FAST injectors...pulse width?

[J-440]

It's kind of like sticking a 950cfm double pumper on a 350sbc. No matter what size jets you change to, it's still overkill for the motor right? I thought the same thing but hey...it's 2012 and I have full control over the motor via laptop and I can program the injectors to do what I want. At least that's what I thought.

[ErikLS2]

Just thinking out loud here but would it be possible to regulate the fuel pressure down and leave the pulse width a little longer until the blower is on there?

[J-440]

Any idea on what the pressure should be? Kind of important on startup being a new motor and all. Considering all of the negative feedback I've been getting from the tech guys.

[Mike Norris]

If the 83lb injectors will be right with the blower on it, then it will still have to idle and low speed cruise with them. Yes, they are way to big for it as an NA setup, but they still need to be dialed in and can be for sure.

What I would do is have the fuel pressure set lower (40-ish) and use a boost only referenced fuel pressure regulator to gain pressure as boost climbs.

We run 80-100lb injectors on quite a few cars these days on FI LS engines and they drive and idle quite well. All in the proper injector data, proper fuel pressure and proper tune.

Mike Norris

[supremeefi]

Originally Posted by camcojb

at idle I don't see how the EFI or engine even knows there is a blower. There would be some extra pressure in front of the throttle body, but the engine wouldn't see that; in other words, it would act just like N/A. I'm amazed my 95's idled perfectly with bank to bank......................

Let's not forget cam specs, typically a blower cam has a wider lobe sep resulting in better idle quality anyway.

Yes you can reduce the pressure when off boost then increase it as boost increases with the suitable regulator.

83's on an 800hp 440 shouldn't be a problem. Sounds like a tuning issue as well. I've run 120's on a 383 Chevy making 1200hp with twin turbos, no issues when tuned right.

[INTMD8]

Originally Posted by Mike Norris

If the 83lb injectors will be right with the blower on it, then it will still have to idle and low speed cruise with them.

Exactly, the thing isn't going to have boost at idle once you install the blower.

If they will idle/cruise correctly with the supercharger than they will do so without the supercharger. It won't be a problem.

[J-440]

Ok, so the injectors will be fine at idle and maybe at a light cruise. I'm assuming the engine will bog down because of too much fuel no matter how much the pulse width is adjusted. That's fine with me because I really want to hear this baby fire. Was only concerned about the excessive fuel wash during break-in.

[camcojb]

Originally Posted by J-440

Ok, so the injectors will be fine at idle and maybe at a light cruise. I'm assuming the engine will bog down because of too much fuel no matter how much the pulse width is adjusted. That's fine with me because I really want to hear this baby fire. Was only concerned about the excessive fuel wash during break-in.

With the correct tuning it'll be fine at all rpm's.