- Most engines are four cycle internal combustion engines. They are composed in their simplest form of a series of vertical cylinders suspended over a connecting crank shaft. Connected to the crankshaft are metal pistons, each designed to run up and down the length of its designated cylinder in a staggered continuous cycle. At the top of each cylinder are four openings. One is the intake valve, the second is the exhaust valve, the third is the spark plug and the fourth is the fuel injector. When the engine is started the first piston in line is fully raised. The intake stroke begins as the intake valve opens to fill the cylinder with oxygen. The fuel injector sprays a small amount of gasoline in as well. Each cylinder is air tight, so the only thing holding the piston at the top of the chamber is the vacuum because it was empty. With the introduction of air into the chamber, the piston slides down to the bottom of the cylinder.
- As the next cylinder in sequence undergoes its intake stroke, the crankshaft is turned by this to cause the first piston to press back up into the first cylinder. This compresses the air/fuel mixture, increasing its combustibility greatly.
- When the piston reaches the top of the cylinder the spark plug flashes out a small electrical charge from the engine's battery. The fuel within the cylinder explodes, driving the piston down to the bottom of the cylinder with great force. This causes the crankshaft to continue to turn so that the second cylinder may undergo its compression stroke and the third cylinder may undergo its intake stroke.
- Upon reaching the bottom of the cylinder, the exhaust valve opens to allow the fumes and byproduct gasses from the explosion to leave the cylinder. The gasses are forced out as the second piston in line undergoes its combustion stroke, the third piston undergoes its compression stroke, and the fourth piston undergoes its intake stroke, all of which would turn the crankshaft and drive the first piston to the top of the cylinder to start the cycle all over again. This process is continued indefinitely by each cylinder in staggered order to ultimately cause the crankshaft to turn smoothly and steadily. Connected to the crankshaft is a fan. Connected to that fan is a fan belt which can be used to transfer the engine's power to do work. In the case of a car it would be used to turn the axles of the wheels to propel the vehicle forward.
