Four-Stroke Cycle

     Automobile engines normally use a four-stroke cycle. Piston stroke is the distance thepiston slides up and down from top dead center (TDC) to bottom dead center (BDC). Thistakes one-half turn of the crankshaft. The crank rotates 1800 during one piston stroke(Fig. 3. 2)．Four separate piston strokes are needed to produce one cycle，which are intakestroke，compression stroke，power stroke and exhaust stroke. The piston must slide down,up，down and up again to complete one cycle.