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Direct-acting Thermostatic Air Cleaner

A component of heated air-intake systems that uses a thermostatic bulb connected to a rod to operate a flapper valve in the air-cleaner snorkel.

Direct-bonded Bearing

A bearing that is formed by pouring molten babbitt directly into the bearing housing and machining the cooled metal to the desired diameter.

Direct-clutch Solenoid

A solenoid that directs fluid flow to engage the direct clutch.

Direct-port System

A nitrous system that uses several nozzles to spray nitrous oxide (and fuel, in most cases) into each intake manifold runner, pretty much like a direct port fuel injection system. A direct-port system can be used to produce the most power of any nitrous system, and it also is the most tunable design, since the flow to each cylinder can be adjusted independently.

Directional Control

The ability to steer the automobile while stopping.

Directional Signals

Lights at either side of both the front and rear of the vehicle that flash to indicate an intended turn.

Directional Stability

The ability to maintain a straight line wile stopping.

Directional Tire

A tire having a tread pattern that must be mounted facing forward.

Dirt Dobber

A circle-track race driver that prefers a dirt track over an asphalt track.

Dirt Tracking

Driving on an asphalt track as if it were a dirt track.

DIS

Direct ignition system or distributor-less ignition system.

DISA

Differential air intake control system.

Disable

1. To remove or inhibit normal capability. 2. A command that prevents further operation of a peripheral device.

Disassemble

To take apart.

Disc

1. An abbreviation for discount. 2. A variant of disk.

Disc Brake

A type of brake that provides a means of slowing or stopping a vehicle using hydraulic pressure to apply pads against a rotor.

Disc Brakes

A newer-design, efficient braking system. As opposed to drum brakes. When a driver steps on the brake pedal, a caliper forces a brake pad against each disc brake rotor. The friction this generates converts the vehicle's forward motion into heat, bringing the car or truck to a stop.

Disc Minimum Thickness

The least thickness, usually stamped or cast into the disc, to which a brake disc can be machined or worn before it becomes unsafe.

Disc-brake Fluid

A special fluid having a high boiling point, about 500 degrees F (260 degrees C). If exposed to air, it will attract moisture and be unsafe for use.

Disc-brake Pad

An assembly consisting of friction material and its steel backing.