A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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A.B.S: Anti-lock braking system.
A.P.I.: American Petroleum Institute.
A.P.I. (C): American Petroleum Institute classification for oils suitable for diesel (compression ignition engines).
A.P.I. (S): American Petroleum Institute classification for oils suitable for gasoline (spark ignition) engines.
A.P.I. SC/CC: Engine lubricating oil classification suitable for basic petrol and diesel engines.
A.P.I. SG/CD: Engine lubricating oil classification suitable for modern engines.
A/C - Air Conditioning: Air conditioning system that uses a refrigerant to remove heat from the air entering the passenger compartment.
A/D Converter: An electronic device used to convert analog values to digital signals for electronic control units and instruments.
A/T: Automatic transmission.
Abrasion: Wearing away.
ABS: Antilock braking system.
Absolute Pressure: The pressure that exists when the forces of gravity are excluded from the actual pressure. Absolute pressure is equal to gauge pressure plus atmospheric pressure.
Absorption: Of heat: Takes in heat energy. Of sound: Takes in sound energy.
AC - Alternating Current: An electrical current that flows in forward and reverse bias alternately.
Acceleration: Increasing velocity or speed.
Accelerator Pump: Carburettor pumping system that introduces flow of fuel into the carburettor choke (venturi) on acceleration, particularly when accelerating from low speeds.
Accumulator: A hydraulic device that dampens the pulses and retains a residual pressure in a hydraulic circuit.
ACEA: Association des Constructeurs Europeens d'Automobiles. The European organisation that sets specifications for lubricants. There are three categories for engine oils. A for gasoline/petrol engines. B for light vehicle diesel engines. C for commercial vehicle diesel engines.
Acid: A corrosive liquid. Sulphuric acid forms part of the electrolyte in a battery.
Acidic Compounds: Harmful chemicals that are formed during
combustion and can contaminate engine oil.
Ackerman Principle: System of steering that produces wheel turning axes around a common point.
ACS: Air conditioning switch.
ACT - Air Charge Temperature: Air charge temperature sensor measures the intake air temperature on fuel injection systems.
Actuators: Electronic components that receive signals from an electronic control unit (ECU) and operate to make a system work.
Adapter: General term used to describe a device that allows one component to fit with another.
Adaptive Memory: A computer memory process that allows for changes in an open-loop mode.
Additive: A chemical added to improve the properties or performance of something.
Adhesion: The oiliness property of a lubricant that gives it the property to stick and remain on a surface.
Adjuster: General term used to describe a component that changes the adjustment of something (brake shoes or brake bands for example).
Aeration: Air mixture in a hydraulic liquid that reduces the performance of a hydraulic system.
Aesthetic Value: A value put on how nice or appealing something looks.
Air Bleed Valve: An automatic device used on fuel injection systems to provide fast idle during cold start and warm up.
Air Charge: Description of the amount of air taken into an engine on the induction stroke.
Air Cleaners/Filters: Canisters holding paper, plastic foam or gauze elements to trap dirt and grit.
Air Flow: Movement of a quantity of air past a point in a set time.
Air Flow Meter: Provides information to fuel injection system electronic control unit (ECU) on engine load. Measures the mass of air entering an engine.
Air Flow Sensor Plate: A plate used to sense the movement of air and therefore control fuel quantity.
Air Gap: The gap between two parts of a component, such as the spark plug electrodes, an inductive sensor or an armature and field shoes of a motor or generator.
Air Horn: The air inlet side of a carburettor or throttle body assembly.
Air Injection: An emission control device that adds air to the exhaust to add oxygen for the conversion of hydrocarbons and carbon monoxide to water and carbon dioxide. Usually fitted upstream of a catalytic converter.
Air Intake Duct: A pipe or similar used as part of the intake manifold or general system.
Air Line: A pipe that delivers compressed air.
Air Lock: A bubble of air in a hydraulic system that can be compressed and therefore reduces the performance or causes failure of the system.
Air Ratchet: A ratchet wrench driven by compressed air.
Air Resistance: Friction force caused by, for example, a vehicle moving through the air.
Air Temperature Sensor: Electronic device that provides information for engine management systems and frost warning indicator.
Air-fuel Ratio: The air and fuel mixture strength ratio.
Airflow Meter: Provides information to fuel injection system electronic control unit (ECU) on engine load. Measures the mass of air entering an engine.
Airflow Sensor Plate: Mechanical fuel injection component that moves in proportion to the air intake and sets fuelling accordingly.
Airline: A pipe that delivers compressed air.
ALCL/ALDL: Assembly line communication or diagnostic link. A multisocket connector for attaching a diagnostic tool to a vehicle electronic system.
Alignment: Bringing into line.
Allen: A name used to describe a hexagonal key.
Alloy: A mixture of metals and other elements to form a metal with specific properties such as phosphor bronze used for bushes.
Alternator: An electrical generator attached to and driven by a motor vehicle engine.
Alternator Brushes: Soft carbon brushes that conduct electricity to the field windings via the slip rings.
Ambient Pressure: Air pressure in the surrounding area.
Ambient Temperature: Ambient means surrounding, so ambient air temperature is a surrounding air temperature.
Ammeter: Instrument for measuring electrical current.
Amperage: Strength of an electrical current in amperes.
Ampere (Amp): Electrical unit for measuring the flow of electricity in a circuit.
Ampere-hour-rate: Discharge rate used to describe what a battery will produce. For example, a 40Ah battery will produce 2A for 20Hrs. The 20hrs is an agreed value used to allow comparisons to be made.
Amplification: An increased electrical voltage and/or current compared to say the original signal.
Amplifier: An electronic device that increases or allows an increased electrical voltage and/or current to flow.
Amplitude: The maximum distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path i.e. half the peak to peak value of a wave.
Amps: Short for Ampere (unit of electrical current)
Anaerobic: Used to describe a sealant that dries when air or oxygen is excluded.
Analogue: A measuring process that uses a variable electrical current to provide a signal for computers and instruments.
Analogue Gauge: An instrument readout that displays using a moving needle or similar method.
Annulus: The outer gear with internal teeth on an epicyclic gear train.
Anode: A positive connection.
Anodised Aluminium: A surface treatment for aluminium that adds an oxidised coating to harden the surface of the component.
Anti-freeze: A chemical such as ethylene glycol, added to the cooling water of an engine to lower the freezing point for winter operation.
Anti-knock: Usually used to refer to an additive that is added to fuel, which makes the burning process more controllable, resulting in reduced tendency to knock.
Anti-roll Bars: Suspension component that reduces vehicle roll.
Anti-trap Function: Facility to prevent electric windows closing and trapping something - your fingers for example! See also Bounce Back.
Antifreeze: Additive put in the cooling system to prevent freezing.
Antimony: A metal, which is added to lead, to improve its mechanical strength. Batteries were traditionaly constructed with lead-antimony.
APS - Absolute Pressure Sensor: A barometric pressure sensor used to compare atmospheric and manifold pressures in electric fuel injection systems.
Aquaplaning: The effect when a vehicle's tyres tend to skid on top of water on the road.
Arcing: Conduction of electricity across a gap. An arc is caused as contacts open.
Armature: Electrical windings around the core fixed to the spindle of a motor or dynamo.
Asbestos: Fibrous silicate material that can be woven into an incombustible fabric. Requires special handling as it is a hazardous substance.
Aspect Ratio: Ratio of two axes at right angles to each other such as the long and short sides of a rectangle. When applied to low profile tyres it refers to the width and depth and is shown as a percentage value in the tyre size marking.
Aspiration: Breathing or induction process of an engine. Non-turbocharged engines may be described as naturally aspirated.
Asymmetrical: A description of objects that are different on each side of their centre line.
ATDC - After Top Dead Centre: The position of the crankshaft when the piston has passed the top of the cylinder and is on the way down.
ATF: Automatic Transmission Fluid.
Atmosphere: The air that surrounds the Earth's surface.
Atmospheric Pressure: Pressure in the atmosphere produced as a result of the Earth's gravity. Measured at sea level it has a value of 1 Bar, 14.7 psi or 100 kPa.
Atom: Smallest particle in a chemical element that can take part in a chemical reaction. A single particle of an element.
Atomic: Relating to the atom...
Atomisation: Breaking up of fuel into fine particles during induction into an engine.
Atomised: The stage in which the metered air/fuel emulsion is drawn in to the air stream in the form of tiny droplets.
Atomization
: Breaking up of fuel into fine particles during induction into an engine.
Atomized: The stage in which the metered air/fuel emulsion is drawn in to the air stream in the form of tiny droplets.
Auto-box: See Automatic Transmission
Automatic Adjusters: Brake components that automatically take up wear to keep brake shoes or pads close to the drum or rotor.
Automatic Choke: A carburettor component using a bimetallic strip that operates at low engine temperatures to improve cold start and idle performance. Operates independently of the driver.
Automatic Transmission: A vehicle gearbox with automatic gear shifts based on engine speed and load conditions. Does not require individual gear shifts by the driver.
Auxiliary Air Flow: Used to describe a flow of air that bypasses the normal route. It is used to control idle speed or idle mixture.
Auxiliary Air Valve: A valve used to control auxiliary air flow.
Auxiliary Components: Components that are outside a a specific system. For example, when working on the engine, an alternator would be described as auxiliary.
Auxiliary Lights: Extra, non-essential lights such as front spotlights or driving lights.
Auxiliary shafts: Shafts that are used on some engines for balance or to drive other components.
Avalanche Diode: A diode that conducts when a value voltage is applied. Used to protect circuits from overload.
AWD: Transmission system that uses all four wheels of a vehicle to provide a drive. This term is usually used on vehicles with a permanent four wheel drive that transfers drive to another axle when some loss of drive occurs on the main drive axle. The term 4WD or 4x4 is used for used for vehicles with selectable four wheel drive.
AWD -
Axial Loading: Along the axis of a shaft.
Axial Motion: Movement along or parallel to the axis of a shaft.
Axis: The centre line through a shaft or axle. The centre about which an object rotates or where the object is in equilibrium.
Axle: Horizontal transverse shaft or beam with spindles on which road wheels are mounted.
Axle Loading: Term used to describe the forces acting on an axle.
Axle Mounting: Method of fixing the axle to the body or springs.
Axle Stands: Vehicle support equipment manufactured with a rated weight capacity. Used to support a vehicle when wheels are removed or when access to the underside is needed. Also known as jack stands.
Axle Windup: A condition in an axle where the driven component locks and the axle casing attempts to rotate on its mountings. Usually caused when a differential lock or limited slip device is used and wheel spin is not possible such as on a dry road.