X-Mozilla-Keys:                                                                                 
Brian D. Cain wrote:

I've been thinking about this difference in BSFC between the rotary and the
boinger style engines.  Does anyone have a good explanation for this because
I can't come up with squat.

B

Its mostly due to the shape of the combustion chamber. A lot
of the mixture does not burn and gets scraped out the peripheral
exhaust port. The new side exhaust port engine will recycle most
of this as it is scraped all the way around inside the 
rotor housing and gets a chance to burn in the next cycle.

This is partially why the exhaust is so hot in the rotary.

The other reason for the exhaust being so hot in
the rotary IMHO is there is no exhaust poppet valve to absorb
heat. This of course is an overwhelming advantage for
the rotary when used as a heavy duty aircraft or boat engine.
The exhaust valve is the achilles heel of the four cycle 
aircraft engine. 

Another factor is the surface to volume ratio is less than
ideal so some heat is lost to the cooling system that otherwise
would result in power out.

On the up side it appears that the rotory can be boosted
to higher pressures without detonation.
 
Paul Lamar
 
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