I am almost finished my supercharger install, so that means another month

Anyway, I know the stock injectors will work but it should be pushing their limits with 9lbs of boost. I don't want the fuel psi to be sky high so I figured injectors were the way to go.

The motor is stock with bolt ons(about 300-310rwhp). I do plan on some heads and cam later but for now it will just be stock with the charger. I have Tunercat so tuning isn't that hard.

Should I go with bigger than needed injectors so I won't have to buy them later, or get just what I need for now?

 

If it were mine, I would use 42's and no FMU.

 

Ditto.

 

SVO 42# injectors are good. Set the injector constant to 45 to start with ... go from there.

Watch out for cold start issues, some have it, some don't. I did/still do .... I leaned out the cold part of the Temp vs A/F ratio table a point or so and that helped quite a bit.

Hope this helps

LWM

 

Why is the fmu not a good idea? Tuning?

At the stock fuel reg setting, using 42lb injectors, what is about the highest hp attainable using the motor that I described? With a liveable duty cycle of course.

A question off topic a bit. About how much hp can the stock fuel lines support?

Thank you guys for the help. I cannot wait to join the boosted crowd.

 

I'm not sure how much the 42 # injectors can support. Probably around 500 RWHP, maybe a little more. The stock fuel lines should be good to say 600 to 650 rwhp. You'll probably need to open up the rails before you need to replace the fuel lines.

 

Your motor will not be stock for long as with 9psi it will self destruct in short order. In the meantime, I do not share the disdain in which most people hold the FMU. After all, the stock FP regulator IS an FMU with a 1:1 ratio and it works fine. The critical point is to be sure the AF ratio is right, so whatever route you choose you need access to a wideband AF ratio meter to verify the tune. But as I said, since you will be rebuilding it soon anyway maybe tuning will be a waste of time!

PS: sorry for the sarcasm, but you really should think carefully about 9psi on a stock shortblock.

Rich Krause

 

I just want a DFI system to let the computer handle all of the fuel and spark requirements for the motor based on boost. Anyone wanna donate to the "Get Chris a DFI Fund"? Just send a dollar to my paypal account. ChrisGainey@bellsouth.net

 

I was just using the info supplied in the instruction manual. It just said never exceed 9 psi on a stock LT1. I figured 9 was ok. If the tune is right, with no spark knock, why would 9 be detrimental? What is the first thing that goes?

I guess I will be using the bigger pulley then which isn't much less than 9 if I remember correctly. It is 3.16" in diameter, not sure what that is.
If 42 will only be good to about 500, should I go a little more on the lb/hr? I will be making over that in the future, just not for a while. Are the 42s still the way to go?

Sorry for all the questions guys. Just trying to do it right.

 

I think the biggest injector you can get that works with the stock computer is a 50 or 55. Can't remember which exactly. If you still want a bigger injector, you need an impedence conversion box which will allow you to run low impedence injectors without fudging the stock computer. Those should go up to 160#/hr injectors which you'll probably never need. I think you'll be fine with a set of 42# injectors for a while. You can always reinstall the FMU from the kit to up the pressure for a little extra juice if needed.

Usually the first thing on the stock bottom end to grenade is the ring lands on the pistons. Cast pistons and boost don't mix well. Usually when people start getting above 450 rwhp on the stock short block is when something tends to fly apart. Is the kit intercooled/aftercooled?

 

I believe Motron just came out with a high impedance 60lb injectors. If not I know that Siemans offers a 57 lb injector.

 

Is the kit intercooled/aftercooled? [/B][/QUOTE]

It's the P600b with the intercooler. I placed it to a front mount. I was thinking about adding a small shot of N20 to help with cooling too.

 

Skip the N2O and install a water/methanol injector. Less stress on the motor.

 

Yes, the stock regulator is 1:1, but it isn't essentially adding any fuel under boost or subtracting it under vacuum, it is merely compensating for the positive or negative pressure inside the intake manifold.

For example, with the stock 1:1 regulator and 2.0 ms inj pw the exact same amount of fuel will be delivered be it zero vacuum and 43psi fuel pressure or 15psi of boost and 58psi fuel pressure. Therefore changes to the PE table are accurate and repeatable.

The FMU, (rising rate regulator), while adding a set ratio of fuel pressure vs boost pressure, doesn't really follow the fuel requirements of the engine. Most cars I see on the dyno with an FMU have less than desirable fuel curves. And yes, you can chang the FMU ratios, and play with bleed valves, etc, but IMO it's inaccurate and unreliable at best.

 

I have lots of dyno graphs of cars tuned with FMU's and nice flat AF ratios. Does take some time but it certainly can be done and I think it's a very viable solution for a relatively mild setup. No matter what though, 9psi on a stock shortblock =

Rich Krause