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.
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.
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
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.
The combustion chamber is the area where compression
and combustion take place. As the piston moves up and down, you can
see that the size of the combustion chamber changes. It has some
maximum volume as well as a minimum volume. The difference between
the maximum and minimum is called the displacement and is measured
in liters or CCs (Cubic Centimeters, where
1,000 cubic centimeters equals a liter). So if you have a
4-cylinder engine and each cylinder displaces half a liter, then the
entire engine is a "2.0 liter engine." If each cylinder displaces
half a liter and there are six cylinders arranged in a V
configuration, you have a "3.0 liter V-6".
Generally, the displacement tells you something about how much
power an engine has. A cylinder that displaces half a liter can hold
twice as much fuel/air mixture as a cylinder that displaces a
quarter of a liter, and therefore you would expect about twice as
much power from the larger cylinder (If everything else is equal).
So a 2.0 liter engine is roughly half as powerful as a 4.0 liter
engine. You can get more displacement either by increasing the
number of cylinders or by making the combustion chambers of all the
cylinders bigger (Or both).
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.
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.
The sump surrounds the crankshaft. It contains some
amount of oil, which collects in the bottom of the sump