Quote:
Originally posted by Dantilla
Jim, I said that rotaries have great attributes, and that I like them. No bashing intended. But do you disagree about their efficiency?
While the horsepower per displacement is spectacular, the horsepower per fuel used is usually less than a piston engine.
You've got gobs of power from your RX-7, but I doubt you would consider it an economy car.
Good points:
-They rarely suffer a catastrophic failure. If one rotor goes, you drive home with less power.
-Smooth.
-High rpms can deliver high horspower numbers.
-Compact design.
The bad:
-The crescent shaped combustion chamber has poor volumetric efficiency. More gas, more emmissions.
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I think the poor efficiency is in part due to Mazda not focusing on it as a high priority. Just a guess but with the attention on oil we have today that could change.
True, Mazda couldn't win Le Mans until they were given some concession for fuel millage (teams are allocated fuel for the race). But it was a marginal problem. I have had a few RX7's and never was concerned about millage. Maybe the old 12A or 13B used 5% / 10% more fuel than say a 280Z or 911 of the day. Not sure but the point is - so what. The fuel efficiency argument was laid down by those looking for a negative and perpetuated because in reality there are few negatives associated with the engine. It is a great engine and the cars are awesome as well. I especially liked the second generation.