Mike wrote:

Paul.
You mention that at 250 horsepower, the rotary would need about an
additional 30 h.p. for the blower.
That's a whopping 10+ percent more power needed! Or even worse, assuming the
same engine gives about 180 h.p.
without the blower (optimistic), it takes 30 h.p. to gain 70 h.p. Does this
sound right?
Can you put me in touch with those that have a blower, and those that use a
turbo?

I'd be very interested in how they come by their s.f.c numbers, as well as
their H.P. estimates.
Furthermore,  I thought it was Bruce that mentioned the rotary breathed so
much better with less exhaust
gas back pressure, that a blower (I don't recall which type) was only about
3% less efficient than a turbo.
Do you have any graphs detailing  s.f.c vs. h.p. with either blower or
turbo.

Thanks for so much information all these years,
Mike Arndt

I am very skeptical about that 3% difference number.

It may be a bit high. There is a curve in the book Street Supercharging by
Pat Ganahl that shows the HP loss for a Paxton super charger at 24 HP max
at max boost. 2400 pounds per hour at 6.5 psi boost.  

A 671 roots will suck down 80 HP at 5200 RPM at 24" HG with a volumetric eff. of 70%.
Archie can fill us in on some of the higher numbers for GM roots blowers.

I have not heard from Tom Jordan lately and I don't have his email address 
or phone number. I run in to him at OSH once in a while. Here is a picture
of his airplane. Last I heard he was in the St. Louis area.

Tom Parkes is on here and he flies a turbo 3 rotor Lancair ES. Tom are you
listening?

No BSFC curves vs HP for a turbo or supercharged rotary. I have a few
for NA rotaries.

Paul Lamar
 
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