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ENGINE TERMS

P=Piston
R=Connecting Rod
C=Crankshaft

In this diagram you can see the reciprocating motion of the piston is transmitted to the crankshaft by the connecting rod and converted to rotary motion.

The crankshaft is that part of an engine which translates linear piston motion into rotation.

TDC

Definition: Abbreviation for Top Dead Center. This is the point at which the piston reaches its uppermost position in the cylinder. Ignition timing is usually expressed as so many degrees before top dead center (BTDC) or after top dead center (ATDC). A timing mark on the crankshaft pulley or flywheel corresponds to the top dead center position of the number one engine cylinder.

BDC

Definition: Abbreviation for Bottom Dead Center. This is the point at which the piston reaches its lowest position in the cylinder.

STROKE

Definition: The distance between the extremes of a piston's travel in a cylinder. A measured distance from TDC to BDC. It also refers to the action of the piston, you can say the piston travels through one stroke.

BORE

Definition: The diameter of a gasoline or steam reciprocating engine cylinder. The displacement can be increased by increasing the diameter (reboring).

RPM

Definition: Abbreviation for Revolutions Per Minute. Engine speed is often expressed as so many revolutions of the crankshaft per minute.

TACHOMETER

Definition: A device used to measure the rotary speed of an engine, shaft, gear, etc., usually in rotations per minute.

As discussed in class the piston requires two strokes to cause the crank shaft to rotate one complete revolution. In an engine which is running at 3000 RPM, the piston will travel through 6000 strokes in one minute. That is equal to 100 strokes per second. Some modern car engines are able to run at 9000 RPM.How many strokes does the piston make per second?