Glossary of automotive terms


(ABS) - Anti-lock Braking System (ABS)
Braking systems that sense wheel rotation and automatically "pump" the brakes for the driver in emergency braking conditions. The pumping and the prevention of wheel lockup allow the driver to retain steering capabilities during the braking emergency.
(AC) Air-conditioning
Introduced during the 1930's in USA by Packard, air conditioning added a level of comfort to driving through the use of a compressor and condensing unit to chill air and distribute through the cab of the vehicle.
Air Brakes
Air is used to compress and decompress calipers at the wheel helping vehicles stop. Usually used in larger vehicles such as trucks and tractors.
Air Injection Systems
Used to reduce exhaust emissions. Injecting fresh air into the engine exhaust ports, combined with the high heat present in the exhaust manifold, causes the burning up of leftover fuel vapors.
Aerodynamic
Aerodynamic vehicles claim to offer increased performance and reduced wind noise while moving.
Alloy Wheels
Any non-steel road wheel. Mostly aluminum, but technically a mixture of two or more metals.
Alternative Fuels
May be alcohol-based, such as ethanol or methanol; compressed natural gas; or combinations of gasoline and alcohol.
All-Terrain Tires
Tires designed to provide good traction in winter snow and slush without wearing too quickly on dry roads.
Anti-sway Bar
A suspension component that improves the way a vehicle handles. A steel rod or tube that connects the left and right suspension members to resist roll or swaying of the vehicle.
A-pillar
Vertical roof support between the windshield and front edge of the front side window.
Automatic Transmission
A system that varies the power and torque to a drivetrain without the use of a manual clutch.
Alternator
An Electrical component of the engine that converts mechanical energy into electrical energy for the purpose of charging the car battery and running all electrical items in an automobile.
B-pillar
Vertical metal roof support between front and rear side windows on the side of the vehicle.
Back Pressure
The pressure produced by restrictions or malfunctions in an exhaust system. It affects the rate at which exhaust gases are extracted from the cylinders and can have adverse effects on engine power.
Ball Joint
A dynamic joint of ball-and-socket configuration used in the steering and suspension systems.
Bore
Engine cylinder diameter that relates to that of the piston stoke length.
Brake Caliper
A hydraulic piston assembly that holds disc-brake pads around disc and compresses to slow rate of speed.
Brake Pad
Replaceable piece of backing plate mounted on the caliper of the braking system.
Brake Rotor
Shiny metal disk that brake pads squeeze to slow the motion of the vehicle.
Brake Shoe
A curved, replaceable piece of friction material used on drum brakes. The wheel cylinder pushes the brake shoes against the brake drum.
Boxer Engine
The cylinders are opposite (180 degrees apart) from each other. Also called flat heads or flat top engines, these are relatively flat compared V styled engines.
C-pillar
The vertical metal roof support between the side edge of the rear windshield.
Cam
An irregularly shaped disc whose rotation creates a rocking motion causing motion of the pistons and exhaust valves
Camber
Inward or outward tilt of the wheels tires. This adjustment affects how the vehicle holds the road and handles cornering.
Camshaft
A metal shaft supporting the cams that cause the open/close operation of the intake and exhaust valves.
Carburetor
Engine component that mixes air with fuel, delivering the mixture into the engine cylinders.
CATS
Computer Aided Traction System, in which a machine automatically adjusts the road holding ability of a car while it covers slippery or uneven ground.
Catalytic Converter
A component of the exhaust system that creates a heat- producing chemical reaction to convert potentially harmful combustion byproducts into carbon dioxide and water.
Center-Locking Differential
On all-wheel drive vehicles, a third differential in addition to those for the front and rear axles. This allows the front and rear wheels to turn at different speeds for cornering on dry pavement. On slippery surfaces, it locks all four wheels together.
Check valve
A safety valve which allows fuel, air or a vacuum to flow in only one direction.
Chassis
All the parts that are connected to the frame of a vehicle.
Choptop
The result of lowering the cab of a vehicle.
Climate-Control System
The term for the heating, ventilation and air-conditioning system (HVAC). Most current vehicles have all three - heating, defrost, and AC.
Clutch
A clutch acts as a coupling device which is used to engage and disengage the transmission from the engine when shifting gears.
CO2 emissions
Carbon dioxide engine pollution expelled from the exhaust pipe.
Coil
A transformer used in the ignition system for stepping up the voltage of the electric current conducted through the spark plugs.
Coil Spring
A heavy-duty, spiraled metal component of the suspension system which forms a connection between the body of an automobile and its chassis.
Compression Ratio
The ratio of the volume within an engine cylinder when the piston is at the bottom of its stroke, compared to the volume in the cylinder when the piston is at the top of its stroke.
(CV Joint) Constant-Velocity Joint
On front-wheel drive and all-wheel drive vehicles, a coupling that allows the front axle to turn at a constant speed at various angles when the vehicle turns. The CV joint is a shaft that transmits engine power from the transmission to the wheel.
Crankcase
The area inside the engine block where the crankshaft, piston rods and other moving parts operate.
Crankshaft
The main shaft of an engine through which the power produced during combustion resulting from the reciprocating motion of the pistons.
Cylinder
One of a group of chambers in the engine within which the process of combustion takes place.
Cylinder Block
The base part of the engine to which other parts are attached.
Cylinder Head
At the top of the engine block is the cylinder head which contains intake and exhaust valves.
Damper/Dampenor
A device which reduces engine or road vibration.
Differential
A mechanical gearbox or fluid coupling that allows wheels to rotate at different speeds. Located on an axle, it allows the outside wheels to turn faster than the inside wheels during cornering.
Disc Brakes
Shiny metal discs, called brake rotors, are attached to the wheel hub, rotating with the wheel. When the brake pedal is depressed, the brake calipers squeeze the discs to slow the vehicle. See Brake Caliper and Brake Rotor.
Displacement
The volume displaced by an engine's cylinders. Formerly measured in cubic inches, it is now more commonly expressed in liters.
Distributor
Part of the ignition (electrical) system. Delivers electricity from the ignition coil to the distributor cap and the spark plug wires in the correct firing order.
Downpipe
The pipe that joins the entire exhaust system to the exhaust manifold.
Double Wishbone Suspension
A type of independent suspension in which the upper and lower support pieces, or members, look somewhat like a wishbone.
Drafting
A phenomena where two cars running nose to tail together can move faster than an individual vehicle.
Drive Axle
Connects the transaxle to the front wheels on a front-wheel drive vehicle.
Drum Brakes
A braking system that uses a metal drum. Brake shoes press against the drum to stop the car.
Drivetrain
Vehicle components which act together to move the vehicle forward or backward. On a rear-drive vehicle, it is the combination of the engine, transmission, differential and drive shaft.
Driveshaft
Shaft connecting the transmission and rear drive axel. The shaft is connected to the components on each end with a universal joint, which allows for movement up and down without bending the shaft.
Electronic Stabilization Program
(ESP) increases vehicle control in situations near the vehicle's limits. It reduces the risk of skidding and helps to keep the vehicle on course.
Electronic Control Module (ECM)
Electronic Control Module. The master computer module in engine newer systems responsible for interpreting electrical signals sent by engine sensors and for activating to produce peak performance.
Electronic Ignition
A system which uses an electronic unit as opposed to an older mechanical style distributor with points (contacts) to control the timing and firing of spark plugs.
Electronic Valve Timing (EVT)
System in which a computer controls the timing of the opening and closing of cylinder valves.
Engine layout
The position the engine sits within the chassis.
Engine management system
A computerized control of the ignition, fuel systems and exhaust making driving more economical, quieter, and power-effective.
Engine cooler
An air intake with a large inducting fan, drawing air through a water cooled piping arrangement, thus preventing engine overheating.
Evaporative Emissions
Evaporated fuel from the carburetor or fuel system which mixes with the surrounding outside air.
Evaporator Core
Part of the climate-control system that contains a liquid refrigerant which turns to gas to absorb heat from the air.
Exhaust Manifold
A cast metal set of pipes for exhaust gases to exit the engine cylinders on their way into the exhaust system.
Exhaust Valves
Devices to open and close passageways from the cylinders for exhaust gases to exit and to maintain cylinder pressure.
Fan Belt
Transmits power from a crankshaft-driven pulley to an engine fan and other accessories.
Fender
A body panel between the front bumper and front-most door edge, encompassing the wheel space in-between.
Firewall
The panel that separates the engine compartment from the passenger compartment.
Forced Induction
Where gas is blown into the engine to increase engine output performance, by a turbo or supercharger.
Four-Wheel Steering
Vehicle on which all four wheels turn when the driver turns the steering wheel.
Fog lights
Two special headlights designed for cutting through foggy conditions along the road ahead.
Firing Order
The sequence that spark plugs fire in an internal combustion engine.
Flywheel
A large disc bolted to the rear end of the crankshaft that meshes with the pinion gear in the starter.
Front Wheel Drive
The front wheels are the ones that are being powered by the engine/transmission, and the rear wheels just follow along.
Fuel Cell
The name for a large fuel tank used in formula racing cars, that sits behind the driver.
Fuel Injection System
Injects fuel into the engine's cylinders with electronic control to time and measure the fuel flow.
Fuel System
There are 2 fundamental types of systems in use today. Carbureted or direct infection systems to deliver fuel to the engine.
Fuel Injector
Electrically controlled valve that delivers a precise amount of pressurized fuel into each combustion chamber.
Gas Shocks
Shock absorbers filled with a low-pressure gas to smooth the vehicle's ride during up-and-down movement.
Gasket
A thin, expanding material used to seal the gaps and imperfections between hard surfaces.
Gear Ratio
The ratio of teeth counts between meshing gears.
Gearbox
A metal housing containing several cogs, each affecting the rate of speed at which the car moves.
Grill
An opening in the front of the vehicle that allows air to reach the radiator.
Ground Clearance
The distance between the ground and the lowest point of the vehicle chassis (usually the axle).
Gross Vehicle Weight Rating
The actual weight of the vehicle plus the maximum load it is designed to carry.
Hardtop
Hardtops do not have the fixed post between the side windows yet resemble a convertible with no center pillar for the side windows.
Hatchback
A passenger car with a full-height rear door that includes a rear window. Usually has a rear folding seat. Called a 'Compact' by leasing companies in USA.
Head Room
The distance from the top of an occupant's head to the headliner.
Headliner
The interior covering of the roof. Headliners often contain consoles with slots for garage-door openers and other devices, as well as dome lights and wiring for electrical and electronic components attached to the headliner. The covering usually includes a sound-absorbing material.
Horsepower (hp)
In general, the higher the horsepower, the higher the vehicle's top speed. One horsepower is the power needed to lift a 550-pound weight one foot in one second.
Hot Rod
A Term for a normal vehicle that has been modified to improve speed and look.
Hydraulic
An integral car component operated by means of liquid under pressure, primarily used in the braking system.
I-Beam Suspension
A suspension beam under the car that supports the body.
Idle Speed
The speed of the engine at minimum throttle.
Ignition System
The system responsible for generating electrical spark needed to ignite fuel in the cylinders.
Injectors
Devices which receive fuel at low pressure and shoot it into the engine cylinders under higher pressure.
Intake Manifold
A cast set of pipes where fuel and air are directed into the cylinders.
Intake Valves
Devices that open passageways for fuel vapor to enter the cylinders.
Independent Suspension
A suspension design that lets each wheel independently of the others.
In-Line Engine
Cylinders are arranged side by side in a row and in a single bank.
Intercooler
Device that cools air as it leaves a turbocharger or supercharger before the air is blown into the engine air intake.
Keyless Entry
A system for locking and unlocking doors of a vehicle with a central locking system without using the key.
Lap/Shoulder Belt
A safety belt that secures the driver and/or passenger in the seat. Also called a three-point safety harness.
Leaf Spring
Suspension spring made up of several thin, curved, hardened-steel or composite-material plates attached at the ends to the vehicle underbody.
Lean or Rich Fuel Mixture
The fuel mixture is lean when it has too much air, and rich when it has too much fuel. These terms can also be used to refer to adjustments the electronic control module makes to the fuel mixture in response to various driving conditions, particularly on engines with variable-valve technology.
Limited-Slip Differential
A device that helps prevent the drive wheels from skidding or losing traction by diverting power from the slipping wheel to the opposite wheel on the same axle.
Live Axle
A solid axle allowing movement of the wheel on one end to affect the opposite wheel. Found on older rear-drive cars and tucks. Also called a rigid axle.
Lowrider
Generally, a car on which the chassis has been lowered; however, other customizations are often present. Some American cars have a hydraulic mechanism that does this action during driving.
M+S Rating
A tire rating which indicates a tire designed to perform well in mud and snow.
MacPherson Strut
A MacPherson strut is a unit that includes a damper or shock absorber cartridge inside a large, long metal spring. MacPherson struts are used over the front wheels of most front-drive cars. Replacement of MacPherson strut cartridges requires a spring compressor.
Manifold Absolute Pressure Sensor (MAP sensor)
Detects engine load by measuring air pressure or vacuum in the intake manifold.
Manual Transmission
A transmission that varies the power and torque through a foot pedal controlled clutch and a floor-mounted or steering-shaft-mounted gear selection lever.
Mass Airflow Sensor
Device that measures the flow of air entering the throttle housing.
Master Cylinder
The primary component for pressurizing fluid in a hydraulic system. Used in the braking system, it supports a reservoir for holding brake fluid and is activated each time the driver depresses the brake pedal.
Max power
Two figure totals given in brake-horse-power by engine revs per minute. [bhp x rpm].
Max torque
The weight of force per foot, given in pounds, and the rpm level, eg 100 lb ft at 1000 rpm.
Metallic paint
A glittery sheen within the paintwork by customer request at an additional cost.
Minivan
A quite large car of saloon capacity but resembling a small van with windows.
Miles Per Gallon / MPG
Fuel economy measurement. Generally, a vehicle maker may offer mpg ratings for city driving, highway driving, and combined driving, so their is no definitive single measure overall.
Muffler
A chamber in the engine exhaust system used to suppress exhaust noise and smooth exhaust pulsations. Also referred to as a "silencer". Motorbike an moped owners sometimes remove these to beef-up their sound.
Multi-Link Suspension
Independent suspension controlled with several link arms that restrict undesired motion of the suspension for a smoother ride and more precise handling.
Multi-Port Fuel Injection
An electronic fuel-injection method that uses individual injectors to spray fuel directly into each intake port, bypassing the intake manifold. Also called multi-point fuel injection.
Muscle car
A term used beginning in the mid-'50's to refer to cars which had very high horsepower and is still in use today. Occasionally called a 'pony car' in USA. The Aston-Martin Vanquish is a perfect example.
Nose
A small frontal body section of a car which extends beyond the bonnet line, typically slanting downwards. The narrower version used on Formula cars is called a shark-nose. 'Nosed' refers to the process of raising a small peak in the center of the bonnet of a car, usually as part of a customized design.
Octane
The hydrocarbon substance in gasoline that reduces engine knock or pinging, which is a noise caused by premature ignition of fuel in the cylinder combustion chamber. The higher the octane number, the less chance of premature ignition. High octane, which has a rating above 91, is useful only when recommended by the manufacturer.
Odometer
Indicates the number of miles a vehicle has been driven, and is also called a Mileometer. It is illegal to tamper with the odometer reading. This illegal practice of rolling a vehicle's odometer back to indicate that it traveled fewer miles than it actually has, is done by 2nd-hand sellers. Odometer Rollover occurs when the vehicle's mileage exceeds the mechanical limits of the odometer - usually 99,999 miles. This must be certified by the seller, under law binding Mileage Acts.
Overhead Cam (OHC)
The camshaft is on top of the cylinder head on overhead-cam engines. Single overhead-cam (SOHC) engines have a single cam above the cylinder head. Dual overhead-cam (DOHC) engines have two cams above the cylinder head.  
(OHV) engine
An overhead-cam engine with overhead-valves, which means the intake and exhaust valves sit atop the cylinder head.
Oversteer
Occurs when the rear tyres lose adhesion under cornering. In motor sports, this is also called loose. Oversteer can lead to a spin if the driver doesn't reduce acceleration. See also Understeer.
Overdrive
A transmission gear with a ratio below 1:1, which improves fuel economy by reducing engine revolutions per minute at highway speeds. On a five-speed manual transmission, the fourth and fifth gears are overdrive. On a four-speed automatic transmission, the fourth gear is overdrive. When an overdrive gear set is engaged, the output shaft turns at a higher rate than the input shaft, reducing engine revolutions at cruising or highway speeds.
Oxygen Sensor
An emissions related device which senses the presence of oxygen in the exhaust. The voltage it puts out is interpreted by the main computer (ECM) along with other sensor input to determine automatic adjustment of the air/fuel mixture.
Passive Restraint
A device or structure that automatically helps restrain vehicle occupants in an impact. This includes airbags, belt pretensioners, padded knee bolsters, and shoulder belts that are motorized, or attached to the door.
Pick-up
The type of light-duty truck with an open cargo bed behind a closed cab.
Pinion
A type of gear that has small teeth that mesh with other, larger gears.
Pinion Gear
The smaller of two meshing gears. A pinion gear is used in a starter motor to engage the flywheel ring gear and also rides along the surface of the steering rack (hence "rack and pinion" steering).
Pitstop
This is the garage area at F1 races, where major mechanical work is done on the cars. The pitlane runs its length.  At Indy racing [in USA] its called the 'gasoline alley'.
Piston
A solid, cylindrically shaped part that alternately compresses fuel vapor within a cylinder (the compression stroke) and is thrust downward (the power stroke) by the force of the explosion that results when the vapor is ignited. Rocker arms connect the pistons to the crankshaft.
Piston Rings
Metal rings seated in grooves on the outside of a piston that are used to ensure a proper seal between the piston and the cylinder wall. Typically, three (3) rings are used: two (2) ensure proper compression is produced and one (1) prevents oil from leaking into the cylinder.
Positive Crankcase Ventilation Valve
An emission device that routes oil pan vapors to the intake manifold to be burned during combustion. Also known as the PCV valve.
Power Steering
A steering system that uses a separate motor or engine power to reduce the effort necessary to turn the front wheels.
Power Steering Fluid
Many power steering systems use hydraulic power. These systems use a power steering pump driven by a belt from the crankshaft. The pump moves fluid under pressure through hoses to the steering gear. The pressure is used in the steering gear to reduce steering effort. A reservoir for fluid is attached to the rear of the pump.
Power-to-Weight Ratio
The maximum power output of the vehicle per unit mass. The higher the ratio, the more powerful the vehicle. In comparing several vehicles, this can be a better measurement than engine horsepower or torque because it considers the weight variable. In other words, a car that seems to have a powerful engine but is also heavy may have less get-up-and-go than a vehicle that has a similar or less powerful engine but also weighs less. Lotus are the best exponents of this. Given in a BHP per tonne value.
Powertrain
The combination of engine and transmission.
Pretensioner
A device that rapidly yanks in shoulder-belt slack when a crash sensor detects an impact. Some pretensioners are activated by a small explosive charge in the belt retractor; some contain their own inertial sensors. So far, pretensioners are still found on more expensive models, particularly those by European manufacturers. By pulling in belt slack within milliseconds of an impact, pretensioners help reduce chest and head injury by restricting occupant motion and preventing the occupant from hitting the belt.
Projector-Beam Headlights
A headlight that uses a spherical reflector to tightly control the light beam. The bulb or light source directs the light inward, toward the reflector at the back of the headlight assembly, which then projects it forward from the vehicle. These lights are more powerful, accurate and expensive than standard sealed-beam and halogen headlights, and are generally found on sport and luxury models.
Pressure Plate
Holds the clutch disc against the flywheel.
PSI
Acronym for pounds per square inch. A pressure measurement used in tyre inflation and turbocharger boost.
Pushrod
A metal rod that transmits the motion of the camshaft to the valve actuators to open and close the valves. Used on engines with overhead valves but without overhead camshafts.
Quarter Panel
Sheet of metal panel that covers the front and rear quarters of the vehicle.
Quality control
A department within a company that ensures its products meet the required standard, such as checking if a car has adequate weather-proofing.
R-134a
The environmentally safe refrigerant now used in air-conditioning systems. It requires a slightly bulkier condenser unit than the older R-12 type. Vehicles equipped with R-12 systems can be converted to use R-134a. Since Freon is now banned, expensive and hard to obtain, the conversion may be a good idea when an R-12-based system needs recharging, particularly if technicians detect a leak.
Rack and Pinion Steering
The steering wheel is connected to a pinion gear that meshes with a toothed bar, also called a rack or linear gear. As the pinion turns, the rack moves side to side, moving the steering linkage and causing the front wheels to turn left or right. The ends of the rack are linked to the steering wheel with tie rods.
RACMSA
The RAC Motor Sports Association is recognized by the FIA as the governing body of motor sport in Great Britain.
Radiator
The copper or aluminum device in front of the engine through which hot engine coolant is circulated and cooled. The liquid is then recirculates back through the engine block to cool it.
Rag Top/Soft-top
A convertible with a soft top, usually made from canvas or a polymer.
Rally
Competing teams, consisting of a driver and a navigator, are given route instructions, which they must follow exactly. Each team follows the course independently, trying to rack up points based on how well they meet a pre-determined schedule.
Rear axel assembly
The drive shaft turns (spins) a set of gears within the rear axle assembly known as the differential, or rear differential. The differential changes the direction of power from the driveshaft out to the rear wheels via the rear axle.
Rear-Wheel Drive (RWD)
The drivetrain in which power is applied through the rear wheels only.
Recirculating Ball
A steering mechanism in which the steering shaft turns a worm gear causing a toothed metal block to move back and forth, turning the front wheels. Ball bearings reduce friction between the worm gear and the metal block.
Redline
The point on the engine tachometer that indicates the maximum RPM the engine can safely withstand.
Release Fork
Disengages the clutch disc from the flywheel by pressing on the pressure plate release springs.
Retractable
A car having a mechanically retractable hardtop such as the late '50's Ford Skyliner.
Restrictor
An electronic safety device preventing high-speeds above 160mph from being reached.
Revolutions Per Minute (RPM)
Describes at which speed the engine crankshaft is turning.
Rocker Panel
The body panel that runs beneath a vehicle's doors.
Rotor
The rotating part of a machine or mechanism. The brake disc itself is referred to as a "rotor," as is the center of a distributor or starter motor.
Rollcage
A protective steel cage to prevent driver injury during a rollover.
Rollover
The type of vehicle impact in which the car or truck rolls over on its side, onto its roof, or turns over completely. The biggest cause of injury in a rollover is ejection of the occupant or any part of the occupant. Rollover is a greater risk in any sport-utility vehicle - because of its high center of gravity - than in a minivan, pickup truck or passenger car. Rollover can occur immediately upon impact or in the seconds after an impact, which makes it more difficult to protect occupants with traditional airbags. Inflatable tubular restraints and similar designs that stay inflated longer than traditional airbags will be more effective in rollover situations.
Scrub radius
The distance from the point where the steering axis intersects the ground to the longitudinal line that runs through the center of the tyre's contact patch. Also called "steering offset."
Sensor Algorithm
An algorithm is a mathematical formula or series of formulas used by an on-board computer or processor to make decision. In an airbag system, a crash-sensor algorithm determines whether the change in velocity indicates an impact of great enough force to require airbag deployment, based on pre-programmed parameters. If the change in velocity is great enough, the processor sends a signal to the device that inflates the airbag.
Sequential Fuel Injection
Similar to multi-port fuel injection, but the injectors spray fuel into the individual intake ports exactly at the beginning of each cylinder's intake cycle. The precise fuel control provides better engine performance.
Semi-trailing-arm suspension
An independent rear-suspension system in which each wheel hub is located only by a large, roughly triangular arm that pivots at two points. Viewed from the top, the line formed by the two pivots is somewhere between parallel and perpendicular to the car's longitudinal axis.
Shift Interlock
On a vehicle with automatic transmission, a safety device that prevents the driver from shifting out of park unless the brake pedal is depressed.
Shift gate
The mechanism in a transmission linkage that controls the motion of the gearshift lever. The shift gate is usually an internal mechanism; however, in some transmissions: including Ferrari five-speeds and Mercedes-Benz automatics: the shift gate is an exposed guide around the shift lever.
Shock absorber
A device that converts motion into heat, usually by forcing oil through small internal passages in a tubular housing. Used primarily to dampen suspension oscillations, shock absorbers respond to motion; their effects, therefore, are most obvious in transient maneuvers. 
Short Block
The lower portion of an engine below the cylinder head.
Side Airbag
An inflatable cushion that fills the space between the door and the occupant to prevent head, torso and pelvis injuries when a vehicle is hit from the side. Side airbags may be stored in the door-trim panel or the outboard side of the seat; they may protect the hip and torso only or also protect the head. A new design, called an inflatable tubular restraint, is stored in the edge of the roof headliner and attached at the base of the A-pillar at the front end and above the doors along the roofline at the other. The device inflates into a somewhat stiff tube that prevents the occupant's head from hitting the side pillar or the window.
Side-Impact
safety regulations require that vehicles absorb a certain amount of force when hit from the side. To meet side-impact standards, automakers have stiffened side-impact beams, which resist intrusion into the passenger compartment, and added safety devices such as side airbags and extra padding, which are designed to push the occupant toward the interior of the vehicle and away from the point of intrusion.
Side mount
A spare tyre mounted on the side of a car, normally on the fender just above and behind the front wheel.
Single Overhead Cam (SOHC)
An engine with a single overhead cam generally has one intake and one exhaust valve per cylinder; the single cam opens and closes both valves. See also Overhead Cam and Dual Overhead Cam.
Slalom
Several soft turns in a row at a race-track, like at Brands Hatch in the UK.
Society of Automotive Engineers
The professional association of transportation-industry engineers. The SAE sets most auto-industry standard for the testing, measuring, and designing of automobiles and their components.
Solenoid
The electromagnetic device positioned above the starter which thrusts the pinion gear against the engine flywheel when starting ("turning over") the engine.
Space frame
A particular kind of tube frame that consists exclusively of relatively short, small-diameter tubes. The tubes are welded together in a configuration that loads them primarily in tension and compression.
Specific output
The amount of BHP produced from 1 litre of fuel.
Spark Plug
Converts voltage into an arc that passes between its electrodes; the arc ignites the fuel-air mixture in the combustion chamber. The mixture explodes, creating power by pushing down the piston.
Speedo
An instrument dial above the steering wheel which informs the driver of the current speed, in MPH and/or KPH.
Spoiler
An aerodynamic device that changes the direction of airflow in order to reduce lift or aerodynamic drag and/or improve engine cooling..
Smart Airbag
There are many designs, but each contains similar elements including a system of sensors and mathematical algorithms to detect the presence or absence of an occupant in the seat; to determine the size, weight and nature of any occupant (including whether it is a rear-facing infant and determine whether the occupant is an adult, a dog, a bag of groceries or a rear-facing infant seat); and to determine whether the occupant is too close to the airbag door for safe deployment. A smart system will use that information to decide whether to inflate the airbag in an impact. Later generations of smart airbags will adjust the rate of inflation based on force of impact and size of the occupant.
Slip angle
The angular difference between the direction in which a tyre is rolling and the plane of its wheel. Slip angle is caused by deflections in the tyre's sidewall and tread during cornering. A linear relationship between slip angles and cornering forces indicates an easily controllable tyre.
Slushbox
A slang for an automatic transmission.
Squat
The opposite of dive, squat is the dipping of a car's rear end that occurs during hard acceleration. Squat is caused by a load transfer from the front to the rear suspension.
Straight-line tracking
The ability of a car to resist road irregularities and run in a straight line without steering corrections.
Stator
As opposed to the moving rotor, the stationary portion of a device. In an alternator, for example, the stator includes an intricate copper winding that picks up the current induced by the rotation of the rotor within a magnetic field.
Starter
An electric motor used to initiate movement of internal engine parts so that combustion can begin. Activating the starter causes the solenoid to thrust the pinion gear in the starter against the engine flywheel ring gear and begin turning it.
Steering axis
The line that intersects the upper and lower steering pivots on a steered wheel. On a car with a strut suspension, the steering axis is defined by the line through the strut mount on top and the ball joint on the bottom.
Steering feel
The general relationship between forces at the steering wheel and handling. Ideally, the steering effort should increase smoothly as the wheel is rotated away from center. In addition, the steering effort should build as the cornering forces at the steered wheels increase. Finally, the friction built into the steering mechanism should be small in comparison with the handling-related steering forces.
Steering gain
The relationship between yaw and the steering wheel's position and effort. All three should be proportional and should build up smoothly.
Steering Ratio
The ratio of the different steering gears. Usually a lower gear means a faster response.
Steering Rack
The device by which the movement of the steering wheel is transferred to the front wheels of an automobile.
Steering Rods
The metal rods on each end of the steering rack that connect it to the front wheels via ball joints (tie rod ends).
Strut
A single, self contained pivoting suspension unit that integrates a coil spring with a shock absorber. Struts are used on front wheel drive automobiles. A suspension element in which a reinforced shock absorber is used as one of the wheel's locating members, typically by solidly bolting the wheel hub to the bottom end of the strut.
Stroke
The up-and-down distance the piston travels within the cylinder. On a traditional internal combustion engine, the piston makes four strokes during the combustion cycle, only one of which is a power stroke. On the power stroke, the piston is near the top of the cylinder, and it has compressed the air and fuel mixture. The spark plug ignites the mixture, and the force of the explosion pushes the piston down into the cylinder, producing the force that turns the crankshaft. The piston returns to the top of the cylinder to expel the exhaust gases on the second, or exhaust, stroke. It slides down to the bottom of the cylinder during the intake stroke, when the valves open to let in air and fuel. The piston rises to the top of the cylinder on the compression stroke to begin the cycle anew. This process repeats hundreds or thousands of times a minute, resulting in the number of crankshaft revolutions per minute at which the crankshaft is rotating. Length measured in millimeters.
Supercharger
Serves the same function as a turbocharger but avoids lag time because it runs off an engine-driven pump. Both turbochargers and superchargers are used to produce more power without increasing engine displacement, but neither are particularly fuel efficient and both can require costly maintenance as vehicles age. A standard piece of equipment of Hotrods and Top Fuel dragsters, this provides more power by blowing a combination of more air and vaporized fuel into the car's engine.
Suspension
Springs, dampers, shock absorbers, hydraulics, wishbones, roll bars, struts, and links used to suspend the frame, body and engine above the wheels.
Sump
The space in the engine block under the crankshaft into which the oil drains from its various applications.
Switch-gear
The variety an quality of function controls the driver can utilize while driving.
Synthetic oil
Engine lubricant not derived from raw petroleum. It has superior engine-protection properties but costs as much as five times more than petroleum oil.
Tachometer
The instrument gauge that shows engine speed, or revolutions per minute. On a vehicle with manual transmission, the driver can use the tachometer to tell when to upshift or downshift. Also called tach.
Tappet
A pivoting actuator that opens and closes cylinder intake and exhaust valves.
Taxometer
A machine which counts the travel-time of a taxi journey.
Throttle-Body Fuel Injection
A form of electronic fuel injection in which the injectors are centrally located in a throttle-body housing that contains a valve to regulate air flow through the intake manifold. Less efficient and precise than multi-port or sequential fuel injection.
Timing Belt
On overhead cam equipped engines, an external belt used to synchronize the operation of intake/exhaust valves with the compression/ignition process occurring in the cylinder head and engine block below.
Timing Valve
A valve in a fuel injection pump which times the delivery of fuel.
Tie Rod End
A type of ball joint which transfers the movements of the steering wheel to the wheels.
Toe-in
A wheel-alignment term that indicates the leading edges of a pair of wheels angle slightly toward each other. Front-drive cars are often aligned with slight toe-in to compensate for the effects of torque steer, or the tendency of the front wheels to pull to the side under hard acceleration.
Toe-out
A wheel-alignment term that indicates the leading edges of a pair of wheels angle slightly away from each other.
Torque
A measure of twisting force, given in foot-pounds (abbreviated as lb.-ft.) or Newton-meters (N-m). In the case of an automobile, it is the twisting or rotational force the engine exerts on the crankshaft. Vehicle specifications often include the maximum torque an engine produces at a specific number of revolutions. An engine that produces 200 lb.-ft. of torque at 3,000 revolutions per minute, or 200 lb.-ft.@ 3,000 rpm, accelerates better at low speeds than an engine that provides 200 lb.-ft.@5,000 rpm.
Torque Converter
An enclosed device connected to the crankshaft that uses a turbine-based system and a thin fluid (ATF) to propel the movement of the automatic transmission mainshaft. As opposed to an automobile equipped with a manual transmission and clutch that must be engaged/disengaged, this "fluid" connection between the engine and the wheels is what enables a car to come to a full stop with its automatic transmission still in gear.
Torque Steer
The tendency of the front wheels on a front-drive vehicle to pull to the side under hard acceleration.
Torque-to-weight
The amount of torque derived power effort, in pounds per foot, over the tonnage of the vehicle.
Torsion Bar
A simple, rugged type of suspension spring that twists as it is compressed or stretched.
Torsional Stiffness
A vehicle body's resistance to twisting motions.
Towing Capacity
The amount of weight a vehicle can tow behind it, eg a trailer carrying a speed-boat.
Traction Control
A system for limiting wheel slip under acceleration, thus maintaining each wheel's contact with the road surface. Traction-control systems generally use the anti-lock braking system to stop wheel spin and reduce power from one or more engine cylinders when an electronic sensor detects wheel spin.
Traction
The amount of friction between the tyre and the ground.
Transfer Case
On four-wheel drive vehicles, a gearbox that allows power to be delivered to front and rear wheels.
Transaxle
A transmission and differential housed together in the same enclosure. This setup is most commonly found in today's front-wheel-drive-dominated car (not truck) market. The transmission and differential are married together because no drive shaft is required in front-wheel drive (front engine) vehicles.
Transmission
The transmission is used to take the high-speed, low-torque power of the engine and convert it to a lower-speed, higher-torque output, which ultimately turns the drive wheels. Transmissions come in a wide variety of choices, but they basically divide into three categories: Manual, Automatic, and Manumatic. Lower gears allow fast acceleration, higher gears provide better gas mileage. Manual transmission uses a system of gears to create the high torque output required from the engine's high speed input. A clutch is used to disengage the transmission from the engine when shifting gears. Automatic transmissions do the shifting for the driver. No clutch is required. The shifting is accomplished by a hydraulic oil system. Manumatic transmissions are a hybrid of manual and automatic transmissions. In most cases they require no manually operated clutch, but they allow for the driver to shift gears manually when desired.
Tread-Wear Index
A tyre rating consisting of a number followed by two letters, such as 300AB. The number indicates the useful life of the tyre, the first letter (A, B, or C, A for best, C for worst) indicates its traction in wet conditions, and the second letter (A, B, or C, A for best, C for worst) its resistance to heat buildup.
Tri-Link Suspension
A fully independent rear suspension featuring a single fiberglass or composite leaf spring.
Trim Decor
the embellishments added to the cars interior that give it identity an character, such as leather, wood, fabric, chrome etc.
Trim Level
The level of options or features added to a model (as like with a GT version). An optional extra as selected by the customer, like an airbag, doesn't instigate a new trim level. Only the car maker selects the attributes to a car to make it a special variant of the basic version, which is the 'factory standard' version, an is the cheapest within the range.
True MPH
The actual velocity a body moves at as opposed to the reading given by internal instrumentation. Used by speed cameras an police with timing guns in speed-traps.
Tune-up
A regularly scheduled maintenance to check normal operation of the vehicle.
Turbine
An integral piece of the turbocharger, this small fan drives the compressor. A rotor with vanes or blades which is driven by the movement of fluid or gases across its surface. The turbine wheel in a turbocharger spins as a result of exhaust gases. In a torque converter, a turbine is used to propel ATF within the unit.
Turbo Lag
The time it takes the turbocharger to kick in after the driver accelerates; the lag results because a turbocharger compressor is spun by exhaust gases in the exhaust manifold.
Turbocharger
Device that compresses and forces extra air into the intake manifold to produce extra power. Both turbochargers and superchargers are used to produce more power without increasing engine displacement, but neither are particularly fuel efficient and both can require costly maintenance as vehicles age. By forcing fuel through the engine, this system allows the car to gather more speed. Usually they're made by specialist component makers like Roots, X-Trac, Bosch, etc.
Turning circle
The minimum distance a car needs to turn around in one step. A low figure is a prerequisite for a proper Taxi deign, an in the venues of big cities is a regulation.
Twist-Beam Axle
A semi-independent rear axle often used on front-drive vehicles. The horizontal beam, which connects the two rear wheels, can twist to reduce the effect of one wheel's motion on the other. Less expensive and more compact than fully independent suspension.
Understeer
Occurs when the front wheels have lost adhesion or the driver is turning the steering wheel too sharply for the vehicle's speed. In understeer, the front wheels do not follow the steering wheel angle, and the car refuses to turn and pushes ahead. In motor sports, this is called push. The driver can regain traction by reducing speed. Also may be called plow.
Universal joint
A joint that transmits rotary motion between two shafts that aren't in a straight line. Depending on its design, a universal joint can accommodate a large angular variation between its inputs and outputs. The simplest kind of universal joint, called a "Hooke joint," causes the output shaft to speed up and slow down twice for every revolution of the input shaft. This speed fluctuation increases with the angular difference between the shafts.
V6
A vehicle with six cylinders. The cylinders are divided into two banks, each of which is angled away from the other at the top, forming a 'V'. Typically, this angle is 60 degrees on V-6 engines.
V8
A vehicle with eight cylinders. The cylinders are divided into two banks, each of which is angled away from the other at the top, forming a 'V'. Typically, this angle is 90 degrees on V-8 engines
V12
A vehicle with a dozen cylinders. The cylinders are divided into two banks, each of which is facing each other at the top, an slightly forms a 'V' shape. Typically this angle is 30 degrees on most V-12 engines. Occasionally two V6 engines can be combined to act as a V12.
Valve Train
The valves and camshaft(s) within an engine, and any parts attached to the valves, such as rockers and pushrods, to move them up and down.
Valves
Many overhead-cam engines, particularly multi-valve models, are described by the total number of intake and exhaust valves in the cylinder head. A 24-valve V-6 engine would have four valves per cylinder: two intake and two exhaust valves. A 16-valve V-8 engine has only the standard single exhaust and single intake valve for each of its eight cylinders.
Valve gear
The valve number per cylinder and the cam number plus its position.
Valve float
A high-rpm engine condition in which the valve lifters lose contact with the cam lobes because the valve springs are not strong enough to overcome the momentum of the various valvetrain components. The onset of valve float prevents higher-rpm operation. Extended periods of valve float will damage the valvetrain.
Valve lifter
Also called a "valve follower": the cylindrically shaped component that presses against the lobe of a camshaft and moves up and down as the cam lobe rotates. Most valve lifters have an oil-lubricated hardened face that slides on the cam lobe. So-called "roller lifters," however, have a small roller in contact with the cam lobe: thereby reducing the friction between the cam lobe and the lifter.
Valvetrain
The collection of parts that make the valves operate. The valvetrain includes the camshaft(s) and all related drive components, the various parts that convert the camshaft's rotary motion into reciprocating motion at the valves, and the valves and their associated parts.
Viscous coupling
A particular kind of fluid coupling in which the input and output shafts mate with thin, alternately spaced discs in a cylindrical chamber. The chamber is filled with a viscous fluid that tends to cling to the discs, thereby resisting speed differences between the two shafts. Viscous couplings are used to limit the speed difference between the two outputs of a differential, or between the two axles of a car.
Van
A box-shaped truck with a forward cab and a cargo area to the back bumper.
Variable-Assist Steering
A power-steering system that varies the amount of assistance it provides according to driving conditions. It provides maximum assistance at low speeds for maneuvers such as turning into a parking space or turning a corner after leaving a stop light. It provides minimum assistance at cruising or highway speeds to provide greater vehicle stability.
Vehicle Identification Number (VIN)
A seventeen-digit identification number, unique to each vehicle, which includes codes for the manufacturer, year, model, body, and engine specifications.
Vented Disc Brakes
A brake disc that has cooling passages between the friction surfaces.
V-Type Engine
In a V-6, V-8 or V-12 engine, the cylinders are divided into two banks, each of which is angled away from the other at the top, forming a 'V'. Typically, this angle is 60 degrees on V-6 engines and 90 degrees on V-8 engines. From the rear are identified by having twin exhaust pipes, an by ear have a deep rumble engine sound. 
Waste gate
A valve used to limit the boost developed in a turbocharger. A waste gate operates by allowing some of the engine's exhaust flow to bypass the turbocharger's turbine section under certain conditions.
Water Pump
The pump that circulates coolant through the engine block, cylinder head and radiator. It is driven by the engine crankshaft.
Weight distribution
Measured in Kg, representing the balance, control an stability, with the centre of gravity acting as the fulcrum.
Wheel Size
Determined by the diameter and width of the wheel on which the tyre is mounted. A 15-inch wheel has a diameter of 15 inches. A 15 X 7 wheel has a 15-inch diameter and a 7-inch width.
Wheelbase
The distance between the center of the front wheels to the center of rear wheels.
Wing
2 body panels that exist either rear side, beneath the trunk cover, partly enclosing the rear-wheel-space.
Winston Cup
The high-point of NASCAR racing, a race that spans the entire season as drivers accumulate points at each of 31 events. The driver that accumulates the most points, not the most wins, becomes the eventual Winston Cup winner.
Woody
Refers to a vehicle which has part of its side body-panels covered or replaced with decorative wood.
X series
The name given to the famous chassis designs used by Jaguar since the 1960s, such as the XJ, XK an X-type.
X-ray detection
This is used by law enforcement agencies when searching for illegal materials concealed within the door panels an bodywork of cars, such as Semtex an heroin.
Yaw
The rotation about a vertical axis that passes through the car's center of gravity.
Yugo
The only car company named after a country that no longer exists, ie Yugoslavia.
Zero-offset steering
A steering system whose geometry has a scrub radius of zero. This configuration minimizes the steering effects produced during acceleration (with front drive) or braking on varying traction surfaces.
Z-axis
The plain of movement a road vehicle cant access.


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