DEFINITION OF TERMS-CONTINUED
Hydrocarbon. A mixture of hydrogen and carbon found
spark at the spark plug gap.
in vehicle emissions.
Ignition Distributor. The component of the ignition
system that closes and opens the circuit between the
Hydromatic. A type of automatic transmission containing
battery and ignition coil, and distributes the resultant
a fluid coupling and automatic controls for shifting from
high-voltage surges from the coil to the proper spark
one gear ratio to another.
Hydrometer. A device to determine the specific gravity of
Ignition Switch. The switch in the ignition system that
a liquid. This indicates the freezing point of the coolant
can be operated to open or close the ignition primary
in a cooling system or, as another example, the state of
charge of a battery.
Ignition Timing. Refers to the timing of the spark at the
Hydrovac Brakes. A type of braking system using
spark plug as related to the piston position in the engine
vacuum to assist in brake operation. The vacuum action
reduces the effort required from the driver to operate the
A type of engine with valves in the cylinder
Hypoid Gearing. A type of gearing configuration in which
the pinion gear meshes with the ring gear below the
Impeller. The rotor of a centrifugal pump that causes the
centerline of the ring gear.
fuel-air in an engine to be thrown into a diffuser chamber
to effect thorough mixing and good distribution.
Idle. The engine speed when the accelerator pedal is
fully released; generally assumed to mean when the
Independent Suspension. A type of suspension system
engine is doing no work.
designed to spring each wheel separately, therefore
allowing each wheel to move independently from the
Idle Circuit. The circuit in the carburetor through which
fuel is fed when the engine is idling.
Indicated Horsepower. A measurement of engine power
Idler Arm. A steering component designed to support
based on power actually developed in the engine
one end of the center link.
Idler Gear. A gear placed between a driving and a driven
Induction. The action or process of producing voltage by
gear to make them rotate in the same direction. It does
the relative motion of a magnetic field and a conductor.
not affect the gear ratio.
Inhibitor. A substance added to a liquid to prevent
The adjustment made on the
carburetor to alter the fuel-air mixture ratio or engine
speed on idle.
Injector. The mechanism, including nozzle, that injects
fuel into the engine combustion chamber on diesel
Ignition. The action of setting fire to; in the engine, the
initiating of the combustion process In the engine
In-Line Engine. An engine in which all engine cylinders
are in a single row, or line.
Ignition Advance. Refers to the spark advance produced
by the distributor in accordance with engine speed and
Insert. A form of screw thread insert to be placed In a
intake manifold vacuum.
tapped hole into which a screw or bolt will be screwed.
The Insert protects the part into which the hole was
Ignition Coil. The component of the ignition system that
tapped, preventing enlargement due to repeated removal
acts as a transformer and steps up battery voltage to
and replacement of the bolt.
many thousand volts; the high voltage then produces a