BPC calculation

[Ronny]

I am coverting to port fuel (EBL) from TBI (EBL).

I need to calc the BPC for 24 lbs injectors ar 43.5 lbs fuel pressure. 5.7L.

I read the formula reads displacement of one cyl divided by injector flow rate in grams per second

Calc's out to .2356

something is wrong?

[RobertISaar]

could estimate based on what you were running compared to what you want to run.

what was your BPC and flowrate with your TBI injectors?

[Ronny]

Two 75 lbs injectors at 21 lbs fuel pressure with a BPC of 87 at 100 MAP/0 VAC TBI

[RobertISaar]

150 lb/hr vs 192 (150/192=0.78125), i would say that taking the BPC down to 78.125% of its value of 87 would get you around where you need to be. so, a BPC of 68.

[Ronny]

Thank you. Makes sense. I was uncertain if BPC is same for TBI vs port fuel. Meaning the pressure differential at injector with the TBI injector out of the air stream and not seeing VAC.


OOPS. I see your post assuming 150 lbs for 75 lbs injs. Not so as TBI injs rated at 12 lbs I am at 21 lbs FP so my lbs are 95.3 x 2 injs or 190.6. 192 / 190.6 = 1.007 about the same on BPC of 87. Right?

[RobertISaar]

yeah, that isn't enough of a change in flow for me to recommend a change in BPC.

[Fast355]

Thank you. Makes sense. I was uncertain if BPC is same for TBI vs port fuel. Meaning the pressure differential at injector with the TBI injector out of the air stream and not seeing VAC.

OOPS. I see your post assuming 150 lbs for 75 lbs injs. Not so as TBI injs rated at 12 lbs I am at 21 lbs FP so my lbs are 95.3 x 2 injs or 190.6. 192 / 190.6 = 1.007 about the same on BPC of 87. Right?

Thats really all Edelbrock did with the TBI to MPFI conversion setups, plus a little VE and timing table tweaks. The vacuum referenced fuel pressure regulator will keep the pressure drop across the injectors constant and therefore the injectors will stay pretty linear as the intake vacuum changes.