RX-7 and RX-8 has two rotors. One rotor is 654cc, two rotor is 1308cc. Rotary engine make power by rotary motion of triangular rotor. Please look lower figure, it is a explanation of Rotary Engine.
Rotary engine has many advantages.
1, Rotary engine is very small and is light in weight.
2, Rotary structure is very simple and is few parts.
3, Rotary engine has rotary motion but not reciprocating motion. Reciprocating engine is inefficiently because reciprocating engine need to change back and forth motion to rotary motion. But Rotary engine is rotary motion from the beginning.
4, Rotary motion has more small oscillation than back and forth motion.
5, Rotary engine spark many times more than reciprocating engine by rev. This is the reason of big power.
6, Rotary engine can get more power easily. Because rotary engine is very small and it is very easy to add more rotor.
Rotary engine has many advantages. But rotary engine have not come into wide use. Why? Because rotary engine is a gas guzzler. Rotary engine's fuel expenses is about 4 miles a liter. If you drive roughly, fuel expenses go from bad to worse about 3 miles... And generation of heat is a high because rotary engine make big power from small engine.
Indeed, it's not widely in use, but isn't the main reason for this is, that Mazda won't license the technology to other manufacturers?
Gas guzzler or not, i think a lot of manufacturers would like to experiment with this concept.
Actually, i wouldn't be surprised if many manufacturers have their own prototype ready to be used, when Mazda will start handing out a license.
Hmm, i wonder if this technology could also be adapted to be used with diesel.
The reason of not widely in use is a poor mileage simply. In point of fact, Mazda don't use Rotary engine to all of their cars. Rotary engine's car is a RX-8 only now. If Rotary engine is a economical, all Mazda's cars will be Rotaries.
And Mazda don't think license the technology to other manufacturers. Because nobody want to the license. On the contrary, there is a manufacturer that demand to stop the production of Rotary engine. It's the Ford. Ford is a main stockholder and parent company of Mazda. Ford could get the Rotary technology, but they regard Rotary as waste. And Ford decided to stop the production of Rotary engine.
But some of Rotary engineers made efforts to survivor. And they improved Rotary engine to more economically. This is the new engine of RX-8.