What Are the Advantages and Challenges of the Wankel Engine?

[bags]

Hey guys,
I just came to know about the wankel engine.It appears pretty much promising as an alternative for regular IC engines used in vehicles.Moreover they must be much more silent in operation also as there we get direct rotary motion for shaft.So why they havn't been used so much or if yes then where?I am curious to know about it.
THANKS...

 

[wolram]

They have been used in the Mazda motor car and Norton motorcycle, for some years, i think (tip seal) is the main problem with them, but i will leave
it to Fred or Brewey etc ,to explain more.

 

[Integral]

I first read of the Wankel engine back in the mid '60s. Even then it looked great on paper. Unfortunately when you compare the average speed of the sealing surface with that of a reciprocating engine the problem becomes clear. In a reciprocating engine the seals come to a complete stop 2 times each cycle (top and bottom of motion) while the Wankel seals never slow down, they are always running at a high speed. This posed major difficulties for the material available in the last half of the 20th century. I believe that they have now developed materials which can provide the continuous high speed seal needed. We may be seeing a better Wankel on the market in the future.

 

[Averagesupernova]

I had (actually still have) a snowmobile with a Sachs rotary engine in it. I believe it is a 1971 Arctic Cat. 303 cc. They came in later model sleds too. I recall a 505 being available. I also own an 85 RX-7 with a 1.3 liter electronic fuel injected rotary. They aren't worth much monetarily, but mine is in well above average condition for an 85. I'm not a huge fan of the Wankel but I can't say I've have anything specific against them. Ignition seems to be more critical in a rotary engine. The spark needs to be a good hot spark or they run poorly if at all. The snowmobile has only one spark plug and one rotor. The Mazda has 2 plugs per rotor for a total of 4 plugs. One plug fires early and the other late in the power portion of the cycle.

 

[mcw3]

Materials have come a long way, but as the RX-8 is currently showing emissions, fuel consumption and oil consumption are still abismal, especially when compared to boingers.
However, compare the time/money that has been invested into developing piston engines with that of the rotaries. It's no wonder they aren't at the same level.