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



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.


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.

Accidental Ground

A condition that exists when a wire, connected to the positive battery terminal, contacts a grounded metal part of the car.

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.

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.

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Balance Control

A control in a stereo amplifier that adjusts the relative output volume from each of the stereo channels.

Balance Pipe

1. A pipe that connects the exhaust pipes in a dual exhaust system to equalize the pressures. 2. A pipe that connects the venturis of dual carburetors.

Balanced Carburetor

A carburetor in which the float bowl is vented to the air horn to compensate for the possible effects of a clogged air filter.


A heavy crankshaft pulley that aids in overall crankshaft balance as it rotates.

Balance Shaft

Found primarily in I­4 and V­6 engines, a rotating shaft incorporating a harmonic balancer or vibration damper designed to counteract the natural vibrations of other rotating parts, such as the crankshaft, in an engine.

Battery (BAT)

A device for storing energy in chemical form so it can be released as electricity.

Battery Acid

An electrolyte used in a battery; a mixture of water (H2O) and sulfuric acid (H2SO4).

Battery Capacity

The energy output of a battery measured in amp/hours.

Battery Cell

That part of a battery made from two dissimilar metals and an acid solution. A cell stores chemical energy for use later as electrical energy.

Battery Charge

The restoration of chemical energy to a battery by supplying a measured flow of electrical current to it for a specified time.

Battery Charger

An electrical device that is used for restoring a battery to its original state of charge by passing a current through the battery in a direction opposite of the discharge current flow.

Battery Charging

The act of charging a battery.

Battery Efficiency

A battery's ability to vary the current it delivers within a wide range, depending on the temperature and the rate of discharge.

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An assembly of two or more wires that may be insulated or bare.


The metal structure that separates the balls of a roller bearing assembly. 2. A shortened term for roll cage.


An electrical device for the temporary storage of electricity. Used in a conventional ignition system in the distributor to reduce arcing across the points and in the electrical charging system to reduce radio interference.


A vacuum-dependent device used to mix fuel with air to form a vapor that is ideal for combustion.

Carburetor kit

A set of gaskets and parts necessary to rebuild a carburetor.


A part that holds, positions, moves, or transports another part or parts.

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The section immediately behind the windshield that houses the instruments, accessory controls, and glove box.


A privately owned sales and service facility representing an automobile manufacturer.


To remove carbon deposits. Also known as decarburize.


A decrease in velocity or speed. 2. To allow the vehicle to coast to idle speed from a high speed.

Diagonal Brake System kit

A dual-brake system with separate hydraulic circuits connecting diagonal wheels together; right front to left rear and left front to right rear.

Diesel Cycle

An engine operating cycle where the air is compressed and the fuel is injected at the end of the compression stroke, causing ignition.

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An abbreviation for: 1. Evaporative emission control. 2. Electronic engine control.

Elapsed time (ET)

The time it takes a vehicle to cover a given distance, usually from a standing start, recorded to the thousandths of a second.

Electric-Drive Cooling Fan

1. An engine-cooling fan driven by an electric motor. 2. An electrically controlled fan that cycles ON and OFF with the air conditioner control, if predetermined system and/or ambient temperatures are exceeded.

Electric Fuel Pump

A device having either a reciprocating diaphragm or a revolving impeller operated by electricity to draw fuel from the tank to the fuel delivery system.

Electronic Climate Control (ECC)

A system used to regulate the temperature and humidity of a vehicle's cabin.

Electronic Level Control (ELC)

A device that automatically regulates the ride height of a vehicle under various load conditions.

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False Air

Air in a fuel-injection system in excess of that required for combustion.

Fast Idle

The higher speed, 1,100 to 1,500 rpm, at which an engine idles during warm-up, when first started.

Fast-Idle Cam

A cam-shaped lever on the carburetor that provides fast-idle action when the engine is cold.

Fast-Idle Screw

A screw in the carburetor linkage to adjust fast-idle speed.

Feed Holes

The holes to supply coolant or oil to an engine.

Fiber Optics

A data-transmission medium made of tiny threads of glass or plastic that transmit huge amounts of data via light waves, at the speed of light.

Fiber Timing Gears

Camshaft timing gears made of fiber composition material that reduce gear noise.

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Gasoline Consumption

A term used for fuel consumption.

Gear Drive

A system of two or more gears, such as one that transmits power from the crankshaft or camshaft.

Geared Speed

A theoretical vehicle speed based on engine rpm, transmission-gear ratio, rear-axle ratio, and tire size, not accounting for slippage.

Gear Lubricant

A type of oil or grease especially formulated to lubricate gears.

Gear Oil

A thick lubricant, generally with an SAE number of 80 or above, used in standard transmissions or differentials. These often contain additives, such as an EP additive, to guard against being squeezed out from between gear teeth.


Mechanical devices containing teeth that mesh that transmit power, or turning force, from one shaft to another.

Gear Shift

1. A floor- or steering-wheel-mounted lever used to manually change gears in the transmission. 2. A linkage-type mechanism by which the gears in a transmission are engaged.

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1. A turn greater than 90 degrees on a road or race course. 2. A crankshaft.

Halogen lamp

A high-output, white-light lamp used as a headlight. Also known as halogen light.

Hang a Left

To make a left turn.

Hang a Right

To make a right turn.

Hang It Out

To deliberately throw the rear end into a slide during a turn.

Hard Pedal

1. A loss in braking efficiency so that an excessive amount of pressure is needed to actuate brakes. 2. A condition whereby the load literally overrides the brakes.

Hazard System

A driver-controlled system of flashing front- and rear-marker lights to warn approaching motorists of a potential hazard.


1. That part of an engine that covers the Back To Top of the cylinders and pistons and usually contains the combustion chambers and valve train. 2. That part of a compressor that covers the valve plates and separates the high side from the low side of an air-conditioning system.

Heavy-Duty Shock Absorber

Shock absorbers having improved seals, a single tube to reduce heat, and a rising rate valve for precise spring control.

Heavy-Duty Vehicle

Any motor vehicle having a gross vehicle-weight rating over 8,500 pounds (3,856 kilograms), that has a vehicle curb weight over 6,000 pounds (2,722 kilograms), or has a frontal area exceeding 45 square feet (4.2 square meters).

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An abbreviation used for internal-combustion engine.

Ideal Air/Fuel Ratio

A term used for Stoichiometric air/fuel ratio.

Idler Gear

A gear connecting two other gears in a manner so that they will turn in the same direction.


The firing of a spark plug to ignite the air/fuel mixture in the combustion chamber.

Ignition Coil

A transformer containing a primary and secondary winding that acts to boost the battery voltage of 12 volts to as much as 30,000 volts to fire the spark plugs.

Ignition Switch

A five-position switch that is the power distribution point for most of the vehicle's primary electrical systems. The spring-loaded START position provides momentary contact and automatically moves to the RUN position when the key is released. The other switch detent positions are ACCESSORIES, LOCK, and OFF.

Ignition System

The major components, such as the battery, coil, ignition switch, distributor, high-tension wiring, and spark plugs, that provide the right spark at the right time to ignite the air/fuel mixture.

Ignition Temperature

The lowest temperature at which a combustible material will ignite and continue to burn independent of the heat source.

Indicated Torque

Torque as calculated from the indicated mean effective pressure, which is an actual indication of output developed within the cylinders.

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Modifying the suspension to raise or lower one corner of an oval-track race car in order to provide better handling characteristics.

Jackrabbit Start

The sudden acceleration from a standing start.


A shaft found in most overhead cam engines that is used to drive the distributor, fuel pump, and oil pump.

Jacobs brake

A device more commonly known as Jake brake

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A small, open, four-wheeled vehicle with a single cylinder, two- or four-cycle gasoline engine.

Keyless Entry

A system using a coded keypad that allows the operator to unlock the doors or the trunk from outside the vehicle without the use of a keykickdown: A downshift to the next lower gear in an automatic transmission when the kick out of gear: To shift to neutral.


The area along the inside bottom of a car door.


A noise within an engine generally caused by detonation or preignition.

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Land Speed Record (LSR)

The maximum speed obtained by: 1. A wheel-driven, internal-combustion engine vehicle. 2. A thrust-driven jet or rocket engine vehicle.

Lateral Weight Transfer

The momentary shift of a vehicle weight from the inside tires to the outside tires, or outside to inside, due to cornering forces.

Lead Sulfate

A hard, insoluble layer that slowly forms on the plates of a discharging battery that may be reduced only by slow charging.

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Main Bearings

The bearings that locate and support the crankshaft in an engine block.

Main-Body Structural Components

The assembly made up of the dash panel, underbody, roof, body panels, doors, and deck lid to form the passenger and luggage compartments.

Main Cap

The structural device that holds the crankshaft in place in an engine block.

Main Hoop

A roll bar placed just behind the driver's seat in a race car.

Main Jets

The nozzle in a carburetor that provides fuel during part- or full-throttle operation.

Maintenance-Free Battery

A sealed battery having no practical provision for the addition of water to the cells, since periodic maintenance is unnecessary.

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A bottle-shaped, low-drag air intake design.

Necking Knob

A knob attached to the steering wheel that permits rapid one-hand steering.

Needle And Seat

A metering assembly to admit fuel into the carburetor.

Nerf Bars

Small, tubular bumpers at the front and rear of an oval-track race car.

Neutral Safety Switch

An electrical switch used on vehicles equipped with automatic transmissions to open the starter control circuit when the transmission shift selector is in any position except PARK or NEUTRAL. Also known as neutral start switch.

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Observed Horsepower

The brake output of an engine as observed on a dynamometer.

Off Highway

A term used for off-road.

Off-Highway Vehicle (OHV)

A vehicle intended for off-road use.

Off-Road Vehicle (ORV)

Any vehicle designed for use in off-road activities oil cooled piston: A piston that is cooled by a jet of oil sprayed under the dome of some diesel- and endurance-race engines.

Oil Cooler

1. A device used to cool oil or automatic transmission fluid. 2. A device used to cool race-car manual transmission and final-drive lubricants.

Oil Dilution

The thinning of oil in the crankcase, usually caused by gasoline seepage past the piston rings from the combustion chamber.

Oil Seal

A seal around a rotating shaft or other moving part to prevent oil leakage.

Oil Seal And Shield

A pair of devices that are used to prevent or control oil leakage past the valve stem and guide into the combustion chamber ports.

Operational Specifications

Specifications used to show how the vehicle operates, such as acceleration, tire inflation, and other general information.

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Pearl Paint

A type of paint that is similar to metallic paint, but instead of minute metal particles it uses mica. Mica is a kind of semi transparent, crystalline mineral that absorbs and reflects light in prismatic fashion. This gives a dramatic, multi-dimensional effect to the paint. Sometimes called "pearl coat."


A gear with a small number of teeth designed to mesh with a larger geared wheel or a rack. Used in rack and pinion steering and the differential ring and pinion.


The up and down movement along an imaginary axis between the front and rear of a vehicle. Often during hard braking, the vehicle's nose will "dive" or pitch down in front. During acceleration the back end will "squat" or pitch down in the rear.


A partly hollow cylindrical part closed at one end, fitted to each of the engine's cylinders and attached to the crankshaft by a connecting rod. Each piston moves up and down in its cylinder, transmitting power created by the exploding fuel to the crankshaft via a connecting rod.

Planetary Gears

A gear set, generally found in automatic transmissions, in which all of the gears are in one plane, grouped around each other like planets around the sun. The central gear is called the "sun gear."


The layers of cord, fiberglass, steel or structural fabric that make up the tire carcass and reinforcing belts.

Ply Rating

A measure of the strength of tires based upon the strength of a single ply of designated construction. An eight-ply rating does not necessarily mean the tire has eight plies, but rather that the tires has the strength of eight standard plies.

Pound-Feet (LB.-FT.)

Pound-feet measure twisting force or torque. Generated by the engine, torque is the "push" that sets a vehicle into motion and accelerates it. Specifications charts usually include the maximum torque the engine can develop, and the RPM at which it is generated (such as 345 lb.-ft. @ 3200 RPM).

Power Band

A subjectively defined RPM range over which an engine delivers a substantial portion of its peak power. The power band usually extends from slightly below the engine's torque peak to slightly above its horsepower peak.


A name applied to the group of components used to transmit engine power to the driving wheels. It can consist of engine, clutch, transmission, universal joints, drive shaft, differential gear, and axle shafts. Powertrain components are matched according to driver needs such as high torque, fuel economy, or convenience.


The undesirable "knock" or "ping" that occurs when the ignition of the air-fuel mixture occurs before the ignition spark. Also known as "pre-ignition".


A general term for any rod that transfers force in compression. In a conventional overhead valve layout, pushrods are used to transfer reciprocating motion from the cam followers to a more distant part of a valve train, typically the rocker arms. Pushrods are eliminated in overhead camshaft designs.

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Quarter Panel

A sheet metal panel that covers the area from the rear-door opening to the taillight area, and from the bottom of the surface to the base of the roof, or from the headlamp area to the front-door opening, and from the bottom of the surface to the base of the hood.

Quartz Halogen Headlamps

A headlamp bulb having a quartz envelope holding the tungsten filament and filled with an inert gas containing iodine or another of the five halogen gases. The gas serves to remove the tungsten deposits from the bulb wall and redeposit them on the filament, preventing blackening of the bulb surface and reduction of light output. This kind of cycle requires very high filament operation temperatures which necessitates the use of quartz instead of glass. These lamps produce more lighting power per watt of electrical power than standard sealed beam headlamps.

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Rack and Pinion Steering

A steering gear in which a pinion on the end of the steering shaft merges with a rack of gear teeth on the major cross member of the steering linkage. When the steering wheel is turned, the pinion gear turns, moving the rack to the left or right, thus steering the wheels.


A conservative projection of the market value of a vehicle at the end of a lease. Residual values are provided by major auto manufacturers or independent companies that specialize in auto valuation.
A higher residual value will lower the monthly payment. However, the vehicle must be resalable at the residual amount or the lessor will lose money. Conversely, adjusting the residual too low will increase the monthly payment and may make the lease payment unattractive. Adjustments to residual may be made for excess mileage or wear and tear.


A small auxiliary muffler that assists the main muffler in reducing exhaust noise.

Ring-and-Pinion Gear

Any gear set consisting of a small gear (the pinion gear) which turns a large-diameter annular gear (the ring gear). Used in rear-drive differentials (rear ends) to transfer power from the driveshaft to the axle and wheels.

Rolling Radius

Tire-rolling radius is the distance from the center of the wheel to the road. Static radium applies when the vehicle is standing still. Dynamic rolling-radius described wheels in motion. The latter is used to measure tire revolutions per mile and is usually slightly higher than static radius.

Rolling Resistance

This is motion resisting force that is present from the instant the wheels begin to turn. On normal road surfaces, rolling resistance decreases with increased tire pressure and increases with vehicle weight. Rolling resistance can also be affected by tire construction and tread design.

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Acronym for the Society of Automotive Engineers. A professional organization that sets standards for measuring horsepower and torque and for many automotive products such as fasteners, lenses, and lubricants.

Sealed Beam Headlamp

A one piece, hermetically sealed headlamp in which the filament is an integral part of the unit and the lens itself is the bulb. Sealed beams are relatively inexpensive and when one burns out or the lens cracks, the whole unit is replaced.


An aerodynamic device, normally on the rear of the vehicle, that changes the direction of airflow in order to reduce lift aerodynamic drag. A spoiler either reduces drag or create a downward force on the car. It is called a spoiler because it "spoils" the normal air flow over the car.

Springs, Torsion Bar

A long straight bar that is fastened to the frame at one end and to a control arm at the other. Spring action is produced by a twisting of the bar.

Steering Ratio

A predetermined ratio of the steering gears. Usually, the lower the steering ratio, the quicker the response.


The distance the piston travels from bottom dead center to Back To Top dead center within the cylinder.


The main support member in a MacPherson suspension system. The strut also serves as the shock absorber.


Supercharging is the compression of an engine's intake charge above atmospheric pressure by means of an air pump driven by a crankshaft. This is not to be confused with a turbocharger which is an air pump that is exhaust driven.
A supercharger can provide boost faster than a turbo and over a much broader engine rpm range. The disadvantages of supercharging are higher power demands, more mechanical noise and more complex control requirements.

Suspension System

Includes springs, shock absorbers/struts, and linkage used to suspend a vehicle's frame, body, engine and drivetrain above the wheels.

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An instrument for measuring the speed of the engine crankshaft in revolutions per minute (RPM).


Throttle-Body Fuel Injection is a type of Electronic Fuel Injection which positions the injector(s) centrally in a throttle-body housing. This housing contains a valve to regulate the airflow through the intake manifold.


Timing refers to the crankshaft angles at which the valves open and close and at which time the ignition system fires the spark plugs.

Tire Ratings

Tires are rated by load capacity, size and speed capacity. For example, a P225/50VR16 printed on the side of the tire means:

·         P = P-Metric (Passenger Type Tire)

·         255 = Section Width (255mm)

·         50 = Aspect Ratio (tire height/section width)

·         V = Speed Rating

·         R = Type of Ply (Radial)

·         16 = Wheel Diameter (16 inches)

Tire and wheel dimensions are the first point of information in any discussion of size and capacities. Among the other terms used to describe tires are: tread, shoulder, carcass, sidewall, bead seal, bead seat, tire diameter, aspect ratio, speed rating and section width.

Toe In

The amount by which the front of a front wheel points inward or outward. A slight amount of toe in is usually specified to keep the front wheels running parallel on the road by offsetting other forces that tend to spread the wheels apart.


A force that produces a twisting or rotating motion.

Torque Converter Clutch

An electronically controlled lockup clutch that is automatically engaged at certain speeds to eliminate the slip between the torque converter's input and output, thereby improving fuel efficiency and performance.

Torque, Engine

Engine torque is the amount of twisting effort exerted at the crankshaft by an engine expressed in foot-pounds of force. A foot-pound represents the force of one pound acting at the right angle to the rotating crankshaft at distance of one foot in length.

Torque Rating

A measure of the engine's power capability, whereby the amount of twisting or rotating effort being exerted on the crankshaft is expressed in lb.-ft. of force. Torque is the force that gets the weight of the vehicle moving, making it an important consideration in trailering.

Torsion Bar

A long straight bar fastened to the frame at one end and to a suspension part at the other. In effect, a torsion bar is merely an uncoiled spring, and spring action is produced by twisting the bar. The main advantage of the torsion bar over the coil spring in the front suspension is the ease of adjusting the front suspension height.

Traction Control

Traction control helps provide smoother, more controlled acceleration by reducing the amount of wheel spin during reduced traction conditions. Traction control utilizes the vehicle's anti-lock braking system and is usually activated only at low vehicle speeds.

Trailing Arm

A rear suspension element consisting of a lengthwise member that pivots from the body at its forward end and has a wheel hub rigidly attached to its trailing end.


A transmission and differential combined in one integrated assembly, eliminating the need for a separate connecting drive shaft. This configuration is typical in front-wheel-drive vehicles.

Tuned Intake and Exhaust Systems

Intake and exhaust systems that increase the flow of intake charge into and out of the combustion chambers by varying the length, shape, or diameter of the component.

Tuned-Port Fuel Injection

Tuned-Port Fuel Injection is almost identical to Multi-Port Fuel Injection, except that tuned runners are used to channel air to the cylinder heads. This results in increased airflow to the cylinders.


Rotary compressor or pump that pressurizes engine intake air. It is driven by the flow of exhaust gases. The increased pressure forces more air into the cylinder than it could normally draw, allowing the engine to burn more fuel and in turn produce more power.

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Unibody Construction

A type of body construction that doesn't require a separate frame to provide structural strength or support for the vehicle's mechanical components. Also called "unitized."

Universal Joint

A joint that transmits rotary motion between two shafts that aren't in a straight line.

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A device that can be opened or closed to allow or prevent the flow of a liquid or gas from one place to another. Most internal combustion engines use intake and exhaust valves to allow fuel/air mixture into the cylinders and to exhaust burnt gases. Some engines have four valves per cylinder, which increases total valve area for increased efficiency and performance.

Valve Lifter

The cylindrical component that presses against the lobe of a camshaft and moves up and down as the cam lobe rotates, opening and closing an intake or exhaust valve. Virtually all modern valve lifters are of an hydraulic design that uses a cushion foil to promote quiet operation.

Valve Train

The collection of parts that make the valves operate, allowing fuel intake, compression and exhaust. Includes the camshaft(s) and all related drive components, and the various parts that convert the camshaft's rotary motion into reciprocating motion at the valves.

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Weight Distribution

That portion of the total weight of a vehicle, including equipment and payload, that will be supported by each axle and tire. Proper distribution of total vehicle weight is critical to the service life of components such as the frame, axles, springs, bearings, and tires and therefore one of the most important requirements in selecting the right truck for your customer's particular job.


Distance, center to center, from front axle to rear axle. Wheelbase is important because it indicates available body length and weight distribution between front and rear axles.

Wholesale Value

The price, based on auction results or retailer trade reports, that a retailer expects to pay for a vehicle.

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The longitudinal axis around which a vehicle structure rolls from side to side.


A conventional chassis design, used until the late 1960s, which narrows in the center, giving the vehicle a rigid structure that is designed to withstand a high degree of twist having a heavy front cross member to support the upper and lower suspension control arms and coil springs.

X-Drilled Crank

A term used for X-drilled crankshaft.

X-Drilled Crankshaft

A crankshaft having two oil passages at approximately 90 degrees apart in the main journals.

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Yellow Bumper

1. A freshman driver in NASCAR competition. Also known as yellow tail. 2. The color of the rear bumper of a first-year driver's car in NASCAR competition.

Yellow Flag

A signal to drivers that there is a hazard on the track in closed-course racing. Also known as yellow light.

Yellow Light

A signal to drivers in closed-course racing that there is hazard on the track. Also known as yellow flag.

Yellow Line

1. A line that separates the apron from the race track. 2. The rev limit of a tachometer before reaching the red line.

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zero-Emissions Vehicle (ZEV)

An electric vehicle.

zero Lash

No clearance between the valve lifter and camshaft lobe.

zero Toe

Adjusting the wheels so they point straight ahead.