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Old 09-06-2007, 07:56 PM   #13
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Member#: 136327
Join Date: Jan 2007
Chapter/Region: MWSOC
Location: Palatine, IL
01 Outback Wagon


Originally Posted by TMessick View Post
Compressor map is in standard mass flow rate (i.e. flow rate at standard atmospheric pressure). As such, the BIG thing you're missing is pressure ratio (manifold pressure over standard atmospheric). You're also missing VE, which will be less than 1.0 and tend to reduce the flow...

Anyhow, from your eq. before:
volume of air (cu ft/min)= (rpm x cid x VE) * (Manifold Pres + 14.7)/14.7
OR (in SI):
flow rate (m^3/s) ~= (RPM * disp * VE) * (MAP/101.7) *(1/120)

disp in m^3
VE in %
MAP in kPa

at 18psi of boost, MAP = 225kPa
m/s = (7000 * 0.002 * 0.85) * (225/101.7) * (1/120) = 0.219, which putts comp. eff off the charts....

thank you for explaining your answer... time to do some more math now that i have the correct equation.
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