<Snip>>

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]

Tom Kendall wrote:

Close, but a bit off.  I'm just surprised that with all the anal-ytical
types on this mailing list, Marc hasn't already received a ration of grief
from everybody ;-)

The 20B has 50% more air flow, fuel flow, hp, etc. than the 13B, all other
things being equal.  3 rotors / 2 rotors = 1.50 = 150%, or 50% more than the
2 rotor version.

My 25 cents worth.

Tom Kendall

 
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