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Penetrating Oil

A special, thin oil that penetrates rust and/or tight threads and helps in the removal of stubborn nuts and bolts.

Pentroof Combustion Chamber

A flat or pancake shaped combustion chamber that has the overhead valve heads that are almost parallel to the top of the pistion and the spark plug at or near the center of the chamber. This design provides a very short distance for the flame front to travel, excellent air flow characteristics and efficient combustion.

PERA

An acronym for Production Engine Remanufactures Association.

Percent

The ratio of one material to another in a mixture as in a fuel mixture.

Percent Of Grade

A value that is determined by dividing the height of a hill by its length, often used to determine the power requirements of trucks or for determining maximum pay load.

Percolation

A condition in which the fuel-bowl vent fails to open when the engine is turned off and internal pressure forces raw fuel through the main jets into the manifold.

Performance Chart

A chart that has been produced from a dynamometer showing the horsepower, torque, and fuel consumption of an engine at various speeds.

Performance Test

1. Readings of the temperature and pressure, under controlled conditions, to determine if an air-conditioning system is operating at full efficiency. 2. A test to determine if a system or sub-system is performing at maximum efficiency.

Perimeter Frame

A conventional chassis frame design that is similar in construction to a ladder frame, having full-length side rails that support the body at its greatest width, providing optimum protection to passengers in the event of a side impact.

Period

The length of time required for one cycle of a periodic wave.

Peripheral Device

Any external device attached to a computer; examples of peripherals include printers, disk drives, keyboards monitors and scantools.

Permaloy

A permanent-magnet allow of Nickel and Iron.

Permanent Magnet

A piece of ferrous material, such as steel, that retains its magnetic properties without the use on an electric current.

Permanent Magnet Generator

A reluctance sensor. A sensor that generates a voltage signal by moving a conductor through a permeant magnetic field.

Permanent Strainer

A device generally of a Y-configuration having an accessible cylindrical strainer element used in horizontal and vertical lines. The element, retained by a plug end which may be plain or fitted with a valve, can be opened for "blow-through" cleaning.

Permatex

A tradename for a brand of engine and transmission sealants.

Permeability

The measure of the ease with which magnetic lines of force can move through a material compared with air.

Permissible Exposure Limit (PEL)

The maximum length of time a person should be exposed to a hazard or hazardous material established by OSHA and expressed as a time-weighted average limit or ceiling exposure limit.

Peta

The prefix representing the number 1,000,000,000,000,000.

Petcock

A small faucet-like valve used for draining liquids, such as that found at the bottom of some radiators.