Figure 1.5. Operating Cycles.
stroke. The intake valve then closes and the piston goes up on the compression stroke, compressing the
air within the cylinder. Fuel is injected through the injector while the air is compressed, and combustion
occurs. The combustion, with resultant pressure, drives the piston back down on the power stroke. The
piston rises again on the exhaust stroke and expels the air through the exhaust valve, a process called
Piston action in the two-stroke cycle engine is basically the same. A difference in scavenging
accounts for two strokes rather than four. Air entering the intake port pushes the oxygen-depleted air,
left from the previous combustion, out through the exhaust valves. The compression stroke then occurs.
Notice, in the lower