How a Four Stroke Engine Works

The K20Z3 motor is what is called a four stroke engine.  This means that each cylinder has four steps to its function.  The stroke of a cylinder is the movement of the piston in an upward or downward motion.  The first stroke or cycle begins when the piston is at its highest point called top dead center.  From this point the piston begins to move downward.  While this is happening the intake valves open letting air and fuel to mix into the chamber.  This first cycle is also referred to as the intake cycle or stroke.  The second stoke of the cylinder is the compression stroke.  This occurs after the piston has passed bottom dead center, and has started to move upward, forcing the air and fuel mixture to compress.  Once the piston has reached close to top dead center once again, the spark plug ignites the mixture, forcing the piston back down and creating the energy that moves the car.  This is the third stroke also known as the combustion or power stroke.  After reaching bottom dead center a second time, the piston begins its fourth and final stroke, the exhaust stroke.  This is where the exhaust valves open and as the piston moves upward, it forces the exhaust fumes out of the cylinder, completing one full cycle of the four stroke engine.