Automotive Glossary of Terms - A -
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Definitions for automotive terms and illustrations from accelerator pump to axle ratio.
ABS
Anti-lock braking system. An electro-mechanical braking system which is designed to minimize or prevent wheel lock-up during braking.ACCELERATOR PUMP
A small pump located in the carburetor that feeds fuel into the air/fuel mixture during acceleration.
ADD-ON TERMS
ADVANCE
Setting the ignition timing so that spark occurs earlier, before the piston reaches top dead center (TDC).AFTER TOP DEAD CENTER (ATDC)
The point after the piston reaches the top of its travel on the compression stroke.
AIR BAG
Device on the inside of the car designed to inflate on impact of crash, protecting the occupants of the car.
AIR CLEANER
An assembly consisting of a housing, filter and any connecting ductwork. The filter element is made up of a porous paper, sometimes with a wire mesh screening, and is designed to prevent airborne particles from entering the engine through the carburetor or throttle body.
AIR INJECTION
One method of reducing harmful exhaust emissions by injecting air into each of the exhaust ports of an engine. The fresh air entering the hot exhaust manifold causes any remaining fuel to be burned before it can exit the tailpipe.
AIR PUMP
An emission control device that supplies fresh air to the exhaust manifold to aid in more completely burning exhaust gases.
AIR/FUEL RATIO
The ratio of air-to-gasoline by weight in the fuel mixture drawn into the engine.
ALIGNMENT RACK
A special drive-on car lift apparatus/measuring device used to adjust a car's toe, caster and camber angles.
ALL WHEEL DRIVE
Term used to describe a full time four wheel drive system or any other car drive system that continuously delivers power to all four wheels. This system is found primarily on station wagon cars and SUVs not utilized for significant off road use.
ALTERNATING CURRENT (AC)
Electric current that flows first in one direction, then in the opposite direction, continually reversing flow.
ALTERNATOR
A device which produces AC (alternating current) which is converted to DC (direct current) to charge the car battery.
AMMETER
An instrument, calibrated in amperes, used to measure the flow of an electrical current in a circuit. Ammeters are always connected in series with the circuit being tested.
AMP/HR. RATING (BATTERY)
Measurement of the ability of a battery to deliver a stated amount of current for a stated period of time. The higher the amp/hr. rating, the better the battery.
AMPERE
The rate of flow of electrical current present when one volt of electrical pressure is applied against one ohm of electrical resistance.
ANALOG COMPUTER
Any microprocessor that uses similar (analogous) electrical signals to make its calculations.
ANTIFREEZE
A substance (ethylene or propylene glycol) added to the coolant to prevent freezing in cold weather.
ANTI-LOCK BRAKING SYSTEM
A supplementary system to the base hydraulic system that prevents sustained lock-up of the wheels during braking as well as automatically controlling wheel slip.
ANTI-ROLL BAR
See stabilizer bar.
ANTI-SWAY BAR LINKS
The link pins and bushings that connect the anti-sway bar to the lower control arms in the front or rear suspension.
ARMATURE
A laminated, soft iron core wrapped by a wire that converts electrical energy to mechanical energy as in a motor or relay. When rotated in a magnetic field, it changes mechanical energy into electrical energy as in a generator.ASE
Acronym for the National Institute for Automotive Service Excellence. ASE is usually affiliated with being a Certified Technician. ASE provides a testing system to recognize a technicians skills and abilities in specific mechanical areas, such as drivetrain, engine performance, electrical, etc.
ATDC
After top dead center.
ATF
:Automatic transmission fluid.
ATMOSPHERIC PRESSURE
The pressure on the Earth's surface caused by the weight of the air in the atmosphere. At sea level, this pressure is 14.7 psi at 32°F (101 kPa at 0°C).
ATOMIZATION
The breaking down of a liquid into a fine mist that can be suspended in air.
AWD
All wheel drive.
AXIAL PLAY
Movement parallel to a shaft or bearing bore.
AXLE CAPACITY
The maximum load-carrying capacity of the axle itself, as specified by the manufacturer. This is usually a higher number than the GAWR.
AXLE RATIO
This is a number (3.07:1, 4.56:1, for example) expressing the ratio between driveshaft revolutions and wheel revolutions. A low numerical ratio allows the engine to work easier because it doesn't have to turn as fast. A high numerical ratio means that the engine has to turn more rpm's to move the wheels through the same number of turns.