Rotary Vs. Piston Engine

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Nearly every car ever made uses one form of a four-cycle reciprocating engine. As with any engineering design the reciprocating engine has certain pro and cons. The rotary engine provides an alternative to the reciprocating engine while being similar enough to use much of the same mechanical principles. The purpose of any combustion engine is to create power by igniting a mixture of air and fuel in a controlled environment, or the engine block. There are three goals that the engine design needs to accomplish: how to get fuel and air into the combustion chamber, how to get extra power from the combustion, and how to remove the spent fuel and air from the chamber. This is done by what is know as the Otto cycle, which is composed of four strokes: the intake, compression, combustion, and exhaust.
The reciprocating engine, or piston engine is composed of about forty simultaneously moving parts. Inside the cylinder there is a piston that is free to move up and down within the cylinder. There is also an intake valve on one side and an exhaust valve on the other. The intake valves opens, letting air and fuel into the chamber, and moving the piston downward. This is the intake stroke. The valves close, and the piston moves back upwards, shrinking the chamber and compressing the air fuel mixture. This is the compression stroke. The mixture is then ignited creating an explosion forcing the piston to move downward again. This is the combustion stroke, the only stroke that produces actual power. Once the piston reaches the bottom of the chamber the exhaust valves open, forcing the spent mixture or exhaust out of the chamber. The cycle is continuous, therefore the cycle will return to the intake stroke. This engine has two disadvantages. The only time the engine is generating power is when the piston is forced down by the combustion , this means that the piston must move up and down twice for each power stroke. The up and down ...