Cars - http://maxpages.com/carsinhistory/P

Pivot: A pin or shaft about which a part moves. The place at which a lever swivels. A lever cannot work without a pivot.

Pivot bolt: A bolt on which the arms of caliper brakes pivot and which also serves as the means for mounting the brakes on the bike frame. Also called "mounting bolt."

Plain gauge tubing: Tubing whose thickness remains constant over its entire length.

Plane: A flat surface. See inclined plane.

Plane sailing: A method of navigation which ignores the earth's curvature, treating its surface as a plane. Colloquially it indicates travel or procedure without difficulty or obstruction.

Planet carrier: That part of a planetary gearset upon which the planet gears are affixed. The planet gears are free to turn on hardened pins set into the carrier.

Planet gear: See planet gears.

Planet gears: Those gears in a planetary gearset that are in mesh with both the ring and the sun gear. They are referred to as planet gears in that they orbit or move around the central or sun gear.

Planetary gears: See planetary gearset.

Planetary gearset: A gearing unit consisting of a ring gear with internal teeth, a sun or central pinion gear with external teeth, and a series of planet gears that mesh with both the ring and the sun gear. Frequently used in overdrives and automatic transmission. Also called epicyclic gearbox.

Planned obsolescence: A policy of manufacturers that encourages motorists to become dissatisfied with their cars so that they are eager to buy the latest model.

Plastic moulding: a process that converts organic-based materials, by means of a general-purpose press and purpose-built tooling under controlled heat and pressure, and injects the hot material into a die cavity shaped in the final form of the intended part.

Plate: 1. The action of coating a material with some metal. Also called "electroplate" or anodize. 2. A flat piece of material. Also see plates.

Plates: 1. Thin sections of lead peroxide or porous lead in a battery. There are two kinds of plates -- positive and negative. The plates are arranged in groups, in an alternate fashion, called "elements," they are completely submerged in the electrolyte. 2. Any basically flat surface often used to mount another device. Also see baffle plate, brake backing plate, breaker plate, and clutch pressure plate.

Platform: primary load-bearing structural assembly of a motor vehicle determining the basic size of the motor vehicle, and is the structural base that supports the driveline and links the suspension components of the motor vehicle.

Platinum: A precious metal sometimes used in the construction of breaker points. It conducts well and is highly resistant to burning.

Platinum spark plug: !!!.

Play: Movement between two parts. See free pedal play.

Plenum: A chamber, located between the throttle body and the runners of an intake manifold, used to distribute the intake charge evenly and to enhance engine breathing.

Plexiglas: A trade name for an acrylic plastic, made by the Rhom and Haas Co.

Plexiglass: See plexiglas.

Plies: See ply.

Plug: A removable "cork" which fills a hole. See core hole plug, core plugs, drain plug, expansion plug, freeze plug, glow plug, oil drain plug, spark plug gap, and spark plug, welch plug.

Plug caddy: !!!.

Plug cap: !!!.

Plug gap: See spark plug gap.

Plug gapping: Adjusting the side electrode on a spark plug to provide the proper air gap between it and the center electrode.

Plug Patch: A tire repair material which is forced into a nail hole to fill it. Although a common procedure, it is not the most satisfactory method of repair

Plug repair: The filling of a nail hole by forcing repair material into the damaged area, often while the tire is mounted and containing air. It is not a satisfactory method of repair.

Ply: A layer of rubber-coated parallel cords which forms a unit of a tire carcass. The plies are made of cord, fiberglass, steel, or structural fabric. See bias tire and tire plies.

Plymouth: The Fury for 1956-58 are milestone cars. The Satellite SS and GTX for 1965-70 are milestone cars. The Barracuda Formula S for 1965-69 are milestone cars. The Roadrunner and Superbird for 1968-70 are milestone cars.

Ply rating: An indication of tire strength load carrying capacity, does not necessarily indicate actual number of plies. A two-ply four-ply rating tire would have the load capacity of a four-ply tire of the same size but would have only two actual plies. This system of measurement has been replaced by the term "load range."

Ply separation: A breakdown of the bonding compounds resulting in the plies detaching from each other. Usually as a result of excessive heat.

Ply turnup: The extension of a carcass ply to its end after wrapping around the bead. Also called "flipper strip"

Pneumatic tire: A flexible, hollow rubber forming the outer part of the vehicle wheel and inflated by air pressure. Originally rubber tires were solid core. Dunlop was the first to invent a tire with an air-filled tube for bicycles. Later, tubeless tires were invented. The tire is filled with enough compressed air to support the weight of the vehicle and cushion road impacts.

Pneumatic trail: See self-aligning torque.

Pneumatics: The study of pressure and flow in gases. A pneumatic drill is operated by compressed air; a pneumatic tire contains compressed air.

PNGV: Acronym for "Partnership for a New Generation of Vehicles".

Pod filter: !!!.

Point: See boiling point, breaker points, cloud point, contact points, coupling point, dry boiling point, dual breaker points, fire point, flash point, ignition points, point gap, pour point, shift point, vacuum runout point, and wet boiling point.

Point gap: The space between the contact points when they are fully open. The distance of the gap will determine the effectiveness of the points.

Points: See boiling point, breaker points, and contact points.

Polar moment of inertia: The resistance of an object to rotational acceleration. When the mass of an object is distributed far from its axis of rotation, the object is said to have a high polar moment of inertia. When the mass distribution is close to the axis of rotation, it has a low polar moment of inertia. A mid-engined car has most of its mass within its wheelbase, contributing to a low polar moment of inertia, which, in turn, improves cornering turn-in. See moment of inertia.

Polarity: 1. Indicates if the pole shoes are so magnetized as to make current low in a direction compatible with the direction of flow as set by the battery. 2. Indicates if the end of a magnet is the North or South pole (N or S). 3. Indicates if the battery terminal (either one) is positive or negative (plus or minus) (+ or -).

Polarizing: The process of sending a quick surge of current through the field windings of the generator in a direction that will cause the pole shoes to assume the correct polarity. This will insure that the generator will cause current to flow in the same direction as normal.

Pole: 1. One end, either North or South, of a magnet. Also see negative pole, and north pole. 2. A post.

Pole Position: !!!.

Pole shoe: See pole shoes.

Pole shoes: Metal pieces about which the field coil windings are placed, when current passes through the windings, the pole shoes become powerful magnets, example: Pole shoes in a generator or starter motor.

Polish: 1. A substance like wax used to make the exterior paint shine or gloss. 2. The act of making the paint shine. 3. To remove the minor obstructions in the exhaust flow. A term sometimes coupled with porting, as in porting and polishing or "port and polish." This is generally a process of blueprinting a two-stroke engine so that the intake and exhaust ports are polished and have no obstructions in the flow of fuel-air mixture or exhaust gases. In this way the engine generally has more performance. A problem may arise when an individual ports and polishes too much.

Pollutant: See exhaust emissions.

Pollution: See air pollution.

Polyester: A synthetic fiber.

Poly-glycotes: See glycote.

Polymer: A material consisting of large units (molecules) made by joining many smaller building blocks (simple molecules). Usually used to describe synthetic rubber.

Polymer coating: A coating that prevents paint from oxidizing and so protects a vehicle from premature fading and rusting. Professionally applied, it will last up to three years.

Pontiac: The Safari for 1955-57 are milestone cars. The GTO for 1964-69 are milestone cars.

Pony car: Small, sporty car along the lines of the Mustang, Firebird, Camaro, etc.

Poppet valve: A valve structure consisting of a circular head with an elongated stem attached in the center, very much like the shape of a mushroom with a flat top. It is designed to open and close a circular hole or port. Its name comes from the fact that it pops up and down. In engines, it is the valve used to open and close the valve port entrances to the engine cylinders.

Pop-up: !!!.

Porcelain: The material used to insulate the center electrode of a spark plug, it is hard and resistant to damage by heat.

Porsche: The Series 356 for 1949-64 are milestone cars. The 356C for 1965 is a milestone car.

Port: 1. Openings in engine cylinder blocks for exhaust and intake valves and water connections. Also see adjustable variable exhaust port, exhaust port, intake port, transfer port, and valve port. 2. To smooth out, align, and somewhat enlarge the intake passageway to the valves or intake chambers (especially in two-stroke engines). 3. A small hole in the master brake cylinder to permit fluid to return to the reservoir. See compensating port and intake port.

Port fuel injection: A type of fuel injection with at least one injector mounted in the intake port(s) of each cylinder. Usually the injector is mounted on the air intake manifold close to the port. Port fuel injection improves fuel distribution and allows greater flexibility in intake-manifold design, which can contribute to improved engine breathing.

Pos: Abbreviation for "positive ground."

Positive camber: See camber.

Positive caster: See caster.

Positive crankcase ventilation: (PCV) A process for preventing the buildup of harmful acid-producing combustion gases within the crankcase. See closed crankcase ventilation.

Positive crankcase ventilation system: (PCV) A process for preventing the buildup of harmful acid-producing combustion gases within the crankcase. See closed crankcase ventilation.

Positive ground: An automotive electrical system where the negative post of the battery was the hot wire and the positive post was connected to the frame of the vehicle. Opposite to negative ground.

Positive pole: The point away from which an electrical current flows through the circuit. It is designated by a plus sign (+).

Positive terminal: The terminal (such as that on the battery), to which the current flows. It is usually marked with the letters "pos" or a plus sign (+).

Post: 1. The round, tapered lead posts protruding above the top of the battery to which the battery cables are attached. See terminal. 2. The pillars which support the roof on a car. See A-post, B-post, C-post, and hardtop. The insert tube to which the seat of a bicycle is attached. See seatpost.

Pot: 1. A colloquial term for "carburetor" or for a "cylinder." 2. An abbreviation for a "potentiometer."

Pot metal: An alloy that is cast as a unit. It is relatively inexpensive to make, but is easily subject to breakage.

Potential: An indication of the amount of available energy.

Potential energy: The mechanical energy possessed by a body due to its position. For example, water in a reservoir above a hydro-electric power station has high potential energy which is converted to work when it drives the turbines of the power station.

Pound foot: The unit of measurement for torque. One pound-foot is equal to the twisting force produced when a one-pound force is applied to the end of a one-foot-long lever.

Pour point: The lowest temperature at which oil will pour, a test of its ability to flow and lubricate in cold weather.

Power: The rate of doing work. It is expressed in mass times distance over a period of time. Also see candle power and horsepower.

Power antenna: (PA) or (P.Ant) A radio antenna which automatically moves up and down whenever the radio is turned on or off. It is a telescoping antenna driven by an electric motor. See antenna.

Power assisted brake: See power brakes.

Power assisted brakes: See power brakes.

Power band: The subjectively defined rpm range over which an engine delivers a substantial fraction of its peak power. The power band usually extends from slightly below the engine's torque peak to slightly above its power peak.

Power booster: A device that uses engine vacuum to assist you in braking the vehicle. Helps the brake pedal to activate the hydraulic pistons in the master cylinder.

Power brake: See power brakes.

Power brakes: (PB) A conventional hydraulic brake system that uses engine vacuum to operate a vacuum power piston, the power piston applies pressure to the brake pedal, or in some cases, directly to the master cylinder piston. This system reduces the amount of pedal pressure that the driver must exert to stop the vehicle. Also called "vacuum-assisted brakes" or "hydraulic-assisted brakes." Also see brake booster.

Powerglide: (PG) A two-speed automatic transmission offered by General Motors.

Power oversteer: In a rear-wheel-drive vehicle, power oversteer creates a skid when too much power is applied and the rear wheels spin.

Powerplant: The automobile engine regardless of its type.

Power seat: (P.seat) The cushions upon which the driver and or passengers sit which is adjusted by a control switch connected to a small electric motor. See also seat.

Power steering: (PS) A steering system using hydraulic pressure to increase the driver's turning effort. As the driver turns the steering wheel, steering effort is reduced. The pressure is used either in the gearbox itself or in a hydraulic cylinder attached to the steering linkage. Also called power-assisted or assisted steering.
Power stroke: The third stroke of the four-stroke cycle. The piston moves downward from top dead center to bottom dead center as a result of the force of combustion acting on the top of the piston.

Power take off: (PTO) The end of the crank (usually on the other side from the magneto or starter) where the motion of the crank is transferred to the transmission or power output.

Power to weight ratio: See power-to-weight ratio.

Power-to-weight ratio: Ratio of horsepower to the weight of a vehicle.

Power train: See powertrain.

Powertrain: An engine and transmission combination. See drivetrain.

Power valve: A valve in a carburetor that is operated by vacuum or mechanical linkage to provide more fuel at wide open throttle.

PPM: Acronym for "parts-per-million." Term used in determining extent of pollution existing in given sample of air.

Pratt and Whitney key: A bar like a flat key except the ends are oval shaped.

Prechamber: See pre-combustion chamber.

Pre-chamber: See pre-combustion chamber.

Precision insert bearing: A very accurately made replaceable type of bearing, it consists of an upper and lower shell, the shells are made of steel to which a friction type bearing material has been bonded, connecting rod and main bearings are generally of the precision insert type.

Precombustion chamber: See pre-combustion chamber .

Pre-combustion chamber: A small chamber located outside the combustion chamber of some cars in which a small amount of rich fuel-air mixture can be ignited to increase fuel efficiency and cut emissions. Found principally on diesel engines and stratified charge engines. Also called "pre-chambers."

Precured tread rubber: Pre-cured rubber, usually of high density and available in various tread designs, is lined with cushion gum before applying to a buffed casing using the cold cap method of retreading. Recently it has been applied in some hot cap molds employing a smooth matrix or other modifications.

Preheating: The application of some heat prior to the later application of more heat, cast iron is preheated to avoid cracking when the welding process is started. A coil (ignition) is preheated prior to testing. Also see converter preheating.

Preignition: The fuel charge being ignited before the proper time. Sometimes causes pinging or detonation. This is the combustion of the fuel-air mixture that is not a result of the spark plug's firing, but by high pressure, a flame, or a hot surface.

Preloading: Adjusting an antifriction bearing, ball joint, or spring so that it is under mild pressure, this prevents bearing looseness under driving stress.

Premium gasoline: !!!.

Pre-owned vehicle: A used vehicle.

Pre-selector gearbox: An arrangement that enables the driver to select a gear speed before he needs it and then depress the clutch pedal when he desires to use the selected gear.

Preselector gearbox: See pre-selector gearbox.

Press, drill: See drill press.

Press fit: An interference fit. A fit so tight that an object must be removed with a puller or a press. Also see drive fit, interference fit, force fit.

Pressure: The force due to the weight of a substance exerted over the area the substance occupies. In metric measure, it is the force acting on each square metre. To calculate pressure, divide the force (in newtons) by the area (in square metres). It is measured in newtons per square metre (N/m²). In Imperial (U.S.) measure, it is measured in pounds per square inch (lb/in.²) (psi). Also see atmospheric pressure, back pressure, boost pressure, center of pressure, clutch pressure plate, extreme pressure lubricant, mean effective pressure, oil-comb ination splash and pressure system, oil-full pressure system, oil pressure gauge, pressure bleeder, pressure cap, pressure radiator cap, pressure relief valve, safety pressure cap, and static pressure.

Pressure bleeder: A device that forces brake fluid under pressure, into the master cylinder so that by opening the bleeder screws at the wheel cylinders, all air will be removed from the brake system.

Pressure buildup: As a tire heats up as it travels on the road, the air inside the tire expands and thus increases the air pressure. Any increase exceeding 15% above starting cold pressure should be investigated. The practice of bleeding the excess or hot pressure should be avoided.

Pressure cap: A special cap for the radiator, it holds a predetermined amount of pressure on the water in the cooling system, this enables the water to run hotter without boiling. In this way, the engine can operate at a higher and a more efficient temperature without danger of overheating. The cap also has a vacuum valve that lets air into the cooling system if the pressure falls too low to prevent outside air pressure from causing a partial collapse of the radiator.

Pressure plate: See clutch pressure plate.

Pressure radiator cap: See pressure cap.

Pressure relief valve: A one-way valve designed to open at a specific pressure to prevent pressures in the system from exceeding certain limits. Also see blowoff valve.

Presta valve: A bicycle tube valve whose stem has a small nut on top, which must be loosened during inflation, instead of a spring such as is found on the Schrader valve.

Pretensioner: !!!.

Primary brake shoe: The brake shoe that is first to press against the brake drum. The other shoe is the secondary shoe. When both shoes are pressing against the drum, the amplification of forces is called "servo action."

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Page Updated Sun May 20, 2001 8:08pm EDT