Here is an idea I had quite a few years ago but I just got around to drawing
it up. Since 50% of the fuel energy goes out the exhaust, on almost all
internal combustion engines, the turbo compound
arrangement has the potential to not only increase the HP out of an engine
by about 20% but reduce the BSFC by 20% in the bargain. The closest thing
you will ever get to a free lunch. The CW R3350 TC BSFC went from 
about .45 to .35 as shown in this chart from Taylor's book.

The rotary is ideal for this combination due to its intrinsic high
RPM operation and lack of exhaust valves.

The CW R3350 turbo compound aircraft engines had reliability problems. 
The exhaust valves as they failed and broke up... the parts  on their way out 
would destroy the blow down turbines. Here is a picture of a R3350 TC 
blow down turbine illustrating that point. The wankel rotary of course has no 
exhaust valves so this failure mode does not apply.

Monty please make a 3D of this drawing if you have time.
I can send the ACAD R12 version of the drawing if it will help.

Paul Lamar
 
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