Lesson 2/Learning Event 1
IMAGE: FIGURE 43. POWER STROKE.
As the piston starts down on the power stroke, the burning fuel is now producing extreme heat. The heat
expands the gases in the cylinder which pushes down on the piston with great force. Just before the piston
reaches the bottom of the power stroke, the exhaust valve opens. The burned gases in the cylinder, still under
some pressure, start to rush out by the open exhaust valve.