Since pushers are flying the prop in somewhat dirty air, would it not be best to go with the largest diameter prop? In the case of a Cozy that is 70"
With the redrive that limits engine redline to 6550 (tip speed @ .85 mach)
There are a lot of variables here to play with.
-in a NA engine, where is the HP curve?
-adding a turbo skews the curve depending on turbo specs
-the info "61 cu in, but breathes like a 2 cycle therefore = 160 cu in".. which one do you plug into the turbo spreadsheet?
-the info "high volumetric efficiency = 120%" ... is this valid for the spreadsheet too?

I realise this engine produces a lot of HP at elevated RPMs but I'd prefer to do what I can to use the larger prop and keep the RPMs down a bit. For one, listening to it screaming it's guts out for 4 hrs going cross country sounds like a real case of fatigue.
Any suggestions?
...Chrissi

Bug Tracy to do a 2.85:1 psru. It is a simple change.
Careful you don't hit that big prop on landing or takeoff.

"listening to it screaming it's guts out for 4 hrs going cross country sounds 
like a real case of fatigue." 

Not true Chrissi! Get your butt down to Tracy's for a ride. You will be amazed.
You have obviously never owned a rotary powered car. Forget what you know about
piston engines.

BTW guys don't bug me with stories about how pushers don't cool when idling or
on the ground. What do you expect out of a down draft cooled engine installed
in an updraft cooled airplane? The exhaust pipes heat the air BEFORE it is
supposed to cool the cylinders.
 
Paul Lamar
 
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