FOUR STROKE CYCLE :

The gasoline engine is an internal combustion heat engine that develops its power by burning a mixture of gasoline and air in the engine's cylinders. This engine is designed to operate on a 4-stroke cycle principle. Each stroke is a movement of a piston, either upward or downward, in its cylinder

The strokes occur in the following sequence:

* Intake stroke

* Compression stroke

* Power stroke

* Exhaust stroke

The intake stroke (downward) serves to draw the air-fuel mixture from the carburetor into the cylinder through an open intake valve. The compression stroke (upward) compresses the mixture to approximately 150 pounds per square inch, a pressure at which the gaseous mixture is suitable for efficient combustion. the power stroke (downward) is the result of the spark plug igniting the compressed fuel charge. The rapid burning of the fuel produces tremendous heat and pressure which expands the gases and raises the combustion pressure to more than four times the compression pressure. This pressure, exerted on the head of the piston, is the force that produces the power that drives the vehicle. The exhaust stroke (upward) forces the burned gases out of the cylinder through the open exhaust valve, into the exhaust system. With the cylinder cleansed of the exhaust gases, the cylinder is ready for another intake stroke and a repetition of the 4-stroke cycle. This cycle of strokes,in the sequence listed, continues as long as the engine is in operation.

Theoretically, each stroke lasts for 180 degrees of crankshaft rotation. In actual practice, however, the length of these strokes is modified somewhat for better engine performance and efficiency.

All the cylinders in an engine are fired in every 720 degrees of crankshaft rotation regardless of the number of cylinders in the engine. The more cylinders an engine has, the more power strokes there will be in these two crankshaft revolutions increasing the engine's output and performance.

FOUR STOKE CYCLE