There are several different types and platforms of combustion engines but I’m just going to talk about a basic piston engine. The simple principle of the engine that it contains an explosion and uses that force to spin a shaft, known as a crankshaft. For simplicity I am going to discuss a 4-stroke engine which most common in consumer vehicles.

For the explosion to happen it requires oxygen, fuel, and something to ignite the combination. As the piston descends down the cylinder it creates a vacuum which pulls an air and fuel mixture into the cylinder which is the first stroke. The second stroke happens when the piston begins to ascend and compress the air and fuel mixture. The third stroke is the combustion; this is when the spark plug sparks and ignites the mixture and creates tremendous pressure inside the cylinder forcing the piston down. The fourth and final stroke happens when the piston begins ascending again after combustion and pushes the exhaust from the combustion cycle out of the cylinder so that it is empty and ready to repeat the process at the first stroke.