Chapter 07: Final Review & Key Terms

WRAP UP: Key Terms

 

anodizing A process used to harden aluminum by electrochemically reacting oxygen with aluminum.

articulating piston A two-piece piston design that uses a separate aluminum skirt connected to an alloy steel crown through a piston pin.

break-in period The operation of an engine after it is initially assembled or rebuilt when the piston ring, cylinder wall, bushing, and bearing surfaces have high initial wear as the moving surfaces conform to each other.

cam ground piston An elliptically shaped piston that expands to a round, symmetrical shape after it is warmed up.

compatibility A property that allows two metals to slide against each other with minimal friction or wear.

compression height The distance from the piston pin to the top of the piston crown.

compression testing A measure of the maximum pressure of engine cylinders when cranking.

crankcase pressure test A measurement of the amount of cylinder blowby; this indicates the sealing ability of the piston rings and cylinder walls.

crevice volume The area between the piston crown and the cylinder wall above the top compression ring.

crosshatch A cylinder wall finish of fine intersecting lines that are used to retain oil.

cylinder glazing A condition that occurs when lubricating oil is first baked and then smoothed into the crosshatch of the cylinder wall. Cylinder glazing prevents the cylinder wall from retaining oil and reduces the ability of rings to seal.

cylinder leakage The percentage of gas leakage past the rings. High leakage rates are usually due to worn cylinders and rings.

dial bore gauge A precision measuring tool used to measure taper wear in a cylinder.

durability requirements Legislated standards for engine durability that require noxious engine emissions to remain below set thresholds through the expected useful life of an engine.

dusting out A condition where dirt is drawn into an engine; this causes premature abrasive wear of the cylinder walls and rings.

forged pistons Pistons made from aluminum alloy billets that are stamped into shape by forging dies.

hydrostatic lock A condition that occurs when fluids in the cylinder of an engine prevent the engine from rotating.

hypereutectic piston A piston that has high silicon content (16–20% silicon).

Magnehelic gauge A gauge that measures both pressure and vacuum using inches or a water column as a measuring unit.

major side thrust Piston side thrust caused by cylinder pressure and the angle of the connecting rod during power.

micro-finish etching A piston skirt finish where many fine lines are machined into the skirt to retain oil.

minor side thrust Piston side thrust caused by compression pressure and the angle of the connecting rod.

mono steel pistons A one-piece piston constructed from steel.

MONOTHERM piston A one-piece piston design made entirely of alloyed steel, which has a compact height and a large reduction of material between the skirt and the crown.

Ni-Resist insert A stainless steel–nickel alloy insert placed in aluminum pistons in the compression ring groove. The insert minimizes groove wear caused by ring movement.

nitriding The process of hardening a metal’s surface by heating the metal and quenching it with cyanide salts.

piston slap A noise in the engine produced by large operating clearances between a piston and a cylinder wall. Piston slap is most often heard when an engine is cold.

shot-peened A technique that uses small steel balls to blast metal surfaces in order to close any small cracks or pores, which have the potential to become larger.

slipper skirt piston A piston design that has a portion of the skirt removed on both non-thrust sides of the piston to provide clearance for the crankshaft counterweights.

soot loading A condition that occurs when engine oil dissolves combustion soot.

split fracture connecting rod A technique used to form a mating surface between a connecting rod and a cap. The mating surfaces are not machined but are produced by fracturing the big end of the rod along a line scribed into the rod.

trapezoidal pin bushing A pin bushing design in which the bearing surfaces absorbing combustion forces are wider on the connecting rod and piston to improve piston and connecting rod load-bearing capabilities.

trunk piston A piston design that is dimensionally longer than it is wide and uses a full piston skirt.

 

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