Lesson 2/Learning Event 1
Most of the present high-speed compression-ignition engines use a cold-weather starting aid. This may be a
heating element located in the combustion chamber or in the intake manifold. The starting aid located in the
intake manifold preheats the air before it enters the engine cylinder. The combustion chamber heating element
directly aids in igniting the fuel-air mixture.
Let's go through the operations of a four-stroke cycle of a diesel compression-ignition engine. By comparing
the diesel cycle with the gasoline cycle you will learn just how the four-stroke-cycle (diesel) works.
IMAGE: FIGURE 41. INTAKE STROKE.
During the intake stroke (downward movement of the piston), the intake valve is open and air enters the
cylinder around the intake valve. With no carburetor and throttle valve, the cylinder fills with air whether the
engine is idling or running wide open.