Lesson 2/Learning Event 2
FIGURE 46. SCAVENGING (INTAKE) STROKE.
When the crankshaft moves the piston all the way down, it uncovers the inlet ports. The Roots-type blower
forces fresh clean air through the ports and into the cylinder. At this time the exhaust valves are open and part
of the clean air passes through the exhaust valves, clearing any exhaust gases that may be left in the cylinder
from the last cycle of operation. This is called scavenging the cylinder, just like the four-stroke-cycle diesel
engine. But it is different in that the intake phase of the two-stroke-cycle diesel takes place during the
scavenging of the cylinder.