PHOTOCHEMICAL SMOGSmog caused by
hydrocarbons and nitrogen oxides reacting
photochemically in the atmosphere. The reactions
take place under low wind velocity, bright sunlight,
and an inversion layer in which the air mass is
trapped Can cause eye and lung irritation
PINGEngine spark knock or detonation that occurs
usually during acceleration. Caused by excessive
advance of ignition timing or low-octane fuel.
PISTONA cylindrical plug that slides up and down
in the cylinder and is joined to the connecting
PISTON BOSSThe reinforced area around the
PISTON CROWNThe top or head of the piston.
PISTON DISPLACEMENTThe volume of air
moved or displaced by the piston as the piston
moves from BDC to TDC.
PISTON HEADThe portion of the piston above the
PISTON LANDSThe spaces in the piston between
the ring grooves.
PISTON PIN-A cylindrical pin that passes through
the piston bore and joins the connecting rod to the
PISTON RINGA split ring (expansion type) placed
in a groove of the piston to seal the space between
the piston and the cylinder wall.
PISTON-RING END GAPThe clearance between
the ends of the piston ring.
PISTON-RING GROOVEThe grooves cut in the
piston into which the piston rings are fitted.
PISTON-RING SIDE CLEARANCEThe
clearance between the side of the ring and the ring
PISTON SKIRTThe portion of the piston that is
below the piston bore.
PISTON STROKEThe distance that a piston moves
between its limits of travel.
POLLUTANTAny substance that adds to the
pollution of the atmosphere. In a vehicle, any such
substance in the exhaust gas from the engine or
escaping from the fuel tank or air cleaner.
POSITIVE CRANKCASE VENTILATION
(PCV)A crankcase ventilation system; uses
intake manifold vacuum to return the crankcase
vapors and blow-by gases to the intake manifold to
be burned, thereby preventing their escape into the
POWERThe rate of doing work or the rate for
expanding energy. The unit for mechanical power
PRONY BRAKEA device using a friction brake to
PRECISION INSERT BEARINGA precision type
of bearing consisting of an upper and lower shell.
engines, a separate small combustion chamber
where combustion begins.
PREIGNITIONIgnition of the air-fuel mixture in
the combustion chamber by some unwanted means,
before the ignition spark occurs at the spark plug.
PRESSURE The amount of force distributed over
each unit of area. Pressure is expressed in pounds
per square inch (psi), inches of mercury, and other
PRESSURE CAPA radiator cap with valves which
causes the cooling system to operate under pressure
at a higher and more efficient temperature.
PRESSURIZE To apply more than atmospheric
pressure to a gas or liquid.
PSIPound per square inch; usually to indicate
pressure of a liquid or gas.
PUSHRODSA special rod used to transit the motion
of the cam and the lifter to the rocker on the cylinder
RADIAL ENGINEAn engine with each cylinder
located on a radius of a circle and with all cylinders
disposed around a common crankshaft.
RADIATORIn the cooling system, the device that
removes heat from coolant passing through it;
receives hot coolant from the engine and sends the
coolant back to the engine at a lower temperature.
RADIATOR CAPThe cap placed on the radiator
RATIOThe value obtained by dividing one number
by another, indicating their relative proportions.