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Exhaust-gas Recirculation (EGR)

An emissions-control system that reduces an engine's production of oxides of nitrogen by diluting the air/fuel mixture with exhaust gas so that peak combustion temperatures in the cylinders are lowered.

Exhaust-gas Recirculation Valve (EGR Valve)

A valve, generally vacuum operated, to regulate the exhaust gas flow into the intake manifold.

Exhaust-gas Speed

The speed at which exhaust gases pass through the header pipes, usually at about 200-300 feet (61-91 meters) per second.

Exothermic

A chemical reaction, such as combustion, that gives off heat.

Exotic

Usually a very expensive, very exclusive sports car, such as a Ferrari or Lamborghini. Most exotics boast an unusual, attention-getting design.

Expansion Control

The grinding of a piston in a slightly oval shape so that it becomes round when it expands with heat.

Expansion Plug

A term used for core plug.

Expansion Tank

1. A coolant-recovery tank. 2. An auxiliary tank, usually connected to the inlet tank or a radiator, that provides additional storage space for heated coolant.

Expansion Tube

A metering device used at the inlet of some evaporators to control the flow of liquid refrigerant into the evaporator core.

Expansion Valve

A term used for thermostatic expansion valve.

Experimental Safety Vehicle (ESV)

A prototype vehicle used to test and evaluate specific safety features.

Explosion-proof Cabinet

Cabinet used in the automotive shop to store gasoline and other flammable liquids.

Exposure Limit (EL)

A term often used for permissible exposure limit (PEL).

Extended Cab Pickup

A pickup truck with a bench seat or jump seats in the rear. Some extra cab pickups have two regular doors only, while some also have one or two rear doors that can be opened only when the front door on that side is already open. These rear doors open opposite from a standard vehicle door (i.e., with the hinge toward the rear of the truck). Also known as an extended cab pickup or king cab pickup. See also crew cab pickup and regular cab pickup.

Extension Housing

An aluminum or iron casting that encloses the transmission output shaft and supporting bearings.

External Combustion Engine

An engine that burns the air-fuel mixture in a chamber outside the engine cylinder, such as a steam engine or a Stirling engine.

External Equalizer

A term used for equalizer line.

External Gear

A gear with teeth on its outside surface.

External In-line Filter

1. Filter placed in the transmission-cooler return line outside the transmission housing. 2. A supplemental filter placed in the air-conditioning system to prevent system damage after repairs.

Externally-tabbed Clutch Plate

Clutch plates having tabs around the outside periphery to fit into grooves in a housing or drum.