Ken Welter wrote:

   My coot is a different bird and the 5 blade warp drive is way off
beat to from what you guys are running but a 8000 ft there is little
difference in hp loss or rpm, the higher I go more rpm I run to keep
the air speed up, at sea level at 6000 rpm I indicate 100 mph at
12000 ft I have to push 6500 rpm to indicate 100 mph do to the fact
that I do not have a controllable prop to grab into the thin air but
I am very impressed at how well the rotary runs at high alt compared
to aircraft engines I fly with a friend in his 180 Comanche and it
runs out of beans at 8 or 9000 ft and my rotary seems to love that
alt however a controllable prop would make a big difference. Also I
have a controllable air ram that make 1000 rpm difference at 15000 ft
and at that alt I can still hold 6500 rpm but I am at full throttle
at that alt but at 13000 ft I cruise at about 80 or 90 percent.

   Ken Welter

Like Tracy says the lower air density is not affecting the RPM but you can
be sure the HP is way down at 8K Ken. No different than a NA piston engine.

BTW  Ken also uses a 3:1 gear box while those
that have reported so far use a 2.17:1 gear box so Ken RPM's will
be much higher. Ken will also have more HP at all altitudes
because of his 3:1 gear box assuming his intake system is free
breathing.

Paul Lamar

Please What is a controllable air ram?
Yvon.

Keep reading Yvon. A picture will be along any minute.

Paul Lamar

I have seen a picture just now. It does not tell what the purpose of the device is... What does it do?.
HAPPY NEW YEAR TO ALL
Yvon

Did you get Ken's explanation? My best guess is it works like a carb choke.
It richens the mixture at low altitudes and leans it out at high altitudes.

Paul Lamar
 
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