We should be able to demonstrate an improvement in BSFC if and when
we get an effective variable pitch prop. In my C182 the best 
economy is obtained by increasing the pitch and throttle opening and 
decreasing the RPM. Most people will tell you not to exceeded "square" in 
an aircraft piston engine. 

   What square means is 2200 RPM and 22" of manifold pressure.
Supposedly if the pressure rises above the RPM you are lugging the
engine and it is bad for it. You are risking bearing or rod failure.

Since the rotary is more robust than any piston engine we may be able
to open the throttle wide (at low altitudes), increase the prop pitch
and decrease the RPM. The lower RPM will result in less engine friction
and the wide open throttle less pumping looses resulting in better
BSFC or lower fuel burn for the same speed.

This principle is widely used to improve the MPG of cars. My Ford
Cougar cruises down the freeway at about 70 MPH and 2000 RPM.
Nothing new. Over drives have been used for decades.

Paul Lamar
 
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