Four Stroke Engine Cycle

This is a quick low-down on how the four stroke engine cycle under your hood work. The four-stroke combustion cycle is made up of these strokes: intake stroke, compression stroke, combustion stroke, and finally, the exhaust stroke.

1. Intake stroke:

The piston first starts at the top of the cylinder. The intake valve opens to let the air into the cylinder. The piston moves down, creating a vacuum that lets the cylinder get filled with the mixture of air and fuel.

2. Compression stroke:

The piston then moves up again. This compresses the mixture of air and fuel. This compression is necessary to make the next stroke, the combustion stroke, more potent.

3. Combustion stroke:

While the piston is at the top of the cylinder, the spark plug gives off a spark. This spark ignites the air and fuel mixture and creates an explosion. This explosion is what drives the piston back down.

4. Exhaust stroke:

When the piston gets to the bottom of the cylinder, the exhaust valve opens. This sucks the exhaust out of the cylinder to exit out of the exhaust piping.

This cycle is also called the Otto Cycle and is repeated over and over again. It seems simple, but this cycle occurs hundreds of times per minute and is the heart of what an engine is.

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