Zachary Carter wrote:

Brian,

The presence of a lot of unburned gases in the exhaust would tend to lower
the exhaust temperature, since the combustion process generates the heat.
The high exhaust temp and exhaust noise typical of rotaries is mostly due to
extremely early port timing.  I forget exactly where the port timing was,
but I recall looking at this and it was extremely early in comparison to a
typical piston engine cam profile, something like 30 or 40 degrees earlier.

This is also the primary contribution to the relatively high fuel
consumption, the peripheral exhaust port rotary simply doesn't extract as
much of the available heat in the form of work as a piston engine does.  All
else being equal (exhaust and intake port timing and such), the rotary
engine cycle actually is more efficient than the carnot cycle, a piston
engine with an exhaust port timing similar to a rotary's would have
significantly lower fuel efficiency.

Zack

 
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