Fuel pump and Injector calculations

[dsm_gsx97]

After writing this all out in another thread (9SR dyno day thread) I thought it would be useful for everyone so they can judge what size of injectors and pump they'd need for the amount of HP they want to put out.

Values I'm using in these calculations are a 20% safty margin (part of the math) and that the BSFC of our cars is .65. I did 700hp (for Shawn) as the example for this calculation.

The equations to determine your fuel requirement is as follows:
? (Power x BSFC) x (1 + Safety Margin) = pounds/hour
? Pounds/hour / 7.25 = gallons/hour.
? 3.785l/gallon (only for fuel pump numbers since they're in liters)

Then...
? ((Power x BSFC) x (1 + Safety Margin))/Number of Injectors = pounds/hour
? cc/min = lbs/hr x 9.71

So...with 20% safty margin for injector duty and fuel pump

(700hp x BSFC = .65) x 1.20 = 546 lbs./hr.
546 lbs./hr. / 7.25 = 75.31 gallons/hour

75.31 gallons x 3.785 liters = 285.05 liters/hour (only needed for fuel pump flow numbers)

So...for injector size
546 lbs./hr. (copied from above) / 4 = 136.5 lbs/hr

cc/min = 136.5 x 9.71 = 1325.42 cc/min

[dsm_gsx97]

For 500hp...

(500hp x BSFC = .65) x 1.20 = 390 lbs./hr.
390 lbs./hr. / 7.25 = 53.79 gallons/hour
53.79 gallons x 3.785 liters = 203.60 liters/hour
390 lbs./hr. / 4 = 97.5 lbs/hr
cc/min = 97.5 x 9.71 = 946.73 cc/min

So a pump that flows 204 liters/hour and injectors that are at least 947cc (will keep injector duties under 80%)

[dsm_gsx97]

For 400hp...

(400hp x BSFC = .65) x 1.20 = 312 lbs./hr.
312 lbs./hr. / 7.25 = 43.03 gallons/hour
43.03 gallons x 3.785 liters = 162.87 liters/hour
312 lbs./hr. / 4 = 78 lbs/hr
cc/min = 78 x 9.71 = 757.38 cc/min

So a pump that flows 163 liters/hour and injectors that are at least 758cc (will keep injector duties under 80%)

[Carl Morris]

In all of this, keep in mind that if you have any interest in running E85 at some point (and I think many of you will), the BSFC number needs to be significantly bigger. My 660s are fine to support my E3-16g on gasoline, but I wish I had at least 850s to run straight E85. If I had a big turbo (that 3065 is sure looking good after the dyno day :-)), I'd want huge injectors and a pump/lines to match. If E85 is more than just a fad, and is available forever, I can see 1600+ injectors getting very popular. 660s will be what people drop into stock setups to they can run E85 with no ECU changes :-).

[rlarsen]

~0.75-0.8 BSFC for pure E85 on a turbo motor. Stoich for pure E85 is 9.7-9.8:1. Chris's previous 0.65 was a little conservative, too. Our engines are closer to 0.55-0.6.

BSFC is a tricky number to work with, and to determine properly.