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
 
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