I am building a 396 and trying to find what size injector is the best suited for my application. The rwhp will be around 400, the car is NA, and the car is a 6 speed. I was thinking of going with the 36lbs injectors but I am not sure if that is big enough. I see racetronix has a sale on the 42lbs injectors. Is it possible to have to big of an injector? Would an adjustable fuel pressure regulator help? and do you need to upgrade your fuel pump when you get bigger injectors?

Thank you,
Aaron

 

i would run a 37lb lucas/dephi from racetronix. the disc injectors pulse down nicely. i would get both a fuel pump and an AFPR.

 

why is your hp so low? what kind of heads/ cam are you running? also what size of fuel pump are you going to get? i know i'm running to small of injectors w/ my set up. i'm only running 36's w/ a 255 holly intank pump...42's will be in before the summer begins though.

 

I think you are underestimating your HP.Unless you went real small on heads and cam.
You can make 480FWHP with 36lb inj@39psi with an 83.3 duty cycle.If you have enough pump and a adj.FPR you can up the pressure and get more.

 

I am working with Lloyd right now on my head and cam set-up. I am going to use LT1 heads and a custom cam. I am going to have all the goodies like Jet Hot LT headers, dual exhaust, 58mm T.B., CAI, delete AIR and EGR, dyno tune, ect. I am using 400rwhp as a nice round number if I get more then that that would be awesome, but for right now that is my goal.

1racerdude
480FWHP is only 408RWHP with a 15% drivetrain loss, so either way I will be close.

fstenuf
I was thinking the Walbro 255 or the racetronix kit.
What do you guys think of that kit? http://www.racetronix.com/Racetronix..._Pump_Kit.html

Thanks again guys for your replies,
Aaron

 

I knew a guy with a 6spd 383 back in 1998 that had ported lt1 heads, 306 cam, and slp shortie headers through a flowmaster muffler (stock i-pipe) that made 400rwhp on stock injectors/fuel pump. It did 120 in the 1/4 on a cold day.

If you are trying at all you should do better than that.

 

42 42 42 42 42 42 42 42 42 hey i was thinkin that the 42's would be a great idea! aeromotive afpr should be a consideration along with a 255lph pump,i would also modify your fuel rail to support the volume you will be needing,the factory fuel system is not for the use we are lookin for,beyond 400hp the factory fuel system is waaaay inadequate!

 

w/ the stock lt1 intake (ported of course) its going to be limited to about 440rwhp. it is possible to over inject one. 42s, jesus, thats enough injector for 550rwhp on a blower/turbo car with a BSFC of .6. the 37s will be big. the last 396 we built made 440 w/ a 240@.050 lift solid roller, a ported stock intake, 12.5:1 compression on a svo 30lb injector w/ a a/f of 12.8:1. and a disc style injector (dephi) atomizes fuel better then a pintle style (bosch) which will let the Brake Specific Fuel Consumption be lower for a give amount of hp. so that means w/ the dephi injectors you can get away with a smaller injector then the svo inj. for a given amount of power.

 

I ran 30's for a few years but just went to 36's by bosch and racetronix 225 and afpr. After reading 93turbo's comments on delphi being a better injector using a disc style vs a pintle style I'll be upgrading again shortly.

 

The Bosch EV-14 (36# 3-bar) is an excellent injector and more than enough to support your power goals.

 

I ran 30#'s with a Hot Cam, ran fine, no need for anything bigger. This was with 38PSI fuel pressure and 12.4/to 1 A/F ratio. Bigger is not always better, and I ran 400rwhp and 428 ft/lbs torque. Now with my 230/236 cam they are fine. anything higher and you are wasteing yuor money. My 2 cents worth.
Injectors are like the bigger the better cam theory, wrong most of the time.
Look what MorePerformance uses on there 396 making the kinda power you want. They , as well as other motor builders have extensive R&D. They use Cranes Cam which is a 847 GM cam (in there larger cam combo), with 30# injectors, CNC LT4 or LT1 heads, long tubes etc and make 535 HP.

 

Im running 42# Motorsport injectors, Racetronix 255 intank with hardwire kit, and an Aeromotive AFPR. No fuel problems here.



Nick

 

what rwhp you pushin? thanks!

 

I will have to let you know in another month or two. I need to get my 4.11's installed, then off for a chassis dyno session with Bryan from PCMFORLESS. Im guessing around 450 RWHP, give or take a few. The motor made 511 FWHP, 496 FWTQ on an engine dyno with the GM dual plane carb intake for LT1/4's, 750 HP carb and MSD billet distributor with 36* total advance. I will post results in the future



Nick

 

With 36#'rs@39lbs FP you can make 480FWHP at a 83.3 duty cycle with a BSFC of .50.If you have an adj pressure regulator and enough pump you can get more. Just remember the smaller the injector the more pump you need to jack up the pressure to get it to flow at your HP level.The bigger the injector the less pressure and pump required to get to your HP level at a 85% duty cycle. Don't believe all this about spray pattern,we ain't going for a fuel efficiency race.As long as the fuel is introduced into the air stream through the nozzle it is fine and will be well mixed at the cyl.If you took that approach a carb would not even run. It would be like dumping a coke bottle full of fuel down each port.
There may be,but I have seen no dyno evidence of power increase from running a small injector and jacking up the pressure for proper amount of fuel delivery and any increase being attributed to atomization.
ALL the formula's can't be wrong.