CC89Formula

sorry if this one is beaten to death, but the search wouldnt work for me right now. ive got an L98 with the 22# injectors (i think???) i sent a rod out the oil pan, so now im planning on a 383 with an LT4 hot cam and 1.6rr. as for now the heads will be stock, no porting or anything done to them. i dont really have any idea how much power ill be making, but i figured someone might know.

also, is there a better choice for a cam in the 383 than the LT4 hotcam?

AtomicTruck

Here's a link for all the math regarding injectors.

http://www.rceng.com/technical.htm

GuitarJunki17

iTrader: (1)

So is it safe to say that stock 22's will not even let a 370hp motor run period?

AtomicTruck

That's not really correct either. They will make it run and run good up to the point that the engine needs more fuel than they can smoothly deliver. I've been told that injectors will even work at 100% duty cycle but only for very short periods of time. I don't really subscribe to that theory but it sounds reasonable.

Its like my wallet. It works good up until I'm broke, then there's nothing left.

3.8TransAM

Dont trust injectors at 100% or close to duty cycle.

Above the 80+ % mark most get unstable and the pintle action is uncontrolled resulting in both lean and rich conditions depending on the exact situation encountered.

A good rule of thumb is to figure an injector capable of supporting your combo at roughly 80% duty cycle to definitely give u a margin for error.

later
Jeremy

AtomicTruck

Absolutely right. 80% duty cycle is the number to use.

Here's a what not to do story about a guy I know... He thinks that more is better in all things. He always overestimates his capabilities (both car and personal). anyway... He went out and bought some huge injectors. I can't remember exaclty what they were but they were big. He thought that the mild cam he had installed (by a mechanic) was going to net 400 hp . So when he put the injectors in (himself) his car ran like $$$t. Go figure.

Too big is also not a good thing. The moral of the story is be honest with your hp calculations/estimates and use the math formulas.

HD4mula

OK, so would it be too bad to try to run a 330RWHP 350ci car with the stock 22 pounders?

Mkos1980

iTrader: (8)

I've hit 300 rwhp with stock ones before.

heat seeker

iTrader: (5)

I would recomend 24# on that engine, a little too much fuel is ok, but not enough fuel is terrible from a performance standpoint.

AtomicTruck

If you go to the link posted above then scroll to the bottom of the page there is a fill in the blank injector calculator. Play with the numbers to find some reasonable ranges and you'll get a good idea of what hp to expect from you injectors.

CC89Formula

ROFL, i like that, thanks for the link atomic!

HD4mula

Yeah. It gave me 30lbs based on the BSFC from my dyno data. But I don't think I need that big. My engine did 236hp/344tq to the wheels before. After adding AFR Eliminator 180s (milled to 10:1), fully ported plenum, AS&M runners, Ported Edelbrock base, 1.6 roler rockers and CC XFI 268 cam I think I can hit 300+ RWHP so I need to know now that the intake is still disassembled. I wasn't planning on that spending.

shaggy56

You can play around with fuel pressures to get more out of smaller injectors. It would be a good idea to get an adjustable fuel regulator to bump up the pressure. Im not sure whats the highest pressure you can run safely though. I have been able to get my regulator up to 60 psi but have never run it that high. I did it just to see if it could be done. Maybe someone here might know the highest you can run the pressure and whats a safe limit.

HD4mula

I have a FPR. I run it at 43psi (under load) in my 350. I can try to get the dought for some Ford or Bosh injectors but this project is way over budget. But if I need them now is the time. To get the fuel rail out I need to remove the valve covers so it is a big PITA if I have to go with this later.

AtomicTruck

I got injectors from http://www.fiveomotorsport.com The guy's name is Bruce.

The overbudget thing is tough but it is always better to do it right the first time rather than do it again later.

One more thought here. Math doesn't lie! If you do the calculations correctly, trust the math! That is why I like to play with the numbers a little bit... go with 80% duty cycle and 0.5 BSFC to get a conservative number, then go with 95% to find the limit. Some of it depends on how you plan on driving. If you'll only hit max rpm once in a blue moon then go with a touch small. I doubt this is the case though. We who have power like to use it.

Stevo

iTrader: (45)

thanks for the info guys