Alright, I've read various articles/posts, etc on injector size over the past few months. Now it's time to decide. The bosch III 22s I have now won't cut it.

At this point, I'm estimating the motor at 425 hp.

I don't want to go too big for idle quality. I'm using the car for 99% street driving. Critique these numbers:

http://www.fuelinjectorconnection.com/shop/docs/widercalc.html

425 hp x .45 bsfc
____________________ = 28.125 lb/hr at 43.5 psi

8 injectors x .85 duty cycle

I used a lower bsfc since it is a modified motor and should generally be more efficient. I used a slightly higher duty cycle since I'm not racing. Should be under a 5800 rpm motor (that's an educated guess with modified tpi set-up). If I need a little more I think the AFPR can account for that. So what do you think about 28 lb/hr injectors?

Matthew

If you will be running a long tube runner intake, 24-28 is plenty. Let the tuner make the call.

im running 32s
if i have 20% drivetrain loss im at 480crank hp
I didnt do all the math. Just bought before I knew anything.

my idle is at 600rpm and very driveable

like petek says talk to your tuner. They will have a better idea what to use

FWIW, TPIS says stock 350 injectors are good for 450+HP.


[quote]
383tpimachine wrote:
im running 32s
if i have 20% drivetrain loss im at 480crank hp
I didnt do all the math. Just bought before I knew anything.

Wow, those are '08-LS3 #'s.

OK -- I'll enter my 2 cents
Lloyd Elliot had me install 30# in my 350
He knew they were on the edge of being overkill but based on airflow and potential future changes to cam specs we went with the Ford SVO 30 pound injector. Bryan Herter also said they would be fine and programmed the tune for the 30# injectors. Your 383 should be well over 400RWHP if heads and cam are done at the same time. Choice is still yours as many people have gone either way. I also do not have an AFPR which I was told was ok for my setup.

RPM is a big factor. My superram makes dogshit for power after 5500 rpm's. Long tube runners combo's rarely go past 5000.

Quote:

what is your duty cycle at peak hp?

Quote:

No idea lol. It "peaks" at 5200rpm. where I set my redline.
It may be ls3 hp level but it isnt as light or have as much potential.

Matt, call FIC directly at the number posted on the website. You'll be able to make a better decision after a short conversation. I had to make a decision based on my local unavailibility of a tuner. I may have to upgrade my injectors later but basically I have what I had in there to start with. Let's just say I was surprised what injectors my 383 crate was built with.

PS To the guys at FIC. The first package never showed up at my end. Thanks for your quick reship and getting me back on the road quickly.

Mick (Mseven) recommended bosch II 30 lbs for my build. I'll trust his recommendation.

Matthew