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

Paul,
Sorry to be so dense (no pun intended) on this, but if I multiply this

out

I get 405 * .0019 =  .7695.  This doesn't appear to match with the turbo
selection chart.  Could the "lbs/min" label be wrong?  Should the chart

be

labeled lbs/hr rather than lbs/min?  As in,
.7695 * 60 = 46.17 lbs/hr, which looks like it would match with the

chart

for a 13B.    This comes out real close to where you drew the lines for

the 13B.

Could be an error.
Paul Lamar

Paul,

    My reference has air weighing  approx 0.076636 lbm/Cubic foot at sea
level. rather than .0019
So if you had 283 cfm you would get an airmass flow of approx .076636*283 =
21.7 lbs/min.  Which is a figure I find fits with the Turbo compressor
curves of interest.

Ed Anderson

 
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