So i sat down tonite and wrote out my calculations from corbin's page and i want to review it here to make sure i didnt go off on a wrong tangent.

I have set a high expectation of running 300hp out of my turbo setup. With this in mind, I chose a BSFC of .65 and a duty cycle of no more than 80%


Step 1:
How much fuel needed for each injectors:

(300hp x 0.65 x 10.5)/4 = 511.9cc/min

Step 2:
Injector sizes:

511.9/0.80 = 639.8cc/min injectors @ 43.5psi (wow!)

Step 3:
If i was going to use 440cc/min injectors, what WOT fuel pressure will I have to run to match a 511.9cc/min injectors @ 43.5 while doing 10psi of boost?

x = ((639.8/440)^2 x 43.5psi) + 10psi
x = (2.1 x 43.5psi) + 10psi
x = 91.35 + 10
x = 101.35 psi

Step 4:
How much fuel will i need from the fuel pump to match the injector flowrate?

y = 639.8 x 4 x 0.015873
y = 40.6GPH @ 101.35psi WOT fuel pressure(with 440cc/min injectors)


Step 5:
What FPR ratio will i need:

(101.35 - 43.5)/10 = 5.8

So I will need a 6:1 FPR ratio.


Does this seem right????
I'm erroring at the side of caution so my calculations will end up being richer than needed for 10psi of boost but I plan on going higher than 10psi.

Thanks for the help and thanks for the great webpage corbin. BTW i will be using a safc to tune all this extra fuel too.

Vinnie
HRC stage 2 + internal mods

Looks right..

But for those sizes and pressures I'd buy an Acell DFI.

My calculations came out slightly differently. I talked to Corbin about the BSFC, b/c as you noticed he used .525 even when figuring out his turbo numbers. This came from when he talked to RC and they told him with our engines, .525 would be safe to use even turbo'd.
Another problem you're going to hit is that I don't think you'll hit 300hp w/ only 10psi. I calculated mine for 300 hp as well, but at either 13-14psi. I don't have my work here in front of me, but I know that I was going to lower the idle FP and get a 3:1 disk (running 440's as well) and that the walbro fuel pump was adequate.
If you want to see my numbers, post back. I have them at work and I can email them to you or post them here on Wednesday.

Matt
Star Stage III

>Step 1:
>How much fuel needed for each injectors:
>
>(300hp x 0.65 x 10.5)/4 = 511.9cc/min

300 is a bit much for only 10 psi (I think). How about 290 hp. And I believe that you can use the 0.525 number. That gives 400 cc/min of fuel per injector.

>
>Step 2:
>Injector sizes:
>
>511.9/0.80 = 639.8cc/min injectors @ 43.5psi (wow!)

With my assumptions, I'm at 500 cc/min.

>
>Step 3:
>If i was going to use 440cc/min injectors, what WOT fuel
>pressure will I have to run to match a 511.9cc/min injectors
>@ 43.5 while doing 10psi of boost?
>
>x = ((639.8/440)^2 x 43.5psi) + 10psi
>x = (2.1 x 43.5psi) + 10psi
>x = 91.35 + 10
>x = 101.35 psi

With my assumptions, I'm at only 66 psi fuel pressure.

>Step 5:
>What FPR ratio will i need:
>
>(101.35 - 43.5)/10 = 5.8
>
>So I will need a 6:1 FPR ratio.

You might try a lower fuel pressure. My static (0 boost) fuel pressure with my 440's was 32 psi. I had to trim -40% with the S-AFC to zero out my long term fuel trim (datalogger). With a higher fuel pressure, you will be near the S-AFC limits of -50% (or you could live with high long term fuel trims).

>
>
>Does this seem right????
>I'm erroring at the side of caution so my calculations will
>end up being richer than needed for 10psi of boost but I
>plan on going higher than 10psi.

The calculations err on the side of caution anyway, probably don't need to add much on your own. If you want to go higher than 10 psi, you may need a real fuel manager as per Dino's suggestion. Or you could follow my lead with the extra injectors (IF it works).

Corbin

'95 ESI-T
HRC+FMIC+ETC...

Hey thanks guys for the input. DarkOne, can you please post up your calculations when you can, that will help.

Yeah, i wasnt sure if your (corbin's) calculations were already err'in at the side of caution or not.

Thanks again for the easy-to-use formula.