Terms Starting with I

Idler arm-A steering linkage component, fastened to the car frame, which supports the right end of the center link.

Idler gear-A third gear placed in a gear train, usually used to reverse the direction of rotation.

Ignition system-The subsystem on the engine used to ignite the air and fuel mixture efficiently.

I-head-A style of valve arrangement in an engine.  I-head refers to the valves being placed directly above the piston in the cylinder head.

Inclined surface-A slope or slanted surface.  An inclined surface is used in valve rotators.

Independent rear suspension-A rear suspension system composed of trailing arms (like the control arms) and Macpherson struts or torsion bars.  The system allows the rear wheels to move independently of each other.

Indicated horsepower-Theoretical horsepower calculated by the manufacturer of the engine.

Inertia-Objects in motion tend to remain in motion.  Objects at rest tend to remain at rest.  Inertia is the force keeping these objects in motion or at rest.

Inertia drive-A drive system on a starter motor using inertia to turn a screw sleeve on a spline.

Inertia switch-A switch used on fuel systems that opens an electrical circuit whenever there is a sudden impact from a vehicle or crash.

Infrared exhaust analyzer-An instrument able to detect and measure hydrocarbons, carbon monoxide, carbon dioxide, and oxygen levels.

Inhibitor-Any substance that slows down or prevents chemical reactions such as corrosion or oxidation.

In-line-Cylinders in an engine that are in one line or row, such as an in-line 4-or 6- cylinder engine.  The cylinders are generally vertical as well.

Insert guides-Valve guides that are small cast cylinders pressed into the cylinder head.

Insulator-A material with five or more electrons in the valence ring.

Intake manifold vacuum-The vacuum produced inside the intake manifold between the valves and the throttle plate.  When the throttle plate is closed, there is high intake manifold vacuum.  When it is open, there is low intake manifold vacuum.

Integral guides-Valve guides that are manufactured and machined as part of the cylinder head.

Integrated circuit-An electrical circuit board with many semiconductors forming a complex circuit.

Interference angle-When valves are ground at 45 degrees and the seat is ground at 44 degrees, the two angles will interfere with each other.  The two angles and their interference angle will help valves seat faster after being ground down.

Interference fit-A fit between two parts that must be pressed together.  Some piston pins have an interference fit with the piston.

Intermittent combustion-Combustion of air and fuel that starts and stops such as the combustion in a four cycle gasoline engine.

Internal combustion-Combustion of air and fuel inside the engine as compared to combustion external to the engine such as a boiler.

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