If you’ve ever turned a wrench on a car, chances are good you know the basic concept of a four stroke motor. The intake stage occurs when the piston is traveling down in the cylinder and the intake valves open, allowing a combustible air / fuel mixture to enter the cylinder. The piston reaches bottom dead center and is driven up the cylinder by the rotation of the crankshaft. The piston compresses the air / fuel mixture in the cylinder; hence, stage two is called the compression stage. The compressed gas mixture is ignited by a spark plug, and this explosion drives the piston downward in the cylinder, creating power. You guessed it – stage three is called the power stage. When the piston reaches bottom again, the exhaust valves open and the rising piston forces the spent gases out of the cylinder in stage four, the exhaust stage.
Sure it’s dry stuff to write about or read about, but it’s damn cool to watch.