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    GLOSSARY TERMS

    A

    A
    An abbreviation for ampere.
    A V-8
    A Ford model A retrofit with a late model V-8 engine.
    A-arm
    A triangular-shaped suspension control-arm device, with two points connected to the chassis and one to the wheel spindle. Control arms are sometimes called A-arms because from the top view, they are shaped like the letter A. Also referred to as A-frame.
    A-cam
    Pattern used for grinding pistons in an oval- or cam-shape with 0.005 inch (0.127 mm) difference between the thrust face and the pinhole side.
    A-Frame
    A term often used for A-arm.
    A-Pillar
    The structural support on either side of the windshield, just ahead of the front doors.
    A-Post
    A term often used for A-pillar.
    A-Shim
    A valve spring-adjuster insert with a thickness of 0.060 inch (1.524 mm) used to balance spring pressure and to correct installed height.
    A-Train
    A combination of two or more trailers in which the dolly (converter or turntable), is connected by a single pintle hook or coupler, and the drawbar connection is at the center, between each vehicle.
    A/C
    An abbreviation for air conditioning.
    A/F
    An abbreviation for air/fuel ratio.
    A/Gas
    One of four classes for non-supercharged coupes and sedans. Under National Hot Rod Association (NHRA) rules, overall weight range is from 6.5 to 8.49 pounds per cubic inch of engine displacement.
    A/T
    An abbreviation for automatic transmission.
    AAA
    An abbreviation for the American Automobile Association.
    AACA
    An abbreviation for the Antique Automobile Club of America.
    AAI
    An abbreviation for the Alliance of American Insurers.
    AAMA
    An abbreviation for the American Automobile Manufacturers Association.
    AARA
    An abbreviation for the Antique Auto Racing Association.
    ABCM
    An abbreviation for anti-lock brake control module. Some refer to it as anti-lock brake computer module.
    ABDC
    An abbreviation for after bottom dead center.
    Abnormal Operating Conditions (AOC)
    Adverse. Other than normal operating conditions, such as rain, snow, sleet, and ice.
    Abnormal Wear
    The excessive wear on a drive or driven member as might be caused by improper tensioning, misalignment, or abrasive materials in the drive environment.
    Abnormal Wear Pattern
    A visual indication that two or more members, such as gears, pulleys, and/or belts are improperly tensioned or aligned or that abrasive materials are present.
    Abort
    The procedure for intentionally terminating a program when a mistake, malfunction, or error has occurred.
    Abrasion Resistance
    A measure of a wire covering's ability to resist surface wear due to mechanical damage.
    Abrasive
    A very hard substance used for the removal of material by cutting, grinding, lapping, or polishing metals.
    Abrasive Finishing
    Any of several processes for removing scale or surface contaminants using abrasives, such as bonded grinding wheels or disks, coated abrasives, honing stones, or bonded abrasive sticks.
    Absolute Pressure
    A pressure measured from absolute zero.
    Absolute Pressure Sensor
    A device for sensing pressures from absolute zero.
    Absolute Rating
    A single eternal explanation for all reality. That point at which all motion in matter ceases, such as absolute zero. Also used in filter ratings to indicate the diameter of the largest particle, normally expressed in micrometers (µm), that will pass through the filter. A filter media with an exact and consistent pore size theoretically has an absolute rating.
    Absolute Zero
    The lowest temperature on the Kelvin temperature scale (0°K), equivalent to −459.7°F (−273.2°C). Temperature measured from 0°K is an absolute temperature. All molecular motion ceases at 0°K.
    Absorb
    To take in by capillary action, as in a sponge.
    Absorbent Medium
    A material akin to a sponge in that it can draw in fluid and retain it within its structure. In this sense, it can act as a filter to remove (absorb) and retain fluid.
    Absorptive Lens
    A filter lens designed to reduce the effects of glare, reflection, and stray light.
    AC
    An abbreviation for alternating current.
    AC Adapter
    A transformer-type power supply that plugs into an ac (alternating current) power outlet and provides low voltage ac or dc to provide power for accessory equipment.
    AC Power Supply
    A source of alternating current (ac), such as an ac outlet, transformer, inverter, or an alternator (ac generator).
    ACC
    An abbreviation for Automotive Communications Council.
    An abbreviation for air conditioning compressor signal switch.
    Abbreviation for accessory.
    Acceleration
    An increase in velocity or speed.
    Acceleration squat
    The tendency of the rear part of a vehicle to press down on the rear springs during hard acceleration.
    Accelerator
    A control, usually a foot-operated pedal, linked to the throttle valve of the carburetor and used to control the flow of fuel into the engine.
    Accelerator Pedal
    A foot-operated device for controlling the flow of fuel into the engine.
    Accelerator Ppedal Position Sensor
    A device designed to send an electrical signal to the central processing unit relative to the position of the accelerator pedal at any given time.
    Accelerator Pump
    A pump in the carburetor connected by linkage to the accelerator pedal that momentarily enriches the air-fuel mixture when the accelerator is depressed at low speed.
    Accelerometer
    An instrument that measures a vehicle's linear or lateral rate of acceleration in g force or feet per second.
    Acceptable Weld
    A weld that meets all the requirements and the acceptance criteria prescribed by the welding specifications.
    Access Fitting
    A service port or service valve. Also may refer to an access valve.
    Access Slot
    An opening that permits access to a device, such as the openings in the backing plates of a brake system that allow access to the star wheel adjuster.
    Access Time
    The time that is required to retrieve information from a system's memory.
    Access Valve
    A service port or service valve. Also may refer to an access fitting.
    Accidental Ground
    A condition that exists when a wire, connected to the positive battery terminal, contacts a grounded metal part of the car.
    ACCS
    An abbreviation for air conditioning cycling-clutch switch.
    Accumulator
    A tank located in the outlet of the evaporator to receive the refrigerant that leaves the evaporator. A component used to store or hold liquid refrigerant in an air-conditioning system. This device is constructed to ensure that no liquid refrigerant enters the compressor.
    A device that cushions the motion of a clutch and servo action in an automatic transmission.
    A register or storage location that forms the result of an arithmetic or logic operation. Commonly used when a series of calculations are to be totaled.
    Accumulator-Dehydrator
    An air conditioner accumulator that includes a desiccant.
    Accumulator-Drier
    A term often used for accumulator-dehydrator.
    Accuracy
    The conformity of an indicated value to a value accepted as a standard.
    ACCUS
    An abbreviation for the Automobile Competition Committee for the United States.
    Acetic Acid
    An activator that is used in RTV/silicone sealants to make them more rubber-like in composition.
    Acetone
    A highly flammable liquid sometimes used as a racing-fuel additive. Acetone CH3COCH3 helps to prevent other chemicals in a fuel mixture from separating.
    A powerful ketone-type lacquer solvent.
    Used as a solvent to clean parts.
    Acetylene
    A highly flammable gas (C2H2) used for metal cutting, welding, and brazing.
    ACID
    An acronym for a four-mode, driving-test cycle used to test exhaust emissions or vehicle driveability; the modes are Accelerate, Cruise, Idle, and Decelerate.
    Hydrogen (H) compounds that yield hydrogen ions when dissolved in water. There are many types of organic and inorganic acids. Though acids are the most important and useful of all the chemicals, acids are not wanted in some environments.
    Acid Dip
    A method of paint stripping. Metal parts can be immersed in an acid dip to remove all traces of old paint and chemical impurities.
    To immerse stock-car-body panels in acid to reduce sheet metal thickness by etching, thus reducing weight.
    Acid Rain
    Corrosive rain formed when sulfur (S) emissions from motor vehicles and industrial plants combine with hydrogen (H) and oxygen (O) in the atmosphere to form sulfuric acid (H2SO4). The mixture of these chemicals with water (H2O) produces an acid solution that is found in rain. Not only is it corrosive to anything it may come into contact with, it also raises the acidity of lakes and ponds, often to the point that fish and other aquatic life cannot survive.
    Acidity
    The presence of acid-type chemicals that are identified by the acid number. Acidity within some environments, such as the crankcase of an engine, causes corrosion, sludge, and varnish to increase.
    Ackerman Principle
    The geometric principle used to provide toe-out on turns. The ends of the steering arms are angled so that the inside wheel turns more than the outside wheel when a vehicle is making a turn, without scrubbing the tire treads on the road surface.
    Ackerman Steering
    A term often used for Ackerman principle.
    ACL
    An abbreviation for automatic chassis lubrication.
    ACM
    An abbreviation for air-control module.
    ACR3
    An abbreviation for an Air Conditioning and Refrigeration Refrigerant Recovery, Reclaim, and Recycle system.
    ACRL
    An abbreviation for American City Racing League.
    ACRS
    An abbreviation for air-cushion restraint system.
    Acrylic
    A polymer-based coating acrylic (CnH2n–2O2) widely used for automotive topcoats. Its physical properties can be controlled in part by the choice of the alcohol used to make the ester.
    ACSI
    Abbreviation for the Automotive Cooling System Institute.
    ACT
    An acronym for air charge temperature.
    Active Coil
    Those coils that are free to deflect under a load.
    Active Plate Material
    The sponge lead in an automotive battery that is spread over the negative-plate grid or the lead peroxide that is spread over the positive-plate grid.
    Active Restraint
    A vehicle occupant restraint, such as a lap belt and/or shoulder harness, that must be attached or connected by the person using it.
    Active Solvent
    A liquid that can dissolve a paint binder when used alone.
    Active Spring Coil
    Active coils in the center of the spring operate during the complete range of spring loading. Also, see inactive spring coil and transitional spring coil.
    Active Suspension System
    Also known as computer-controlled suspension system, a computerized system able to control body roll, body pitch, brake dive, acceleration squat, and ride height. Suspension systems that are controlled by double-acting hydraulic cylinders or solenoids (actuators) mounted at each wheel. The actuators support the vehicle's weight, instead of conventional springs or air springs.
    Actual Cash Value (ACV)
    The true value of a product, such as a used vehicle.
    Actual Throat
    A welding term indicating the shortest distance between the weld root and the face of a fillet weld.
    ACV
    An abbreviation for air-control valve.
    An abbreviation for actual cash value.
    Adapter
    Any of various pieces of hardware that permits non-matching parts to connect, mesh, or function together.
    A device used to connect an engine and a transmission not originally designed to be used together.
    Welds under a spring seat to increase mounting height of the fit seal to the axle.
    Adaptive Memory
    The feature of a computer memory that allows the microprocessor to automatically compensate for changes in the dynamics of the process being controlled. Anything stored in adaptive memory is lost when power to the computer is interrupted, such as when the battery is disconnected.
    Adaptor
    Another way of spelling adapter.
    Add-On
    Any device or system added to a vehicle by the dealer, independent garage, or owner.
    A component or device added to a computer system to increase its storage capacity, to modify its architecture, or to upgrade its performance; circuitry or system that can be attached to a computer.
    Add-On Coolers
    A method of increasing the transmission system's cooling capacity by adding an external fluid cooling unit.
    A device to provide cooling for the power-steering fluid.
    Additive
    Any material added to a lubricating grease or oil to improve its suitability for service. It may improve a property that the lubricant already possesses or give it properties that it does not naturally possess.
    Any material added to the cooling system to inhibit rust, increase the boiling point, and/or decrease the freezing point.
    Any one of a number of special chemicals added to a paint to bring about special effects.
    Address
    A number identifying the location of a word in computer memory.
    Adhesion
    The ability of a tire to remain in contact with the road surface.
    The property of oil that causes it to cling to metal surfaces, such as bearings.
    Adhesive Bonding
    A technique for bonding metals and/or plastics together during assembly of panels and bodies.
    A process used to attach aftermarket body kits, such as rocker panels and spoilers.
    Adiabatic Engine
    An engine having combustion chambers insulated with a high-temperature material. Heat loss is kept at a minimum and is retained rather than being allowed to dissipate through the cooling and exhaust systems. This results in a higher proportion of thermal energy being converted to useful power.
    Adjust
    To bring the parts of a component, system, or device to a specific relationship, dimension, temperature, or pressure.
    Adjustable Shock
    Another term used for adjustable shock absorber.
    Adjustable Shock Absorber
    A shock absorber having an external means of adjustment to calibrate it precisely for a specific operating condition.
    Adjustable Strut
    A strut with a manually operated adjustment for strut firmness. The strut adjusting knob, usually accessible without raising the vehicle, varies the strut orifice opening. Also see travel-sensitive strut.
    Adjustable Torque Arm
    A member used to retain axle alignment and, in some cases, control axle torque. Normally one adjustable and one rigid torque arm are used per axle so the axle can be aligned. This rod can be extended or retracted for adjustment purposes.
    Adjusting Cam
    Eccentric bolts that are used to automatically or manually adjust the brake shoe-to-drum clearance. Positioned in the backing plate of drum brakes, the cam positions the shoe(s) closer to the drum.
    Adjusting Shim
    A metal shim, available in various thicknesses, used to change the valve clearance in some overhead cam engines.
    Adjusting Sleeve
    An internally threaded sleeve located between the tie rod ends. The sleeve is rotated to set toe in/toe out.
    Adjustment
    To make a necessary or desired change in clearance, fit, or setting.
    Adsorb
    To collect a very thin layer on the surface of a material.
    Adsorbent Media
    Generally used in filters for the removal of odors, smoke, fumes, and some impurities. The chief adsorptive granular media used for filters are activated charcoal and similar forms of carbon, Fuller's earth, and other active clays. Also see canister filter and filter.
    Adsorption
    The attraction and/or retention of particles by molecular attraction or electrostatic forces present between the particles and a filter medium.
    Advance Curve
    A term generally relating to spark advance curve.
    AEA
    An abbreviation for the Automotive Electrical Association.
    AERA
    An abbreviation for Automotive Engine Rebuilders Association.
    Aerobic Sealer
    A silicone rubber sealing compound that requires oxygen for curing, such as RTV, used to hold parts together.
    Aerodynamic
    The ease with which air can flow over the vehicle during higher speed operation. An aerodynamically sound vehicle has very little wind resistance.
    Aerodynamic Drag
    The resistance of air against an object, such as an automobile, trying to pass through it. Also referred to as air drag and air resistance.
    Aerodynamic Force
    A force created aerodynamically, such as by an air foil.
    Aerodynamic Resistance
    Resistance of the air against an object, such as a vehicle, trying to pass through it. The result of four factors; coefficient of drag, frontal area, vehicle speed, and air density. Also referred to as air drag, air resistance, and aerodynamic drag.
    AESMC
    An abbreviation for the Automotive Exhaust Systems Manufacturing Council.
    AFR
    An abbreviation for air/fuel ratio.
    After Bottom Dead Center (ABDC)
    The position of a piston as it begins its compression or exhaust stroke.
    After Top Dead Center (ATDC)
    The position of a piston as it begins its intake or power stroke.
    Afterboil
    The boiling of fuel in the carburetor or coolant in the engine immediately after the engine has been stopped.
    Afterburner
    A type of engine exhaust manifold that burns any HC and CO remaining in the exhaust gas.
    Aftermarket
    Equipment sold to consumers after the vehicle has been manufactured. Aftermarket equipment and parts are sold by catalog, dealers, independent garages, and parts houses.
    Afterrunning
    A term often used when an engine continues to run after the ignition has been turned off. More often referred to as dieseling.
    Aging
    A time-temperature dependent change in the properties of certain materials occurring at room or slightly elevated temperatures following hot or cold working, or following quenching after thermal treatment.
    AHRA
    An abbreviation for the now-defunct American Hot Rod Association.
    AIA
    An abbreviation for the Automobile Importers of America.
    An abbreviation for Automotive Industries Association.
    An abbreviation for the Asbestos Information Association.
    AIADA
    An abbreviation for the American International Automobile Dealers Association.
    AIAM
    An abbreviation for the Association of International Automobile Manufacturers.
    Aiming Screws
    Self-locking screws for adjusting the headlamp in horizontal and vertical positions and for retaining the proper position.
    AIR
    The combination of gases that make up the earth's atmosphere: nitrogen (76–78%), oxygen (18–21%), and small amounts of carbon dioxide, argon, and other gases. When air is drawn into an engine, the oxygen combines with the fuel during combustion, producing carbon dioxide and water vapor.
    An acronym for air-injection reactor.
    Air Bag
    Passive restraint with an inflatable air bag located in the steering wheel in front of the driver and in the dash in front of the right front seat passenger.
    An inflatable bladder used in the place of a spring in an air suspension system. Also see air lift.
    Air Bag Igniter
    A combustible device that converts electric energy into thermal energy to ignite the inflator propellant. The igniter is an integral component of the inflator assembly.
    Air Bag Inflator
    A term often used for air bag igniter.
    Air Bag Module
    The air bag and inflator assembly together in a single package. This module is mounted in the center of the steering wheel.
    Air Bag System
    The air bag system is designed as a supplemental restraint. In the case of an accident it will deploy a bag from the steering wheel or passenger side dash panel to provide additional protection against head and face injuries.
    Air Bleed
    Holes or tubes in the carburetor to allow air to premix with gas flow.
    Air Box
    An enclosed chamber to direct air into a carburetor or intake manifold.
    Air Brake
    A moveable dynamic spoiler that can be raised against the wind to slow a high speed vehicle.
    The braking system on some heavy duty trucks that uses compressed air to expand the brake shoes by cam or wedge against the brake drums.
    Air Carbon Arc Cutting
    A carbon arc-cutting process that removes molten metal with a jet of air.
    Air Charge Temperature (ACT)
    The temperature of incoming air in a fuel-injection system.
    Air Cleaner
    A device connected to the carburetor in a manner that all incoming air must pass through it. Its purpose is to filter dirt and dust from the air before it passes into the engine.
    Air Compressor
    Engine-driven mechanism for supplying high pressure air to truck brake systems. There are basically two types of compressors: those designed to work on in-line engines and those that work on V-type engines. The in-line type is mounted forward and is gear driven, while the V-type is mounted toward the fire wall and is camshaft driven.
    A gasoline engine or electric-motor-driven mechanism for supplying shop air for the lift, air tools, and paint spraying equipment.
    Air Conditioner
    A device used for the automatic control of the temperature, humidity, cleanness, and movement of air in a given space.
    Air Conditioning (A/C)
    The process of adjusting and regulating, by heating or refrigerating, the quality, quantity, temperature, humidity, and circulation of air in a space or enclosure; to condition the air.
    Air Conditioning and Refrigeration Refrigerant Recovery, Reclaim, and Recycle System (ACR3)
    Equipment that is used to recover, reclaim, and recycle refrigerant from an air, conditioning or refrigeration system.
    Air Control Valve (ACV)
    A component used to route air from the pump to either the exhaust manifold or to the catalytic converter.
    Air Cooled
    Removing heat from the engine by circulating air across the cylinder block and heads.
    Air Cooling
    Simple method of engine cooling that relies on forced airflow over extended metal fins on the cylinder head and the block to maintain proper operating temperature.
    Air Core
    A method of constructing coils or transformers in which the wire is wound on a hollow, air-filled form instead of one using magnetic material in the core.
    Air Cushion Restraint System
    A term used for air bag system.
    Air Dam
    A panel across a race car's front end, designed to reduce the air pressure beneath the vehicle for a better ground effect.
    Panels around the radiator to ensure that all air passes through, not around, the radiator.
    Air Delivery System
    The component that contains the air ducts, doors, blower, evaporator core, heater core, and controls that deliver air to the interior via the various outlets.
    Air Door
    A door in the duct system that controls the flow of air in the air conditioner and/or heater.
    Air Drag
    The resistance of air against an object, such as an automobile, trying to pass through it. Also referred to as aerodynamic resistance and aerodynamic drag, air resistance.
    Air Duct(s)
    Tubes, channels, or other tubular structures used to carry air to a specific location.
    Air Filter
    A filter that removes dust, dirt, and particles from the air passing through it.
    Air Foil
    The inverted wing of a race car designed to increase downward aerodynamic force and, with it, vehicle traction.
    Air Gap
    A small space between parts that are mated magnetically or electrically.
    Air Hoist
    A hoisting device using compressed air in a cylinder, acting against a piston, with suitable outside connections, such as a hook.
    Air Horn
    A horn that is actuated by compressed air.
    A tubular passage containing the choke valves in the atmospheric side of a carburetor venturi through which the incoming air must pass.
    Air Hose
    Air lines between the tractor and trailer supplying air to the trailer brakes.
    Air Inlet Valve
    A movable door in the plenum blower assembly that permits the selection of outside air or inside air for both heating and cooling systems.
    Air Intake and Exhaust System
    The parts on the automobile engine used to get the air into the engine and the exhaust out of the engine, including air cleaner, muffler, tail pipe, and associated ducting.
    Air Intake System
    A system that allows fresh clean air to enter a component such as an air conditioner, passenger compartment, or engine.
    Air Jack
    A device that uses compressed air to lift a vehicle. On some Indy and sports GT cars, the jacks are built into the chassis, permitting the whole car to be raised instantly. This enables the pit crew to change all four tires simultaneously.
    Air Lift
    A tradename for a pneumatic helper spring with a Schrader valve that simplifies increasing or decreasing air pressure to compensate for changes in load.
    Air Line
    A hose, pipe, or tube through which air passes.
    Air Lock
    A pocket of air that blocks the normal flow of liquid in a system.
    Air Nozzle
    The tube through which air is delivered to the exhaust gas in an air-injection system.
    A device used to direct a stream of air into the desired area.
    Air Outlet Valve
    A movable door in the plenum blower assembly that directs airflow into the heater core or into the duct-work that leads to the evaporator.
    Air Pollution
    The introduction of impurities and contaminants, many of which are caused by humans, into the atmosphere.
    Air Pressure
    Atmospheric pressure.
    The pressure produced by an air pump or compressor in a cylinder.
    Air Pump
    A belt- or direct-driven vane-type pump that supplies the air needed for most air-injection systems.
    A term often used for air compressor.
    Air Resistance
    The resistance of air against an object, such as an automobile, trying to pass through it. Also referred to as air drag, aerodynamic drag, and aerodynamic resistance.
    Air Scoop
    Openings at the front and/or along the side of a vehicle's bodywork to channel cool, ambient air to the radiator, engine, induction system, oil cooler, or brakes.
    Air Shifting
    Process that uses air pressure to engage different range combinations in the transmission's auxiliary section without a mechanical linkage to the driver.
    Air Shock
    Also known as load-leveling shock absorber. A shock operating on principles of air pressure; may also have a hydraulic section.
    Air Shock Absorber
    A term often used when referring to an air shock or load-leveling shock absorber.
    Air Slide Release
    An air-operated release mechanism for positioning a sliding fifth wheel, operated from the cab of a tractor by actuating an air-control valve.
    Air Spring
    Also known as air bag. An air-filled device that functions as the spring on axles that utilize air pressure in the suspension system.
    Air Spring Suspension
    A single or multiaxle suspension relying on air bags for springs and weight distribution of axles.
    Air Suspension Speaker
    A speaker mounted in a closed box so that the enclosed air acts as a spring against the back side of the speaker cone.
    Air Suspension System
    A suspension system that uses contained compressed air for vehicle springing.
    Air Temperature Sensor
    A unit consisting of an aspirator, bimetallic sensing element, and a vacuum modulator used to sense in-car temperature.
    Air to Water Intercooler
    A heat exchanger on a turbocharged engine that uses ambient air to cool air coming from the turbo to the intake manifold.
    Air-Conditioner Muffler
    A tank-like device usually located in the compressor discharge line to reduce compressor pumping sounds.
    Air-Control Module (ACM)
    A component of the fuel control system that monitors intake air volume and meters fuel accordingly.
    Air-Cooled Engine
    An engine that is cooled by the passage of air, generally forced, around and over the cylinders.
    Air-Injection Reactor (AIR)
    An air-injection system comprised of a vane pump, diverter valve, and check valve; a type of emission control system that pumps fresh air into the exhaust.
    Air-Injection System
    One that supplies fresh air to the exhaust stream, which helps oxidize HC and CO, and, gives the catalyst in the catalytic converter the extra air it needs to oxidize those pollutants.
    Air-Injector System
    Engine emission-control system that injects fresh air at each exhaust port. The injected air mixes with the hot exhaust gases prolonging combustion, which reduces hydrocarbon and carbon monoxide exhaust emissions.
    Air-Over-Hydraulic Brakes
    Brakes utilizing a hydraulic system assisted by an air pressure system.
    Air/Fuel Mixture
    The proportion of air to fuel provided by a carburetor or fuel-injection system.
    Air/Fuel Ratio (A/F, AFR)
    The relative proportions of air and fuel entering an engine's cylinders as produced by the carburetor or fuel-injection system; the measure of the amount of air and fuel needed for proper combustion. The ideal or stoichiometric ratio for gasoline is 14.7: 1 air to fuel by weight. A higher ratio would contain more air and less fuel, and would be considered a lean mixture. A lower ratio with more fuel and less air would be a rich mixture. The air/fuel ratio is determined by the orifice size of the main jets inside a carburetor, the dwell duration of the mixture control solenoid inside a feedback carburetor, or the orifice opening and fuel pulse duration of a fuel injector.
    Airborne
    A term used to describe contaminants floating in air through the engine. The contaminants are light enough to be suspended in the air stream.
    Airflow Sensor (AS)
    An instrument for measuring airflow in an electronic fuel-injection system to be processed by the electronic control module with other sensory data to calibrate the air/fuel mixture.
    Airless Blasting
    A method of surface cleaning parts using propelled shot.
    Airtight Container
    A container used to hold waste and oily rags, so that spontaneous combustion is prevented.
    A container in a part of a sealed system.
    AK Steel
    A term often used for aluminum-killed steel.
    Al
    Symbol for Aluminum.
    ALCL
    An abbreviation for assembly line communications link.
    Alcohol
    A colorless volatile liquid; some forms can be used as a fuel for racing engines.
    ALDL
    An abbreviation for assembly line data link.
    Algorithm
    Step-by-step specification of the solution to a problem, usually represented by a flow chart that is finally translated into a readable and understandable program.
    Align Bore
    A stationary or portable boring machine used to correct an engine's out-of-round and/or warped main bearing housings.
    Align Hone
    A stationary machine operation that corrects an engine's out-of-round and/or warped main bearing housings using a special honing mandrel.
    Align Ream
    A machine or hand process to enlarge the inside diameter of bushings to the proper size.
    Alignment
    The act of lining up or the state of being in a true line.
    Alignment Gap
    The distance between two adjacent auto-body panels.
    Alignment Pin
    A pin or pins used to align one part with another, such as the pins used to align a cylinder head on an engine block.
    Alignment Stud
    A stud or studs used to align one part with another, such as the studs used to align a cylinder head on an engine block.
    Alky
    A performance term used for alcohol, usually methanol, used as a fuel for racing car engines.
    Alkyd
    A coating based on a polyester binder. The polyester binders are chemical combinations of molecules that contain more than one acid or alcohol group. Alkyds are widely used in water-based house paints and automotive primers.
    All-Season Tire
    Tires with special tread designed to improve traction on snow or ice (generally provides 37% higher average snow traction compared with non-all-season tires), while providing acceptable noise levels on smooth road surfaces.
    All-Terrain Cycle
    A small, three-wheeled, off- road vehicle by Honda.
    All-Terrain Vehicle
    A small, lightweight, four-wheeled vehicle with high flotation tires designed primarily for off-highway use.
    All-Wheel Drive (AWD)
    A vehicle drivetrain with a center differential having all four wheels under power at all times.
    Alliance of American Insurers (AAI)
    An association of insurance companies that write auto, liability, property, and worker's compensation coverage insurance.
    Allotropic
    A term that applies to elements that appear in more than one form, though their atomic composition is the same. For example, the properties of graphite and diamond are the same as the element carbon (C). Since their physical properties are entirely different, both are called an allotropic of carbon.
    Alloy
    A metal containing additions of other metallic or nonmetallic elements to enhance specific properties such as strength and corrosion resistance.
    Alloy Powder
    Powder prepared from a homogeneous molten alloy or from the solidification product of such an alloy.
    Alloy Steel
    Steel containing specified quantities of alloying elements added to effect changes in mechanical or physical properties.
    Alloys
    Light-weight aluminum or magnesium alloy wheels. Also see mags.
    Alpha Particle
    A particle that is a by-product of radioactive decay. It has a positive electrical charge that is twice the negative charge of an electron.
    Alphanumeric
    Set of all machine-processable alphabetic letters (a to z), numeric digits (0 to 9), and special characters (such as those that appear on a typewriter).
    Alt
    An abbreviation for alternator. Also, may be used as an abbreviation for alternate or altitude.
    Altered
    A drag-racing vehicle with a stock-looking coupe, roadster, or sedan body, but without normal street equipment. The engine and/or cockpit may be moved to the rear for better weight distribution.
    Alternating Current (ac or AC)
    The type of electrical current actually produced in an alternator.
    Alternator
    An electricity-generating device that converts mechanical energy to electrical energy in the form of alternating current. Diodes rectify the alternating current into direct current.
    Altitude
    The distance of a point above sea level. Important to automotive emissions control because the higher the altitude, the fewer oxygen molecules per given volume of air, which alters the effective compression and air/fuel ratios.
    Altitude Compensation System
    An altitude barometric switch and solenoid used to provide better driveability at more than 4,000 feet (1,219 meters) above sea level.
    Alum
    A crystallized double sulfate of aluminum (Al) and potassium (K).
    More commonly, an abbreviation for aluminum (Al).
    Aluminized Coating
    A metal spray process used to coat engine components subject to high temperatures for long periods of time to increase heat dissipation to the ambient atmosphere.
    Aluminized Valve
    A valve with a thin layer of aluminum sprayed on the valve face and, sometimes, on the top of the valve head to provide a thin, hard, corrosion-resistant coating.
    Aluminum (Al)
    A versatile engineering and construction material that is light in weight and resists corrosion. Automobile manufactures have increased the use of aluminum due to its many benefits, one of which is increased fuel efficiency due to weight reduction
    Aluminum Cylinder Block
    An engine block cast of aluminum or aluminum alloy, usually with cast iron sleeves installed as cylinder bores.
    Aluminum-Killed Steel
    Steel alloy in which aluminum has been added to kill it in the molten stage and refine its grain structure. A process of stopping molten steel from bubbling and combining with oxygen after being poured into ingots. Also see silicone-killed steel.
    Amber Lens
    The color lens used for turn signals and flashers on modern motor vehicles.
    Ambient Air
    The air that surrounds an object.
    Ambient Air Temperature
    The temperature of the air that surrounds an object.
    Ambient Compressor Switch
    An electrical switch that energizes the air conditioner compressor clutch when the outside ambient air temperature is 47°F (8.3°C) or above. Similarly, the switch turns off the compressor when the air temperature drops below 32°F (0°C).
    Ambient Sensor
    A sensor used on computerized automatic temperature-control systems that senses the outside air temperature and uses this information as an input to the system; a thermistor used in automatic temperature-control units to sense ambient temperature. Also see thermistor.
    Ambient Switch
    A switch used to control compressor operation by turning it ON or OFF. The switch is regulated by ambient temperature.
    Ambient Temperature
    The temperature of the air surrounding a vehicle.
    Ambient Temperature Sensor
    A sensor that measures the outside air temperature as it enters the evaporator.
    American Automobile Association (AAA)
    A motor club providing travel information, emergency road service, and other services to its members.
    American Automobile Manufacturers Association (AAMA)
    A trade association of Chrysler, Ford, and General Motors that sponsors research, disseminates information, and lobbies on behalf of the American automotive industry in the United States.
    American City Racing League
    A racing series sanctioned by the Sports Car Club of America (SCCA) for three-car teams representing specific cities and running 2000 spec cars with 2.0 liter Ford engines.
    American Hot Rod Association (AHRA)
    A drag-racing sanctioning body that is no longer in existence.
    American International Automobile Dealers Association (AIADA)
    An association of auto dealers and their employees who sell and service automobiles manufactured in the United States and abroad.
    American National Standards Institute (ANSI)
    A privately funded organization that promotes uniform standards in such areas as measurements.
    American Petroleum Institute (API)
    A petroleum-industry lobbying and public information group.
    American Society of Mechanical Engineers (ASME)
    An association to which mechanical engineers can belong. Through ASME, members can keep current on new technologies and procedures in the engineering field.
    American Society of Test Engineers (ASTE)
    An association to foster improved communications among those involved in the testing industry.
    American Society of Testing and Materials (ASTM)
    A professional organization to develop and promote standards for products, materials, systems, and services.
    American Trucking Association (ATA)
    A national federation of commercial trucking associations.
    American Wire Gauge (AWG)
    A standard for the measurement of the size of wire. The higher the gauge number, the smaller the wire.
    Ammeter
    An instrument used to determine the amount of amperage (current draw) in a circuit by the strength of the magnetic field that is created by the current flowing through the wire.
    Ammeter Shunt
    A low-resistance conductor used to increase the range of an ammeter. It is shunted (placed in parallel) across the ammeter movement and carries the majority of the current.
    Amp
    An abbreviation for ampere.
    Amp/Hour
    Amperes per hour; a standard measure for a rate of current flow.
    Ampacity
    The current-carrying capacity of conductors or equipment, expressed in amperes.
    Amperage
    The amount of current, expressed in amperes.
    Amperage Capacity
    An indication of the length of time a battery can produce an amperage, or the amount of amperage that a battery can produce before being discharged.
    Ampere (A)
    A unit of measure for current.
    Anaerobic Sealants
    A chemical sealant placed on a gasket in an engine to aid in sealing and to position the gasket during installation.
    Anaerobic Sealer
    Liquid or gel that bonds two parts together in the absence of air.
    Analog Computer
    A computer that measures continuously changing conditions, such as temperature and pressure, and converts them into quantities.
    Analog Instrument
    An instrument having a needle on a dial used for taking measurements, such as temperature and engine RPM.
    Analog-to-Digital Converter
    Mechanical or electrical device used to convert continuous analog signals to discrete digital numbers.
    Anaroid Tube
    A thermo-mechanical device in a fuel-injection system that regulates the amount of fuel being injected according to differences in temperature and pressure in the intake manifold.
    Anchor
    A slang expression for brakes.
    A mounting point on a vehicle structure for a stressed, non-structural component, such as a seat belt or a seat.
    Anchor End
    That end of a brake shoe that is attached to a fixed point on the backing plate.
    Anchor Pin
    A steel pin rigidly attached to the backing plate of drum brakes. Return springs are attached to the anchor pin and to the brake shoes to hold the shoes against the anchor pin in a non-applied position. In an applied position, it prevents the shoes from rotating with the drums.
    Anchors
    Performance term for brakes.
    Aneroid Bellows
    An accordion-shaped temperature sensor charged with a small amount of volatile liquid. Temperature change causes the bellows to contract or expand, which, in turn, opens or closes a switch, such as a thermostat.
    Angle Block
    A cylinder block that does not have a deck at 90 degrees to the cylinders.
    Angle Mill
    A machining operation to mill the deck surface at a shallow angle on the exhaust side of the engine block in order to increase the compression ratio by decreasing the combustion chamber volume.
    Angle Plug Head
    A cylinder head having spark plugs that are angled toward the exhaust valves.
    Anneal
    A heating and cooling of steel in the solid state, usually requiring gradual cooling.
    To heat aluminum to 640°F (338°C) and then cool it to 450°F (232°C) to soften it to make it ductile.
    Annealing
    A heat-treatment process to reduce hardness or brittleness, relieve stresses, improve machinability, facilitate cold working, or produce a desired microstructure or property.
    Annulus
    Any type of ring gear, including the ring part of the ring and pinion in the rear end, and the gears in the planetary gear set of an automatic transmission.
    Anode
    The positively charged electrode in an electrolytic cell toward which current flows.
    Anodize
    A protective oxide coating to a metal surface using the metal as the anode in an electrical cell and allowing an electrolyte to act upon it.
    ANSI
    An abbreviation for the American National Standards Institute.
    Ant
    An abbreviation for antenna.
    Antenna
    A wire or other conductive metallic structure used for radiating or receiving electromagnetic signals, such as those for radio, television, or radar.
    Anti-Backfire Valve
    A valve that is used in the air-injection system to prevent backfiring in the exhaust system during deceleration.
    Anti-Drive
    A suspension geometry that resists a vehicle's tendency to drop or dive on the front springs when braking.
    Anti-Foam Agent
    An additive that reduces foaming caused by the churning action of the crankshaft in the engine oil.
    Anti-Fouler
    A device installed on a spark plug in an oil-burning engine to reduce the fouling of the plug.
    Anti-Icers
    Chemicals added to gasoline to prevent it from freezing.
    Anti-Knock Additive
    A compound that may be added to gasoline to increase its octane, thereby decreasing its knock.
    Anti-Knock Index
    The average of the motor octane number (MON) and the research octane number (RON); a measure of a fuel's anti-knock characteristics.
    Anti-Lock Brake
    A type of braking system that senses the speed of each wheel and, in conjunction with a computer, controls the hydraulic braking pressure, thereby eliminating wheel lockup.
    Anti-Lock Brake Control Module
    The computer used to control an anti-lock braking system.
    Anti-Lock Brake System
    A term often used for anti-lock brake.
    Anti-Oxidant
    A substance that prevents or slows down oxidation of plastic material that is exposed to air and the elements.
    Anti-Percolation Valve
    A device used to prevent fuel from evaporating from the fuel bowl of a carburetor while the engine is running. It is connected to the throttle linkage, so it is closed when the throttle is open, and open when the throttle is closed. With the engine off, hot fuel vapors boil out through the vent line and into the charcoal canister.
    Anti-Rattle Hardware
    Clips, springs, and washers to prevent disc pads or brake shoes from rattling and vibrating.
    Anti-Rust Additive
    A solution that is added to coolant to retard rust formation inside a cooling system.
    Anti-Seize Compound
    A thread compound designed to protect threaded connections from damage due to rust or corrosion.
    Anti-Siphon System
    A small passage in a carburetor to prevent fuel from siphoning from the float bowl into the engine.
    Anti-Skid Control
    Accessory for the brake system that operates on rear wheels, or all four wheels, to prevent wheel lockup during braking. Braking pressure is reduced to wheel(s) that are about to lock up and skid, by electronic controls.
    Anti-Smog Device
    A part or parts designed to reduce or eliminate vehicle exhaust emissions.
    Anti-Squat
    Suspension geometry that will resist a vehicle's tendency to drop or squat on the rear springs when accelerating.
    Anti-Static Agents
    Treatment used during, and/or after the molding process to minimize static electricity in plastic materials.
    Anti-Sway Bar
    A suspension component, often called a sway bar, intended to prevent side-to-side body movement in relation to the axles and wheels.
    Anti-Theft System
    Deterrent systems designed to scare off would-be car thieves by sounding alarms and/or disabling the ignition system. Common components used in an automobile anti-theft system include an electronic control module, door switches at all doors, trunk key cylinder switch, hood switch, starter inhibitor relay, horn relay, and alarm.
    Antifreeze
    A chemical solution added to the coolant (water) to prevent freezing; usually ethylene glycol and anticorrosion chemicals. Ethylene glycol resists evaporation, but the anticorrosion elements in the antifreeze may be used up in one year, depending on the amount and type of driving.
    Antifriction Bearing
    The term applies to almost any ball-roller or taper-roller bearing.
    Antique
    Any automobile built before 1930.
    Antique Auto Mobile Club of America (AACA)
    An association of collectors, hobbyists, and others interested in the preservation, maintenance, and restoration of antique automobiles.
    Antique Auto Racing Association (AARA)
    An association of persons interested in the history of auto-racing; preserving, restoring, and driving antique race cars.
    AOC
    An abbreviation for abnormal operating conditions.
    APAA
    An abbreviation for the Automotive Parts and Accessories Association, Inc.
    Apex
    The innermost point of a turn or corner on a roadway or race course.
    Apex Seal
    A seal used to retain the combustion pressure at all three tips of the rotor in a rotary engine.
    Apexes
    The peaks on the rotor, formed by the meeting of two adjoining rotor faces in a rotary engine.
    API
    An abbreviation for American Petroleum Institute.
    API Degrees
    Another term used for API gravity.
    API Gravity
    The scale for the density (gravity) of a liquid petroleum product, expressed in API degrees. The lighter the product the higher the number.
    API Ring
    The information printed, in a ring, on the top or side of an oil or lubricant container providing the API specifications and ratings of the contents.
    Appearance Money
    The payment of money to a popular driver to encourage competition in a race, so his or her participation can be advertised in advance, thereby trying to attract a larger paying crowd.
    Application Cable
    The line or cable that engages the vehicle's emergency brake system.
    Apply Devices
    Devices that hold or drive members of a planetary gear set. They may be hydraulically or mechanically applied.
    Apply Side
    The side of a piston on which force or pressure is exerted to move the piston to do work.
    Appraiser
    An insurance company's representative who estimates a vehicle's damage and authorizes payment to the collision repair/refinishing shop. Also see estimator.
    Approach Angle
    The maximum angle, in degrees, of a line running upward and forward from the front tire contact point to the lowest obstruction under the front of the vehicle. Also see departure angle.
    APRA
    Abbreviation for Automotive Parts Rebuilders Association.
    Apron
    The inner edge of a race track.
    Aquaplaning
    A tire unable to remain in contact with the ground or pavement in wet weather that rides on the water itself. Also known as hydroplaning or, more simply, planing.
    ARA
    An abbreviation for:
    Automotive Recyclers Association.
    Automotive Retailers Association.
    Arbor
    A tapered metal shaft used to secure a cutting tool or a part being turned on a lathe.
    Arbor Press
    A manual- or power-operated press used to force arbors or mandrels into or out of holes and for similar assembly or disassembly operations.
    Arc
    To run flat out on an oval track.
    The discharge of electrical current across a gap between two electrodes.
    Arc Blow
    In welding, the deflection of an arc from its normal path because of magnetic forces.
    Arc Braze Welding
    A braze welding process that uses an arc to provide the heat.
    Arc Cutter
    A term often used for thermal cutter.
    Arc Cutting
    The thermal cutting process that severs or removes metal by melting it with the heat of an arc between an electrode and the work piece.
    Arc Force
    The axial force developed by an arc plasma during a welding procedure.
    Arc Gouging
    A thermal gouging that uses an arc-cutting process to form a bevel or groove.
    Arc Length
    The distance from the tip of the welding electrode to the adjacent surface of the weld pool.
    Arc Spraying
    A thermal spraying process using an arc between two consumable electrodes of surfacing materials as a heat source, and a compressed gas to atomize and propel the surfacing material to the substrate.
    Arc Welding
    A welding process that produces fusion of work pieces by heating them with an arc with or without the application of pressure and with or without filler metal.
    Architecture
    The physical structure of a computer's internal operations, including its registers, memory, instruction set, input/output structure, and so on.
    Arcing
    A term that applies to the spark that occurs in an electrical circuit in an air gap, such as a spark plug.
    Arcing Time
    The time elapsing from the severance of the circuit to the final interruption of current flow.
    Arithmetic-Logic Unit
    A basic element of the central processing unit (CPU) in a computer. That portion of the CPU where arithmetic and logical operations are performed.
    Arm
    To turn on a theft-deterrent system.
    Crankshaft throw. Also see long arm and short arm.
    Armature
    A part moved by magnetism.
    A part moved through a magnetic field to produce current.
    Armco
    The trade name of a particular type of guard rail or barrier used on public roadways and race courses.
    Arming
    In an automobile anti-theft system, arming means placing the alarm system in readiness, enabling it to detect an illegal entry. Arming is accomplished when the ignition switch is turned off and the doors are locked.
    Armored Ring Groove
    A metal ring groove cast into a piston during manufacturing to increase resistance to wear.
    Arnoid Gauge
    An instrument used to align the center of a crankshaft journal with the centers of a crankshaft grinder.
    Arnoid Hydrocarbons
    Compounds having carbons linked in a closed ring by alternating single and double bonds.
    Aromatic
    A type of solvent based on benzene ring molecules. Aromatics are often used as diluents in acrylic lacquers. Typical examples are benzene, xylol, and toluol.
    Articulated Vehicle
    Large trucks or buses with two or more wheeled units, so designed for ease of cornering.
    Articulating Upper coupler
    A bolster plate kingpin arrangement that is not rigidly attached to the trailer but provides articulation and/or oscillation about an axis parallel to the rear axle of the trailer.
    Articulation
    The action of a chain joint in flexing from the straight to an angle and back to the straight as the joint passes around a sprocket or other path.
    Vertical movement of the front driving or rear axle, relative to the frame of the vehicle to which they are attached.
    AS
    An abbreviation for airflow sensor.
    ASA
    An abbreviation for the Automotive Service Association.
    Asbestos
    A fiber mineral that is heat resistant and nonburning. Once used in brake linings, gaskets, and clutch facings, it is no longer used due to health hazards.
    Asbestos Information Association (AIA)
    An association to provide industry-wide information on asbestos and health, and on industry efforts to eliminate existing hazards.
    ASE
    An abbreviation and registered trademark of the National Institute for Automotive Service Excellence.
    ASIA
    An abbreviation for the Automotive Service Industry Association.
    ASME
    An abbreviation for the American Society of Mechanical Engineers.
    Aspect Ratio
    Also known as tire profile. A measurement of a tire; the percentage of the tire's height to the width.
    Asphalt Eater
    A top-performing drag car.
    Aspirator
    A device that uses suction to move air, accomplished by a differential in air pressure; a one-way valve attached to the exhaust system of an engine that admits air during periods of vacuum between exhaust pressure pulses. Used to help oxidize hydrocarbon (HC) and carbon monoxide (CO), and to supply additional air that the catalytic converter may require. Can be used instead of a belt-driven, air-injection pump in some applications.
    Aspirator Valve
    A device used to draw out fluids by suction. In this case, a pollution device is used to draw fresh air by suction into the exhaust flow to reduce emissions.
    Assembly
    Any unit made up of two or more parts.
    Assembly Line Communications Link
    An electrical connector used to check a vehicle's operating system while it is still on the assembly line.
    Assembly Line Data Link
    The information processed for use in assembly-line diagnostics.
    Assembly Lube
    A special lubricant used to coat parts that rub or rotate against each other during initial assembly.
    Association of International Automobile Manufactures (AIAM)
    A trade association of United States subsidiaries of international automobile companies.
    Assy
    An abbreviation for assembly.
    ASTE
    Abbreviation for American Society of Test Engineers.
    ASTM
    Abbreviation for American Society of Testing and Materials.
    Asymmetrical Cam
    A camshaft having different profiles for the intake and exhaust lobes.
    Asymmetrical Rear-Leaf Spring
    A spring on which the rear axle is not located in its center.
    AT
    An abbreviation for automatic transmission.
    ATA
    An abbreviation for the American Trucking Association.
    Atari Dashboard
    A digital instrument panel; so called due to its resemblance to an Atari video game.
    ATC
    A trade name by Honda for a three-wheeled all-terrain cycle.
    An abbreviation for automatic temperature control.
    ATC Servo Programmer
    A mechanically operated switch to control blower speed whenever the blower switch is in the AUTO position on some car lines.
    ATDC
    An abbreviation for after top dead center.
    ATF
    An abbreviation for automatic transmission fluid.
    Atmo
    A racing engine running on atmospheric pressure.
    An abbreviation for atmosphere.
    Atmosphere
    The mass of air that surrounds Earth.
    Atmospheric Ozone
    As ultraviolet (UV) rays from the sun reach Earth, they are combined with smog and other pollutants to produce atmospheric ozone. Atmospheric ozone, unlike stratospheric ozone, is considered harmful. Whenever possible it is to be avoided.
    Atmospheric Pollution
    Impurities and contaminants in the atmospheric environment, many of which are caused by humans.
    Atmospheric Pressure
    The pressure of the atmosphere at any given location. At sea level, it is 14.696 psia (101.33 kPa absolute).
    Atmospheric Pressure Sensor
    A device designed to send an electrical signal to the central processing unit relative to the atmospheric pressure at any given time.
    Atom
    A basic unit of matter consisting of protons, neutrons, and electrons.
    Atomization
    The breaking down of a liquid into small particles, like a mist, by the use of pressure.
    Atomized
    A liquid is atomized when it is broken into tiny droplets of the liquid, much like a mist or spray form.
    ATRA
    An abbreviation for Automatic Transmission Rebuilders Association.
    Attenuation
    The decrease in the strength of a signal as it passes through a control system.
    Attrition
    The wearing down by rubbing or friction; abrasion.
    ATV
    An abbreviation for all-terrain vehicle.
    Auto
    Shortened form for automatic or automobile.
    Auto Control
    Another term used for automatic control.
    Auto Ignition
    Short for automatic ignition.
    Autocross
    A form of automotive competition that is held on a tight, closed course. Vehicle handling and agility is stressed, rather than flat out speed.
    Automatic
    Having the power of self-motion, self-moving or self-acting.
    Automatic Adjuster
    A drum-brake mechanism that adjusts the lining clearance as wear occurs. It is commonly actuated on reverse stops or when the parking brake is set.
    Automatic Chassis Lubrication (ACL)
    A system where the chassis is automatically lubricated at predetermined intervals.
    Automatic Choke
    A mechanism that positions the choke valve automatically in accordance with engine temperature.
    Automatic Control
    A dial on the instrument panel that is set at a desired temperature level to control the condition of the air automatically.
    Any system that reacts to a predetermined condition rather than responding to external commands.
    Also known as auto control.
    Automatic Door Locks
    A passive system used to lock all doors when the required conditions are met. Many systems lock the doors when the gear selector is placed in drive, the ignition switch is in RUN, and all doors are properly shut.
    Automatic Headlight Dimming
    Automatically switches the headlights from high beams to low beams under two different conditions: when light from oncoming vehicles strikes the photocell-amplifier, or light from the taillights of a vehicle being passed strikes the photocell-amplifier.
    Automatic Ignition
    A condition where the engine continues to run after the ignition has been shut off. Often called dieseling or running on. Also known as auto ignition.
    Automatic Level Control
    A shock-absorber system operated by air pressure and provided as an accessory on some vehicles to automatically maintain the correct riding height under various load conditions.
    Automatic on/off with Time Delay
    To turn on the headlights automatically when ambient light decreases to a predetermined level.
    To allow the headlights to remain on for a certain amount of time after the vehicle has been turned off.
    Automatic Steering Effect
    The tendency of a vehicle to travel straight out of a turn when the steering wheel is released.
    Automatic Temperature Control (ATC)
    An air-conditioner control system designed to maintain a pre-selected, in-car temperature and humidity level automatically.
    Automatic Tensioning
    The constant tension of a device, maintained at a proper value by some automatic means, to minimize the attention required.
    Automatic Transmission (AT ? A/T)
    A transmission in which gear ratios are changed automatically.
    Automatic Transmission Cooler
    A device, often found in the radiator, through which automatic transmission fluid circulates to be cooled by surrounding air or engine coolant.
    Automatic Transmission Fluid (ATF)
    A red, petroleum-based fluid used to transfer power and control, lubricate, cool, and clean the automatic transmission.
    Automatic Transmission Rebuilders Association (ATRA)
    A trade association for transmission repair shops, technicians, and suppliers of transmission repair equipment, parts, and tools.
    Automation
    Semi-automatic or automatic material handlers, loaders, unloaders, and other labor-saving devices.
    Automatic cycle control of machines or equipment by tracer, cam, plugboard, numerical control, or computer.
    The application of machinery and equipment to perform and control semi-automatically or automatically and continuously all operations in a manufacturing plant.
    Automobile Competition Committee for the United States (ACCUS)
    With representatives of NASCAR, SCCA, IMSA, and USAC, the American affiliate of FISA, coordinating major United States racing events with the international calendar.
    Automobile Emissions
    Certain impurities that may enter the atmosphere during vehicle operation, such as hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOX).
    Automobile Importers of America (AIA)
    A professional organization of importers of cars and trucks into the United States.
    Automotive Air Conditioning
    The process of transferring heat from inside to outside the passenger compartment. The cooled air is also dehumidified, purified, and circulated.
    Automotive Air Pollution
    Evaporated and unburned fuel, and other undesirable by-products of combustion that escape from a motor vehicle into the atmosphere.
    Automotive Battery
    An electro-chemical device that stores and provides electrical energy for the operation of a vehicle.
    Automotive Body Shop
    A term often used for body shop.
    Automotive Communications Council (ACC)
    A professional association of advertising, marketing, and communications executives.
    Automotive Cooling System
    The many components that operate to absorb and dissipate heat developed in the combustion process, thus maintaining the desired engine-operating temperature.
    Automotive Cooling System Institute (ACSI)
    A Motor and Equipment Manufacturers Association subgroup made up of cooling-system product manufacturers.
    Automotive Electrical Association (AEA)
    A trade association absorbed in 1991 by the Automotive Service Industry Association (ASIA).
    Automotive Emissions
    Another term for automotive air pollution.
    Automotive Engine Rebuilders Association (AERA)
    An association of machine shops and others dedicated to engine rebuilding.
    Automotive Exhaust Systems Manufacturers Council (AESMC)
    An association that provides technical information and lobbying efforts on behalf of the exhaust-system-replacement market.
    Automotive Industries Association (AIA)
    A Canadian aftermarket trade group of distributors, suppliers, wholesalers, and retailers.
    Automotive Parts and Accessories Association, Inc. (APAA)
    A trade association for aftermarket retailers, wholesalers, manufacturers, and distributors.
    Automotive Parts Rebuilders Association (APRA)
    A trade association of automotive parts rebuilders and suppliers of remanufactured parts.
    Automotive Power Brakes
    A brake system having a vacuum and atmospheric air-operated power booster or hydraulic power boost to multiply braking force.
    Automotive Retailers Association (ARA)
    An association of the automotive retailers, sales and service, including collision repairs, mechanical repairs, used car sales, auto wrecking, and towing.
    Automotive Service Association (ASA)
    A trade organization for body, mechanical, and transmission shop owners.
    Automotive Service Industry Association (ASIA)
    A trade association for those who manufacture, distribute, and sell parts, tools, and equipment to the do-it-yourself (DIY) market and professional aftermarket.
    Automotive Warehouse Distributors Association (AWDA)
    An association of major manufacturers and warehouse distributors of aftermarket parts.
    Autronic Eye
    A trade term for automatic headlight dimmer.
    Aux
    An abbreviated form of auxiliary.2. An auxiliary item of equipment, such as aux fuel tank.
    Auxiliary
    A spare; an extra; a back-up system.
    Auxiliary Air Valve
    A device that allows air to bypass a closed throttle during engine start-up and warm-up.
    Auxiliary Drum Parking Brake
    The incorporation of an auxiliary parking-brake drum inside a rear rotor on some four-wheel drive disc-brake systems.
    Auxiliary Seal
    A secondary seal mounted outside the seal housing:
    To prevent refrigeration oil from escaping and entering the clutch assembly.
    To aid in the prevention of the loss of fluid from a system.
    Auxiliary Section
    The section of a transmission housing the auxiliary drive gear, main shaft assembly, countershaft, and synchronizer assembly, where range shifting occurs.
    Auxiliary Shaft
    A separate shaft, in an overhead cam engine, that drives devices such as the fuel pump, oil pump, and distributor.
    Auxiliary Springs
    A second or third valve spring with a different resonant frequency to cancel out harmonic vibrations that limit engine speed.
    The spring(s) added to a vehicle, generally in the rear, to support a heavy load.
    Auxiliary Venturi
    A small secondary venturi mounted inside the main venturi of a carburetor to provide increased air velocity. May also be called a booster venturi.
    Available Voltage
    The maximum voltage that can be produced in the secondary circuit of a conventional ignition system.
    Avalanche Diode
    A semiconductor designed to operate in the breakdown region to produce a constant voltage across the diode for regulating through the current though it may vary.
    Avgas
    Slang for aviation gasoline; generally higher octane than automobile gasoline.
    AWD
    An abbreviation for all-wheel drive.
    AWDA
    An abbreviation for Automotive Warehouse Distributors Association, Inc.
    AWG
    An abbreviation for American wire gauge.
    Axial Compressor
    A compressor designed so that the cylinders are arranged parallel to the output shaft.
    Axial Leads
    Wires that extend from the ends of an electronic component, such as a capacitor, along the axis of the unit.
    Axial Load
    A type of load placed on a bearing that is parallel to the axis of the rotating shaft.
    Axial Motion
    Motion that occurs along the axis of a revolving shaft or parallel to the axis of a revolving shaft.
    Axis
    The center line of a rotating part.
    Axle
    A cross member supporting a vehicle on which one or more wheels are mounted.
    A pair of wheels at either end of a vehicle. Some brake repair shops and turnpike tolls charge a per axle rate.
    Axle Bearing
    A bearing that supports an axle or half shaft in an axle housing.
    Axle Boot
    The flexible cover that retains grease and/or oil in a transmission or a constant velocity joint.
    Axle Carrier Assembly
    A cast-iron framework that can be removed from the rear-axle housing for service and adjustment.
    Axle Gears
    Bevel gears that transfer power from the differential pinion gears to the splined axle shafts.
    Axle Hop
    The tendency of the axle housing to rotate with the wheels slightly and then snap back during hard acceleration. This action may be repeated several times, creating a loss of traction until the driver releases the accelerator.
    Axle Housing
    Designed in the removable carrier or integral carrier types to house the drive pinion, ring gear, differential, and axle shaft assemblies.
    Axle Ratio
    The ratio between the rotational speed (rpm) of the drive shaft and that of the driven wheel; gear reduction through the differential, determined by dividing the number of teeth on the ring gear by the number of teeth on the drive pinion.
    Axle Seat
    Suspension component used to support and locate spring on the axle. Also known as a spring chair.
    Axle Shaft
    Alloy steel shaft that transfers torque from the differential side gears to the drive wheels. This shaft also supports vehicle weight on most passenger cars.
    Axle Tramp
    The tendency of a live axle housing to rotate with the wheels slightly and then snap back during hard acceleration. This action may be repeated several times, creating a loss of traction until the driver releases the accelerator.
    Axle Windup
    A term often used for axle tramp.
    Axle-Shaft End Thrust
    A force exerted on the end of an axle shaft that is most pronounced when the vehicle turns corners and curves.
    Axle-Shaft Tubes
    Tubes that are attached to the axle housing center section to surround the axle shaft and bearings.
    Azeotrope
    A mixture of two or more liquids, such as refrigerants, that when mixed in precise proportions, behave like a compound.
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