X-Mozilla-Keys:                                                                                 
Jeff Spitzer wrote:

Gaddy, Robert G wrote:

I was just thinking (sometimes my brain runs without my permission), "what
if you had a table full of various turbochargers, which one would you
choose?".

I suppose that you would consider a turbo that could only make the desired
manifold pressure at sea-level with no waste gate at all at full throttle
(less weight, complexity, etc.).  I suppose this turbo would have a large,
less restrictive to flow (but possibly heavier), exhaust housing.  If
the turbo seized, the restriction to normally aspirated flow would be
minimized, making the most horsepower until you could get home.  If you
got just a little more manifold pressure than desired, a fixed by-pass

could

be made for fine tuning.  I understand Paul Yaw has to provide a by-pass on
the turbo engine he built for George.

You might think, "what's the point, I'm not making much boost?"  This
would be true, but the turbo speed would increase with altitude, carrying
more
(maybe sea level) pressure up to cruise altitude.  I just don't like waste
gates.  I have a turbo truck (diesel) with no waste gate, and don't miss
it. I have a dune buggy with turbo and waste gate, and always have to

"fuss"

with it. I would hate to try to make moving parts survive a 1,700 deg F,
corrosive atmosphere. My general understanding is that the waste gate is
provided to produce power sooner at lower RPMs, not an issue with an
airplane.

This is what I will be trying to do with my installation.  I came up with a
really neat idea for an exhaust manifold last night.  I'll share it when
the solidworks model is done.

Jeff Spitzer

I had a lot of time to think about this on the drive back from
Oshkosh and I too have decided to do away with the waste gate.
I will just limit the throttle opening on takeoff to limit
the boost and consequently the sea level HP. I know the
rotary won't self destruct like a piston engine does if
temporarily over boosted. 


I am going to 
try for significant boost at 30K altitude. Be real nice
to get above a lot of the weather. 

Jeff you mentioned you have decided to use a TO-4. Any recommendations
on wheel diameters or trims? Is it practical to get to 30,000 feet
with a four place 30 foot span 2600 pound gross (KIS TR-4 Cruiser)
and a 13B/TO-4? 

I know the turbo speeds up as altitude increases. 
What is the TO-4 turbo RPM max limit? I plan on monitoring it.

Can you get an Inconel turbine wheel for the TO-4?
or are Inconel tips available  for  TO-4 turbine wheels.

Have you run any numbers on boost verses altitude for such
a beast?

Paul Lamar
 
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