Damper
A device, better known as a shock absorber, used for controlling and smoothing the motion generated from the suspension reacting to road irregularities.

Dead Axle
A rear axle that does not turn or transmit torque but simply carries the vehicle weight. The Chevrolet Celebrity uses a dead axle, for example.

Decklid
A hinged panel providing access to the luggage compartment.

Detonation
Excessively rapid burning of the compressed air/fuel charge in an engine, often resulting in noise called "pinging" or "knocking.

Dieseling
A condition in which gasoline continues to fire after the ignition has been shut off. In late-model engines, dieseling, or run-on, is caused by heat and the unusually high manifold pressure that result from retarding the spark at idle. In fuel injected cars when the engine is turned off, fuel is automatically shut off, eliminating dieseling.

Differential
A system of gears located in the center axle housing between the driving wheels on rear-wheel drive cars or as part of the transaxle on front-wheel drive cars. Its purpose is to transmit engine torque to both driving wheels regardless of whether the vehicle is traveling straight or turning a corner. This gearing allows each wheel to rotate at different speeds, such as required when turning a corner.

Digital Instrumentation
An instrument panel where digital displays replace the traditional analog (needle) instruments and gauges. Often, digital instrumentation utilizes LCDs (liquid crystal display) to indicate the various functions. The advantage of digital readout is the instant recognition of the numeric display.

Directional Stability
A vehicle's ability to maintain a true course of travel, despite bumps, crosswinds, uneven road surfaces, etc.

Disc Brake
A type of brake consisting of a flat rotor (disc) that turns with the wheel and a stationary component called the caliper.

Displacement
Refers to the primary measure of engine size, representing the theoretical volume of the air/fuel mixture that can be inducted by all the cylinders on their intake stroke. Most engine sizes are measured in metric denominations (ex: 2.0 Liter equals 2,000 cubic centimeters) or cubic inch displacement (CID). The formula is (Pi * r²) * stroke.

Distributor
A component of the ignition system, usually driven by the camshaft, that distributes the electrical power to the spark plugs.

Double Wishbone Suspension ("A" Arm Suspension)
A system of independent suspension in which each wheel is located on a "knuckle" that is connected by ball joints to an upper A arm and a lower A arm. Usually, the lower A arms are longer. This system provides minimal changes in track and camber when the suspension is under load, as when going over bumps or in hard cornering.

Drag Coefficient (Cd)
A number used in calculating the aerodynamic drag action on a car. The drag coefficient is a function of such factors as the shape of the car and airflow through the car for cooling or ventilation. It can be found experimentally in wind-tunnel tests or by coast down tests performed on the actual car. The higher the drag coefficient, the greater the aerodynamic drag force a car's engine must overcome at any given road speed.

Driveshaft (Propeller Shaft)
The long, hollow tube with universal joints at both ends that carries the power from the transmission to the differential in rear wheel drive cars.

Drivetrain
The power-transmitting components in a car, including clutch, gearbox (or automatic transmission), driveshaft, universal joints, differential and axle shafts.

Dual Braking System
A brake system designed to prevent complete loss of braking in case of hydraulic or other brake failure in one part of the system

Dynamometer
A device which absorbs and measures the power derived by an internal combustion engine.

Electrical System
The system that cranks the engine for starting, furnishes high voltage to the spark plugs, powers the lights and operates other accessories.

Electrolyte
Any solution that conducts an electrical current, such as a mixture of sulfuric acid and distilled water found in automotive batteries.

Electronic Automatic Transmission
Electronic sensors send information to a microcomputer that selects the optimum shift characteristics and the proper gear for varying road conditions. These electronic sensors measure vehicle speed and engine load. The electronic transmission can be found as an option on Pathfinders, Hardbodys and 240SX.

Electronic Concentrated Control System (ECCS)
An electronically controlled system that gives continuous, precision control to a number of engine operating characteristics -- air/fuel mixture ratio, ignition timing, idle speed, exhaust gas recirculation. This system provides optimum driveability, fuel economy, power and emissions control.

Electronic Fuel Injection (EFI)
(See Fuel Injection)

Ergonomics
In a car, it refers to the design and positioning of controls, switches, instruments, seats, pedals and the steering wheel so they are properly located for easy and comfortable operation. ("Human Engineering")

Exhaust Emission Controls
These systems are designed to limit harmful gases in an engine's exhaust. Such controls can be grouped into two broad categories: those designed to reduce or eliminate the formation of harmful pollutants in the engine itself (retarded spark settings are one example) and those designed to destroy or otherwise alter the pollutants after they have been formed (air injection and catalytic converters fall into this category). Evaporative emission controls prevent gasoline vapors from escaping into the atmosphere from the fuel tank and the carburetor, and crankcase controls recycle fumes from the crankcase through the engine. Japanese emission requirements are among the most stringent in the world.

Exhaust-Gas Recirculation (EGR)
An exhaust-emission control system in which a portion of the exhaust gas is picked up from the exhaust manifold and sent back to the intake manifold to be reburned in the engine. Mixing exhaust gases with the fresh air/fuel mixture lowers the combustion temperature and reduces the formation of oxides of nitrogen in the exhaust.

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