Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Pi"

Pick:: See prospector's pick

Pick and finishing hammer:: A widely used type of body hammer with a pointed end on one side and a shallow domed end for finishing on the other side

Picker:: See electro picker

Picker set:: See lock picker set

Pick hammer:: A hammer with a round head for conventional planishing and a small pick-shaped head for working away in sharp or tight corners. It should not be confused with a bullet-point pick hammer, which has a more blunt pick, nor with a pein hammer

Picking:: See panel picking

Pickle park:: Trucker slang for Rest area as in "I don't often park overnight in the pickle parks."

Pickle park pinger:: Trucker slang for A CB with a roger-beep as in "I don't care much for them pickle park pingers."

Pickling:: The removal of oxide or mill scale from the surface of a metal by immersion, usually in an acidic or alkaline solution

Pickling attack:: The initial chemical reaction between phosphating solutions and metal surfaces in phosphate treatment

Pickum-up:: Trucker slang for Pick-up truck, light truck as in "Watch out for that pickum-up truck broke down in the right lane."

Pickup:

A utility truck with a closed cab and an open box. In Australia it is called a "utility" or "ute."
The transfer of material, as between bearing and shaft, caused by friction and heat due to lack of oil; can lead to seizure.
A pick-up coil
A yoke -- a triangular metal piece used to connect the main brake cable with the stirrup cable in a bicycle's centerpull brake system

Pick-up:

A utility truck with a closed cab and an open box. In Australia it is called a "utility" or "ute."
The transfer of material, as between bearing and shaft, caused by friction and heat due to lack of oil; can lead to seizure.
A pick-up coil or yoke.

Also See:
inductive pulse pick-up
magnetic pick-up
magnetic pick-up assembly
magnetic pick-up tool
oscillating pick-up ignition system
transistorized ignition with inductive pick-up
transistorized ignition with magnetic pick-up

Pick-up assembly:: See magnetic pick-up assembly

Pickup camper:: See:
truck camper

Pickup coil:: See pick-up coil.

Pick-up coil:: The coil in which voltage is induced in an electronic ignition.

Pick-up ignition:: See oscillating pick-up ignition system

Pick-up ignition system:: See oscillating pick-up ignition system

Pick-up module:: A trigger-activated device which sends a signal to the ignition unit of an electronic ignition system

Pick-up pipe:: See oil pick-up pipe

Pick-up screen:: See oil pump strainer

Pick-up tool:: A tool with a flexible or rigid shaft and a claw type pick-up end; used to retrieve small objects from hard-to-reach areas. Compare magnetic pick-up tool

Picture:: See scavenging picture

Picture machine:: Trucker slang for Radar as in "Watch out for the picture machine at the corner of 9th and Wilcox."

Picture taker:: Trucker slang for Police with radar as in "There's a picture taker at the 27 mile marker."

Piece:: See:
blanking piece
distance piece
extension piece
pole piece
sill end piece

Pien hammer:: See ball pien hammer

Pierce-Arrow:: A vehicle brand of which the 1925-1948 models are classic cars.

Piezoelectric:

Property of quartz crystal that causes it to vibrate when a high frequency (500 kHz or higher) voltage is applied. Concept is used to atomize water in a humidifier.
Having the ability to generate a voltage when mechanical stress is applied, as in a piezoelectric crystal.

Piezoelectric ignition:: A system of ignition that employs the use of a small section of ceramic-like material. When this material is compressed, even a very tiny amount it emits a high voltage that will fire the plugs this system does not need a coil, points or condenser.

Piggyback:: A semitrailer built with reinforcements to withstand transport by a railroad flatcar. See TOFC

Pig iron:: Produced in blast furnaces, pig iron is the raw material for practically all iron and steel products; contains about 3-5 % carbon

Pigment:: Finely ground powders in the paint that give it its color.

Pigtail:

A cable used to transmit electrical power from the tractor to the trailer. So named because it is coiled like a pig's tail.
See wiring pigtail

Pile:: This is a steel or concrete bar which is driven into the ground to form part of the foundations for a building. Also see scrap pile

Piling:: The build-up of metal on a contact breaker point. The opposite is pitting

Pill:: A jet in the fuel-return line which establishes the mixture

Pillar:: A shaft or upright member or support holding up the roof. Also called a post. The A-post holds up the windshield. The B-post is behind the front door about in the middle of the side of the roof. The C-post holds up the rear window. In station wagons, another post is placed between the B-post and the last post so that it becomes the C-post and the last post is the D-post.
Also See:
A-pillar
B-pillar
C-pillar
cabin pillar
center pillar
D-pillar
dogleg pillar
dogleg pillar
door pillar switch
door pillar
front pillar
hinge pillar reinforcement
hinge pillar
latching pillar
latch pillar
lock pillar
rear cabin pillar

Pillared hardtop:: See four-door pillared hardtop

Pillar jack:: See tower jack

Pillar light:: A courtesy light mounted on the central pillar within the passenger compartment

Pillar reinforcement:: See hinge pillar reinforcement

Pillars:: See:
roof pillars
windshield pillars

Pillar switch:: See door pillar switch

Pillion pad:: A backrest pad which is mounted behind the seat on a motorcycle.

Pilot bearing:: A small bearing in the center of the flywheel end of the crankshaft, which carries the forward end of the clutch shaft. The British term is "spigot bearing." See clutch pilot bearing.

Pilot circuit:: Secondary circuit used to control a main circuit or a device in the main circuit.

Pilot hole:: When using a large drill bit, it is sometimes hard for the drill to cut through the metal and do it evenly in a straight line. A pilot hole is first made with a small bit. Then, when you use the large bit, the drilling is much easier.

Pilot house:: The enclosed space on the navigating bridge from which a ship is controlled when under way. See bridge

Pilot jet:: A jet in the idling circuit of a fixed jet carburetor which measures and admits fuel

Pilot operated absolute:: See POA suction throttling valve

Pilot operated absolute valve: (POA): A suction throttling device used on some GM and Ford air conditioner system.

Pilot shaft:: A dummy shaft that is placed in a mechanism as a means of aligning the parts. It is then removed and the regular shaft installed.

Pilot valve:: A small valve used to control action of a larger valve

Pin:: A small cylinder used for fastening something or as a pivot.
Also See:
bonnet pin
carbon pin
cotter pin
dowel pin
floating piston pin
fulcrum pin
gudgeon pin boss
gudgeon pin circlip
gudgeon pin end
gudgeon pin
hair pin
hitch pin
hood pin kit
hood pins
kingpin
knuckle pin
locating pin
lock pin
pad retainer pin
pawl
piston pin
piston pin boss
piston pin circlip
piston pin end
pivot pin
roll pin
shear pin
spiral wrapped pin
split pin
swivel pin
tri pin
worm and taper pin
wrist pin

Pin boss:: See:
gudgeon pin boss
piston pin boss

Pinch-off pliers:: See hose pinch-off pliers

Pin circlip:: See:
gudgeon pin circlip
piston pin circlip
wrist pin circlip

Pin end:: See:
gudgeon pin end
piston pin end
wrist pin end

Ping:: See pinging.

Pinging:: A metallic rattling sound produced by the engine during heavy acceleration when the ignition timing is too far advanced for the grade of fuel being burned. The noise is caused by vibrations in the cylinder walls, head, and piston. When an engine pings, the normal, controlled even spread of the flame front is disrupted by the spontaneous combustion of pockets of fuel. Their collision sets off the pressure waves that result in the pinging sound. Pinging can be caused by bad timing, inadequate octane rating, incorrect fuel-air mixture, a hot spot in the combustion chamber caused by a glowing piece of carbon, or an overheat condition. Also called "knocking." Also see detonation.

Pinhole:: See rust pinhole

Pinholing:: Tiny bubbles in the paint finish that are often grouped together. It is caused by trapped solvents, moisture or air released from the film. Compare solvent pop

Pinion:: A small, tapered gear which meshes with a larger gear or rack. It is found in two primary places in an automobile: the differential pinion and the rack and pinion steering.
Also See:
crown wheel and pinion
drive pinion
inertia pinion
planet pinion
rack and pinion gearbox
rack and pinion
ring and pinion

Pinion carrier:: That part of the rear axle assembly that supports and contains the pinion gear shaft.

Pinion gear:: The smaller of two meshing gears. A pinion gear is used in a starter motor to engage the flywheel ring gear and also rides along the surface of the steering rack (a rod with grooves cut in it to mesh with the gear) See rack and pinion gearbox.

Pinion gearbox:: See rack and pinion gearbox

Pinion shaft:: A short drive shaft in the rear axle connecting the prop shaft to the crown wheel via the final drive pinion

Pinion steering:: See rack and pinion steering

Pinking:: A British term for pinging

Pin kit:: See:
bonnet pin kit
hood pin kit

Pin lock:: A pin with a hole at one end through which a hair pin cotter is thrust to secure it in place.

Pinned piston ring:: A steel pin, set into the piston, is placed in the space between the ends of the ring. The ring is thus kept from moving around in the groove.

Pinned ring:: A steel pin, set into the piston, is placed in the space between the ends of the ring. The ring is thus kept from moving around in the groove.

Pinning:: Procedure for repairing cracks in the combustion chamber using threaded pins

Pin punch:: A tool with a parallel shaft for use with a hammer to drive out pins, shafts, rivets, etc. Compare drift punch)

Pin slider caliper disc brake:: A disc brake design with a sliding caliper. The major components are: caliper (a casting with one cylinder and piston), caliper frame (casting), guide pins, Teflon or rubber sleeves/bushings. The caliper floats on the sleeves over the guide pins. The guide pins are threaded or riveted to the caliper frame. The caliper frame is bolted to the suspension

Pin spanner:: A wrench with pins on forked ends, used to turn an adjustable cup on a bottom bracket of a bicycle.

Pinstripe:: A thin, precisely contoured lines along certain body features; they may extend along the whole car and finish off in elaborate, bouquet-like designs. Striping usually refers to simple decorative lines, e.g., on motorcycle tanks, while pinstriping mostly refers to custom work, i.e., more elaborate and sharply curved lines

Pinstriping:: A thin, precisely contoured lines along certain body features; they may extend along the whole car and finish off in elaborate, bouquet-like designs. Striping usually refers to simple decorative lines, e.g., on motorcycle tanks, while pinstriping mostly refers to custom work, i.e., more elaborate and sharply curved lines

Pinstriping tool:: A painting tool used to apply thin, precise lines on the body, e.g., on motorcycle tanks and to enhance car body contours.

Pintaux nozzle:: A pintle-type diesel fuel injector nozzle with a hole in the side through which a very small amount of fuel is sprayed when the needle valve is partly opened at low pressure, before the main hole comes into use

Pintle:

The needle of the injection valve in a diesel fuel injector.
A vertical bolt or pin in a towing bracket, to which the towbar is attached.
The top of some types of valves
The pins or bolts that hinge the rudder to the gudgeons on the rudder post or sternpost

Pintle Hook: A coupling device used in a double trailer, triple trailer, and truck-trailer combinations. It has a curved, fixed towing horn and an upper latch that opens to accept the drawbar eye of a trailer or dolly.

Pintle nozzle:: An injector nozzle containing the pintle

Pin wrench:: A wrench with a pin that can be fitted into a hole in a nut to exert extra pressure

PIP:: Acronym for profile ignition pickup

Pipe:: A tube used to transfer liquid or gas.
Also See:
air pipe
balance pipe
brake pipe
breather pipe
chain pipe
discharge pipe
downpipe
exhaust pipe
feed pipe
flexible brake pipe
front pipe
hawse pipe
heater air pipe
impact pipe
induction pipe
inlet pipe
intake pipe
kickup pipe
oil breather pipe
oil pick-up pipe
outlet pipe
overaxle pipe
overflow pipe
pick-up pipe
side pipe
sounding pipe
suction pipe
tail pipe
twin front pipe
Y-pipe

Pipes:: See:
exhaust system
lake pipes
lakes pipes

Pipework:: A system of pipes

Pipe wrench:: An adjustable wrench with serrated jaws. The most common type of pipe wrench is the so-called "Stilison wrench." Also called a "monkey wrench." Also see chain pipe wrench

Piping:

A system of pipes.
A rubber or plastic strip inserted between two removable panels, i.e., between a bolt-on fender and the body, to cover up the joint and to prevent water getting in; with the piping inserted, only the round bead along the upper edge of the piping is visible

Pip mark:: A little dot or indentation which indicates the top side of compression ring

Piquet, Nelson:: A three-time, World Driving Champion from Brazil and is considered one of the all-time great Formula One drivers

Piston:: A round or cylindrical plug, which closed at one end and open at the other. It slides up and down in the cylinder. It is attached to the connecting rod and when the fuel charge is fired, will transfer the force of the explosion to the connecting rod then to the crankshaft.
Also See:
accumulator piston
alloy piston
autothermic piston
belted piston
brake piston
cam-ground piston
charging piston
collapsed piston
damper piston
deflector piston
flat-topped piston
flat-top piston
floating piston pin
floating piston
full-skirt piston
light-alloy piston
molybdenum piston ring
operating piston
oval piston
oversize piston
pent crown piston
pinned piston ring
primary piston
secondary piston
slipper piston
slotted piston
split skirt piston
stepped piston

Piston bore:: The diameter of the hole in the cylinder block in which the piston moves back and forth between top dead center (TDC) and bottom dead center (BDC)

Piston boss:: The built-up area around the piston pin hole. Also see boss.

Piston charging pump:

The function of the piston of the two-stroke engine to pre-compress the fresh charge induced into the crankcase.
A separate piston used in earlier two-stroke engine designs to provide a supercharging effect

Piston collapse:: A reduction in the diameter of the piston skirt caused by heat and constant impact stresses. Also see collapsed piston.

Piston compressor:: A compressor in an air-conditioning system with one or more pistons arranged in either an in-line, axial, radial, or V-configuration

Piston crown:: The very top of the piston. The piston crown transmits the pressure created during the ignition of the air/fuel mixture to the piston pin, then to the connecting rod, and from there to the crankshaft. The diameter of the piston crown is slightly smaller than the piston skirt. Also called piston dome.

Piston-crown combustion chamber:: The volume in the cylinder above the piston on the compression stroke that is used in diesel truck engines and in some European gasoline automobile engines. The advantage in simply machining a flat surface on the cylinder head is offset by the added cost of machining the bowl in each piston and by increased piston weight.
Also See:
hemispherical combustion chamber
bathtub combustion chamber
wedge combustion chamber
squish combustion chamber

Piston damper:: A small damper piston in an SU or Stromberg carburetor which reduces the movement of the large air piston in the venturi

Piston diaphragm:: A flexible membrane which displaces under pressure, imparting movement to the piston in a Stromberg carburetor

Piston displacement:

Amount (volume) of air displaced by a piston when moved through the full length of its stroke.
Volume obtained by multiplying area of cylinder bore by length of piston stroke.
Also see displacement.

Piston dome:: The top surface of a piston. It is often shaped for better combustion and to prevent a valve from contacting the surface. Also called piston crown. See piston head.

Piston engine:: A form of internal combustion engine. It is a heat engine in which the expansion of gas causes (by the explosion or a fuel and air mixture or the introduction of steam) a piston inside a cylinder to move and turn a crank shaft.

Piston expansion:: Because pistons are usually made of aluminum and the cylinder walls are made of iron, the piston will expand more rapidly than the cylinder when they get hot. Some type of compensation needs to be made for this expansion or the piston will seize in the cylinder.
Also See:
split skirt
T-slot
steel strut
cam-ground piston

Piston extension screw:: A stroke limiting screw between the primary piston and secondary piston stop

Piston head:: That portion of the piston above the top ring.
Also See:
piston dome
piston crown

Piston land:: That portion of the piston which is between the ring grooves.

Piston lands:: That portion of the piston which is between the ring grooves.

Piston lifter:: A pin in the base of the piston chamber in an SU or Stromberg carburetor, used to check the strength of the mixture and the free movement of the piston

Piston material:: The materials from which pistons are made are grey cast or light alloys; most light alloys consist of an aluminium-silicon alloy

Piston pin:: A steel pin that is passed through the piston, it is used as a base upon which to fasten the upper end of the connecting rod. It is round and may be hollow. Also called "wrist pin" or "gudgeon pin." See floating piston pin.

Piston pin boss:: See piston boss.

Piston pin circlip:: A circlip which is used on either end of the piston pin to hold the pin in place. Also called "snap ring."

Piston pin end:: The small end of the connecting rod through which the piston pin is inserted

Piston ring:: A metal, split ring installed in the groove on the outside wall of the piston. The ring contacts the sides of the ring groove and also rubs against the cylinder wall thus sealing the space between the piston and the wall. Poor rings can cause poor compression and severe blowby. Often seen as blue smoke out the exhaust pipe.
Also See:
compression ring
dykes ring
molybdenum piston ring
oil control ring
pinned piston ring

Piston ring, chrome:: A piston ring which has a thin layer of chrome plate on the outer edge.

Piston ring clamp:: A special automotive tool used for installing pistons. The clamp is slipped over the piston and when tightened, compresses the piston rings into the piston grooves. With the piston rings compressed, the piston can be installed into the cylinder by light tapping

Piston ring, compression:: See compression ring.

Piston ring end gap:: The distance left between the ends of the ring when installed in the cylinder.

Piston ring expander:: A spring device placed under a piston ring to hold it snugly against the cylinder wall. Also see expander.

Piston ring flutter:: The oscillations of a piston ring which mainly occur at high engine speed and thus can cause breakage

Piston ring gap:: See piston ring end gap.

Piston ring groove:: One of the channels into which the piston rings reside.

Piston ring groove cleaner:: A special automotive tool to remove carbon and varnishes from piston grooves before installing piston rings

Piston ring job:: Reconditioning the cylinder and installing new rings.

Piston ring, oil control:: See oil control ring.

Piston ring, pinned:: A steel pin, set into the piston, is placed in the space between the ends of the ring. The ring is thus kept from moving around in the groove.

Piston ring pliers:: A pliers-like special automotive tool used to spread and slip piston rings over a piston for removal and installation

Piston ring ridge:: That portion of the cylinder above the top limit of ring travel. In a worn cylinder, this area is of a smaller diameter than the remainder of the cylinder and will leave a ledge or ridge that must be removed.

Piston ring side clearance:: The space between the sides of the ring and the ring lands.

Piston ring stop:: A pin pressed into the ring grooves of a two-stroke engine in order to prevent the rings from rotating, which would allow the open ends to become jammed in the ports

Piston rocking:: See piston slap

Piston rod:: A shock absorber rod which operates the piston in a telescopic damper

Piston seal:: A fluid seal on a disc brake caliper piston

Piston seizure:: A sudden stalling of the engine, caused by the piston becoming stuck in the bore; this is often caused by overheating or lack of lubrication and often leaves severe score marks in the cylinders and on the skirt of the piston.

Piston skirt:: The portion of the piston below the rings and bosses. It absorbs the thrust caused by the crankshaft as it makes contact with the cylinder wall. (Some engines have an oil ring in the skirt area, though not common.)

Piston skirt expander:: A spring device placed inside the piston skirt to produce an outward pressure which increases the diameter of the skirt.

Piston skirt expanding:: Enlarging the diameter of the piston skirt by inserting an expander, by knurling the outer skirt surface, or by peening the inside of the piston.

Piston slap:: The condition caused by too much clearance between the piston and the cylinder walls. The piston rattles or slaps against the wall of the cylinder. It makes a hollow, muffled, bell-like sound.

Piston speed:: The speed of the piston for a given engine rpm

Piston spring:: A coil spring in an SU carburetor which counteracts the upward movement of the piston

Piston stops:: Tabs, or protrusions, on a backing plate positioned to prevent the wheel cylinder pistons from leaving the wheel cylinder.

Piston thrust:: The pushing action of the piston which occurs at the sides of the piston 90° away from the piston pin as it pushes against the cylinder wall.

Piston top:: See piston crown

Piston-type compressor:: A compressor in an air-conditioning system with one or more pistons arranged in either an in-line, axial, radial, or V-configuration

Piston-valve engine:: A two-stroke engine that relies on the ports in the cylinder walls to control admission and exhaust of the air/fuel mixture; it is not equipped with other control elements such as rotary valves

Pit:

Area at a race track for fuelling, tire changing, making mechanical repairs, etc.
Small craters in the surface of metal.

Also See:
cockpit
inspection pit

Pitch:

The back and forth rocking motion of a vehicle which compresses the front springs and extends the rear springs so that the nose of the vehicle is down while the tail is up. Then the action reverses so that the nose is up and the tail is down (i.e., dive and squat).
The distance between two threads on a bolt or screw.
The distance between a point on one gear tooth and the same point on the next gear tooth.
The quality of sound with respect to the frequency of vibration of the sound waves.
The angle at which something is tilted. See variable pitch stator.
In Britain, a parking space or site for a trailer, camper, etc.

Also See:
coarse pitch
height hamper pitch control
thread pitch

Pitch circle:: (PC) the circumference on which the centers of the wheel bolt holes are located

Pitch circle diameter:: (PCD) The diameter of the stud holes/bolt holes for fixing the wheel to the hub. The pitch circle (PC) is usually shown as a double number, e.g., 5-5.5. The first number indicates the number of holes, and the second, the diameter of the PC

Pitch control:: See height hamper pitch control

Pitch diameter:: On a straight thread the diameter of the coaxial cylinder the surface of which would pass through the thread profiles at such points as to make the width of the groove equal to one-half of the basic pitch. Approximately half way between the major and minor diameters.

Pitch gauge:: See:
screw pitch gauge
thread pitch gauge

Pitch stator:: See variable pitch stator

Pitman arm:: A short lever arm splined to the steering gear cross shaft, the pitman arm transmits the steering force from the cross shaft to the steering linkage system. In this way rotary motion of the steering wheel is turned to lateral movement of the arm. The British term is "drop arm." Also see idler arm.

Pitman shaft:: See rocker shaft

Pitot tube:: A tube for measuring the pressure and velocity of a fluid flow; in some CVTs, used in conjunction with a valve arrangement to control ratio changes

Pit road:: The paved roadway that leads into the pit area from the racetrack.

Pits:

Area at a race track for fuelling, tire changing, making mechanical repairs, etc.
Cavities extending from the surface into the metal as a result of pitting corrosion or rust.

Also see shallow pits

Pit stop:

A stop at the pits by racer, for fuel, tires, repairs, etc.
Colloquial term for going to the toilet.

Pittards:: Leather A high quality, natural, supple, and quick drying leather

Pittards leather:: A high quality, natural, supple, and quick drying leather

Pitted:: Eroded contact breaker points

Pitting:: Surface damage to a metal in the form of pits or holes. The opposite is piling

Pitting corrosion:: A corrosion process resulting in pits

Pitting factor:: The ratio of the depth of the deepest pit to the average penetration as calculated from weight loss

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

Pivot axis:: See swivel axis

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."

Pivot pin:: See kingpin

Pivot ring:: See fulcrum ring

Pivot swing axle:: See low pivot swing axle

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