Capri Definitions

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The vertical, or sometimes diagonal, roof-support member at the extreme rear of the roof or greenhouse structure on wagons, minivans, sport utility vehicles and some sedan body styles.


Department of Transportation; federal and state agencies that govern most highway and traffic legislation, including minimum standards for pressurized containers traveling on public highways.

    Dampening Effect

The effect shocks have on reducing suspension-spring oscillations.

    De Dion Axle

The nineteenth-century axle principle of Count de Dion. The wheels tied by a transverse tube curved to clear the final drive unit rigidly mounted to the car's chassis frame. Drive to the wheels is by universally jointed half shafts. The tube moves vertically on a slide to allow the wheels to rise and fall independently. General use was dropped in 1914, but still is used on many sports and racing cars.

    Dead Pedal

A footrest to the left of the leftmost pedal, giving a driver a place to brace his/her leg.

    Dead Spot

The momentary loss of power in an engine while increasing its speed.


A firm that buys and sells, adding some value for the consumer in the process. Dealer often means a firm which operates closer in the distribution channel to the consumer than a distributor or wholesaler, and may add more value for consumers than either of the above-mentioned terms.


A retail outlet that carries one (or in some cases in the U.S., a number of) manufacturer's product line and sells to general consumers and fleet operators. The outlet will also provide service and sell parts for the brand of vehicle that it carries. In some instances, a dealer may dual for another manufacturer's product line.


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


Careful, in-depth cleaning and polishing of a vehicle's surface finish and or interior surfaces.


A condition in which, after the spark plug fires, some of the unburned air-fuel mixture in the combustion chamber explodes spontaneously, set off only by the heat and pressure of air-fuel mixture that has already been ignited. Detonation, or "knock," greatly increases the mechanical and thermal stresses on the engine.


Solid or hollow form used for shaping materials by stamping, pressing, extruding, drawing or threading.

    Diesel Engine

An internal-combustion engine in which the fuel is injected into the cylinder near the end of the compression stroke and is ignited by the heat of the compressed air in the cylinder. No spark plug or carburetor is needed.


A special gearbox designed so that the torque fed into it is split and delivered to two outputs that can turn at different speeds. Differentials within axles are designed to split torque evenly; however, when used between the front and rear axles in four-wheel-drive systems (a center differential), they can be designed to apportion torque unevenly.


The way in which innovations spread through market or non-market channels.

    Disc Brakes

Properly called caliper disc brakes: a type of brake that consists of a disc that rotates at wheel speed, straddled by a caliper that can squeeze the surfaces of the disc near its periphery. Disc brakes provide a more linear response and operate more efficiently at high temperatures and wet conditions than drum brakes.


In an engine, displacement is the total volume of air-fuel mixture that an engine theoretically is capable of drawing into all cylinders during one operating cycle.


A device that transfers voltage to the spark plug. A rotor in the distributor spins and touches contacts that are connected to spark plug wires. The wires then conduct the voltage to the spark plug. The moving part of the internal-combustion engine ignition system that directs the high-voltage current from the coil to the spark plugs in the proper firing order.

    Direct Drive Buffer

Detailers use polishers and buffers to speed the task of polishing and waxing. A direct drive buffer operates at high speeds and works well to buff the top layer of paint to a smooth, high gloss finish. In the hands of a novice (or rushed detailer), a direct drive buffer can create swirl marks or burn through the paint. In the hands of a pro, direct drive buffer can create a beautiful finish.


The dipping of a car's nose that occurs when the brakes are applied. Dive is caused by a load transfer from the rear to the front suspension; this transfer occurs because the car's center of gravity, through which all inertial forces pass, is higher than its contact patches, the points where the braking forces are exerted on the ground.

    Do-It-Yourself Market (DIY)

The vehicle maintenance and repairs conducted by the vehicle owner or friend/relative who purchase auto parts from a retail outlet.


A vehicle produced in Canada, United States or Mexico.

    Door Rates

The hourly rates charged by dealers on standardized units of service work. Hourly rates may or may not correspond to an actual hour of work.


A four-seater auto in which four passengers face each other or sit back-to-back. Seldom seen after the early 1900s.


A vertical force directed downward, produced by airflow around an object: such as a car body.

    Drag Coefficient

A dimensionless measure of the aerodynamic sleekness of an object. A sleek car has a drag coefficient, or "Cd," of about 0.30; a square, flat plate's is 1.98. Also signified by Cx.

    Dream Car

A one-of-a-kind futuristic, experimental automobile usually appearing at auto shows to stimulate interest in the manufacturer's products. Much design benefit spurs from dream cars and many reach the production stage.


Protective coatings for trim, tires and dash boards are often called dressings or protectants. Dressings are applied after washing and waxing to beautify and protect.


The general qualitative evaluation of a powertrain's operating qualities, including idle smoothness, cold and hot starting, throttle response, power delivery, and tolerance for altitude changes.


Everything in the drivetrain, less the engine and the transmission.


The driveshaft transmits power from the transmission or transfer gearbox to the differential. A four-wheel drive vehicle has at least two driveshafts - one running to the front differential and one to the rear. Driveshafts are also known as propeller shafts or prop shafts.


All of the components required to deliver engine power to the road surface.

    Drophead Coupe

See Convertible. Also called cabriolet on the Continent.

    Drum Brakes

A type of brake that has an iron casting shaped like a shallow drum that rotates with the wheel. Curved brake shoes are forced into contact with the inner periphery of this drum to provide braking.

    Dry Sump

Type of internal-combustion engine in which the lubricating oil is stored either in a separate tank or cooling radiator instead of in the crankcase pan. The oil is pumped to and taken from the engine by separate pumps.


The time, in crankshaft degrees, that a camshaft holds an exhaust or intake valve open.

    Dual Overhead Camshaft (DOHC)

An engine that has two camshafts in each cylinder head; one camshaft operates the intake valves, the other actuates the exhaust valves.


A machine on which a vehicle may be driven, simulating actual driving conditions for emissions and diagnostic purposes.

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