- H -

Hertz

A measure of frequency--i.e., the number of vibrations or cycles completed by a signal in one second. Used to measure such things as sound. Abbreviated Hz.

Hertz Cycle

Named for Heinrich Rudolf Hertz (1857 - 1894 ) The number of electrical events per second.

Hesitation

A momentary lack of throttle response or pause in the rate of acceleration.

Hexadecimal

The base 16 numbering system in which binary numbers are arranged in groups of four bits each.

Hf

Hafnium An element with the atomic number of 72.

HFC

High fan control.

HFC-134a

A hydrofluorocarbon gas that is not damaging to the environment and ozone layer and that can be used in automotive air-conditioning systems and to replace CFC-12.

HFP

High fuel pump.

Hg

Mercury An element with the atomic number of 80.

HHV

An acronym for higher heating value.

Hi-po

High performance.

Hi-rev Kit

A set of auxiliary springs to keep roller lifters in contact with the camshaft lobes.

Hi-side Box

See top mount box.

Hi-test

Gasoline that has an octane number near 90-95.

HIC

Hot idle compensator.

HID

High Intersity Discharge A lightingsystem that uses an arc across electrodes inside of a filament.

Hidden Hitch

A trailer hitch assembly that tucks up under a vehicle's rear bumper for an unobtrusive look. Some hidden hitches even place the receiver behind a fold-down license plate frame, so it isn't visible when it isn't in use.

High CG Load

Any application in which the load center of gravity of the trailer exceeds 40 inches (102 centimeters) above the top of the fifth wheel.

High Desert Racing Association (HDRA)

A professional off-road racing association that stages desert races in Nevada and adjacent states.

High Gear

The condition achieved from a planetary gear set when any two members, sun gear and planet gears or planet gears and internal gears, are locked together.