Probably a fuel forum topic but this is a boosted car. What fuel injectors do I need? I just pulled a 124% DC with 72# low Z injectors rated at @ 3 bar. What size are some of you higher boosted guys running? Im thinking maybe 96#, but Im kinda at a loss. I guess I could up the fuel pressure, and retune, but how much fuel pressure is too much? help.....

 

Personally I don't think I'd go over 4bar, the higher the pressure the harder everything has to work (pump, injectors, regulator diapragm? and such). If you went from 3 bar to 4 bar you'd still be high on the duty cycle @ 107%.

96# @3bar injectors would drop the duty cycle to 93%, running at 4bar would drop your duty cycle to 80.5%, so you might even want to go bigger than 96.

 

Yikes, bigger then 96#ers, huh? I want to keep the setup at 3 bar, due to the boost referenced fuel regulator. Ill have to see what else is out there, as I thought 96 was about as big as you could go.

 

I'm sure low Z injectors come much larger.

 

what kind of power are you making to need that big of an injector ? 72s should be good to over 800 hp.

 

could you describe your fuel system? have you made sure your fuel pressure isnt falling?

 

I don't know on the power, 383 LT4 with 22-25# boost from a YSi Vortech, probably 900+RWHP
Speed Inc fuel cell, A1000 pump, -10AN supply, -6AN return, Versafueler, and modified rails. Not sure on the fuel pressure falling, but I'm showing about 3% rich (11.4 targeted AFR) @ 6400 RPMs @255kPa, with a 124% injector duty cycle. I need to get a gauge in the car, but I doubt it is falling, the A1000 should be good to 1500 HP. Do you see any flaws in the fuel system?

 

Now you do realize that you can't actually run a duty cycle of 124%.

That may be an estimate of what the computer thinks you need, but you can't actually run it.

The period(time) of the injector cycle is every two revolutions of the crank. This time changes with rpm, but for an example at 3000 rpm that's 40mSec. When you run 80% duty cycle the injector is on for 32mSec and off for 8mSec, then the cycle repeats on for 32mSec off for 8mSec. So if you are at 100% duty cycle the injector is just on all the time. There is no way to have the injector on for more than 100% of the time, just as there is no way of putting 6 gallons of water into a 5 gallon bucket.

 

What if it's frozen?

 

Why don't you get a methanol kit to help take the load off the injectors. I'm running 60's with my F1A and squirting a ton of 100% methanol at full boost. BTW doesn't water get bigger when it freezes? LOL

 

That is some good info right there, I had never looked at it that way.

I have a twin nozzle Alky control on it now, turned up pretty good. I was still showing the 124% with it activated. May be the reason it didn't go lean?? How much boost with your F1A???

 

15 psi with pretty well ported LT1 heads on a 355.

 

lol Stack the ice!

I would Never use methanol to help make up for a poor fueling system, especially on a high power engine!
I would just get appropriately sized injectors.