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11-19-2012, 09:56 PM | #1 |
Scooby Newbie
Member#: 260994
Join Date: Oct 2010
Location: Powers, Oregon
Vehicle:2005 WRX modified Black |
AFR math problem
Hey guys,
I have been struggling with an AFR calculation. I want to know how many CFM it takes to match up with 650 cc injectors. The RC Fuel Injection web site calculator for 350chp shows 66 lbs /hr or 1.1 lb/minute which is slightly over the 80% IDC for the 650cc injectors. Based on a 11.5 AFR it would seem like 1.1 fuel x 11.5 AFR = 12.65 lbs air. My info shows 1 lb air = to approx 13 cubic feet. So 12.65 x 13 = 164.45 CFM. That CFM seems way too low based on the FAQ turbo list. What am I missing ??? Thanks in advance for your help. Richard
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11-19-2012, 10:03 PM | #2 |
Scooby Specialist
Member#: 181298
Join Date: May 2008
Chapter/Region:
MAIC
Location: MAIC
Vehicle:2019 KUV 21 Crystal White |
350C with what kinda fuel, and turbo
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11-19-2012, 10:10 PM | #3 |
Scooby Specialist
Member#: 234407
Join Date: Jan 2010
Chapter/Region:
MAIC
Location: Smithfield, VA
Vehicle:04 Self-tooned STi |
To simplify this 650's will get you over 300whp and be able to keep up with any turbo that flows under 47lbs/min. I'm on the safe side as most don't like taking injectors past 85% even know in at 94%idc haha
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11-19-2012, 10:20 PM | #4 |
Scooby Specialist
Member#: 206851
Join Date: Mar 2009
Chapter/Region:
MWSOC
Vehicle:56 Belair Pro Street |
pretty much this, you should tell us your turbo and if you have any other VE mods like ewg, op.
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11-19-2012, 11:33 PM | #5 |
Scooby Newbie
Member#: 260994
Join Date: Oct 2010
Location: Powers, Oregon
Vehicle:2005 WRX modified Black |
Thanks for the input. The reason I am trying to calculate the air required is to size a turbo to match the injectors. Right now all I have is a stock '05 WRX. Going by the turbo list they are all flowing way more CFM than the number I came up with. Just trying to work out the numbers before buying parts. As far as fuel, the RC site doesn't give any options other than the Brake Specific Fuel consumption rate
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11-20-2012, 05:47 AM | #6 |
Scooby Newbie
Member#: 242246
Join Date: Mar 2010
Chapter/Region:
RMIC
Location: Montana + Indiana
Vehicle:2002 Impreza WRX WRB |
Correct me if I'm wrong, but isn't the CFM you calculated for only one injector, and therefore only one cylinder? Shouldn't the CFM based on the equations you used actually total 164.45 x 4 = 657.8?
Just checked: 650 CFM is almost 47 lb/min at STP. ppayer38 definitely had the right answer from the get-go |
11-20-2012, 09:55 AM | #7 |
Scooby Newbie
Member#: 260994
Join Date: Oct 2010
Location: Powers, Oregon
Vehicle:2005 WRX modified Black |
Bingo, Viral E, that's the answer I was looking for. Actually you were all correct. I just couldn't figure why the math was wrong. Thanks for your help.
Richard |
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