sbrown99ta

Is there a general rule of thumb for guessing how much horsepower you are making based on MAF readings? Thanks.

sunvet

The nominal fuel consumption is 0.5 lb per hour per HP (brake specific fuel consumption, bsfc). An estimate of the maximum power available from a set of injectors is to multiply an injector's rating in lb/hr by 8 (#of cylinders) and then divide by 0.5. For example, 24 lb/hr injectors should be good for 24*8/0.5 = 384 HP.

For max power, we want an AFR of something like 13.5:1. So that means we need 13.5*.5 = 6.75 lb/hr per HP. EFILive measures MAF in lb/min, so we want 6.75/60 = .1125 lb/min per HP.

So to get approximate HP, take the MAF reading in lb/min and divide by .1125. For example, MAF of 25 lb/min divided by .1125 = 222 HP.

-Jim
:auto:

gojo

I multiply MAF lbs/min by 10 and use that only to judge changes. It's not accurate, just somewhat directional..

V8_Club

Thanks for the info. :cheers:

'97 C5

(((MAF * 3600)/453.6)/known AFR)/BSFC

This simplified is

(7.9365 * MAF) / (AFR * BSFC)

On my 427 (506 RWHP) the peak MAF was 384 g/s. Using
a BSFC of 0.45 and the W/B AFR of 13.2:1...this formula yielded 513

(7.9365 * 384) / (13.2 * 0.45) = 513




[Modified by '97 C5, 9:22 PM 12/29/2003]

sbrown99ta

So, if I'm following this correctly, if we max out the MAF (454gms/sec) at 5200rpm, that means we should be making in the ballpark of 530rwhp at that RPM? Does that sound right?

sunvet

Based on '97 C5's calculations:

"On my 427 (506 RWHP) the peak MAF was 384 g/s. Using
a BSFC of 0.45 and the W/B AFR of 13.2:1...this formula yielded 513 "

If we convert 384 g/s to lb/min:
(384/453.6) * 60 = 50.8 lb/min

Multiplying by 10 gives 508 HP, which is pretty close to the formula's result of 513 HP.

So gojo is right on the mark.

:yesnod:

gojo

You can log Lb/Min with EFI which makes it easy to quickly see the results of tuning changes. I don't know about other scanners.

Bink

Hey Joe!

Great thread... I didn't know this ....do now. Thanks guys! :D
joel