Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - View Single Post - Turbo Sizing Tips and Compressor Map How-To's

uiuc240 · 11-27-2002, 02:11 PM

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Kreator @ Nov. 26 2002,4:08)</td></tr><tr><td id="QUOTE">OK, but if at 7000rpm my engine requires 200CFM n/a, how much would it require at 8 psi? is it CFM*(pressure ratio) or something?</td></tr></table><span id='postcolor'>
I'm not sure what your question is asking, but I have re-ran the numbers and gotten MUCH better info.  Here goes:

V = 292 CFM @ 6900
n = (24.7*292*29)/(10.73*535) = 36.43 lbs/min
Va = 292*.85 = 248 CFM
intercooled n = (24.7*248*29)/(10.73*535) = 28.08 lbs/min
T-out = 535 + (535*(-1+1.68^0.263))/.72 = 643 R = 183 F
corrected flow for Turbonetics maps:
(28.08*(535/545)^0.5)/(14.7/13.949) = 26.4 lbs/min
P = 1.68 (10 psi guage)

So, with a P of 1.68 and flow of 26.4 lbs/min, I went to the chart for the T04B H-3 compressor.

Wow.

You'll be in the 74% range with that turbo at full throttle at redline with 10 psi.  Simply awesome.

Unless I'm totally missing something.

If you lower the PSI, that lowers the airflow and the outlet temp.

I reran the numbers for 8 psi.

n [corrected] = 25.57 lbs/min
P = 1.54

That still leaves you in the 74% range!!!

Wow.  I think there were some SERIOUS problems with the last formula.  This one is much better.

Eric

11-27-2002, 02:11 PM	#32
uiuc240 Nissanaholic! Join Date: Apr 2002 Location: Naperville, IL Age: 42 Posts: 2,093 Trader Rating: (0)	</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Kreator @ Nov. 26 2002,4:08)</td></tr><tr><td id="QUOTE">OK, but if at 7000rpm my engine requires 200CFM n/a, how much would it require at 8 psi? is it CFM(pressure ratio) or something?</td></tr></table><span id='postcolor'> I'm not sure what your question is asking, but I have re-ran the numbers and gotten MUCH better info.  Here goes: V = 292 CFM @ 6900 n = (24.729229)/(10.73535) = 36.43 lbs/min Va = 292.85 = 248 CFM intercooled n = (24.724829)/(10.73535) = 28.08 lbs/min T-out = 535 + (535(-1+1.68^0.263))/.72 = 643 R = 183 F corrected flow for Turbonetics maps: (28.08(535/545)^0.5)/(14.7/13.949) = 26.4 lbs/min P = 1.68 (10 psi guage) So, with a P of 1.68 and flow of 26.4 lbs/min, I went to the chart for the T04B H-3 compressor. Wow. You'll be in the 74% range with that turbo at full throttle at redline with 10 psi.  Simply awesome. Unless I'm totally missing something. If you lower the PSI, that lowers the airflow and the outlet temp. I reran the numbers for 8 psi. n [corrected] = 25.57 lbs/min P = 1.54 That still leaves you in the 74% range!!! Wow.  I think there were some SERIOUS problems with the last formula.  This one is much better. Eric __________________ 2002 Mazda Protege5 1989 S13 w/SR20DET (sold)