As cylinders are added to an engine, each one
must complete the four steps of the cycle during
two revolutions of the crankshaft. The number
of power impulses for each revolution also
increases, producing smoother operation. If there
are more than four cylinders, the power strokes
overlap, as shown in figure 3-8. The length of
overlap increases with the number of cylinders.
The diagram for the six-cylinder engine shows a
new power stroke starting each 120° of crankshaft
rotation and lasting 145°. This provides an
overlap of 25°. In the eight-cylinder engine, a
power stroke starts every 90° and continues for
145°, resulting in a 55° overlap of power. Because
the cylinders fire at regular intervals, the power
overlap will be the same regardless of firing order
and will apply to either in-line or V-type engines.
POWER LOSSES AND FAILURE
Power failures can result from minor troubles,
such as loose or bare wires and disconnected or
damaged fuel lines. When reported by the
Figure 3-8.-Power strokes in one-, four-, six-, and eight-cylinder engines.