DICTIONARY OF AUTOMOTIVE TERMS - "Po"

POA:

Acronym for pilot operated absolute valve used in some air conditioning systems

POA suction throttling valve:

A term standing for "pilot operated absolute" and is a modification of a suction throttling valve which has a metal bellows with a vacuum instead of a diaphragm; it provides more accurate evaporator pressure control, allowing for lower evaporator temperatures without cone icing

Pocket:

See:
door pocket
still-air pocket
gas pockets

Pocket caliper:

A small slide-type caliper for inside and outside measurement up to about 100 mm or 4 inches

Pocket slide caliper:

A small slide-type caliper for inside and outside measurement up to about 100 mm or 4 inches

Pod:

A housing for a gauge mounted on the dash.
Also See:
induction pod
sidelight pod

Pod filter:

A foam filter which is like a sock (open at one end and closed at the other) and is clamped on the horn of a carburetor

Point:

See:
bead point
boiling point
breaker point
breaker points
brittle point
charging point
check point
cloud point
contact breaker point
contact point
contact points
coupling point
dew point
dry boiling point
dual breaker points
fire point
flash point
ignition point file
ignition point
ignition points
jacking point
lifting platform take-up point
lubrication point
point gap
points
pour point
shift point
vacuum runout point
wet boiling point

Point file:

See ignition point file

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.

Point gauge:

See sighting point gauge

Point injection:

See single point injection

Points:

See:
boiling point
breaker points
contact breaker points
contact points
dual breaker points
ignition points
point

Points file:

A thin, fine-toothed file for cleaning and smoothing off the piles on contact breaker points

Points gap:

A gap between the contact breaker points when fully open; measured with a feeler gauge

Point steering:

See center point steering

Poke:

A colloquial term for power or acceleration

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 -).
4. The terms (positive, negative, north, and south) that indicate the direction of current and flux flow in electrical and magnetic circuits at any given instant

Also See:
direct polarity
reversed polarity
straight polarity

Polarization resistance:

The transition resistance between the electrodes and the electrolyte; part of the internal resistance of a battery. Compare internal resistance

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.

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.

Pole:

1. One end, either North or South, of a magnet.
   Also See:
   negative pole
   north pole
   positive pole
   south pole
2. A post or long shaft.
3. The best starting position in an auto race. It is the inside space on the first row of drivers. Most races begin with the cars in a formation of rows of two. Most events begin with a standing start or a rolling start.

Pole piece:

A soft magnetic core of the inductive winding in a magnetic pick-up assembly; stator

Pole position:

The best starting position in an auto race. It is the inside space on the first row of drivers. Most races begin with the cars in a formation of rows of two. Most events begin with a standing start or a rolling start.

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.
   Also See:
   automobile polish
   car polish
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 port has been polished too much. Also see ground and polish

Polishing:

See:
chemical brightening
chemical polishing

Polishing barrel:

A barrel used for a polishing process in which the aluminum surface is smoothed in the presence of metallic or ceramic shot by a rotating movement of the barrel

Pollutant:

Hydrocarbons, carbon monoxide, and nitrogen oxides.
Also See:
exhaust emissions
exhaust pollutants

Pollution:

See air pollution.

Polycarbonate:

(PC) A polyester polymer in which the repeating structural unit in the chain is of the carbonate type; used for bumpers, body and roof panels

Polychlorinated biphenyl:

(PCB) Dielectric fluid used in capacitors and transformers that is very toxic. Use of PCB in transformers and capacitors is strictly regulated by the Environmental Protection Agency.

Polyellipsoidal:

A curve which is an ellipse in every direction so that the light of the bulb which is positioned at the focal point will bounce into the same forward direction.

Polyellipsoidal headlight:

A headlight with a gas discharge lamp and a polyellipsoidal reflector

Polyester:

A synthetic fiber.

Polyester filler:

A body repair material for smoothing dents in body panels; includes a resin base filler paste and a catalyst which is added to the base filler and hardens by chemical reaction

Polyester powder:

A powder used for electrostatic powder coating

Polyethylene:

(PE) A polymer prepared by the polymerization of ethylene as the sole monomer; very resistant to chemical attack. High-density polyethylene (HDPE) is used, e.g., for blow-molded parts such as tanks for fuel, coolant, washer and brake fluid; low-density polyethylene (LDPE) is used for plastic film and sheet

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. See *ablative polymer

Polymer alloy:

A mixture of two or more different compatible polymers

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.

Polymerization:

The bonding of two or more monomers (by chemical reaction) to produce a polymer. Plastic parts produced from specific polymer alloys usually give better performance in respect to thermal and mechanical properties as compared to those of parts consisting of the respective individual components

Polymethyl methacrylate:

(PMMA) A thermoplastic polymer derived from methylacrylate; transparent solid with excellent optical qualities and weather resistance; typical automotive applications are the lenses of rear lights. Also called Perspex

Polyphase motor:

Electrical motor designed to be used with a three-or four-phase electrical circuit.

Polyphenylene oxide:

(PPO) The characteristics of this plastic are high impact strength, good thermal and dimensional stability as well as excellent flame-resistance

Polypropylene: (PP)

An extremely versatile plastic, available in many grades and also as a copolymer (ethylene/propylene). PP has the lowest density of all thermoplastics (900 kg per cubic meter) and is characterized by excellent strength, stiffness, fatigue, and chemical resistance. Also used in fabric because it is extremely hydrophobic, fast drying, does not absorb moisture, lightweight, strong, and abrasion resistant.

Polystyrene:

Plastic used as an insulation in some refrigerated structures.

Polysulphide:

Synthetic rubber compounds used in adhesives, coatings and sealers. When cured, they are almost unaffected by aliphatic or aromatic solvents; and retain flexibility and shock resistance at low temperature. Flow characteristics, odor and high relative cost limit their use as adhesives to very specialized applications. High performance sealers of this base are widely used for aircraft and marine requirements

Polytetrafluoroethylene:

(PTFE) The major advantages of this material are its excellent chemical resistance and its extremely low coefficient of friction; automotive uses are parts where these characteristics are relevant, such as in valve stem seals, friction bearings, and joints

Polyurethane: (PUR)

1. A thermoplastic material with high strength, good chemical and abrasion resistance; used mainly for foamed reaction injection moldings and for adhesives, such as for flush-bonded body glass
2. Any synthetic rubber polymers produced from the polymerization of an HO and NCO group from two different compounds. Often used in insulation and molded products.

Polyurethane paint:

A type of two-pack paint based on polyurethane substances

Polyurethane powder:

A powder used for electrostatic powder coating

Poly-V-belt:

A drive belt with multiple Vs; flat, similar to the toothed belts used as timing belts, but with lengthwise V-shaped ribs rather than transverse cogs; used increasingly on new engines instead of conventional V-belts

Polyvinyl chloride:

(PVC) Both plasticized and unplasticized PVC types are marked by good weathering resistance, excellent electrical insulation properties, and good surface properties; they are self-extinguishing

Poop:

A superstructure fitted at the after end of the upper deck of a ship

Ponded roof:

Flat roof designed to hold a quantity of water which acts as a cooling device.

Pontiac:

A vehicle brand of which the Safari for 1955-57 are milestone cars. The GTO for 1964-69 are milestone cars.
Click image for books on Pontiac

Pontiac Fiero:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Fiero

Pontiac Firebird:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Firebird

Pontiac Grand Am:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac Grand Am

Pontiac Grand Prix:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac Grand Prix

Pontiac GTO:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac GTO

Pontiac Le Mans:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac Le Mans

Pontiac Sunbird:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac Sunbird

Pontiac Tempest:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac Tempest

Pontiac Trans Am:

A model of automobile manufactured by Pontiac division of General Motors
Click image for books on Pontiac Trans Am

Pony car:

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

Poor opacity:

A paint fault in which the color of underlying coats or fillers remains visible through the topcoat; may be caused by insufficient paint thickness, overthinning, etc.

Pop:

See solvent pop

Pop-off valve:

A one-way valve that opens to the atmosphere above a certain set pressure to relieve excessive internal pressure buildup; often used with a turbocharger installation to limit boost pressure to the engine.

Popper:

See snap fastener

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.

Popping:

See solvent pop

Popping back:

See blowback

Pop rivet:

A type of tubular rivet which initially has a hard steel pin (like a nail) passing through it; when the pop rivet is fitted with a pop rivet gun, the head of the pin expands the inner end of the tubular rivet, closing it; the head of the pin then snaps off; used when a joint can be accessed from only one side

Pop tester:

An injector testing tool used for measuring opening pressure, leakoff pressure, and spray patterns of injectors

Populaire:

A randonneur bicycle event under the regulations and pace of a standard brevet which is less than 200 kilometers.

Pop-up:

A towable tent that pops up when parked to expand its space. These types have a furnace, three way refrigerator, a/c, and more options.

Pop-up headlights:

See concealed headlights

Porcelain:

1. The material used to insulate the center electrode of a spark plug, it is hard and resistant to damage by heat.
2. Ceramic china-like coating applied to steel surfaces.

Porcelain enamel:

A glassy material obtained by melting a mixture of inorganic materials; this can then be applied in one or more layers on a metal surface to which it is firmly bonded after firing; typical automotive applications are for badges and trim. The British term is "vitreous enamel"

Pore:

A small opening in a surface

Porosity:

Presence of gas pockets or voids in the metal.

Porous:

Permeable to air or fluids

Porsche:

A vehicle brand of which the Series 356 for 1949-64 are milestone cars. The 356C for 1965 is a milestone car.
Click image for books on Porsche

Porsche-type synchromesh:

A sophisticated synchromesh technology depending on the frictional forces created by a spreading synchronizer ring

Port:

1. An opening in an engine cylinder block for exhaust and intake valves and water connections.
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.
4. The left-hand side of a ship when facing forward.

Also See:
adjustable variable exhaust port
cargo port
compensating port
exhaust port
freeing port
inlet port
intake port
metering port
replenishing port
third scavenging port
transfer port
valve port
variable exhaust port
vent port

Portable service cylinder:

Container used to store refrigerant. Two most common types are disposable and refillable.

Port area:

The cross-section area of the port of a two-stroke engine; this value is one of the factors determining the gas flow and the power of a two-stroke engine

Port bar:

If the ports of the two-stroke engine have to be exceptionally wide, as in the case of the exhaust, a port bar is sometimes formed vertically across the port to give support to the rings, which might otherwise expand into the port and be jammed and broken

Port bridge:

If the ports of the two-stroke engine have to be exceptionally wide, as in the case of the exhaust, a port bar is sometimes formed vertically across the port to give support to the rings, which might otherwise expand into the port and be jammed and broken

Port cover:

See transfer port cover

Ported EGR valve:

Operated by a vacuum signal from the carburetor EGR port. The port signal actuates the valve diaphragm. As vacuum increases, spring pressure is overcome, opening the valve and allowing EGR flow. The amount of the flow is dependent on the position of the tapered pintle or poppet whose position reflects the strength of the vacuum signal

Ported vacuum:

A slot-type port located right at the throttle plates, used for controlling various devices that must work in proportion to throttle plate opening, such as the EGR valve. When the throttle plates are closed at idle, there is virtually no vacuum signal at this slop. But as the throttle plates open during acceleration, they expose the slot to a progressively increasing amount of intake manifold vacuum

Ported vacuum advance:

(PVA) A series of restriction devices between the distributor advance unit and the carburetor advance port to ensure that there is no vacuum advance during idle, but increasing ignition advance as the throttle opens

Ported vacuum switch:

(PVS) a temperature actuated switch that changes vacuum connections when the coolant temperature changes (originally used to switch spark port vacuum; now used for any vacuum switching function that requires coolant temperature sensing)

Port fuel injection:

(PFI) 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. Also called multi-point injection

Porthole:

A styling accessory popularized by the Buicks of the early 1950s where three or four round chrome surrounds were fitted to the sides of both fenders for decorative purposes; this trim detail was soon imitated by other manufacturers and was offered as an option for many models, even in Europe. The T-bird had a porthole window on each the rear sail panels.

Port induction:

See third port induction

Port timing:

In 2-stroke engines the critical moment when ports are covered or uncovered by the piston

Pos:

Abbreviation for "positive ground."

Position:

See:
driving position
flat position welding
flat position
horizontal position
overhead position
pole position
projected spark position
recessed spark position
spark position
vertical position

Position sensor:

See:
crankshaft position sensor
throttle position sensor

Position welding:

See flat position welding

Positioning Satellite:

See global Positioning Satellite

Positive camber:

See camber.

Positive caster:

When an imaginary line extending through the steering axis cuts the wheel axis ahead of the extended vertical axis through the wheel center. See caster.

Positive clutch:

See dog clutch

Positive connections:

Connections in an electric circuit out of which electricity constantly flows. The positive connections out of which electricity flows may also be termed that into which electrons flow; and the negative connection into which electrons flow; and the negative connection into which the electricity flows may be considered that pole out of which the electrons flow.

Positive crankcase ventilation:

(PCV) A process introduced in 1963 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 crankcase ventilation valve:

(PCVV) a one-way valve which controls the flow of vapors from the crankcase into the engine

Positive displacement compressor:

A pump which provides a measured amount of gas or liquid per stroke or cycle and requires some form of mechanical drive arrangement, usually a belt drive from the crankshaft; typical positive displacement compressors are piston compressors, roots compressors and vane-type compressors

Positive electrode:

The positive plate of a battery

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 offset:

1. A steering geometry layout where the steering axis cuts the wheel axis at or below the wheel center plane.
2. The distance between the mounting face of a disc and the wheel centerline; the offset is referred to as positive when the inner attachment face of the wheel disc is shifted towards the outer side of the wheel. The opposite is negative offset

Positive plate:

The chocolate-colored plate during battery discharge which acts as cathode. The opposite to negative plate

Positive pole:

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

Positive temperature coefficient:

(PTC) a thermistor (temperature sensor) whose resistance increases as the temperature increase. The opposite of a negative temperature coefficient (NTC) thermistor

Positive temperature coefficient thermistor:

(PTC) Electronic thermistor which increases in resistance as temperature increases.

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 (+) and is usually red.

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.
3. The insert tube to which the seat of a bicycle is attached.

Also See:
A-post
B-post
battery post
C-post
D-post
door post
hardtop
hinge post
pulling post
seatpost
terminal post

Postheating:

1. Temperature to which a metal is heated after an operation has been performed on the metal (welding, cutting, forming, etc.).
2. The heating of glow plugs after the engine is started to prevent blue smoke and misfiring during the warm-up phase

Post-ignition:

The ignition of the air-fuel mixture after the electrical ignition has been shut off

Pot:

1. A colloquial term for "carburetor."
2. An abbreviation for a "potentiometer," also called a "rheostat"
3. A cylinder.
4. A dashpot.
5. Also see mush pot

Potassium permanganate:

Used in carbon filters to help reduce odors.

Potato chipped wheel:

A bicycle wheel which has been damaged so that it is bent like a potato chip. Also called a taco wheel for a similar reason.

Potential, electrical:

Electrical force which moves, or attempts to move, electrons along a conductor or resistance.

Potential relay:

Electrical switch which opens on high voltage and closes on low voltage.

Potentiometer:

Instrument for measuring or controlling by sensing small changes in electrical resistance. Also called a "rheostat."

Pothole:

A deep hole in the surface of a road.

Pot joint:

A universal joint in which the rollers or balls can move freely in an internally grooved cylinder.
Also See:
constant velocity joint
slip joint

Pot life:

The rating in hours of the time interval following the addition of accelerator before a chemically curing adhesive or sealer will become too thick to pass viscosity (consistency) requirements. Closely related to working life.

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:

See foot-pound

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.

Pound force:

Force applied to a 1-lb. mass; has an acceleration of 32.173 ft/s2.

Pour point:

The lowest temperature at which a liquid (e.g., oil) will pour or flow, a test of its ability to flow and lubricate in cold weather.

Powder:

See:
electrostatic powder coating
polyester powder
polyurethane powder

Powder coating:

See electrostatic powder coating

Powder slush molding:

A processing technique applied to produce PVC skins. In a preheated rotating mold, a thin layer of PVC dry blend is evenly spread across the mold surface. The mold is transferred to an oven to fuse the PVC skin and is finally cooled in a water-bath

Power:

1. The rate of doing work. It is expressed in mass times distance over a period of time.
2. Time rate at which work is done or energy emitted.
3. To provide power to something, e.g., "Power up the radio."
4. Source or means of supplying energy.

Also See:
absorptive power
candle power
constant power distribution
equal power distribution
equal power split
fifty-fifty power split
four-stroke power cycle
horsepower
hydro-electric power
in-line power steering
integral-type power assisted steering
integral-type power steering
linkage power steering
load-controlled power distribution
maximum brake power
maximum power
peak power
propelling power
propulsive power
pump power output
rated power

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-assist brakes:

A braking system that uses engine intake manifold vacuum (or hydraulic pressure) and atmosphere pressure to reduce the braking effort required at the pedal.

Power assisted brake:

See power brakes.

Power assisted brakes:

See power brakes.

Power-assisted steering:

(pas) A steering system in which a hydraulic pump powered by the engine helps the driver to turn the steering wheel. Compare power steering. Also see integral-type power assisted steering

Power band:

1. 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.
2. A certain rpm range in which an engine makes most of its power

Power booster:

A device that uses engine vacuum or hydraulic power 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.

Power chamber:

The main housing of a vacuum booster internally partitioned in half by a flexible diaphragm. Pressure differentials between the halves move the diaphragm and creaate application force.

Power closing:

See automatic closing system

Power cut-off:

A battery master switch

Power cut-off switch:

A battery master switch

Power cycle:

See four-stroke power cycle

Power distribution:

A specific drive torque distribution between front and rear axles in a 4WD system. Compare asymmetric power distribution equal power distribution load-controlled power distribution

Power element:

Sensitive element of a temperature-operated control.

Power factor:

1. Correction coefficient for the changing current and voltage values of ac power.
2. A measurement of the time-phase difference between the voltage and current in an AC circuit. It is represented by the cosine of the angle of the phase difference. Zero degrees has a power factor of 100%. That means the watts and volt-amperes are equal and there is nothing more than resistance in the circuit. Ninety degrees of angle represents nothing in the way of resistance and only inductance in the circuit. Power factor is also found by the formula:
   Power Factor = True Power (TP) divided by Apparent Power (AP)

Powerglide:

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

Power hood:

British term for electric top

Power output:

See pump power output

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.

Powerpoint:

A socket for inserting an auxiliary component. It looks very much like a cigarette lighter socket.

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 so that the seat can be moved forward or back, up or down, or be tipped forth and aft. See also seat.

Power servo:

A vacuum-operated or electrically-powered device that actuates the duct doors and switches on systems equipped with automatic temperature control

Powershift transmission:

A transmission which can be shifted without declutching or decelerating

Power split:

See:
asymmetic power distribution
equal power split
fifty-fifty power split

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."
Also See:
in-line power steering
integral-type power steering
linkage power steering
speed-sensitive steering
variable assist power steering
variable ratio steering

Power steering pump:

A pump which supplies hydraulic pressure for the power steering system

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)

1. 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.
2. A device (usually a pulley) on an engine or wheel which drives a secondary device. A PTO often drives a hydraulic pump, which can power a dump body, concrete mixer or refuse packer. Some designs mount to a standard opening on the transmission, while others attach at the front or rear of the engine.

Power to weight ratio:

See power-to-weight ratio.

Power-to-weight ratio:

The relationship of a vehicle's horsepower to the weight of a vehicle. The greater the horsepower is in relation to the weight of the car, the faster the car will go and the faster it will accelerate.

Power train:

See:
powertrain.

Powertrain:

An engine and transmission combination. Sometimes includes the drive shaft, and drive axle.
Also See:
drivetrain
direct drive powertrain

Powertrain control module:

(PCME) An electronics module or a computer that receives input from various engine and/or powetrain related sensors to determine the operating condition of the engine and/or other powertrain components at a particular moment. The module or computer responds to these signal inputs by sending signals to various engine controls to meet predetermined operating instructions for "basic engine management." A PCME is the only PCM that could include all other PCMs in one unit. Also see transmission powertrain control module

Powertrain control signals:

Signals sent from a powertrain control module to actuators, relays, or solenoids to control the operations of those devices.

Powertrain input signals:

Signals from sensors, switches, or solenoids sent to a powertrain control module describing the operational state or condition of those devices at a particular moment.

Power valve:

An enrichment unit in a carburetor that is operated by vacuum or mechanical linkage to provide more fuel at wide open throttle.

Power window:

A side window which is raised and lowered by an electric motor which is operated by a switch. The British term is "electric window"

Power window lock-out switch:

A switch that renders inoperable all electric window controls on the individual windows, except for the master controls on the driver's door

Power windows:

Side windows which are raised and lowered by an electric motor which is operated by a switch. The British term is "electric windows"

Pozidriv screwdriver:

A proprietary type of screwdriver whose tip resembles the Phillips cross-head configuration but with four additional wedges, making eight flanks altogether, which allows a more positive drive and a higher torque.

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