Figure 2-24. Measuring Crankshaft Rotation
is actually more than one engine, all operating a common
Figure 2-26 also demonstrates how the equally spaced
crankshaft. Engines in automotive use are usually built
power strokes in a four-cylinder engine reduce the
using four-, six-, or eight-cylinder engines. Whenever
periods when the flywheel is carrying the engine. With
engines are built with more than one cylinder, it is
four power strokes for every 720 degrees of rotation, one
important that the cylinders give their power strokes in
can be made to begin every 180 degrees. This leaves
equal increments of crankshaft rotation. Figure 2-25
the engine with four equally spaced periods of 35
degrees each that the flywheel must carry the crankshaft.
If the engine has more than four cylinders, the power
strokes overlap, meaning that before one power stroke is
Figure 2-26 illustrates how much of the engine rotation is
finished, another one begins. As illustrated in figure 2-
taken up by power stroke in a one-cylinder engine.
25, a six-cylinder engine has a 25-degree power overlap
Figure 2-25. Typical Multiple-Cylinder Configurations.