- D -

Dual Master Cylinder

A master cylinder, associated with a dual-brake system, having two sections for displacing fluid under pressure; generally one section for front brakes and one section for rear brakes or, in some applications, one for left brakes and the other for right brakes.

Dual Overhead Cam

Abbreviated dohc. An overhead cam engine with two camshafts located in one cylinder head. In a V-shaped engine (e.g., a V6 or V8), there are two cylinder heads, each with two camshafts, for a total of four cams. In an inline engine (e.g., an inline 4-cylinder), there is only one head with two camshafts. Many dohc engines have four valves per cylinder

Dual Overhead Camshaft

Two cams in a single-cylinder head.

Dual Playback

Head units that incorporate both a cassette deck and a CD player in one unit are said to be "dual playback" models, since they can accommodate two kinds of playback media.

Dual Quads

Two four-barrel carburetors.

Dual Trace

A feature that allows the oscilloscope to display two separate waveforms at the same time.

Dual-Area Diaphragm

An automatic transmission shift control that receives its vacuum signal from the intake manifold and the EGR port.

Dual-Bed Catalytic

A term used for dual-bed catalytic converter.

Dual-Bed Catalytic Converter

A catalytic converter that passes different gases through an upper or front chamber coated with platinum and rhodium and a lower or back chamber coated with platinum and palladium.

Dual-Bed Converter

A term used for dual-bed catalytic converter.

Dual-Brake System

A brake system that uses two hydraulic circuits; should one fail, the other remains operational.

Dual-Diaphragm Advance

A vacuum-advance mechanism with two diaphragms; one for normal ignition timing and the other to retard the spark during idling and part-throttle operation.

Dual-Diaphragm Distributor

A distributor incorporating a dual-diaphragm advance.

Dual-Fuel Engine

1. An engine designed to run on two separate fuels, such as gasoline or propane. 2. An engine designed to run on two fuels simultaneously, such as gasoline, alcohol, or a combination of the two.

Dual-Idler Gear Drive

A timing-gear system having two idler gears for the crankshaft to drive the camshaft.

Dual-Ignition System

An ignition system having two coils and two distributors, with two spark plugs for each cylinder.

Dual-lid Box

See double-lid box.

Dual-Mass Flywheel

A flywheel that consists of two parts separated by springs used to absorb vibrations in the driveline.

Dual-Plane Crankshaft

A crankshaft with two throws in two planes at right angles.

Dual-Plane Manifold

An intake manifold with two air cavities to provide air/fuel mixture to the cylinders.