vehicle manufacturers recommend replacing the filter each and every time the oil is changed while others such as Honda generally recommend changing the oil filter every other oil change.

Magnetic oil lilters

These use a permanent magnet, or an electromagnet, to capture particles, however only ferromagnetic contaminants can be filtered by this method. An advantage of magnetic filtration is that maintaining the filter simply requires one to wipe the magnet clean. High-performance engines and jet engines often have one or many 'mag plugs' which insert into the oil lines, however these are not specifically filters, but are inspected to test the wear of the engine.

Sedimentation Oil Filters

A sedimentation, or gravity bed, filter allows the heavier-than-oil contaminants to sink to the bottom of a container under the influence of gravity, filtering the oil in the process.

Centrifugal Oil Filter

The operation of this filter is a simple process that uses the oil pressure from the main oil pump. Pressurized oil enters the centre of the filter housing and passes into a "drum rotor". The drum rotor is free to turn about, as it rests on a bearing and seal assembly. The rotor also has two jet nozzles that are arranged to direct a stream of the pressurised oil at the inner housing in a manner that will make the drum rotate. The stream of oil will then slide to the bottom of the housing wall and in the process leave small particles struck to the inner walls. This particle build-up will eventually need to be cleaned. If left too long the particle thickness will be enough to stop the rotation of the drum thus forcing un-filtered oil to be re-circulated. Under usual circumstances, the clean oil will collect in the base of the filter lubricating the bearing, before draining to a convenient location for general lubrication of the engine. When maintaining this filter the engine must be switched off and a period of time allowed (see manufacturer's instructions) to make sure that the rotor is stationary before dismantling. After disassembly, the particles are cleaned off and the whole unit reassembled using a little clean engine oil to pre-lubricate the unit if necessary.

Oil Filters Uses

A chief use of the oil filter is in the reciprocating engine, typically found in automobiles and light aircraft and various naval vessels. Vehicles may have automatic transmission or demanding gearboxes that benefit from an oil filter. Additionally turbine engines, such as those on jet aircraft, require the use of oil filters. A multitude of industrial applications, such as mining equipment, generators, metalworking machinery, make use of oil filtration in some form. Of course the oil-production, oil-transmission and oil-recycling industries themselves employ filters.

Power generating stations use upwards of 40,000 gallons of turbine lube oil to lubricate large bearings. Hydraulic lines are used in industry for many purposes. All of this oil needs to be filtered and the level of filtration is much more stringent than that of standard automobile filtration. Industrial applications do not "change their oil" frequently as changing tens of thousands of gallons of oil at $10 a gallon quickly adds up. This is why much higher quality filters are usually used. Subsequently the cost for an industrial grade oil filter can be anywhere from $50 to $1000 (depending on size). You can not purchase an industrial grade filter and expect it to fit on your car, as these filters are sometimes 6" in diameter and upwards of 60" long. Nor would you want to, as in automobile filtration problems often result from the additives package breaking down, more so than particle contamination. Major players in industrial oil filtration are Pall, Donaldson, Parker, Kaydon, and Vickers. The industrial oil filtration market is full of retrofitted or will-fit filter elements. Every major manufacturer has a filter element that will fit in another manufacturers housing. Some manufacturers specialize in only retro-fitting other manufacturers filters elements, usually for 1/4 to 1/2 the cost.

Oil Filters Manufacturers

Major brands of oil filters available in the U.S. include FRAM (a Honeywell brand), WIX (an Affinia Group brand), Purolator (a joint venture of MANN+HUMMEL and Bosch), AC Delco (a General Motors brand) and Motorcraft (a Ford Motor Company brand). Some brands, such as Ford's Motorcraft and GM's AC-Delco, are manufactured by other companies (i.e. Purolator for Motorcraft) but are generally designed and quality tested by the brand selling them. Many of the brands manufacture filters for a wide variety of makes and models of vehicles. For instance, Motorcraft sells oil filters that fit GM, Chrysler, Honda, and Toyota vehicles, in addition to Fords. The manufacturer usually provides a list of what makes and models they supply filters for.

Oil Filters Comparisons

Some have argued that there is a major difference in quality of various oil filter brands, and some studies have proven it. Generally speaking, those branded by automotive manufacturers (such as Motorcraft and AC Delco as listed above) usually meet higher standards without costing significantly more than cheaper-made (and poorer performing) brands such as FRAM or Pennzoil brand. Very expensive brands such as Amsoil, Mobil and K&N perform excellently, but cost a lot more than traditional brands.

Many major auto parts stores (such as AutoZone, which sells the Valucraft brand and NAPA, which sells NAPA Select and NAPA Gold) offer their own brands of oil filters, but these are also made by other major oil filter makers.

Perhaps the largest original design manufacturer of filters in the U.S. is Champion Laboratories, which manufactures at least some of the SuperTech, AC Delco, Valucraft, and many other filters. STP (licensed from Clorox) and Champ are their own brands. Champion was also a major supplier to Bosch USA until Bosch bought an interest in the Purolator company.

Oil pump

An oil pump is a pump designed to supply pressurised oil to a closed system.

In automotive engineering, an oil pump is part of a lubrication system, transporting the oil to various moving parts inside the engine.

In hydraulics, the oil pump is used to deliver mechanical energy to remote actuators via tubes, pipes and hoses.

Oil pump Internal combustion engines

In an internal combustion engine, the oil pump is usually a gear pump driven by the camshaft or crankshaft. Oil pressure varies quite a bit during operation, with lower temperature and higher RPM's increasing pressure. To ensure that the oil pressure doesn't exceed the rated maximum, a spring-loaded pressure relief valve routes oil back to its source once pressure exceeds a preset limit.

Rack and pinion

Rack and pinion animationA rack and pinion is a pair of gears which convert rotational motion into linear motion. The circular pinion engages teeth on a flat bar - the rack. Rotational motion applied to the pinion will cause the rack to move to the side, up to the limit of its travel.

For example, in a rack railway, the rotation of a pinion mounted on a locomotive or a railcar engages a rack between the rails and pulls a train along a steep slope.

The rack and pinion arrangement is commonly found in the steering mechanism of cars or other wheeled, steered vehicles. This arrangement provides a lesser mechanical advantage than other mechanisms such as recirculating ball, but much less backlash and greater feedback, or steering "feel". The use of a variable rack was invented by Arthur E Bishop, so as to improve vehicle response and steering "feel" on-centre, and that has been fitted to many new vehicles, such as the 2008 Honda Accord, after he created a hot forging process to manufacture the racks, thus eliminating any subsequent need to machine the form of the gear teeth.

Enclosed steering rack in an automobileFor every pair of conjugate involute profile, there is a basic rack. This basic rack is the profile of the conjugate gear of infinite pitch radius.

A generating rack is a rack outline used to indicate tooth details and dimensions for the design of a generating tool, such as a hob or a gear shaper cutter.

For rack and pinion railways see Rack and pinion railway.

Radiators

One might expect the term "radiator" to apply to devices which transfer heat primarily by thermal radiation (see: infrared heating), while a device which relied primarily on natural or forced convection would be called a "convector". In practice, the term "radiator" refers to any of a number of devices in which a liquid circulates through exposed pipes (often with fins or other means of increasing surface area), notwithstanding that such devices tend to transfer heat mainly by convection and might logically be called convectors. The term "convector" refers to a class of devices in which the source of heat is not directly exposed.

Radiator Automobiles

A typical automobile coolant radiatorIn automobiles with a liquid-cooled internal combustion engine a radiator is connected to channels running through the engine and cylinder head, through which a liquid (coolant) is pumped. This liquid is typically a half-and-half mixture of water and ethylene glycol or propylene glycol (with a small amount of corrosion inhibitor) known as antifreeze. The radiator transfers the heat from the fluid inside to the air outside, thereby cooling the engine. Radiators are generally mounted in a position where they will receive airflow from the forward movement of the vehicle such as behind the grill.

Radiator Heater

A system of valves or baffles, or both, is usually incorporated to simultaneously operate a small radiator inside the car. This small radiator, and the associated blower fan, is called the heater core and serves to warm the cabin interior. Like the radiator, the heater core acts by removing heat from the engine. For this reason, mechanics often advise operators to turn on the heat if the engine is overheating.

Radiator Temperature control

The engine temperature is primarily controlled by a wax-pellet type of thermostat, a valve which opens once the engine has reached its minimum operating temperature. When the engine is cold the thermostat is closed. Coolant flows to the inlet of the circulating pump and is returned directly to the engine, bypassing the radiator. Directing water to circulate only through the engine allows heat to build up. One the coolant reaches the thermostat's activation temperature it opens, allowing water to flow through the radiator. Optimum operating temperature is maintained by the cyclic opening and closing of the thermostat valve.

Other factors influence the temperature of the engine including radiator size and the type of radiator fan. The size of the radiator (and thus its cooling capacity) is chosen such that it can keep the engine at the design temperature under the most extreme conditions a vehicle is likely to encounter (such as climbing a mountain while fully loaded on a hot day). On modern vehicles, further regulation of cooling rate is provided by either variable speed or cycling radiator fans. Electric fans are controlled by a thermostatic switch or the engine control unit. Pulley driven fans are often regulated by a friction-drive clutch which increases the fan speed when coolant temperature increases.

Radiator Coolant pressure

Because the thermal efficiency of internal combustion engines increases with internal temperature the coolant is kept at higher-than-atmospheric pressure to increase its boiling point. A calibrated pressure-relief valve is usually incorporated in the radiator's fill cap.

As the coolant expands with increasing temperature its pressure in the closed system must increase. Ultimately the pressure relief valve opens and excess fluid is dumped into an overflow container. Fluid overflow ceases when the thermostat modulates the rate of cooling to keep the temperature of the coolant at optimum. When the coolant cools and contracts (as conditions change or when the engine is switched off) the fluid is returned to the radiator through additional valving in the cap.

Radiator Boiling or overheating

On this type system, if the coolant in the overflow container gets too low, fluid transfer to overflow will cause an increased loss by vaporizing the engine coolant.

Severe engine damage can be caused by overheating, by overloading or system defect, when the coolant is evaporated to a level below the water pump. This can happen without warning because, at that point, the sending units are not exposed to the coolant to indicate the excessive temperature.

To protect the unwary the cap often contains a mechanism that attempts to relieve the internal pressure before the cap can be fully opened. Some scalding of one's hands can easily occur in this event. Opening a hot radiator drops the system pressure immediately and normally causes a sudden eruption of super-heated coolant which can cause severe burns (see geyser).

Radiator History

The invention of the automobile water radiator is attributed to Karl Benz. Wilhelm Maybach designed the first honeycomb radiator for the Mercedes 35hp.

Supplementary radiators

Some engines have an oil cooler, a separate small radiator to cool the engine oil. Cars with an automatic transmission often have extra connections to the radiator, allowing the transmission fluid to transfer its heat to the coolant in the radiator.

Turbo charged or supercharged engines may have an intercooler, which is an air-to-air or air-to-water radiator used to cool the incoming air charge not to cool the engine.

Radiator Buildings

A cast iron household radiatorIn buildings a radiator is a heating device, which is warmed by steam from a boiler, or by hot water being pumped through it from a water heater (usually, if not quite accurately, referred to as a "boiler").

Such radiators transfer the majority of their heat by radiation and by convection.

Conventional radiators

A conventional hot-water radiator consists of a sealed hollow metal container, usually flat in shape. Hot water enters at the top of the radiator by way of pressure, from a pump elsewhere in the building, or by convection.

As it gives out heat the hot water cools and sinks to the bottom of the radiator and is forced out of a pipe at the other end. The pipe either has a large surface area or attached fins to increase its surface area and therefore contact with surrounding air. The air near a radiator is then heated and produces a convection current in the room drawing in cold air to heat.

If set up improperly, radiators, and their supply and return pipes, can make loud banging noises like someone hammering on the pipes. This is due to either the pipes rubbing on surrounding surfaces while expanding and contracting due to heat changes or to sudden fluctuations of the supplied water pressure. Proper mounting of the radiators and supply pipes will reduce expansion noises, while upward-mounted stub ends with a trapped bubble of air (not interfering with flow, as would an un-bled radiator) will provide a cushion against pressure fluctuations, an anti-hammer device.

Stereotypical cast iron radiators (as pictured) are no longer common in new construction, replaced mostly with copper pipes which have aluminum fins to increase their surface area. In the U.K., modern domestic radiators tend to be of sheet steel construction (often with steel fins), though copper/aluminium is often found in industrial Air Handling System heat exchangers.

The radiator was invented in 1855 by Franz SanGalli. He was the first to produce a system of central heating and patented his invention in Germany and the US.

There are many designs and varieties of radiators, from conventional to modern style. Radiators are sometimes seen as an art form, much like sculpture.

Radiator Steam

Single-pipe steam radiatorSteam has the advantage of flowing through the pipes under its own pressure without the need for pumping. For this reason, it was adopted earlier, before electric motors and pumps became available. Steam is also far easier to distribute than hot water throughout large, tall buildings like skyscrapers. However, the higher temperatures at which steam systems operate make them inherently less efficient, as unwanted heat loss is inevitably greater.

Steam pipes and radiators are also prone to producing banging sounds (known as "water hammer") if condensate fails to drain properly; this is often caused by buildings settling and the resultant pooling of condensate in pipes and radiators that no longer tilt slightly back towards the boiler.

Fan assisted radiators

A more recent type of heater used in homes is the fan assisted radiator. It contains a heat exchanger fed by hot water from the heating system. A thermostatic switch senses the heat and energises an electric fan which blows air over the heat exchanger.

Advantages of this type of heater are its small size and even distribution of heat around the room. Disadvantages are the noise produced by the fan, and the need for an electricity supply.

Radiator Underfloor heating

During construction, tubing is placed on the floor throughout the room, and later covered with a concrete layer.The current trend in radiant heating is towards underfloor heating, where warm water is circulated under the entire floor of each room in a building. A network of pipes, tubing or heating cables is buried in the floor, and a gentle heat rises into the room. Because of the large area of this type of radiator, the floor only needs to be heated a few degrees above the desired room temperature, and as a result, convection is almost non-existent. These systems are reputed to have a high level of comfort, but are generally difficult to install into existing buildings. For best results, a floor covering that conducts heat well (such as tiles) should be used.

The hypocaust was a Roman heating system using a similar principle of operation.

Radiator Bleeding

All "radiant" (ie. heat radiates from hot water) systems need to be bled, or purged of air, on occasion.

If there is air (or other gases such as Hydrogen) trapped inside the radiator, then the water cannot rise to the top, and only the bottom area gets hot. A bleed screw near the top of the radiator allows the trapped air to be 'bled' from the system, and thus restore correct operation. Often radiators located on upper floors will accumulate more air than ones on lower floors as the air will tend to rise to the topmost point in the system. These may have to be bled more often. Usually radiators are bled once or twice per season, or as needed. Another reason to exclude air is to minimise corrosion of the steel pressed radiators. Note that most central heating systems need a corrosion inhibitor added into the circulating hot water, so that the production of Hydrogen is minimised. This is created in untreated systems, by the action of the hot water on the iron in the absence of air (stripping off the oxygen atom to leave hydrogen as H2 when iron oxide is created). Note that if air is getting into the radiators frequently, this may be the sign of a leak somewhere, such as a dripping valve, or loose joint.

Radiator Electronics

In electronics, a radiator is also known as a radiating element. Radiating elements are a basic subdivision of an antenna. Radiating elements are capable of transmitting or receiving electromagnetic energy.

Rear-view mirrors

The rear-view mirror of a Mazda 626. It shows cars parked behind it.

A rear-view mirror (or sometimes, rear-vision mirror in British English) is a functional type of mirror found on automobiles and other vehicles, designed to allow the driver to see the area behind the vehicle through the back window.

Rear-view mirrors are sometimes confused with side-view mirrors, a different type of mirror found on the left- and right-hand sides of most modern vehicles. Though these mirrors do face backwards, they are meant to show the driver the traffic to the left- and right-hand sides of the automobile. Inside rear-view mirrors (and driver-side side-view mirror) are specifically mandated by legislation to have "unit magnification" and thus are not convex. The driver is close enough to both these mirrors for simple head motion to be sufficient significantly to expand the field of view. The passenger side side-view mirror is far enough away for the field of view to be fixed, despite movement of the driver and a convex mirror is desirable to expand the field of view.

Typically, the rear-view mirror is affixed to the top of the windscreen on a swivel mount allowing it to be freely rotated. Certain car models have the rear-view mirror mounted on top of the dashboard. When adjusting the mirror, it is advised to sit in the driver's seat in the same manner that you will be sitting while driving. Their utility may be diminished in cars with large spoilers or tiny back windows, obstructions in the back seat or trailer. Vanity mirrors attached to sun visors do not meet the adjustment requirements of rear-view mirrors and cannot be used as such. Inside rear-view mirrors are designed to break away upon collision to minimize injury to occupants who are thrown against it.

Rear-view mirror History

Ray Harroun's Marmon "Wasp" with its rear-view mirror mounted on struts above the car on display in the Indianapolis Motor Speedway Hall of Fame Museum.Although many people imagine the rear-view mirror was designed for safety, in fact its origins are much more varied. The earliest known use and mention of a rear view mirror is by Dorothy Levitt in her 1906 book The Woman and the Car which noted that women should "carry a little hand-mirror in a convenient place when driving" so they may "hold the mirror aloft from time to time in order to see behind while driving in traffic" therefore inventing the rear view mirror before it was introduced by manufacturers in 1914. The earliest known semblance of a rear-view mirror mounted on a motor vehicle appeared in Ray Harroun's Marmon racecar at the inaugural Indianapolis 500 race in 1911. According to Al Binder of Ward's Auto World:

As per the custom of the day, all cars except Harroun's carried riding mechanics who, among other things, helped the driver keep track of other vehicles during the race. Unable to find a mechanic to ride with him, Harroun installed a mirror on his car so he could view what was happening behind him and be alert to any cars overtaking him. Automotive historians credit this as the first use of a rear view mirror on an automobile. Although Harroun's use is the first known use of such a mirror on a motor vehicle, Harroun himself claimed he got the idea from seeing a mirror used for the same purpose on a horse-drawn vehicle in 1904.

The invention seems to have worked Harroun won the race, netting a US$14,250 prize, equivalent to about US$270,000 in 2003 dollars.

However, the rear-view mirror had to wait for Elmer Berger, the man usually credited with inventing the rear-view mirror, to first develop them for street use.

Power mirrors

Side-view mirrors have the mirror's face mounted on a swivel, while the encasement is usually fixed. They are adjusted by various devices, ranging from simple direct manipulation of the mirror to sticks or knobs inside the vehicle to motorized controls inside the vehicle ("power mirrors").

In many modern vehicles (e.g. Saab 9-5), the side-view mirrors can be power-adjusted and are linked into the electrically adjustable driver's seat memory controls, so that different drivers can store individual settings, restoring them at the push of a button. This same model has an extra control, for depressing the passenger door mirror (for viewing the curb when parking) and a further control for retracting the side-view mirrors, out of harm's way, when entering a very narrow space or when leaving the car parked.

Rear-view mirror Cameras

Some cars (i.e. Mazda Hakaze Concept) have cameras instead of mirrors.

Rear-view mirror Augmentations and alternatives

Recently, rear-view video cameras have been built into many new model cars. This was partially in response to the rear-view mirrors' inability to show the road directly behind the car, due to the rear deck or trunk obscuring as much as 3-5 metres (10-15 feet) of road behind the car. For example, as many as 50 times a year, small children are killed by SUVs in America because the driver cannot see them in their rear-view mirrors. These camera systems are usually mounted to the bumper or lower parts of the car allowing for better rear visibility. In addition, rear-facing sonar arrays and back up beepers help avoid accidents while reversing.

Aftermarket secondary rear-view mirrors are available. They attach to the main rear-view mirror and are independently adjustable to view the back-seat. This is useful to parents to monitor their children in the backseat.

Aftermarket mirrors can be attached as extensions to the door mirrors, that allow a driver to see behind when towing a caravan.

A similar device can be fitted to the rear of a van or SUV, to allow viewing down behind the vehicle, for close parking.

Rear-view mirror Dimming

A traditional rear-view mirror can be tilted to reduce the brightness and glare of lights, mostly for headlights shining directly on the eye level at night. This manual tilt mirror is made of a piece of glass that is wedge-shaped in cross section it's front side and back (silvered) side are not parallel, unlike normal mirror glass. In the default day view, the front side is tilted and the back side (which has a reflective coating, usually with silver like a mirror) is head-on and will give a strong reflection. When the mirror is tilted, its front side is head-on and the back is tilted. This view is actually a reflection off the clear, front piece of the glass rather than the back silver-coated part. Since the front part allows most of the light to go through, only a small amount of light is now reflected into the driver's eyes.

Some rear-view mirrors have electronic auto-dimming features built in (mirrors with automatic anti-glare function) while others are adjustable so that a lower light level setting may be used. Because of this it is advisable to set the darker setting to be aimed lower in the car than the lighter setting. This is mostly because at night when you readjust the mirror to use the darker setting the lighter angles will be pointed to the lower contrast roof of the vehicle instead of the higher contrast areas such as the backs of the seats.

Rear-view mirror Bicycles

Some bicycles have rearview mirrors. However, motorcycles carry that feature more frequently than pedal bikes.

Rear-view mirror In art

In modern art, particularly music and poetry, the rear-view mirror has become a common metaphor for reflecting upon the past, whether upon one's own memories or a time even more distant. For example, Jane Sequoya's "Scene Through the Rear-View Mirror" expresses a woman's regret for a lost love partly by comparison with the lost Native American people of the prairies.

In popular music, artists ranging from Alicia Keys to Meat Loaf to the Starland Vocal Band as well as Pearl Jam have written songs with "Rear View Mirror" in the title. The metaphor is particularly prominent in country music, where it is featured in hits such as Jo Dee Messina's "Bye Bye", Chely Wright's "Shut Up and Drive", Doug Supernaw's "She Never Looks Back", and Julie Roberts' "Break Down Here". Also another song it is used in is Tupac Shakur's "Starin' Through My Rearview", featured in the film Gang Related.

Spark plugs

A spark plug (also, very rarely nowadays, in British English: a sparking plug) is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark. Spark plugs have an insulated center electrode which is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder. Early patents for spark plugs included those by Nikola Tesla (in U.S. Patent 609,250 for an ignition timing system, 1898), Richard Simms (GB 24859/1898, 1898) and Robert Bosch (GB 26907/1898). Karl Benz is also credited with the invention. But only the invention of the first commercially viable high-voltage spark plug as part of a magneto-based ignition system by Robert Bosch's engineer Gottlob Honold in 1902 made possible the development of the internal combustion engine.

Internal combustion engines can be divided into spark-ignition engines, which require spark plugs to begin combustion, and compression-ignition engines (diesel engines), which compress the air and then inject diesel fuel into the heated compressed air mixture where it autoignites. Compression-ignition engines may use glow plugs to improve cold start characteristics.

Spark plugs may also be used in other applications such as furnaces where a combustible mixture should be ignited. In this case, they are sometimes referred to as flame igniters.

Spark plug Operation

Components of a typical, four stroke cycle, DOHC piston engine. (E) Exhaust camshaft, (I) Intake camshaft, (S) Spark plug, (V) Valves, (P) Piston, (R) Connecting rod, (C) Crankshaft, (W) Water jacket for coolant flow.The plug is connected to the high voltage generated by an ignition coil or magneto. As the electrons flow from the coil, a voltage difference develops between the center electrode and side electrode. No current can flow because the fuel and air in the gap is an insulator, but as the voltage rises further, it begins to change the structure of the gases between the electrodes. Once the voltage exceeds the dielectric strength of the gases, the gases become ionized. The ionized gas becomes a conductor and allow electrons to flow across the gap.

As the current of electrons surges across the gap, it raises the temperature of the spark channel to 60,000 K. The intense heat in the spark channel causes the ionized gas to expand very quickly, like a small explosion. This is the "click" heard when observing a spark, similar to lightning and thunder.

The heat and pressure force the gases to react with each other, and at the end of the spark event there should be a small ball of fire in the spark gap as the gases burn on their own. The size of this fireball or kernel depends on the exact composition of the mixture between the electrodes and the level of combustion chamber turbulence at the time of the spark. A small kernel will make the engine run as though the ignition timing was retarded, and a large one as though the timing was advanced.

Spark plug construction

Diagram of single-ground spark plug (the bottom hook "side electrode" is the single ground electrode).A spark plug is composed of a shell, insulator and the conductor. It pierces the wall of the combustion chamber and therefore must also seal the combustion chamber against high pressures and temperatures, without deteriorating over long periods of time and extended use.

Parts of the spark plug

Spark plug Terminal

The top of the spark plug contains a terminal to connect to the ignition system. The exact terminal construction varies depending on the use of the spark plug. Most passenger car spark plug wires snap onto the terminal of the plug, but some wires have spade connectors which are fastened onto the plug under a nut. Plugs which are used for these applications often have the end of the terminal serve a double purpose as the nut on a thin threaded shaft so that they can be used for either type of connection. These are a necessary part of the spark plug.

Spark plug Ribs

By lengthening the surface between the high voltage terminal and the grounded metal case of the spark plug, the physical shape of the ribs functions to improve the electrical insulation and prevent electrical energy from leaking along the insulator surface from the terminal to the metal case. The disrupted and longer path makes the electricity encounter more resistance along the surface of the spark plug even in the presence of dirt and moisture.

Spark plug Insulator

The insulator is typically made from an aluminium oxide ceramic and is designed to withstand 550 °C and 60,000 V. It extends from the metal case into the combustion chamber. The exact composition and length of the insulator partly determines the heat range of the plug.

Spark plug Seals

As the spark plug also seals the combustion chamber of the engine when installed, the seals ensure there is no leakage from the combustion chamber. The seal is typically made by the use of a multi-layer braze as there are no braze compositions that will wet both the ceramic and metal case and therefore intermediary alloys are required.

Spark plug Metal case

The metal case (or the "jacket" as many people call it) of the spark plug bears the torque of tightening the plug, serves to remove heat from the insulator and pass it on to the cylinder head, and acts as the ground for the sparks passing through the center electrode to the side electrode. As it acts as the ground, it can be harmful if touched while igniting.

Spark plug Insulator tip

The tip of the insulator surrounding the center electrode is within the combustion chamber and directly affects the spark plug performance, particularly the heat range.

Spark plug Side electrode, or ground electrode

The side electrode is made from high nickel steel and is welded to the side of the metal case. The side electrode also runs very hot, especially on projected nose plugs. Some spark plug designs use multiple side electrodes that do not overlap the center electrode.

Spark plug Center electrode

The center electrode is connected to the terminal through an internal wire and commonly a ceramic series resistance to reduce emission of radio noise from the sparking. The tip can be made of a combination of copper, nickel-iron, chromium, or precious metals. In the late seventies, the development of engines reached a stage where the ‘heat range’ of conventional spark plugs with solid nickel alloy centre electrodes was unable to cope with their demands. A plug that was ‘cold’ enough to cope with the demands of high speed driving would not be able to burn off the carbon deposits caused by stop-start urban conditions, and would foul in these conditions, making the engine misfire. Similarly, a plug that was ‘hot’ enough to run smoothly in town, could actually melt when called upon to cope with extended high speed running on motorways, causing serious damage to the engine. The answer to this problem, devised by the spark plug manufacturers, was a centre electrode that carried the heat of combustion away from the tip more effectively than was possible with a solid nickel alloy. Copper was the material chosen for the task and a method for manufacturing the Copper cored center electrode was created by Floform.

The center electrode is usually the one designed to eject the electrons (the cathode) because it is the hottest (normally) part of the plug; it is easier to emit electrons from a hot surface, because of the same physical laws that increase emissions of vapor from hot surfaces (see Thermionic emission). In addition, electrons are emitted where the electrical field strength is greatest; this is from wherever the radius of curvature of the surface is smallest, i.e. from a sharp point or edge rather than a flat surface (see Corona discharge). It would be easiest to pull electrons from a pointed electrode but a pointed electrode would erode after only a few seconds. Instead, the electrons emit from the sharp edges of the end of the electrode; as these edges erode, the spark becomes weaker and less reliable.

At one time it was common to remove the spark plugs, clean deposits off the ends either manually or with specialized sandblasting equipment and file the end of the electrode to restore the sharp edges, but this practice has become less frequent as spark plugs are now merely replaced, at much longer intervals. The development of precious metal high temperature electrodes (using metals such as yttrium, iridium, platinum, tungsten, or palladium, as well as the relatively prosaic silver or gold) allows the use of a smaller center wire, which has sharper edges but will not melt or corrode away. The smaller electrode also absorbs less heat from the spark and initial flame energy. At one point, Firestone marketed plugs with polonium in the tip, under the questionable theory that the radioactivity would ionize the air in the gap, easing spark formation. (See external link below)

Spark plug gap

Spark plug gapping: The center electrode (dark rod) is a cylindrical rod, and the top ground electrode (a hook) has square edges. When regapping, the hook is raised or lowered to adjust the gap, often .035-.050.

Gap gauge: A disk with sloping edge; the edge is thicker going counter-clockwise, and a spark plug will be hooked along the edge to check the gap.Spark plugs are typically designed to have a spark gap which can be adjusted by the technician installing the spark plug, by the simple mechanism of bending the ground electrode slightly to bring it closer to or further from the center electrode. The belief that plugs are properly gapped as delivered in their box from the factory is only partially true, as proved by the fact that the same plug may be specified for several different engines, requiring a different gap for each. It can depend on the engine: new spark plugs might be pre-gapped for a V-8 engine, installing all 8 plugs unchanged; however, for a 6-cylinder engine, all (6) plugs would be re-gapped.

A spark plug gap gauge as a disk with a sloping edge, or with round wires of precise diameters, is used to measure the gap; use of a feeler gauge with flat blades instead of round wires, as is used on distributor points or valve lash, will give erroneous results, due to the shape of spark plug electrodes. The simplest gauges are a collection of keys of various thicknesses which match the desired gaps and the gap is adjusted until the key fits snugly. With current engine technology, universally incorporating solid state ignitions and computerized fuel injection, the gaps used are much larger than in the era of carburetors and breaker point distributors, to the extent that spark plug gauges from that era are much too small for measuring the gaps of current cars.

The gap adjustment can be fairly critical, and if it is maladjusted the engine may run badly, or not at all. A narrow gap may give too small and weak a spark to effectively ignite the fuel-air mixture, while a gap which is too wide might prevent a spark from firing at all. Either way, a spark which only intermittently fails to ignite the fuel-air mixture may not be noticeable directly, but will show up as a reduction in the engine's power and fuel efficiency. The main issues about spark plug gaps are:

Spark plug eroded: note the center electrode (dark bump) had been a cylindrical rod, and the top ground electrode (like a claw) formerly had square edges.As a plug ages, and the metal of both the tip and hook erode, the gap will tend to widen; therefore experienced mechanics often set the gap on new plugs at the engine manufacturer's minimum recommended gap, rather than in the center of the specified acceptable range, to ensure longer life between plug changes. On the other hand, since a larger gap gives a "hotter" or "fatter" spark and more reliable ignition of the fuel-air mixture, and since a new plug with sharp edges on the center electrode will spark more reliably than an older, eroded plug, experienced mechanics also realize that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs; therefore, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace and/or regap the plugs much more frequently, as soon as the tip begins to erode.

Spark plug Variations on the basic design

Over the years variations on the basic spark plug design have attempted to provide either better ignition, longer life, or both. Such variations include the use of two, three, or four equally spaced ground electrodes surrounding the center electrode. Other variations include using a recessed center electrode surrounded by the sparkplug thread, which effectively becomes the ground electrode. Also there is the use of a V-shaped notch in the tip of the ground electrode.

Spark plug Sealing to the cylinder head

Most spark plugs seal to the cylinder head with a hollow metal washer which is crushed slightly between the flat surface of the head and that of the plug, just above the threads. If the torque used to install the plugs is not excessive, the washer can be reused when the plug is removed and reinserted, although this practice is, strictly speaking, not recommended and replacement washers are available.

Ford engines, however, were once distinct in using a tapered hole and a matching taper on the bottom of the plug above the threads, in order to seal the plug. The torque for installing and removing these plugs was higher and it was easier to break them if the wrench were applied partially off axis.

More recently, some types of Ford Fiesta, and Ka also had a similar sealing system. The torque required to install these plugs is less than with the above type, and it is extremely critical that they not be overtightened, since overtightening can result in it being difficult or impossible to remove them. In addition, they have been known to corrode into the cylinder head, particularly if left in too long between removals. In such a situation, it is not unknown for a plug to snap below the hexagonal nut, leaving just the threaded portion (and the outer electrode) in the cylinder head. Ford has on occasion issued Technical Service Bulletins reminding technicians to use the correct methods of installation.

Spark plug Tip protrusion

Three different sizes of spark plug. The leftmost plug and right plug are identical in threading, electrodes, tip protrusion, and heat range. The center plug is a compact variant, with smaller hex and porcelain portions outside the head, to be used where space is limited. The rightmost plug has a longer threaded portion, to be used in a thicker cylinder headThe length of the threaded portion of the plug should be closely matched to the thickness of the head. If a plug extends too far into the combustion chamber, it may be struck by the piston, damaging the engine internally. Less dramatically, if the threads of the plug extend into the combustion chamber, the sharp edges of the threads act as point sources of heat which may cause preignition; in addition, deposits which form between the exposed threads may make it difficult to remove the plugs, even damaging the threads on aluminium heads in the process of removal. The protrusion of the tip into the chamber also affects plug performance, however; the more centrally located the spark gap is, generally the better the ignition of the air-fuel mixture will be, although experts believe the process is actually much more complex and dependent on combustion chamber shape. On the other hand, if an engine is "burning oil", the excess oil leaking into the combustion chamber tends to foul the plug tip and inhibit the spark; in such cases, a plug with less protrusion than the engine would normally call for often collects less fouling and performs better, for a longer period. In fact, special "antifouling" adapters are sold which fit between the plug and the head to reduce the protrusion of the plug for just this reason, on older engines with severe oil burning problems; this will cause the ignition of the fuel-air mixture to be less effective, but in such cases, this is of lesser significance.

Spark plug Heat range

The operating temperature of a spark plug is the actual physical temperature at the tip of the spark plug within the running engine. This is determined by a number of factors, but primarily the actual temperature within the combustion chamber. There is no direct relationship between the actual operating temperature of the spark plug and spark voltage. However, the level of torque currently being produced by the engine will strongly influence spark plug operating temperature because the maximum temperature and pressure occurs when the engine is operating near peak torque output (torque and RPM directly determine the power output). The temperature of the insulator responds to the thermal conditions it is exposed to in the combustion chamber but not vice versa. If the tip of the spark plug is too hot it can cause pre-ignition leading to detonation/knocking and damage may occur. If it is too cold, electrically conductive deposits may form on the insulator causing a loss of spark energy or the actual shorting-out of the spark current.

A spark plug is said to be "hot" if it is a better heat insulator, keeping more heat in the tip of the spark plug. A spark plug is said to be "cold" if it can conduct more heat out of the spark plug tip and lower the tip's temperature. Whether a spark plug is "hot" or "cold" is known as the heat range of the spark plug. The heat range of a spark plug is typically specified as a number, with some manufacturers using ascending numbers for hotter plugs and others doing the opposite, using ascending numbers for colder plugs.

The heat range of a spark plug (i.e. in scientific terms its thermal conductivity characteristics) is affected by the construction of the spark plug: the types of materials used, the length of insulator and the surface area of the plug exposed within the combustion chamber. For normal use, the selection of a spark plug heat range is a balance between keeping the tip hot enough at idle to prevent fouling and cold enough at maximum power to prevent pre-ignition leading to engine knocking. By examining "hotter" and "cooler" spark plugs of the same manufacturer side by side, the principle involved can be very clearly seen; the cooler plugs have more substantial ceramic insulators filling the gap between the center electrode and the shell, effectively carrying off the heat, while the hotter plugs have less ceramic material, so that the tip is more isolated from the body of the plug and retains heat better.

Heat from the combustion chamber escapes through the exhaust gases, the side walls of the cylinder and the spark plug itself. The heat range of a spark plug has only a minute effect on combustion chamber and overall engine temperature. A cold plug will not materially cool down an engine's running temperature. (Too hot of a plug may, however, indirectly lead to a runaway pre-ignition condition that can increase engine temperature.) Rather, the main effect of a "hot" or "cold" plug is to affect the temperature of the tip of the spark plug.

It was common before the modern era of computerized fuel injection to specify at least a couple of different heat ranges for plugs for an automobile engine; a hotter plug for cars which were mostly driven mildly around the city, and a colder plug for sustained high speed highway use. This practice has, however, largely become obsolete now that cars' fuel/air mixtures and cylinder temperatures are maintained within a narrow range, for purposes of limiting emissions. Racing engines, however, still benefit from picking a proper plug heat range. Very old racing engines will sometimes have two sets of plugs, one just for starting and another to be installed once the engine is warmed up, for actually driving the car.

Spark plug Reading spark plugs

The spark plug's firing end will be affected by the internal environment of the combustion chamber. As the spark plug can be removed for inspection, the effects of combustion on the plug can be examined. An examination, or "reading" of the characteristic markings on the firing end of the spark plug can indicate conditions within the running engine. The spark plug tip will bear the marks as evidence of what is happening inside the engine. Usually there is no other way to know what is going on inside an engine running at peak power. Engine and spark plug manufacturers will publish information about the characteristic markings in spark plug reading charts (e.g. a general spark plug reading chart)

A light brownish discoloration of the tip of the block indicates proper operation; other conditions may indicate malfunction. For example, a sandblasted look to the tip of the spark plug means persistent, light detonation is occurring, often unheard. The damage that is occurring to the tip of the spark plug is also occurring on the inside of the cylinder. Heavy detonation can cause outright breakage of the spark plug insulator and internal engine parts before appearing as sandblasted erosion but is easily heard. As another example, if the plug is too cold, there will be deposits on the nose of the plug. Conversely if the plug is too hot, the porcelain will be porous looking, almost like sugar. The material which seals the center electrode to the insulator will boil out. Sometimes the end of the plug will appear glazed, as the deposits have melted.

An idling engine will have a different impact on the spark plugs than one running at full throttle. Spark plug readings are only valid for the most recent engine operating conditions and running the engine under different conditions may erase or obscure characteristic marks previously left on the spark plugs. Thus, the most valuable information is gathered by running the engine at high speed and full load, immediately cutting the ignition off and stopping without idling or low speed operation and removing the plugs for reading.

Spark plug reading viewers, which are simply combined flashlight/magnifiers, are available to improve the reading of the spark plugs.

Two spark plug viewersOnce again, however, the practice of reading spark plugs has largely become obsolete now that cars' fuel/air mixtures and cylinder temperatures are maintained within a narrow range, but is still valuable for racing applications.

Spark plug Indexing spark plugs

A matter of some debate is the "indexing" of plugs upon installation, usually only for high performance or racing applications; this involves installing them so that the open area of the spark gap, not shrouded by the ground electrode, faces the center of the combustion chamber, towards the intake valve, rather than the wall. Many experts believe that this will maximize the exposure of the fuel-air mixture to the spark, and therefore result in better ignition; others, however, believe that this is useful only to keep the ground electrode out of the way of the piston in ultra-high-compression engines if clearance is insufficient. In any event, this is accomplished by marking the location of the gap on the outside of the plug, installing it, and noting the direction in which the mark faces; then the plug is removed and additional washers are added so as to change the orientation of the tightened plug. This must be done individually for each plug, as the orientation of the gap with respect to the threads of the shell is random.

Speedometers

Speedometer gauge on a car, showing the speed of the vehicle in kilometres per hour. Also shown is the tachometer, which displays the rate of rotation of the engine's crankshaft.A speedometer is a vehicle instrument that measures the instantaneous speed.

Traditional automotive speedometers are driven by a flexible, sleeved cable that is rotated by a set of small gears in the tail shaft of a transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.

The most common form of speedometer relies on the interaction of a small permanent magnet affixed to the rotating cable with a small aluminum cup affixed to the shaft of the pointer. As the magnet rotates near the cup, the changing magnetic field produces eddy currents in the cup, which themselves produce another magnetic field. The effect is that the magnet 'drags' the cup--and thus the speedometer pointer--in the direction of its rotation with no mechanical connection between them.

The pointer shaft is held toward zero by a fine spring. The torque on the cup increases with the speed of rotation of the magnet (which, recall, is driven by the car's transmission.) Thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. When the torque due to the eddy currents in the cup equals that provided by the spring on the pointer shaft, the pointer will remain motionless and pointing to the appropriate number on the speedometer's dial.

The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tailshaft gears that drive the flexible cable, the final drive ratio in the differential, and the diameter of the driven tires. The speedometer mechanism often also drives an odometer plus a small switch that sends pulses to the vehicle's engine computer.

Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the car's wheel or transmission. The watch mechanism endeavors to push the speedometer pointer toward zero, while the vehicle-driven pulsator tries to push it toward infinity. The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms.

The speedometer was invented by Josip Beluic of Croatia in 1888. Modern speedometers are electronic. A rotation sensor, usually mounted on the rear of the transmission, delivers a series of electronic pulses whose frequency corresponds to the rotational speed of the driveshaft. A computer converts the pulses to a speed and displays this speed on an electronically-controlled, analog-style needle or a digital display, the latter of which is more common nowadays. Pulse counts may also be used to increment the odometer.

As of 1997, federal standards in the United States allowed a maximum 5% error on speedometer readings (per "Auto Tutor", American Automobile Association of California magazine, Oct. 17, 1997). Aftermarket modifications, such as different tire and wheel sizes or different differential gearing, can cause speedometer inaccuracy.

Speedometer Error

Speedometers are not totally accurate, and most speedometers have tolerances of some 10% plus or minus due to wear on tires as it occurs. Modern speedometers are said to be accurate within 5% but as this is legislated accuracy, this may not be entirely correct. This can make it difficult to accurately stay on the speed limits imposed; most countries allow for this known variance when using RADAR to measure speed. Although levels of some 3 km/h, or 3% are also used, where tough enforcement is used. This causes many arguments due to motorists complaining that they were not doing the speed as reported. Revenue is being increasingly blamed for these stricter measures. There are strict United Nations standards in place but it seems not being enforced leaving this matter in limbo for many countries. Excessive speedometer error after manufacture can come from several causes but most commonly is due to nonstandard tire diameter, in which case the

percent error = 100x("standard diameter"/"new diameter" - 1). Nearly all tires now have their size shown as "T/A_W" on the side of the tire, and the tire's

diameter in inches = TxA/1270 + W. For example, a standard tire is "185/70R14" with diameter = 185x70/1270 + 14 = 24.196850 in. Another is "195/50R15" with 195x50/1270 + 15 = 22.677165 in. Replacing the first tire (and wheels) with the second (on 15" wheels), a speedometer reads 24.19../22.67..=1.0670139 times the correct speed or 6.7% too high.

Speedometer GPS

GPS devices may indicate the true speed of travel on the user interface. Unlike instrumental speedometers which provide a continious reading, most GPS speed readouts have a one-second update interval.

The reading is based on reception of data from the satellites in orbit, and is therefore independent of the car's transmission components. Discrepancies between the two readings may be caused by instrument error (on the vehicle), or by changing directly influential factors, such as tire sizes.

Starter ring gears

A starter ring gear, sometimes called a starter ring or ring gear, is a steel ring with teeth that is fitted on the periphery of a flexplate or flywheel of an internal combustion engine, mostly for automotive applications.

The teeth of the starter ring are driven by the smaller gear (the pinion) of the starter motor. The primary function of the starter ring is to transfer torque from the starter motor pinion to the flywheel or flexplate to rotate the engine to begin the cycle.

The starter ring gear is most commonly made by forming a length of steel into a circle and welding the ends together. There then follow various heat-treatment and machining operations, including the machining of the teeth and finally a heat-treatment operation. The teeth of the starter ring need to be hardened in order to increase their strength and resist wear. The body of the ring is generally left untreated.

Engines with manual transmission usually have a heavy flywheel, typically 5 to 10 kg of cast iron, with the starter ring gear shrunk onto the outside. This is done by heating the ring to around 200 °C to expand the ring which is then placed onto the flywheel and allowed to cool. The starter ring is thereby firmly attached to the flywheel.

Engines with automatic transmissions instead have a pressed steel plate with the starter ring gear usually welded onto the outside of the plate.

Steering wheels

A steering wheel (also called a driving wheel or hand wheel) is a type of steering control in vehicles and vessels (ships and boats). This article deals with steering wheels in vehicles; see steering wheel (ship) for the use in vessels.

Steering wheels are used in most modern land vehicles, including all mass-production automobiles as well as light and heavy trucks. The steering wheel is the part of the steering system that is manipulated by the driver; the rest of the steering system responds to such driver inputs. This can be through direct mechanical contact as in recirculating ball or rack and pinion steering gears, without or with the assistance of hydraulic power steering HPS, or as in some modern production cars with the assistance of computer controlled motors EPS. With the introduction of federal vehicle regulation in the United States in 1968, FMVSS 114 required the imparement of steering wheel movement, to hinder motor vehicle theft; in most vehicles this is accomplished when the ignition key is removed from the ignition lock.

Steering wheel History

The first automobiles were steered with a tiller, but Packard introduced the steering wheel on the second car they built, in 1899. Within a decade, the steering wheel had entirely replaced the tiller in automobiles.

C S Rolls introduced the first car in Britain fitted with wheel steering as he imported a 6 hp Panhard & Levassor from France in 1898. Arthur Constantin KREBS replaced the tiller with an inclined steering wheel for the Panhard car he designed for the

Steering wheel Passenger cars

Steering wheels for passenger automobiles are generally circular in form, and are mounted to the steering column by a hub connected to the outer ring of the steering wheel by one or more spokes (single spoke wheels being a rather rare exception). Other types of vehicles may use the circular design, a butterfly shape, or some other shape. In countries where cars must drive on the left side of the road, the steering wheel is typically on the right side of the car (right-hand drive or RHD); the converse applies in countries where cars drive on the right side of the road (left-hand drive or LHD).

Besides its use in steering, the steering wheel is the usual location for a button to activate the car's horn. Additionally, many modern automobiles may have other controls, such as cruise control and audio system controls built into the steering wheel to minimize the extent to which the driver must take his hands off the wheel.

An airbag, used to protect the driver in event of a frontal collision, is mounted inside a cover in the center of the steering wheel. Therefore, to prevent injury from the airbag deployment, it is important that the driver does not sit too close. Typical recommendations are a distance of at least 1-foot (30 cm) between the surface of the airbag cover and the driver's chest.

Before airbags, designs for energy-absorbing hubs existed, but were not used in mass production cars PDF Page 4.

Power steering and power assist steering both give the driver an easier means by which the steering of a car can be accomplished. Modern power steering have almost universally relied on a hydraulic system, although electrical systems are steadily replacing this technology. Mechanical power steering systems (ex. Studebaker, 1952) have been invented, but their weight and complexity negate the benefits that they provide.

While other methods of steering passenger cars have resulted from experiments, none have been deployed as successfully as the steering wheel.

Steering wheel Other designs

A modern Formula One car's steering wheel has buttons and knobs to control various functionsThe steering wheel is centrally located on certain high-performance sports cars, such as the McLaren F1, and in the majority of single-seat racing cars.

As a driver may have his hands on the steering wheel for hours at a time these are designed with ergonomics in mind. However, the most important concern is that the driver can effectively convey torque to the steering system; this is especially important in vehicles without power steering or in the rare event of a loss of steering assist. A typical design for circular steering wheels is a steel or magnesium rim with a plastic or rubberized grip molded over and around it. Some drivers purchase vinyl or textile steering wheel covers to enhance grip or comfort, or simply as decoration. Another device used to make steering easier is the brodie knob.

A similar device in aircraft is the yoke. Water vessels not steered from a stern-mounted tiller are directed with the ship's wheel, which may have inspired the concept of the steering wheel.

Adjustable steering wheels

1963 General Motors image showing the movement range of its Tilt Wheel feature. Notice how the angle of the steering wheel changes as it is moved upward and downward.Tilt Wheel

Developed by General Motors' Saginaw Steering Gear Division, the seven position Tilt Wheel was made available in several General Motors products in 1963. Originally a luxury option on cars, the tilt function helps to adjust the steering wheel by moving the wheel through an arc in an up and down motion. Tilt Steering Wheels rely upon a ratchet joint located in the steering column just below the steering wheel. By disengaging the ratchet lock, the wheel can be adjusted upward or downward while the steering column remains stationary below the joint. Some designs place the pivot slightly forward along the column, allowing for a fair amount of vertical movement of the steering wheel with little actual tilt, while other designs place the pivot almost inside the steering wheel, allowing adjustment of the angle of the steering wheel with almost no change it its height.

Telescope Wheel

Developed by General Motors Saginaw Steering Gear Division, the telescoping wheel can be adjusted to an infinite number of positions in a 3-inch range. The Tilt and Telescope steering wheel was introduced as an exclusive option on Cadillac automobiles in 1965.

Adjustable Steering Column

In contrast, an adjustable steering column allows steering wheel height to be adjusted with only a small, useful change in tilt. Most of these systems work with compression locks or electric motors instead of ratchet mechanisms; the latter may be capable of moving to a memorized position when a given driver uses the car, or of moving up and forward for entry or exit.

Swing-away Steering Wheel

Introduced on the 1961 Ford Thunderbird, and made available on other Ford products throughout the 1960s, the Swing-away steering wheel allowed the steering wheel to move nine inches to the right when the transmission selector was in Park, so as to make driver exit and entry easier.

Buttons on the steering wheel

The first button added to the steering wheel was a switch to activate the car's electric Horn. Traditionally located on the steering wheel hub or center pad, the horn switch was sometimes placed on the spokes or activated via a decorative horn ring which obviated the necessity to move a hand away from the rim. A further development, the Rim Blow steering wheel, integrated the horn switch into the steering wheel rim itself.

When speed control systems were introduced in the 1960s, some automakers located the operating switches for this feature on the steering wheel. In the 1990s, a proliferation of new buttons began to appear on automobile steering wheels. Remote or alternate adjustments for the audio system, the telephone and voice control, acoustic repetition of the last navigation instruction, infotainment system, and on board computer functions can be operated comfortably and safely using buttons on the steering wheel. This ensures a high standard of additional safety since the driver is able in this way to control and operate many systems without even taking hands off the wheel or eyes off the road.

The scroll buttons can be used to set volume levels or page through menus.

The buttons can be adjusted manually for reach and height.

Steering wheel Gaming imitations

Certain game controllers available for arcade cabinets, personal computers and console games are designed to look and feel like a steering wheel and intended for use in racing games. The cheapest ones are just paddle controllers with a larger wheel, but most today's examples employ force feedback to simulate the tactile feedback a real driver feels from a steering wheel. This contributes to steering "feel" and is one of the hallmarks of a true "driver's car" or sports car.

Tachometers

A tachometer is an instrument that measures the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analog dial, but digital displays are increasingly common. The term comes from Greek, tachos, "speed", and metron, "to measure".

Tachometer History

The first, mechanical, tachometers were based on measuring the centrifugal force. The inventor is assumed to be the German engineer Diedrich Uhlhorn; he used it for measuring the speed of machines in 1817. Since 1840, it was used to measure the speed of locomotives.

Tachometer In automobiles, trucks, tractors and aircraft

Tachometers on automobiles, aircraft, and other vehicles show the rate of rotation of the engine's crankshaft, and typically have markings indicating a safe range of rotation speeds. This can assist the driver in selecting an appropriate throttle and gear settings for the driving conditions. Prolonged use at high speeds may cause excessive wear and other damage to engines. This is more applicable to manual transmissions than to automatics. On analog tachometers the maximum speed is typically indicated by an area of the gauge marked in red, giving rise to the expression of "redlining" an engine running it at (dangerously) high speed. The red zone is superfluous on most modern cars, since their engines typically have a rev limiter which electronically limits engine speed to prevent damage. Diesel engines with traditional mechanical injector systems have an integral governor which prevents over-speeding the engine, so the tachometers in vehicles and machinery fitted with such engines often lack a redline.

In vehicles such as tractors and trucks, the tachometer often has other markings, usually a green arc showing the speed range in which the engine produces maximum torque, which is of prime interest to operators of such vehicles. Tractors fitted with a power take off (PTO) system have tachometers showing the engine speed needed to rotate the PTO at the standardised speed required by most PTO-driven implements. In many countries, tractors are required to have a speedometer for use on a road. To save fitting a second dial, the vehicle's tachometer is often marked with a second scale in units of speed. This scale is only accurate in a certain gear, but since many tractors only have one gear that is practical for use on-road, this is sufficient. Tractors with multiple 'road gears' often have tachometers with more than one speed scale. Aircraft tachometers have a green arc showing the engine's designed cruising speed range.

In older vehicles, the tachometer is driven by the pulses from the low tension (LT) side of the ignition coil, while on others (and nearly all diesel engines, which have no ignition system) engine speed is determined by the frequency from the alternator tachometer output. This is a special circuit inside the alternator to convert from rectified sine wave to square wave, and the electrical potential difference is directly proportional to engine speed. Tachometers driven by a rotating cable from a drive unit fitted to the engine (usually on the camshaft) also exist- usually on simple diesel-engined machinery with basic or no electrical systems. On modern engine management systems found on modern vehicles, the tachometer is driven directly from the engine management ECU.

Tachometer Hours meters

When used in stationary engines or vehicles where an odometer would not give an accurate reading of the vehicle's use (such as in aircraft or tractors), tachometers frequently incorporate a display showing the total number of hours the engine has run. Service intervals are given and measured in hours. Generally, hours meters are accurate only at one specific engine speed an hours meter calibrated for, say, 'Hours At 2000 RPM' will only advance one hour per hour if the engine is run at 2000 RPM. If the engine is run below this speed, hours will accumulate more slowly, and if the engine is run above the meter will gain hours more quickly. This discrepancy does not detract from the accuracy of service intervals, for an engine running at slow speeds may gain hours more slowly, but will also be put under less mechanical stress and will not require servicing work as frequently as an engine used generally at high speeds. To prevent lightly- or little-used engines going unserviced, manufacturers also apply a calendar limit services take place (for example) 'every 200 hours or 12 months'.

Tachometer In trains and light rail vehicles

Speed sensing devices, termed variously "wheel impulse generators" (WIG), speed probes, or tachometers are used extensively in rail vehicles. Common types include opto-isolator slotted disk sensors and Hall effect sensors.

Hall effect sensors typically use a rotating target attached to a wheel, gearbox or motor. This target may contain magnets, or it may be a toothed wheel. The teeth on the wheel vary the flux density of a magnet inside the sensor head. The probe is mounted with its head a precise distance from the target wheel and detects the teeth or magnets passing its face. One problem with this system is that the necessary air gap between the target wheel and the sensor allows ferrous dust from the vehicle's underframe to build up on the probe or target, inhibiting function.

Opto-isolator sensors are completely encased to prevent ingress from the outside environment. The only exposed parts are a sealed plug connector and a drive fork, which is attached to a slotted disk internally through a bearing and seal. The slotted disk is typically sandwiched between two circuit boards containing a photo-diode, photo-transistor, amplifier, and filtering circuits which produce a square wave pulse train output customized to the customers voltage and pulses per revolution requirements. These types of sensors typically provide 2 to 8 independent channels of output that can be sampled by other systems in the vehicle such as automatic train control systems and propulsion/braking controllers.

The opto devices, mounted around the circumference of the disk, provide signals that are phase-shifted relative to one another and thus allow the vehicle computer to determine the direction of rotation of the wheel. This is a legal requirement in Switzerland to prevent rollback when starting from standstill. Strictly, such devices are not tachometers since they do not provide a direct reading of the rotational speed of the disk. The speed has to be derived externally by counting the number of pulses in a time period. It is difficult to prove conclusively that the vehicle is stationary, other than by waiting a certain time to ensure that no further pulses occur. This is one reason why there is often a time delay between the train stopping, as perceived by a passenger, and the doors being released. Slotted-disk devices are typical sensors used in odometer systems for rail vehicles; such as are required for train protection systems - notably the European Train Control System.

A weakness of systems that rely on wheel rotation for tachometry and odometry is that the train wheels and the rails are very smooth and the friction between them is low, leading to high error rates if the wheels slip or slide. To compensate for this, secondary odometry inputs employ Doppler radar units beneath the train to measure speed independently.

As well as speed sensing, these probes are often used to calculate distance travelled by multiplying wheel rotations by wheel diameter.

They can also be used to automatically calibrate wheel diameter by comparing the number of rotations of each axle against a master wheel that has been measured manually. Since all wheels travel the same distance, the diameter of each wheel is proportional to its number of rotations compared to the master wheel. This calibration must be done while coasting at a fixed speed to eliminate the possibility of wheel slip/slide introducing errors into the calculation. Automatic calibration of this type is used to generate more accurate traction and braking signals, and to improve wheel slip detection.

Tachometer In medicine

In medicine, tachometers are used to measure the rate of blood flow at a particular point in the circulatory system. The specific name for these devices is haematachometer.

Tachometer In analog audio recording

In analog audio recording, a tachometer is a device that measures the speed of audiotape as it passes across the head. On most audio tape recorders the tachometer (or simply "tach") is a relatively large spindle near the ERP head stack, isolated from the feed and take-up spindles by tension idlers.

On many recorders the tachometer spindle is connected by an axle to a rotating magnet that induces a changing magnetic field upon a Hall effect transistor. Other systems connect the spindle to a stroboscope, which alternates light and dark upon a photodiode.

The tape recorder's drive electronics use signals from the tachometer to ensure that the tape is played at the proper speed. The signal is compared to a reference signal (either a quartz crystal or alternating current from the mains). The comparison of the two frequencies drives the speed of the tape transport. When the tach signal and the reference signal match, the tape transport is said to be "at speed." (To this day on film sets, the director calls "Roll sound!" and the sound man replies "Sound speed!" This is a vestige of the days when recording devices required several seconds to reach a regulated speed.)

Having perfectly regulated tape speed is important because the human ear is very sensitive to changes in pitch, particularly sudden ones, and without a self-regulating system to control the speed of tape across the head the pitch could drift several percent. This effect is called a wow-and-flutter, and a modern, tachometer-regulated cassette deck has a wow-and-flutter of 0.07%.

Tachometers are acceptable for high-fidelity sound playback, but not for recording in synchronization with a movie camera. For such purposes, special recorders that record pilottone must be used.

Tachometer signals can be used to synchronize several tape machines together, but only if in addition to the tach signal, a directional signal is transmitted, to tell slave machines in which direction the master is moving.

Thermostats

Bi-metallic thermostat for buildingsA thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by controlling the flow of heat energy into or out of the system. That is, the thermostat switches heating or cooling devices on or off as needed to maintain the correct temperature.

Thermostats can be constructed in many ways and may use a variety of sensors to measure the temperature. The output of the sensor then controls the heating or cooling apparatus.

Thermostat Mechanical

Thermostat Bi-metal

The examples and perspective in this article or section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

On a steam or hot-water radiator system, the thermostat may be an entirely mechanical device incorporating a bi-metal strip. Generally, this is an automatic valve which regulates the flow based on the temperature. For the most part, their use in North America is now rare, as modern under-floor radiator systems use electric valves, as do some older retrofitted systems. They are still widely employed on central heating radiators throughout Europe, however.

Mechanical thermostats are used to regulate dampers in rooftop turbine vents, reducing building heat loss in cool or cold periods.

An automobile passenger compartment's heating system has a thermostatically controlled valve to regulate the water flow and temperature to an adjustable level. In older vehicles the thermostat controls the application of engine vacuum to actuators that control water valves and flappers to direct the flow of air. In modern vehicles, the vacuum actuators may be operated by small solenoids under the control of a central computer.

Thermostat Wax pellet

This type of thermostat operates mechanically. It makes use of a wax pellet inside a sealed chamber. The wax is solid at low temperatures but as the engine heats up the wax melts and expands. The sealed chamber has an expansion provision that operates a rod which opens a valve when the operating temperature is exceeded. The operating temperature is fixed, but is determined by the specific composition of the wax, so thermostats of this type are available to maintain different temperatures, typically in the range of 70 to 90 °C (160 to 200 °F). Modern engines are run hot, that is, over 80 °C (180 °F), in order to run more efficiently and to reduce the emission of pollutants. Most thermostats have a small bypass hole to vent any gas that might get into the system (e.g., air introduced during coolant replacement), this small bypass hole is under normal circumstances used to have a small flow when the thermostat is still closed. Without this flow it would be impossible for the thermostat to react correctly on the heating up water. Modern cooling systems contain a relief valve in the form of a spring-loaded radiator pressure cap, with a tube leading to a partially filled expansion reservoir. Owing to the high temperature, the cooling system will become pressurized to a maximum set by the relief valve. The additional pressure increases the boiling point of the coolant above that which it would be at atmospheric pressure.

Thermostat Gas Expansion

This type of thermostat is sometimes used to regulate gas ovens. It consists of a gas-filled bulb connected to the control unit by a slender copper tube. The bulb is normally located at the top of the oven. The tube ends in a chamber sealed by a diaphragm. As it heats up the gas expands applying pressure to the diaphragm which reduces the flow of gas to the burner.

Thermostat Electrical

Thermostat Simple two wire thermostats

Thermostat MechanismThe illustration is the interior of a common two wire heat-only household thermostat, used to regulate a gas-fired heater via an electric gas valve. Similar mechanisms may also be used to control oil furnaces, boilers, boiler zone valves, electric attic fans, electric furnaces, electric baseboard heaters, and household appliances such as refrigerators, coffee pots, and hair dryers. The power through the thermostat is provided by the heating device and may range from millivolts to 240 volts in common North American construction, and is used to control the heating system either directly (electric baseboard heaters and some electric furnaces) or indirectly (all gas, oil and forced hot water systems). Due to the variety of possible voltages and currents available at the thermostat, caution must be taken.

Set point control lever. This is moved to the right for a higher temperature. the round indicator pin in the center of the second slot shows through a numbered slot in the outer case. Bi-metallic strip wound into a coil. The center of the coil is attached to a rotating post attached to lever (1). As the coil gets colder the moving end carrying moves clockwise.

Flexible wire. The left side is connected via one wire of a pair to the heater control valve.

Moving contact attached to the bi-metal coil.

Fixed contact screw. This is adjusted by the manufacturer. It is connected electrically by a second wire of the pair to the thermocouple and thence to the heater's controller. Magnet. This ensures a good contact when the contact closes. It also provides hysteresis to prevent short heating cycles, as the temperature must be raised several degrees before the contacts will open.

As an alternative, some thermostats instead use a mercury switch on the end of the bi-metal coil. The weight of the mercury on the end of the coil tends to keep it there, also preventing short heating cycles. However, this type of thermostat is banned in many countries due to its highly and permanently toxic nature if broken. When replacing these thermostats they must be regarded as chemical waste.

Not shown in the illustration is a separate bi-metal thermometer on the outer case to show the actual temperature at the thermostat.

Thermostat Millivolt thermostats

As illustrated in the use of the thermostat above, the power is provided by a thermocouple, heated by the pilot light. This produces little power and so the system must use a low power valve to control the gas. This type of device is generally considered obsolete as pilot lights waste a surprising amount of gas (in the same way a dripping faucet can waste a huge amount of water over an extended period), and are also no longer used on stoves, but are still to be found in many gas water heaters. (Their poor efficiency is acceptable in water heaters, since most of the energy "wasted" on the pilot light is still being coupled to the water and therefore helping to keep the tank warm. For tankless (on demand) water heaters, pilot ignition is preferable since it is faster than hot-surface ignition and more reliable than spark ignition.)

Existing millivolt heating systems can be made far more economical by turning off the gas supply during non-heating seasons and re-lighting the pilot when the heating season approaches. During the winter months, most of the small amount of heat generated by the pilot flame will probably radiate through the flue and into the house, meaning that the gas is wasted (during a time when the system isn't actively heating) but the pilot-warmed flue continues to add to the total thermal energy in the house. In the summer months, this is wholly undesirable.

Some programmable thermostats will control these systems.

Thermostat 24 volt thermostats

The majority of heating/cooling/heat pump thermostats operate on low voltage (typically 24VAC) control circuits. The source of the 24 VAC is a control transformer installed as part of the heating/cooling equipment. The advantage of the low voltage control system is the ability to operate multiple electromechanical switching devices such as relays, contactors, and sequencers using inherently safe voltage and current levels. Built into the thermostat is a provision for enhanced temperature control using anticipation. A heat anticipator generates a small amount of additional heat to the sensing element while the heating appliance is operating. This opens the heating contacts slightly early to prevent the space temperature from greatly overshooting the thermostat setting. A mechanical heat anticipator is generally adjustable and should be set to the current flowing in the heating control circuit when the system is operating. A cooling anticipator generates a small amount of additional heat to the sensing element while the cooling appliance is not operating. This causes the contacts to energize the cooling equipment slightly early, preventing the space temperature from climbing excessively. Cooling anticipators are generally non-adjustable. Electromechanical thermostats use resistance elements as anticipators. Most electronic thermostats use either thermistor devices or integrated logic elements for the anticipation function. In some electronic thermostats, the thermistor anticipator may be located outdoors, providing a variable anticipation depending on the outdoor temperature. Thermostat enhancements include outdoor temperature display, programmability, and system fault indication.

Most modern gas or oil furnaces or boilers will be controlled by such systems, as will most relay-operated electric furnaces:

Thermostat Line voltage thermostats

Line voltage thermostats are most commonly used for electric space heaters such as a baseboard heater or a direct-wired electric furnace. If a line voltage thermostat is used, system power (in the United States, 120 or 240 volts) is directly switched by the thermostat. With switching current often exceeding 40 amperes, using a low voltage thermostat on a line voltage circuit will result at least in the failure of the thermostat and possibly a fire. Line voltage thermostats are sometimes used in other applications such as the control of fan-coil (fan powered from line voltage blowing through a coil of tubing which is either heated or cooled by a larger system) units in large systems using centralized boilers and chillers.

Some programmable thermostats are available to control line-voltage systems. Baseboard heaters will especially benefit from a programmable thermostat which is capable of continuous control (as are at least some Honeywell models), effectively controlling the heater like a lamp dimmer, and gradually increasing and decreasing heating to ensure an extremely constant room temperature (continuous control rather than relying on the averaging effects of hysteresis). Systems which include a fan (electric furnaces, wall heaters, etc.) must typically use simple on/off controls.

Thermostat Combination heating/cooling regulation

Depending on what is being controlled, a forced-air air conditioning thermostat generally has an external switch for heat/off/cool, and another on/auto to turn the blower fan on constantly or only when heating and cooling are running. Four wires come to the centrally-located thermostat from the main heating/cooling unit (usually located in a closet, basement, or occasionally attic): one wire supplies a 24 V AC power connection to the thermostat, whilst the other three supply control signals from the thermostat, one for heat, one for cooling, and one to turn on the blower fan. The power is supplied by a transformer, and when the thermostat makes contact between power and another wire, a relay back at the heating/cooling unit activates the corresponding function of the unit.

Thermostat Heat Pump Regulation

The heat pump is a refrigeration based appliance that reverses refrigerant flow between the indoor and outdoor coils. This is done by energizing a "reversing", "4-way", or "change-over" valve. During cooling, the indoor coil is an evaporator removing heat from the indoor air and transferring it to the outdoor coil where it is rejected to the outdoor air. During heating, the outdoor coil becomes the evaporator and heat is removed from the outdoor air and transferred to the indoor air through the indoor coil. The reversing valve, controlled by the thermostat, causes the change-over from heat to cool. Residential heat pump thermostats generally have an "O" terminal to energize the reversing valve in cooling. Some residential and many commercial heat pump thermostats use a "B" terminal to energize the reversing valve in heating. The heating capacity of a heat pump decreases as outdoor temperatures fall. At some outdoor temperature (called the balance point) the ability of the refrigeration system to transfer heat into the building falls below the heating needs of the building. A typical heat pump is fitted with electric heating elements to supplement the refrigeration heat when the outdoor temperature is below this balance point. Operation of the supplemental heat is controlled by a second stage heating contact in the heat pump thermostat. During heating, the outdoor coil is operating at a temperature below the outdoor temperature and condensation on the coil may take place. This condensation may then freeze onto the coil, reducing its heat transfer capacity. Heat pumps therefore have a provision for occasional defrost of the outdoor coil. This is done by reversing the cycle to the cooling mode, shutting off the outdoor fan, and energizing the electric heating elements. The electric heat in defrost mode is needed to keep the system from blowing cold air inside the building. The elements are then used in the "reheat" function. Although the thermostat may indicate the system is in defrost and electric heat is activated, the defrost function is not controlled by the thermostat. Since the heat pump has electric heat elements for supplemental and reheats, the heat pump thermostat provides for use of the electric heat elements should the refrigeration system fail. This function is normally activated by an "E" terminal on the thermostat. When in emergency heat, the thermostat makes no attempt to operate the compressor or outdoor fan.

Thermostat Digital

Newer digital thermostats have no moving parts to measure temperature and instead rely on thermistors. Typically one or more regular batteries must be installed to operate it although some so-called "power stealing" digital thermostats use the common 24 volt AC circuits as a power source (but will not operate on thermopile powered "millivolt" circuits used in some furnaces). Each has an LCD screen showing the current temperature, and the current setting. Most also have a clock, and time-of-day (and now day-of-week) settings for the temperature, used for comfort and energy conservation. Some now even have touch screens, or have the ability to work with X10, BACnet, LonWorks or other home automation or building automation systems.

Digital thermostats use either a relay or a semiconductor device such as triac to act as switch to control the HVAC unit. Units with relays will operate millivolt systems, but often make an audible "click" noise when switching on or off.

More expensive models have a built-in PID controller, so that the thermostat knows ahead how the system will react to its commands. For instance, setting it up that temperature in the morning at 7am should be 21 degrees, makes sure that at that time the temperature will be 21 degrees (a conventional thermostat would just start working at that time). The PID controller decides at what time the system should be activated in order to reach the desired temperature at the desired time. It also makes sure that the temperature is very stable (for instance, by reducing overshoots).

Most digital thermostats in common residential use in North America are programmable thermostats, which will typically provide a 30% energy savings if left with their default programs; adjustments to these defaults may increase or reduce energy savings. The programmable thermostat article provides basic information on the operation, selection and installation of such a thermostat.

Household thermostat location

The thermostat should be located away from the room's cooling or heating vents or device, yet exposed to general airflow from the room(s) to be regulated. An open hallway may be most appropriate for a single zone system, where living rooms and bedrooms are operated as a single zone. If the hallway may be closed by doors from the regulated spaces then these should be left open when the system is in use. If the thermostat is too close to the source controlled then the system will tend to "short cycle", and numerous starts and stops can be annoying and in some cases shorten equipment life. A multiple zoned system can save considerable energy by regulating individual spaces, allowing unused rooms to vary in temperature by turning off the heating and cooling.

Thermostat Terminal Codes

NEMA National Electrical Manufacturers Association in 1972 standardized the labels on thermostat terminals. These standards specify alphanumeric codes to be used for specific functions in thermostats:

R, or RH for heat or RC for cool (red): "hot" side of transformer

W (white): heat control

W2 (pink or other color): heat, second stage

Y2 (blue or pink): cool, second compressor stage

C or X (black): common side of transformer (24 V)

G (green): fan

O (orange): Energize to cool (heat pumps)

L (tan, brown, grey or blue): service indicator lamp

X2 (blue, brown, grey or tan): heat, second stage (electric)

B (blue or orange): energize to heat

B or X (blue, brown or black): common side of transformer

E (blue, pink, gray or tan): emergency heat relay on a heat pump

T (tan or gray): outdoor anticipator reset

Universal joints

A universal jointA universal joint, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of ordinary hinges located close together, but oriented at 90° relative to each other.

Universal joint History

The concept of the universal joint is based on the design of gimbals, which have been in use since antiquity. One anticipation of the universal joint was its use by the Ancient Greeks on ballistae. The first person known to have suggested its use for transmitting motive power was Gerolamo Cardano, an Italian mathematician, in 1545, although it is unclear whether he produced a working model. Christopher Polhem later reinvented it and it was called "Polhem knot". In Europe, the device is often called the Cardan joint or Cardan shaft. Robert Hooke produced a working universal joint in 1676, giving rise to an alternative name, the Hooke's joint. It was the American car manufacturer Henry Ford who gave it the name universal joint.

Universal joint Angular speed

Angular output shaft speed for different angles of the input shaft Output shaft angle for different angles of the input shaft

When the two shafts are at an angle other than 180° (straight), the driven shaft does not rotate with constant angular speed in relation to the drive shaft; the more the angle goes toward 90° the jerkier the movement gets (clearly, when the angle = 90° the shafts would even lock). However, the overall average speed of the driven shaft remains the same as that of driving shaft, and so speed ratio of the driven to the driving shaft on average is 1:1 over multiple rotations. the angular acceleration.

Universal joint Double cardan

A configuration known as a double cardan joint drive shaft partially overcomes the problem of jerky rotation. In this configuration, two U-joints are utilised where the second U-joint is phased in relation to the first U-joint in order cancel the changing angular velocity, and an intermediate shaft connects the two U-joints. In this configuration, the assembly will result in an almost constant velocity providing both the driving and the driven shaft are parallel and the two universal joints are correctly aligned with each other - usually 45°. This assembly is commonly employed in rear wheel drive vehicles.

In practice, it is often impossible to maintain a strict geometric relationship between the driving and driven shafts, and the intermediate shaft, giving rise to vibrations and mechanical stresses. Under all geometric conditions, the intermediate shaft will maintain a sinusoidal angular velocity, which contributes to vibration and stresses. The stresses can be reduced by the use of a smaller and lighter intermediate shaft, ensuring the driven and driving shafts share as close to the same angle in relation to the intermediate shaft, and reducing the angle of the joints.

Joints have been developed utilizing a floating intermediate shaft and centering elements to maintain equal angles between the driven and driving shafts, and the intermediate shaft. This overcomes the problem of differential angles between the input and output shafts.

A recent innovation, the Thompson coupling is a further development of the double cardan joint, which doesn't rely on friction or sliding elements to maintain a strict geometric relationship within the joint, and which is capable of transmitting torque under axial and radial loads with low frictional losses.

Windshield wipers

A common design for a "wiper" on a ship. A round portion of the windshield has two layers, the outer one of which is spun at high speed.A windscreen wiper (windshield wiper in North America) is a device used to wipe rain and dirt from a windscreen. Almost all automobiles are equipped with windscreen wipers, often by legal requirement -- though, confusingly, some legal systems require wipers without requiring a windscreen.

Wipers can also be fitted to other vehicles, such as buses, trams, locomotives, aircraft and ships.

A wiper generally consists of an arm, pivoting at one end and with a long rubber blade attached to the other. The blade is swung back and forth over the glass, pushing water from its surface. The speed is normally adjustable, with several continuous speeds and often one or more "intermittent" settings. Most automobiles use two synchronized radial type arms, while many commercial vehicles use one or more pantograph arms. Mercedes-Benz pioneered a system called the Monoblade in which a single wiper extends outward to get closer to the top corners, and pulls in at the ends and middle of the stroke, sweeping out a somewhat 'W'-shaped path.

Some larger cars are equipped with "hidden" (or "depressed-park") wipers. When wipers are switched off, a "parking" mechanism or circuit moves the wipers to the lower extreme of the wiped area, near the bottom of the windshield, but still in sight. To hide the wipers, the windshield extends below the rear edge of the hood, and the wipers park themselves below the wiping range at the bottom of the windshield, but out of sight.

Wipers may be powered by a variety of means, although most in existence today are powered by an electric motor through a series of mechanical components, typically two 4-bar linkages in series or parallel. Vehicles with air operated brakes sometimes use air operated wipers, run by bleeding a small amount of air pressure from the brake system to a small air operated motor mounted just above the windscreen. These wipers are activated by opening a valve which allows pressurized air to enter the motor.

Early wipers were often powered by manifold vacuum, but this had the drawback that manifold vacuum alters depending on throttle position and is almost non-existent under wide-open throttle; the wipers would slow down or even stop. This problem was overcome somewhat by using a combined fuel/vacuum booster pump. Some cars, mostly from the 1960s and 1970s, had hydraulically driven wipers.

On the earlier Citroën 2CV, the windscreen wipers were powered by a purely mechanical system: a cable connected to the transmission, to reduce cost this cable powered also the speedometer. The wipers' speed was therefore variable with car speed. When the car was waiting at a crossroad, the wipers were not powered, thus a handle under the speedometer allowed to power them by hand.

Most windscreen wipers operate together with a windscreen washer; a pump that supplies water and detergent (usually a blend called windscreen wiper fluid) from a tank to the windscreen through small nozzles, mounted on the hood or on the wipers, known as a 'wet-arm' system.

Some automobiles have small 'windscreen' wipers/washers on the headlights. In more modern vehicles, these have been replaced with a powerful jet spray, without wipers.

Some vehicles are fitted with wipers (with or without washers) on the back window as well. Rear-window wipers are typically found on hatchbacks, station wagons, sport utility vehicles, minivans, and some sports cars. They were first implemented in the 1970s, but SUVs did not use them until the 1980s.

Nowadays some cars include intelligent (automatic) windscreen wipers that detect the presence and amount of rain using a rain sensor, and automatically adjusts the speed of the blades according to the amount of rain detected.

Windshield wiper History

Inventor J. H. Apjohn came up with a method of moving two brushes up and down on a vertical plate glass windshield in 1903.

Mary Anderson is said to have invented the windshield wiper swinging arm in the United States, where she patented the idea in 1905. The idea was initially met with resistance, but was a standard feature on all American cars by 1916.

In April 1911, a patent for windscreen wipers was registered by Sloan & Lloyd Barnes, patent agents of Liverpool, England, for Gladstone Adams of Whitley Bay. The first designs for the windscreen wiper are also credited to Józef Hofmann, the world-famous concert pianist and Mills Munitions, Birmingham who also claimed to have been the first to patent windscreen wipers in England.

In the late 1950s, a feature common on modern vehicles first appeared, operating the wipers automatically for two or three passes when the washer button was pressed, making it unnecessary to manually turn them on as well. Today, a simple electronic timing circuit is used, but originally a small vacuum cylinder mechanically linked to a switch provided the delay as the vacuum leaked off.

In 1969, the first intermittent wipers were introduced with an adjustable delay between wipes, making it possible to select the degree of wiping action required. Robert Kearns is the recognized inventor of this system although it took years of concerted effort and legal action before he was eventually compensated.

In 1970. Saab Automobile introduced headlight wipers across the product range. These operated on a horizontal reciprocating mechanism, with a single motor. They were later superseded by a radial spindle action wiper mechanism, with individual motors on each headlamp.

In the late 20th century, rain-sensing windshield wipers appeared on various models, one of the first being Buick's Park Avenue Ultra. As of early 2006, rain-sensing wipers are standard on all Cadillacs, and are available on many other GM, Chrysler, Jeep, Peugeot, Citroën, Toyota, Mercedes, Honda and Renault as well as many other main-stream manufacturers.

Windshields

Panoramic (wrap-around) windshield on a 1959 Edsel Corsair.The windshield (also known as the windscreen) of an aircraft, automobile, bus, motorcycle, or tram is the front window. Modern windshields are generally made of laminated safety glass, which consists of two (typically) curved sheets of glass with a plastic layer laminated between them for safety, and are glued into the window frame.

Motorcycle windscreens are often made of high-impact acrylic plastic. As the name implies, their main function is to shield the driver from the wind, though they do not do so as totally as those of a car.

Windshield Usage

In daily use, windshields mainly protect the vehicle's occupants from wind, temperature extremes, and flying debris such as dust, insects, and rocks, as well as providing an aerodynamically formed window towards the front. UV Coating may be applied to screen out harmful ultraviolet light.

Windshield Safety

Early windscreens were made of ordinary window glass, but that could lead to serious injuries in the event of a crash. They were replaced with windshields made of toughened glass and were fitted in the frame using a rubber or neoprene seal. The hardened glass shattered into many mostly harmless fragments when the windscreen broke. These windshields, however, could shatter from a simple stone chip. Especially in police cars this was seen as a problem and it led to the development of the laminated glass windows most cars use. Ford Motor Company adopted laminated glass as standard windshield equipment for all its cars in 1928.

However, there have been some concern over the risk of decapitation and some cars instead use a windscreen of lexan.

Split and raked windshield on a 1952 DeSoto. Note the panes of glass are flat.The modern, glued-in screens contribute to the vehicle's rigidity, but the main force in innovating the windshield has historically been the need to prevent injury from sharp glass fragments. Modern windshields, now almost universally required in all nations, do not fragment, but tend to stay in one piece even if broken, except if pierced locally by a strong force. Properly installed automobile windshields are also essential to safety; along with the roof of the car, they provide protection in the case of a roll-over accident in the vehicle.

Windshield Other aspects

In many places, laws restrict the use of heavily tinted glass in vehicle windshields; generally, laws specify the maximum level of tint permitted. Some vehicles have noticeably more tint in the uppermost part of the windshield of motor vehicles that blocks glare from the sun.

In aircraft windscreens, a current is applied through a conducting layer of tin(IV) oxide to generate heat to prevent icing. A similar system for automobile windshields, introduced on Ford vehicles as "Quickclear" in Europe ("InstaClear" in North America) in the 1980s, uses very thin heating wires or conductive-film layer embedded between the two laminations.

Using thermal glass has one downside: it prevents some navigation systems from functioning correctly, as the embedded metal jams the satellite signal. This can be resolved by using an external antenna for the navigation system.

Windshield Terminology

The term windshield is used generally throughout North America, although windscreen is often used for motorcycles and similar vehicles. The term windscreen is the usual term in the UK and Australia/New Zealand for all vehicles. In Japanese English, it is called "front glass".

In the USA, windscreen refers to the mesh or foam screen placed over a microphone to minimize wind noise, while a windshield refers to the front window of a car. In the UK, the meaning of these terms is reversed.

Today’s windshields are a safety device just like seat belts and air bags. The installation of the auto glass is done with an automotive grade urethane designed specifically for automobiles. The adhesive creates a molecular bond between the glass and the vehicle. If the adhesive bond fails at any point on the glass it can reduce the effectiveness of the air bag and substantially compromise the structural integrity of the roof. (Raymond Clough)

Brookland aeroscreen on a 1931 Austin Seven Sports.Auto windscreens less than 20 cm (8 inches) in height are sometimes known as aeroscreens since they only deflect the wind. The twin aeroscreen setup (often called Brooklands) was popular among older sports and modern cars in vintage style.

A wiperless windshield is a windshield that uses a mechanism other than wipers to remove snow and rain from the windshield. The concept car Acura TL features a wiperless windshield using a series of jet nozzles in the cowl to blow pressurized air onto the windshield.

Windshield Stone chip and crack damage

Many types of stone damage can be successfully repaired. Bullseyes, cracks, starbreaks or a combination of all three, can be repaired without removing the screen, eliminating the risk of leaking or bonding problems sometimes associated with replacement.

Windshield Repair

When repairing a windshield, it is important to start with a clean work area. Any dust, dirt, or contaminants in or on the glass can result in scarring or trapped particles that will permanently be visible in the final repair. Any moisture can cause future cracks when the glass cools or heats. Many chips in automotive safety glass will never grow but insurance compaines in the United States often waive the deductible to insure they do not have to pay for the replacement of the auto glass.