Other Parts of an Engine

Spark Plug. The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

Valves. The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

Piston. A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston rings. Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

· They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.

· They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Connecting rod. The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

Crank Shaft. The crank shaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.

Sump. The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).