James Phillips wrote:

I was wondering if anyone knows how much less power to expect from an engine with
86 n.a. rotors as opposed to one with the later, lighter, higher compression
rotors.
I have a set of 4 port end-housings that I will run with n.a. rotors like Tracy's
latest motor built by Bruce T. The thing is that I have a good set of 86 n.a rotors
on hand and would have to purchase a set of later rotors and they aren't exactly
cheap. I'm wondering if the increase in power would be enough to make it worth it.

If they are the same compression ratio and you are running the engine at the
same RPM there will be no power differences. Light weight rotors allow the engine
to rev higher but if you have a fixed pitch prop you will not be able to
take advantage of this. 

Light weight rotors would only make sense if you had
a 3:1 PSRU or higher and a variable pitch  or constant speed prop.

Given that last scenario the increase in engine speed and probably HP (with
peripheral ports) could be calculated from m2*V2^2 = m1*V1^2 where m1 is
the mass of rotor one and m2 is the mass of rotor two.
V1 is the tangential velocity of the rotor CG in with rotor one and
V2 is the tangential velocity of rotor two in feet per second.
r is the distance of the CG of the rotor from the e-shaft center line.

Solving for V2:    V2 = the square root of (m1*V1^2/m2).

To convert weight to mass divided weight by 32. PL

Also can anyone tell me how to tell if my end-housings have been street ported. The
port looks pretty big but It may be right for a 4-port. Is there a measurement I
can take to tell? The engine had been recently over-hauled and may have been ported
then. Unfortunately this motor swallowed something. I don't know what because
there's nothing missing from the rotor or chamber. But it did a number on one rotor
and the rotor housing. The end-housings look fine.

Usually street porting is evident by the hand grinding of the port to smooth
the flow of air into the engine. If the edges are sharp and look like as cast
it was not street ported. The picture is of Able Ibarra's 700 HP turbo
13B street port. PL

Which brings me to my next point. I'm looking for one 4-port rotor housing in
excellent shape if anyone knows of one. Thanks, James Phillips

 
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