The Four Stroke Cycle Principal

Most cars on the road today use the four stroke cycle engine to get it power from. This engine is sometimes called the Otto Cycle because it was Nicholas Otto who invented this engine in 1867. A four stroke cycle engine works on the four steps that you see listed below. Check out the four strokes to examine how this engine works.

The Intake Stroke. - The first stroke in the four stroke cycle engine.
The Compression Stroke - The second stroke in the four stroke cycle engine.
The Power Stroke - The third stroke in the four stroke cycle engine.
The Exhaust Stroke - The fourth stroke in the four stroke cycle engine.

 


Fig. 6.1 - The Intake Stroke


 


Fig. 6.2 - The Compression Stroke

With the Intake Valve open, the piston moves down in the cylinder, creating a vacuum. This vacuum sucks in air and gasoline through the intake valve. This is the Intake Stroke.
 
Then intake valve closes, and the piston moves upward on the compression stroke. The air-fuel mixture becomes greatly compressed in the small space between the top of the piston and the cylinder head (compression chamber).

 

 


Fig. 6.1 - The Intake Stroke


 


Fig. 6.2 - The Compression Stroke

In the Power Stroke, with both the intake and exhaust valve closed., the spark plug fires or sparks, igniting the air and gas mixture. This explosion pushes the piston down.
 
The exhaust valve opens, and the upward movement of the piston on the exhaust stroke forces the burnt gases out of the cylinder through and open exhaust valve. This is the last stroke in the four stroke cycle. After this stroke this process starts all over again.

 

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