Figure 7-2.—Comparison of events in diesel and gasoline four-cycle engines.
then passes through the intake manifold, where
The diesel engine uses neither spark plugs nor
it starts to vaporize. Then the mixture enters the
a carburetor. On the intake stroke, only fresh air
cylinder through the intake valve. Here it is
is drawn into the cylinder through the intake valve
completely vaporized by the heat of compression
and manifold. On the compression stroke, the air
as the piston moves upward on the compression
is compressed and the temperature in the cylinder
stroke. When the piston is near the top of its
rises to a point between 700 °F and 1200 °F. At
stroke (top dead center or TDC), the mixture is
the proper time, the diesel fuel is injected into the
ignited by a spark from the spark plug.
cylinder by a fuel injection system. When the fuel
7-2
