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.
A piston is a cylindrical piece of metal that moves up and down inside the cylinder and provides the motion to turn your axels through the crank shaft. Notice the image below…the pistons are moving up and down by an explosion of gas that pushes the piston in the opposite direction.
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.
Most cars that “burn oil” and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly. Many modern vehicles use more advance materials for piston rings. That’s one of the reasons why engines last longer and can go longer between oil changes.
The crankshaft turns the piston’s up-and-down motion into circular motion just like a crank on a jack-in-the-box does.
The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).
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.