Bulent Aliev wrote:

Hi Paul,
For the purpose of prop making I need some initial HP numbers on my engine.
It's all guess work, but you are more qualified since your engine is more or
less like mine. I need the engine HP output at 2,3,4,5,6,7 K RPM. I'm sure
later the numbers will be revised, but have to start somewhere.
I use the same turbo like you and the 2.17 Tracy PSRU.
Thanks.
Bulent

It is kind of unusually to need to know the HP of an aircraft engine
at all RPMs as it is impossible to generate max HP at less than max prop
RPM. That is because prop load is a square law function and not an
inertia function. In other words accelerating a car is an inertia function.
The mass of the car will absorb all the HP you can generate up to
the point the tires squeal. Sorry I can't think of a simpler way of
putting it.

Having said all that prop load changes with pitch and diameter so I 
guess the information could be used. NA Rotary HP curves with simple tuned
intake systems  are very nearly a straight line function of RPM. In other
words if you have 200 HP at 6000 RPM you will have about 100 HP at 3000 RPM. 

The amount of NA max HP generated can be moved up and down the the RPM
point by changing the length of the tuned intake system. You then choose
a prop RPM and adjust the length of the intake pipes. You could probably
increase the HP by about 10% using this technique.

Turbo and superchargers are whole different ball games. All sorts of
HP can be generated at all sorts of RPM's depending on a whole
host of factors. My guess with a stock 91 turbo and better intercooler
you can see 250 HP at 6500 RPM. Your guess is as good as mine as to
what max HP it will generate at 3000 RPM. Only a dyno can tell you
and then it will depend somewhat on the amount of air going through the
intercooler.

Paul Lamar
 
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