Just got this note from Greg:
"My old notes show a TO-4E housing with a 55 compressor and

P

trim.  .81

A/R

ratio.  The rationale was for a pressure ratio < 3.0.  Given

that

MAP is

dropping with altitude,

but our need for power is also dropping, we can use this

turbo

to

provide 250++ HP for takeoff

while pushing a relaxed 180 HP through the air at altitude.

This is like flying a IO-360 on the deck except with less

drag

at the

higher elevation, so your TAS is much higher.  The .81 A/R

keeps

you out

of

the surge range and in the middle of the 55 map.  A 1.0 A/R

pushes you

closer to the edge of the map than I'd like to see."

I had also sent Greg a copy of Cliff Manzke's turbo notes

from

the

Rotary

Engine Best Practices site- 29/APR/2001, his comments were:

"I agree, as you know,  that a wastegate is decorative dead

weight, but

disagree with his need for a larger intercooler.  He is

making

the same

error I made that you can avoid: cooling all the charge air.

Put your

POV

_ahead_ of the cooler and cool only what you intend to run

through the

rotorset." [POV = intake manifold Pop Off Valve. Limits

intake

manifold pressure]

So there you have it finally....

"TO-4E housing with a 55 compressor and P trim.  .81 A/R

ratio."

...Chrissi

Cozy Mk-IV 13B-turbo
www.CozyGirrrl.com
Chrissi@BlueMountainAvionics.com

Thanks Crissi

Paul Lamar

Is there a way to extrapolate this for the 20b?  I'm assuming

the

.81 A/R

ratio and TO4E housing would stay the same.

Thanx a bunch Chrissi.

Barny MGDQ

-Mark Steitle wrote:

As I recall, Chuck Harbert's 20B was turbo charged.  Maybe the

person

that

bought Chuck's engine package can provide the specs on that turbo?
Mark

I don't think that you can size a turbo that way. First, you base it on
the airflow of the engine, in cu in, or liters at a certain rpm.
Certainly the 20B has 1/3 more airflow at any rpm than a 13B. So you
handle a lot more air thru the turbine (and compressor), and you need a
correspondingly larger housing and blades, depending on what you want to
accomplish (big assumption). I suggest you read a few books on the
subject and go thru a few calc to try out the sizing. As Paul suggested,
both the Hugh McGinness and Corky Bell books are worth their weight in
gold.

By no means do I suppose I will understand it all (I'm not all that
smart), but at least I will give it a try-that's why we do this stuff. I
do know what works and will try to emulate that in better ways.
FWIW, my installation WILL have a wastegate, and a blow off valve, an
intercooler, and maybe even be slightly over-normalized (via upper deck
pressure and ambient pressure sensors) instead of "always boosted".
Also I attach an old turbo calc sheet in Excel by Jeff Spitzer (is he
still here?) that was sent some time ago to the list. Have fun with it.
[Marc Wiese]

 
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