I was wondering what size injectors i need for my car i am running 24lb lt1 injectors right now and it seems to surge cruising at low rpms and even holding it at higher rpm's im not sure if this is my problem but i think 24's are too small anyways. i am estimating about 400hp to the motor. anyone have something maybe i could calculate it myself or let me know what i need i can get some 28's or 36's right now. thanks guys!

 

Here is the formula for calculating injector size in pounds per hour:

Injector lbs./hr. = horsepower x BFSC/number of cylinders


BFSC is short for Brake Specific Fuel Consumption, which is the amount of fuel required to produce one horsepower. According to Accel, a BFSC of .45 is a good general figure for normally aspirated engines, and .55 is good for supercharged engines.

/N.

 

let me get this straight......
400hp x .45= 180 divided by 8=22.5lbs per hr.?

 

yes...this it with 100% Duty cycle........most people calculate with 80% duty cycle.. so

400hp x .45= 180 divided by 8=22.5lbs per hr. /0.80= 28.125lbs

/N.

 

ok gotcha, i have the option of getting some 28's so i think ill jump on that. thanks for the help.

 

Ford SVO#30 are nice ones ....and not to expensive.....

 

well he has 28's and 30's the 30's are used and untested off e-bay(he bought them off ebay and now has them) and he has new 28's. same price($110) but should i worry about them not being tested?

 

You say you're getting a surge at low load/low RPM. Surging would be a lean condition, and at low load/low RPM, you're not maxing out the flow rate of the injectors. If the capacity of your injectors was a problem, you'd see it at high load/high RPM.

I think you have a tuning problem. Or dirty injectors.

FWIW, I have 30 lb/hr Ford injectors in my 406. But until you get the low RPM surging fixed (re-tuned), I think changing the injectors isn't going to help. Just my $.02

-Dave

 

i was thinking the same thing but maybe im running my FP too high and its making it run odd..... i have to check it out i dont even remember what i set it at.