Both rotary and piston (reciprocating) engines rely on expansion pressure created by the fuel-air mixture. Rotary engines are, in many ways, better then piston engines, but their use is somewhat limited. Most rotary engines use only two rotors to generate power, which allows them to be smaller engines with less moving parts; lasting longer and remaining more efficient. Rotary engines are also very inexpensive, especially for the amount of horsepower that they put out. Also, the small, compact size allows you to keep a low center of gravity leading to better handling. Though there are many types of rotary and piston engines, in this essay I will be focused primarily on why the Wankel rotary engine outperforms basic reciprocating engines.
The more popular, two-rotor, rotary engine has only three moving parts that do more that half the work as compared to the piston engine which has forty moving parts, giving the rotary a longer life span and greater efficiency. The three parts move at the same time which reduces vibration for a smoother ride even at full throttle. The rotor and housing form three chambers, so there is action in every chamber, every rotation of the eccentric shaft. The rotary engines design allows it to intake or exhaust air, combust, and compress in one rotation of the rotor unlike the constant moving and combustion inside the cylinder of a piston engine. The engine intakes air, combusts the air and fuel mixture, and compresses it all at the same time making it much more efficient and resulting in a smoother ride with less vibration. During the whole acceleration process, the rotor turns at only one third the engine speed. Because of the low rotor to engine speed ratio, the rotary engine can withstand driving under higher load and at higher RPM's thus having high top speed, and incredible horse power as well as overall power in the higher rpm's.
Rotary engines are cost efficient to make and have tremendously more horsepower for far little displacement as compared to a reciprocating engine.