Old 09-01-17, 12:15 PM
  #21  
dabac
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Originally Posted by Juan Foote View Post
It is my understanding that the rotary engine as we know it is much less efficient than it should be. The 'wives tale' goes that some high up oil guru bought the original design features that made it super efficient and left Wankel with the light, high power version we see used much today. Bad on gas and emissions.
Nah, that's just conspiracy theories.

The wankel have two basic design challenges:
1) the shape of the combustion chamber, surface area vs volume. Wankels have a very shallow and elongated combustion chamber. It's harder to get a good burn through that squished shape as compared to a regular cylinder. There tends to be unburnt residue clinging to the periphery of the chamber.
2) the seals, overall length and fit. Piston engines have piston rings. Quite easy to make, and they have a fairly easy job. Wankels have seals instead. The overall length of seal is greater in a wankel, and due to how they fit and how parts move, wankel seals wear out a lot faster than piston rings. That's the main cause for the dreaded, early engine rebuild.

There were hopes that improvements in material technology would allow a rebirth of the wankel.
Ceramic surfaces in the combustion chamber would run warmer, giving a cleaner burn.
Slicker, more wear-resistant materials to make the seals last longer.

But so far, This has failed to happen.
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