Dictionary of Automotive Terms: I

ICEI: Internal Combustion Engine Institute.

ICING: Formation of ice (under certain atmospheric conditions) on throttle plate, air horn walls, etc., caused by lowering of fuel mixture temperature as it passes through air horn.

ID: Inside diameter.

IDLE: Indicates engine operating at its normal slow speed with throttle closed.

IDLE VALVE or IDLE NEEDLE: Needle used to control amount of fuel mixture reaching cylinders during idling. It, or they, may be adjusted by turning the exposed heads.

IDLER ARM: Steering system part that sup ports one end of center link.

IDLER GEAR: A gear, between two other gears, that's driven by one and drives other. This permits both driving and driven gear to rotate in same direction with no change in gear ratio.

IGNITION: Lighting or igniting fuel charge by means of a spark (gas engine) or by heat of compression (diesel engine).

IGNITION SWITCH: Key operated switch in driver compartment for connecting and disconnecting power to ignition and electrical system.

IGNITION SYSTEM: Portion of car electrical system, designed to produce a spark within cylinders to ignite fuel charge. Consists basically of battery, key switch, resistor, coil, distributor, points, condenser, spark plugs and necessary wiring.

IGNITION TIMING: Refers to relationship between exact time a plug is fired and position of piston in degrees of crankshaft rotation.

I-HEAD ENGINE: Engine having both valves in the head.

IHP: Indicated Horsepower.

IMEP: Indicated Mean Effective Pressure.

IMI: Ignition Manufacturer’s Institute.

IMPACT WRENCH: An air or electrical driven wrench that tightens or loosens nuts, cap screws, etc., with series of sharp, rapid blows.

IMPELLER: Wheel-like device upon which fins are attached. It is whirled to pump water, move and slightly compress air, etc.

IN.: Inch.

INCLUDED ANGLE (Steering): Angle formed by center lines drawn through steering axis (kingpin inclination) and center of wheel (camber angle) as viewed from front of car. Combines both steering axis and camber angles.

INDEPENDENT SUSPENSION: A suspension system that allows each wheel to move up and down without undue influence on other wheels.

INDICATED HORSEPOWER (ihp): Mea sure of power developed by burning fuel within cylinders.

INDIRECT FUEL INJECTION: Fuel is sprayed into intake manifold.

INDUCTION: Imparting of electricity into one object, not connected, to another by the influence of magnetic fields.

INERTIA: Force which tends to keep stationary object from being moved, and tends to keep moving objects in motion.

INERTIA SWITCH: An electrical switch designed to be operated by a sudden movement, such as that caused by a collision.

INHIBITOR: Substance added to oil, water, gas, etc., to prevent action such as foaming, rusting, etc.

INJECTOR: Refers to valve mechanism (used in fuel injection system) that squirts or injects measured amount of gasoline into in take manifold in vicinity of intake valve. In diesel engine, fuel is injected directly into combustion chamber.

INJECTOR TIMING (Diesel): Relationship between instant of fuel injection in any one cylinder, to position of piston in degrees of crankshaft rotation.

IN-LINE ENGINE: Engine in which all cylinders are arranged in straight row.

INPUT SHAFT: Shaft delivering power into mechanism. Shaft from clutch into transmission is transmission input shaft.

INSERT BEARING: Removable, precision made bearing which insures specified clearance between bearing and shaft.

INSULATION: Material used to reduce transfer of noise (sound insulation), heat (heat insulation), electricity (electrical insulation).

INSULATOR (Electrical): Material that will not (readily) conduct electricity.

INTAKE MANIFOLD: Connecting tubes between base of carburetor and port openings to intake valves.

INTAKE STROKE: Portion of piston’s movement devoted to drawing fuel mixture into engine cylinder.

INTAKE VALVE (Engine): Valve through which fuel mixture is admitted to cylinder.

INTEGRAL: Part of. (The cam lobe is an integral part of camshaft.)

INTERMEDIATE GEAR: Any gear in auto transmission between 1st and high.

INTERMITTENT: Not constant but occur ring at intervals.

INTERMITFENT FUEL INJECTION: Fuel system in which injectors are only open for short periods and remain closed rest of the time. Amount of fuel delivered is controlled by how long injector is held open.

INTERNAL COMBUSTION ENGINE: Engine that burns fuel within itself as means of developing power.

IN FERNAL GEAR: A gear with teeth cut on an inward facing surface. Example: Outer gear in a planetary gearset. Teeth face in ward towards center.

ION: Electrically charged atom or molecule produced by electrical field, high temperature, etc.

IONIZE (Air): To convert wholly or partly, into ions. This causes air to become a conductor of electricity.