Wednesday, 24 April 2024, 1:26 PM
Site: IMI eLearning
Course: IMI eLearning (IMI eLearning)
Glossary: Automotive Glossary
P
P/BPower Bakes |
P/NPark and neutral position switch for sending signals to the PCM. |
P/SPower Steering Pressure Switch. Also PSP switch. |
PAPressure Air |
PaceThe relative speed of progress or change. |
PaintA material which, when applied as a liquid to a surface, forms a solid film for the purpose of decoration and/or protection. Generally, any paint contains a binder, solvent, and pigment plus other chemicals or additives giving the paint its special characteristics or properties. |
Paint RemoverA chemical, usually a mixture of acid and solvents that breaks down an old paint finish by liquefying it, thus allowing it to be completely removed from the substrate. |
Paint StrainerA disposable fine mesh filter used to clean paint as it is poured into the gun cup. |
Paint thickness gaugePrecision instruments to accurately measure the dried film thickness of painted objects by non-destructive testing. On ferrous substrates, they operate by measuring the resistance to the flow of magnetism between two probes, and on non-ferrous surfaces special gauges use the 'Eddy Current' principle |
PAIRPulsed Secondary Air Injection |
PanAlternative name for a sump. |
Panel LightsIllumination for instruments and other displays. |
Panhard RodRear axle transverse link between the chassis and axle beam. It is used to hold the axle in relation to the body during cornering or for sideways forces. |
ParaffinA petroleum based thin and colourless fuel oil, (kerosene in US English). |
ParallelThe condition that exists when the centre lines of two or more items or components or lines do not converge. The extended lines in both directions will always remain at an equal distance apart. |
Parallel circuitA circuit that splits into two or more branches. A break in one will not stop current flowing in the other(s). |
Parallel hybridThe engine and motor can both be used to drive the vehicle (most hybrid vehicles use this system). |
Parasitic drawAn unwanted, usually small, current flow from a battery. |
Parking BrakeMechanical system of braking to hold vehicle stationary. |
Parking GearThe component(s) in an automatic box that lock the drive when 'Park' is selected. |
Particle SizeThe size of the pigment particles in a dispersion (e.g. paint). |
ParticulatesExhaust pollution consisting of very small particles of matter (soot) that are produced as a by-product of combustion. Seen as smoke in a vehicle exhaust, particularly from diesel engines. |
PASPower Assisted Steering. |
Pascal (Pa)Standard unit of pressure (N/m2) named after a scientist who studied pressure in liquids. Pascal's principle of the transmission of pressure in fluids established that the pressure in a completely filled container is equally applied throughout and any change in pressure is transferred to all parts of the fluid and walls of the container. |
PassivationThe conversion of a metal surface to a less reactive state. A process used by vehicle body manufacturers to reduce the corrosion rate of a metal surface, particularly low-carbon steel. |
Passive RestraintSafety features of a vehicle that act only in an accident. Seat belts, head restraints, air bags and pre-tensioners are examples. |
PasswordPersonal Identification, used in conjunction with a Smart Card to access the MOT database via the VTS device. Can be numbers or letters, or a combination of both. |
PawlPart of the ratchet mechanism that holds the ratchet. A pivoted tooth that engages in the teeth of the ratchet wheel to either prevent the pawl lever or the wheel from rotating in one direction only or in some mechanisms to drive the wheel forward. |
PCMPowertrain Control Module. |
PCVPositive Crankcase Ventilation. A series of pipes and valves connecting the engine crankcase to the inlet manifold or air cleaner in order to reduce oil vapour emission to atmosphere. |
PDUPower drive unit |
Pearls (Pearlescents)Finishes which include mica flakes in addition to the pigment and binder. These finishes are highly decorative and often give the impression that the colour alters as the viewing angle is changed. |
PECVPower Enrichment Control Valve |
PeelingThe failure of a paint film to adhere to its substrate. Peeling results when contaminated surfaces are painted, when there is an excessive difference between paint and surface polarity or thermal expansion, or when there is solvent incompatibility. |
PentagonThe Pentagon, is a government building with five sides that serves as the headquarters of the United States Department of Defence. A pentagon, is a five sided shape. |
PercentThe proportion of one part of something to the whole. Usually out of 100 (‘per' means ‘out of' and ‘cent' means ‘hundred'). |
Percentage ChangeChanged amounts divided by the original value, then multiplied by 100. |
Perceptual SafetyA reference to how safe the driver and passengers feel. |
PerimeterThe sum of all the outside edges of a shape. |
PerishingDescription of how some components, particularly if rubber-based, can decay. |
PerpendicularAt ninety degrees to another plane or line. |
PetrolVolatile hydrocarbon fuel for spark ignition engines. Also gasoline. |
Petroleum JellyA type of grease used for battery terminals. Vaseline is a refined version. |
PferdestärkeThe German word for horsepower. Pferdestärke. 1PS equals 0.986bhp. |
PFIPort Fuel Injection. |
PGPulse Generator. |
PH valueA measure of the acidity of a substance in an aqueous solution. Pure water has a pH value of 7 and is classified as neutral. Below 7 is acid and above 7 is known as basic. The scale is from 0 (strong acid) to 14 (strong base). |
PhaseThe time span between the start and end of a single wave moving from zero to positive and negative positions and returning to zero. |
Phase SensorSensor that indicates camshaft position and hence where the engine is in its cycle. |
Phasing (diesel injection)There are a number of phases of injection: fill phase, spill phase, injection phase and the pressure reduction phase. |
Phosfor BronzeSee Phosphor Bronze. |
PhosphatingA process used by vehicle body manufacturers which results in the formation of a layer of zinc, iron, or manganese phosphate crystals on the surface of the part to be painted. In modern vehicle construction plants, phosphating is achieved by complete body immersion. |
Phosphor bronzeA material that can absorb oil making it ideal for making bushes/bearings. |
Phosphoric AcidAn acid commonly used as a catalyst to speed up the cure of Etch primers and some baking finishes, usually alkyd/nitrogen resin combinations. Also a cleaner used for removing surface corrosion from ferrous metals. |
PhotoelectricThe generation of an electrical current by light shining on certain materials such as some semiconductor devices. Photoelectric cell, photodiode or phototransistor. |
PhototransistorA transistor that is operated by light. |
PhraseA group of words in sequence. |
Physical layerHardware, actual components and wires as opposed to software. |
Pi3.141592 (3.142). |
Pick Up PipeOil pipe that picks up oil from the oil pan. |
PicklingThe use of a chemical solution (usually acidic) to prepare a surface for painting or bonding by dissolving away surface oxides and other impurities. |
PIDParameter ID |
Piezo-resistiveA special crystal that changes resistance as pressure is applied. |
PiezoelectricVoltage produced by shock waves on a piezo crystal. Used in engine knock sensors. |
PigmentSmall particles added to paint to influence properties such as colour, corrosion resistance, mechanical strength, etc. Pigments may be coloured, semi-transparent, black, white, or colourless. They must be incorporated into a paint system by very efficient dispersion processes. |
Pilot BearingSmall bearing usually where two shafts meet. See also Spigot. |
PingingNoise heard from an engine when the ignition of fuel occurs too early (advanced) in the cycle. Also 'ping'. |
PinholingA defect consisting of tiny holes in the dried paint surface. Defects such as pin holing, popping, bubbling, and cratering are usually caused by solvent vapours forming from the substrate or the paint and rising to the surface. |
PinionA small gear wheel or the driver of a meshing pair of gear wheels. |
Pinion GearA small gear wheel or the driver of a meshing pair of gear wheels. |
Pinion ShaftA shaft on which a small gear runs. |
PinkingNoise heard from an engine when the ignition of fuel occurs too early (advanced) in the cycle. Also 'ping'. |
PintauxType of injector for an indirect injection engine. Similar to pintle but with additional small injection orifice for low engine speeds. |
PintleType of injector for an indirect injection engine. Uses a spring-loaded needle that is raised by fuel pressure to allow a spray of fuel to enter the pre-combustion chamber. |
PIPProfile Ignition Pick Up Signal. |
Pipe UnionA joint in a pipe. |
PistonReciprocating component, usually in the form of a cylinder closed at one end, that operates under fluid pressure within a smooth walled cylinder. In a reciprocating engine, gas pressure on the piston crown provides the prime force that is converted into rotating mechanical power by the crankshaft. |
Piston BlowTerm used to describe gases blowing past the piston rings. |
Piston CrownThe top of the piston. |
Piston RingSealing rings usually made of cast iron. Fitted on to a piston to make a gas tight seal. |
Pitch(1) Distance that two points are apart. Examples are thread dimensions and pitch circle diameters of concentric drillings. (2) Vehicle body movement from back to front or from front to back. |
Pitman ArmThe output arm on a steering gearbox. Also known as a drop arm. |
PittingThe appearance of holes or pits in a paint film while it is wet. May also refer to the damage caused by more serious rusting on steel panelwork |
Pivot BoltA simple bolt on which something pivots (turns). |
Pivot PointThe point about which something pivots! |
Planet CarrierFrame with spindles that the planet gears rotate on as part of an epicyclic gear set. |
Planetary GearsGears that rotate around sun gears (differential, epicyclic gearing, etc.) |
PlanningThe act of forming and following a program to achieve a specific goal. |
PlanometerA flat metal plate for gauging the accuracy of a plane surface in precision metalworking, which is also known as a surface plate |
Plastic FillerA compound of resin and heavy pigments used to fill dents on car bodies. |
PlasticizerA low molecular weight substance added to polymeric materials such as paints to improve their flexibility. |
PlastigaugeBrand name of a product that is used to determine bearing clearance. |
Plate GridsBasket like holders to contain the active material in a battery. |
Plate LugA connection point on the battery plate. |
PlenumA chamber in the air inlet system to provide even air supply to all cylinders. |
PliesRayon cords used in tyre construction. |
Plug ThreadScrewed thread that is designed for a spark plug. |
Plunge JointA shaft joint or coupling with provision for axial or plunging movement. |
PlungerAlternative term for a piston or needle in a pump, slave cylinder or injector. |
Ply (Tire)Fabric layer used in the construction of a tire. |
Ply (Tyre)Fabric layer used in the construction of a tyre. |
Ply RatingLoad rating of a tyre. |
PneumaticTransfer of force by air or gas. |
Pneumatic SuspensionSuspension system using air or gas springs. |
PNPPark/Neutral Switch |
PodgerA tool in the form of a short bar, usually tapered and often incorporating a spanner/wrench at one end. |
PointsThe switching contacts of an ignition contact breaker. |
Polarised LightLight that has been filtered so that its rays oscillate only in one direction. |
PolarityA description of a component that must have positive and negative connections connected correctly. |
Polarity (Electrical)Electrical positive and negative charges. |
Polarity (Magnetic)Magnetic north and south poles. |
Polarized LightLight that has been filtered so that its rays oscillate only in one direction. |
PoleThe ends of a magnet where the field lines are emitted. |
PolishA specially formulated blend of components designed to remove minor paint surface imperfections, such as fine scratches, light oxidation, water spots, and swirl marks left by the use of rubbing compounds. |
PolishingThe use of polishes, either by hand or machine, to level and provide more gloss to a finish. |
Polishing CompoundA mild abrasive material applied to a vehicle's painted surface which removes minor imperfections with minimal cutting action. Buffing restores film to a high gloss appearance. |
Polishing WaxA combination of wax and polish that contains mild abrasives. The abrasives remove minor paint imperfections. The wax and other ingredients produce a durable, high-gloss finish. |
PollutionProducts or by-products that destroy purity or make environments foul or filthy. |
PolyesterA 2K resin used as the binder for plastic fillers, fibre glass laminations and high-build primers |
Polyester StopperA finer grade 2K plastic filler material used to fill minor imperfections such as pinholes in filler prior to priming. |
PolymersA naturally occurring or synthetic compound consisting of large molecules. Used for many purposes, one of which is as a polish. |
PolypropyleneManmade plastic material used for electrical insulation, bumpers and other trim components. |
PolyurethaneA 1K or 2K plastic-based paint finish that is characterised by durability and high gloss. Also, used for manufacturing some plastic and flexible parts. |
Poppet ValveConventional inlet and exhaust valves having a circular plate at right angles to a central stem that runs through a guide tube. |
PoppingA paint defect characterized by raised domes in the surface caused by solvent vapour forming within the paint after it has begun to "skin over." Often caused by baking at too high a temperature or before adequate flash-off time has been allowed. |
Population of UKNumber of people that live in the UK. |
PorosityProperty of a material that allows fluid to soak into or through it. |
PortHole or aperture shaped to facilitate the flow of gas or liquid into or from a chamber. Usually denoted by its function, as inlet port or exhaust port. |
Port Fuel InjectionPetrol electronic fuel injection system with injectors in each inlet manifold spraying fuel in towards the inlet valves in the ports of each cylinder. Also known as multipoint injection. |
PortfolioThis is usually a folder that contains the evidence chosen to illustrate competence to satisfy individual key skills requirements. |
Position SwitchA switch used to feedback position of a moving component. |
Positive CamberSteering geometry where the road wheel leans outward at the top. |
Positive CastorAngle in side elevation between the steering and vertical axis. Steering axis hits the ground in front of the vertical axis. |
Positive CommunicationA comment or statement expressing approval. |
Positive Crankcase VentilationA series of pipes and valves connecting the engine crankcase to the inlet manifold or air cleaner in order to reduce oil vapour emission to atmosphere. |
Positive DisplacementA term applied to pumps which transfer liquid in the same quantity as the volume in the pumping chamber for each action of the pump. |
Positive Offset (Wheel)The position of the wheel nave or disc when outside the centre line of the wheel. |
Positive ScrubPositive scrub radius steering geometry where a line through the steering swivel axis meets the road surface inside of the tyre centre line. |
Positive Temperature CoefficientType of resistor that has resistance increasing with increases in temperature. The normal response for metal conductors. These resistors are used in electrical circuits to give temperature sensing and control. |
PotentialEnergy stored in a stationary object or chemical combination that has the capacity to do work. |
Potential DifferenceDifference of electric potential between points (pd) volts. |
PotentiometerA variable resistor with manual operation that provides an output voltage from a sliding terminal on a resistor block. |
Pounds FeetOld unit of torque. Also foot pounds. Torque is now given in the SI units of Newton metres Nm. |
Pour PointApplied to fuel oils (diesel) to indicate the temperature where it will still flow under its own weight. The pour point specified value is 3 degrees above the point where it will only just flow. |
Powder CoatingsAny protective coating which is applied to the surface as a dry, finely ground powder and then carefully heated above its melting point so that the powder particles flow together to form a continuous film. |
PowerThe rate of doing work. It is measured by the standard unit called the watt (W) and is equal to one joule per second. This is a very small unit and kilowatt (kW) or megawatt (MW) is more often used. Also, Horsepower which is the old term for power. |
Power Assisted SteeringThe use of a hydraulic or electrical system to increase the driver's effort on the steering wheel thus reducing the effort that the driver has to apply. |
Power BoosterHydraulic or pneumatic brake pedal or hydraulic pressure booster. |
Power DistributionA central point from which various components are supplied. |
Power OutputPower developed by an engine. |
Power split hybridA combination of a series and parallel hybrid that uses a mechanical splitting device. |
Power StrokePart of the four-stroke cycle following combustion. |
PowertrainTerm used to describe the engine, transmission and driveline components as a unit. |
PPEPersonal protective equipment |
PPMParts Per Million |
Pre-ignitionSpontaneous ignition in a petrol engine that occurs before the controlled ignition point. Can be caused by an overheated engine, incandescent particles in the combustion chamber or incorrect fuel. |
PreignitionSpontaneous ignition in a petrol engine that occurs before the controlled ignition point. Can be caused by an overheated engine, incandescent particles in the combustion chamber or incorrect fuel. |
PreloadAdditional tightening of a bearing or component after the backlash or free play has been eliminated. Used to eliminate backlash after the bearings have bedded in. Usually set by a Nm or angular torque. |
PresentationThe way in which something is displayed. |
PressurePressure is the product of a force multiplied by the area on which the force is applied. The standard unit of pressure is the Pascal which is equivalent to one N/m2. |
Pressure BleederA brake/clutch bleeder that forces fluid through the system. |
Pressure CapCap used to pressurise cooling system. |
Pressure ChamberAn area used to hold a pressure as something expands of to supply pressure. |
Pressure ChargedAn engine using a pressure-charger to boost the air charging pressure above atmospheric pressure, to increase the air mass entering the cylinders of the engine. |
Pressure ConsciousVariable opening valve used for sensing and adjusting the pressure in brake circuits to restrict force to the rear brakes. |
Pressure DifferentialThe difference in pressures between two sides of a component or areas in a system that are used to operate the component or system. Atmospheric pressure is often used in conjunction with a vacuum to provide a force. |
Pressure GaugeAn instrument for measuring pressure of a fluid or a gas. |
Pressure ModulatorA device for controlling pressure in a system. |
Pressure PlateComponent of the clutch. |
Pressure RegulatorA valve in a hydraulic system that controls line pressure. |
Pressure Relief ValveThe valve in an oil or hydraulic circuit that opens to release excess fluid pressure and return fluid to the feed side of the pump. |
Pressure SwitchA pressure sensitive switch used to provide a signal voltage to an instrument, lamp or electronic control module. |
Pressure Wave SuperchargerA supercharger using the exhaust pressure waves to boost the inlet air pressure. This supercharger uses a drum with longitudinal drillings that is rotated in time with the engine and ported to match inlet and exhaust pressure waves together. |
Pressure-feed GunA spray gun equipped with a separate paint container that is pressurized and connected to the spray gun by means of a solvent-resistant fluid hose, in addition to the normal air hose. |
Primary ShoeA brake shoe that has a leading edge making first contact when applied. Also leading shoe. |
Primary WindingThe low tension (primary circuit) coil of wire in an ignition coil. |
PrimerThe first coat of paint applied to a substrate. Depending on the formulation of a particular primer, its function can be to provide any combination of">adhesion, build, scratch-filling, ground coating and corrosion resistance. |
Primer-sealerAn undercoat which improves adhesion of the topcoat, by sealing off old painted surfaces that have been sanded; usually does not require sanding when dry. |
PrimingLifting fuel into the system components to remove air. |
Priming PumpA manually operated pump that lifts fuel into the system. |
PrinterAn output device that allows data from the computer to be displayed on paper. |
ProcessorThe central processing unit oversees all of the other components of the system. Can be thought of as the brain of the computer. |
ProgressionInitial acceleration of the throttle after the idle position. Going onward/upward. |
Progressive CarburettorUsually a carburettor with two chokes, the second of which only opens as the throttle is pushed further down. |
PROMProgrammable Read Only Memory. |
Propeller ShaftConnects gearbox to final drive and transmits torque on rear wheel and four wheel drive vehicles. |
Propellor ShaftSee Propeller Shaft. |
ProportionThe relation of one thing to another. |
Proportioner ValveA valve used in hydraulic brake circuits to split the force between the front and rear brake circuits. |
PropshaftConnects gearbox to final drive and transmits torque on rear wheel and four wheel drive vehicles. |
Propshaft JointsUniversal joints used to allow a propshaft to work through an angle. |
PropulsionApplication of a driving force. |
ProtonOne of a number of particles in the nucleus of an atom. The proton has a positive polarity and is electrically positive in opposition to the negative charge of the electrons. |
PrototypeA working version of a new design. |
ProvenanceThe origins of information. |
PSThe German word for horsepower. Pferdestärke. 1PS equals 0.986bhp. |
PsiPound per square inch. A measure of pressure in old units. The SI unit of pressure is the Pascal (Pa). |
PSPPower Steering Pressure |
PSPSPower Steering Pressure Switch. |
PTPart Throttle. |
PTCPending Trouble Code |
PTO - Power Take OffA supplementary drive from a vehicle transmission that is used to drive to auxiliary units. |
Pull-in WindingA winding in a starter motor solenoid that actuates the solenoid to pull the switch contacts together. It is often earthed through the armature so that the drive pinion rotates as it moves into mesh with starter ring gear. |
Pull-off SpringA simple return spring to open or close something after it is switched off. |
PullerA tool for applying a pulling force. For example, to remove a gear from a shaft. |
PulleysUsed to transmit or receive drive from a belt. The alternator pulley is a good example. |
PulsationOn/off or increase/decrease in pressure or position. |
Pulsation DamperAny device, such as a hydraulic accumulator, for damping pulsations in a fluid system, as for example the pressure pulses from a fuel pump. |
PulseA change in electrical or mechanical signal. |
Pulse Air InjectionAn emission control system that uses exhaust pressure pulsations to draw air into the exhaust gas flow to increase the available oxygen in the catalytic converter. |
Pulse GeneratorInductive electronic device that provides information to the ignition amplifier or ECU on engine position. |
Pulse ShapingThe action carried out in an ECU to a signal from a sensor. For example, a sine wave may be changed to a square wave. |
Pulse WheelToothed sensor wheel used to induce or affect electrical currents in magnetic inductive pulse generators, such as engine speed and position sensors. |
Pulse WidthThe operating phase of an actuator when it is energised by an electronic control unit. |
PumpDevice that is electrically or mechanically driven to pressurize a fluid or gas. |
PunctuationThe use of marks and signs to form words, sentences, paragraphs etc. |
Purge ValveThe valve in a fuel vapour evaporative system operated from the ECM under specific conditions to draw air back through the evaporative canister. An emission control device to prevent hydrocarbon fuel vapours from the fuel tank escaping into the atmosphere. |
Push FitThe relationship between the dimensions of two components where one fits inside the other. In this instance the fit is one where the inner dimension of the outer component is the same as the outer dimension of the inner component. Also known as a transition fit. |
Push RodA rod that transfers movement from a cam follower to a rocker arm. |
PWRPower to Weight Ratio |
PyrotechnicExplosive devices! |
Pyrotechnic InflaterAn explosive device used to produce a large quantity of gas to inflate an air bag. |