The Internal Combustion Engine

Most automotive engines include a carburetor or fuel injector, pistons, cylinders, and spark plugs. Fuel mixes with air in the carburetor or is sprayed through a fuel injector. The mixture goes into a cylinder, essentially a long air pocket, like a steel can with one end open. In a spark-ignition engine, the mixture is ignited by a spark from the spark plug, releasing heat. This heat increases the pressure inside the cylinder, which moves the piston, a metal plug that fits snugly into the cylinder but is loose enough to slide up and down.