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How a car engine works Part 3

The core of the engine is the cylinder, with the piston moving up anddown inside the cylinder. The engine described above has one cylinder.That is typical of most lawn mowers, but most carshave more than one cylinder (four, six and eight cylinders are common).In a multi-cylinder engine, the cylinders usually are arranged in oneof three ways: inline, V or flat.

 Different configurations have different advantages and disadvantages interms of smoothness, manufacturing cost and shape characteristics.These advantages and disadvantages make them more suitable for certain vehicles.

Let's look at some key engine parts in more detail.

Spark plug

The spark plugsupplies the spark that ignites the air/fuel mixture so that combustioncan occur. The spark must happen at just the right moment for things towork properly.


The intake and exhaust valves open at the proper timeto let in air and fuel and to let out exhaust. Note that both valvesare closed during compression and combustion so that the combustionchamber is sealed.


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.

Mostcars that "burn oil" and have to have a quart added every 1,000 milesare burning it because the engine is old and the rings no longer sealthings properly.

Connecting rod

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


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).

Watch this space for more on this series!!

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