Paul,
I have attached a dyno chart for the turbo 13b you posted earlier

(exhaust

manifold pic) from Paul Yaw's web site.  The chart indicates it
is  producing 262 hp at 6500 rpm with 6.4psi boost, flowing 405cmf.

From

this information, could I deduce that a similarly prepped turbo 20B

would

flow 607.5 cfm (405 x 1.5).  Since I won't be running quite that high of
rpm's, I figure I could reduce this figure by about 10%, to about

550cfm,

assuming the dyno chart is accurate.

As for the specifics for the above engine:  "The turbo (From

Turbonetics)

is a Garrett TO4E, 50 trim compressor, P trim exhaust, with a modified

1.3

AR ratio housing. The turbine wheel is made of inconel. The center

section

is water cooled. The turbo feeds the engine through a small intercooler
made by Spearco.  Boost is 6.4 psi at 6500 rpm. (43" Hg. manifold

pressure.)

How do I convert cfm to lbs/min to use in the turbonetics chart and

maps?

Thanks,
Mark

Air density at sea level is about  .0019 pounds per cubic foot.
So CFM X .0019 = pounds/min

Paul Lamar

Where did you get that number? ICAO std atmosphere tables says .076475 or
.00237 slugs
Vance

I've used a multiplier of 4.5 to convert CFM to pounds per hour of air. That agrees pretty closely
with Vance's number (4.5 / 60 = .075).

Jon Lauter

 
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