I have an LT1 bored and stroked. Aka 383 stroker. Stock injectors are finally giving way, as well as the o-rings for them. The car is off the road until Spring '07 when I hope to have some cash for a new rear. In the meantime, what is an ideal lb injector and or brand to go with. Just a general idea is what im looking for. I have a fueal pres. reg. and walbro fuel pump already....so..........

thanks - Gio

 

definitley need more info....heads, cam, intake ect.

 

Hopefully he's not running stock top end, that would be a huge problem and the injector size wouldn't be much different. Would need only a tune then. If the case is that the heads/cam/intake aren't stock, go with atleast 36# injectors. Going with 50# in my 388.

 

I am using 42lber's for my 383 with ported lt1 castings and 236/242 cam. Theyre a little on the big side I think, but they work fine.

 

thanks for the input.....i dont recall the cam specs off hand....although it has the lt1 heads ported and polished......motor bored ..030 over ...eagle crank..hydraulic hi lift lifters.....hmm....i dropped the oil pan on it to check stuff out - i dont recall the manufac. of the pistons and rods....none-the-less - i can rev out to 6700 rpm via the limiter and 7000 rpm 'shouldnt be a problem'.....anyways,

 

The formula for calculating the injector size is

hp=(flow rate*#of injectors*duty cycle)/bsfc

bsfc runs between .55 and .45, with the lower number being for forced induction. You generally don't want to run more than 90% duty cycle for race applications, but for street 100% is ok.

 

you may have to translate that into english - and if your talking about on and off time of the fuel injector when you refer to duty cycle.....how could you have 90% duty cycle - that would mean the injector is grounded or open 90% of thetime.....the pintle is gonna be either closes or open almost all the time.....way rish or way lean - so you gotta explain that one then

 

Tell me how much HP ya figure on making and I will figure it for ya on my program.

 

You are right. Duty cycle is the amount of time that the injector is open or delivering fuel. Let's say that your motor requires 30lbs of fuel to be delivered to each cylinder at max power and rpm. If your injectors flow 30lbs each, then they will operate at 100% duty cycle. If you swap to 36lb injectors, they will operate at about an 80% duty cycle. This is preferred because at 100% duty cycle, the injector could become overheated and operation will become erratic and this could lead to a lean condition and possibly engine failure. You would not want to run this in a race engine.

 

With 45# fuel pressure and a .50BSFC
36# injectors-550FWHP- with a 89.5 duty cycle
42# injectors-650FWHP-with a 90.6 duty cycle

Choose your weapon.

 

No... you use the HIGHER number for forced induction and nitrous.

I wouldn't recommend running 100% DC for the street. Good way to run lean.

To get in the ballpark on a naturally aspirated motor, assuming a good (efficient) tune, and no more than 85% DC, multiply flywheelHP time 0.07

example: 450 flywheelHP x 0.07 = 31.5#/HR

If you plan to do future mods, add 10-20% to the injector size.