lunitic5454

iTrader: (1)

I have an LS1 based 408 stroker with an 88mm turbo. I'm looking for about 1200+ hp (crankshaft). The car will be primarily a street car, so drivability is important. I plan on using HP Tuners.

My tuner said that this hp level would not be a problem if I use E85 with 120 lbs/hr injectors, but I want to keep the convenience of 91 octane pump gas also. He said tuning E85 for drivability and idle wouldn't be a problem, but switching to pump gas and making it idle would be very difficult and didn't sound confident he could do it with a factory computer and the 120 lb injectors.

I want to stick with the factory intake manifold so I only can use 8 injectors (unless you have other ideas).

Do you guys think it is possible to tune 120 lb/hr injectors on 91 octane with a factory computer for good drivability?

Is there a certain year of factory computer that would be better?

If you agree with him, would a piggy back sysrem (i.e. mega squirt) used to control fueling work, or are 95 lb/hr injectors my best bet?

Thank you in advance.

P.S.
Does anyone know if HP Tuners is compatible with Flex Fuel? (In case I go that route)

fucter

iTrader: (5)

why would e85 make a difference in idle?

lunitic5454

iTrader: (1)

He said to make the horsepower levels I want that pump gas isn't an option, but if I use E85 because of the cooling effects it has in the combution camber I could run more boost and get to my goal. But you need to use more E85 than regular gas to make the same amount of power.

So... idleing with E85 the injector pulse width is say 5 milliseconds (for example), but switching to 91 octane, because of the increased energy per volume, the injector pulse width would be more like 2-3 milleseconds (again, for example). And he didn't think the factory computer was capable of supporting the injector pulse width necessary for idle using 120 lb injectors.

I hope I explained myself better and thanks again for your help.

5.7 ute

He means that the minimum pulsewidth of the 120lb injectors will still be too rich on pump gas. Whereas the extra fuel required running E85 will help alleviate this problem.

jrocstar

iTrader: (31)

exactly. it takes far too little fuel at idle for pump gas on 120 lb injectors. but it can all come down to the injector. research the brand you are buying and check minumum pulse width. I will be running 96's with higher pressure looking about at the same flow rate. but i am using a aeromotive fuel presure regulator that is progressive taht makes the fuel pressure lift at higher boost. it lets me flow less fuel at idle and normal street driving but get me that little extra bump when under boost. same engine/turbo setup as you. your biggest problem will be that you will have to reflash the pcm everythime you switch fuels since I do not know of any ls1 based vehicles that had any flex fuel tables. Besides for your power goals just go stand alone. Big stuff 3. it will be easier and less tempormental than the factory pcm. Hp tuners will get you there but it will be alot more work.

lunitic5454

iTrader: (1)

I did actually call about acceleronix about their 120 lb injectors and he said that he has personally fired the injectors for 1.5 milliseconds. But he was concerned that a factory computer might not be able to do it. Some people said that running 120 lbers shouldnt be a problem, but I would like to hear from somebody that has actually done it.

I did remember hearing one time that after a certain year the factory computer got faster processors in them, I dont know if that would allow to fire the injector faster or not. I have never used HP Tuners before.

I prefer not to use a BS3 if I not have to. HP Tuners is way cheaper. Even if I have to piggy back a Mega Squirt, that would still be way cheaper. But if I just cant do it with a factory set-up then I'll have to upgrade. I would just like to hear for sure from some one that has done it.

5.7 ute

Are these injectors low or high impedence. High impedence you will have no problems firing them with the standard pcm. Low impedence however will need a convertor to fire them.
FWIW the speed of the pcm has no bearing whatsoever on the minimum pw that the injector can be fired. It is an injector dynamic that sets this calibration.
You will have to do some major scaling of tables IMO to get this system to work on a stock pcm. I would ensure you understand the principles of this before you start or you will be running into all sorts of issues.

jrocstar

iTrader: (31)

I do not believe they have an high impndance 120 lb/hr injector. I could be wrong but I would guess that you are looking at low impendance so the factory computer is going to be out of the question regardless as you will need an injector driver. but the low pulse for idle required will still be a problem. you could always raise the revs.

Texas_WS6

iTrader: (9)

Do you have a 1:1 Boost reference fuel pressure regulator on it? If so you might be able to switch to a 1.5:1 or a 2:1 regulator and set the idle fuel pressure lower then you can with the 1:1, making the 120lbs injectors deliver less fuel at idle.

Just a thought.

lunitic5454

iTrader: (1)

I called another local dyno yesterday and he pretty much agreed with the first one I talked to. He said...... its possible to get 120lbers to idle with a factory computer, but barely. It would be on the ragged edge of both the injectors and the PCM. (btw, yes the 120's would require a driver box, but the factory PCM will still work). The injector pulse required to idle with 120's would be low enough that they wouldn't be linear anymore and the spray pattern wouldn't be consistent and regular. And..... the factory PCM doesn't really have the resolution to fire the injectors that quick anyway. All-in-all, he said it can be done, but it would have to idle in open loop cuz the 12:1 AFR is probably the best we can achieve. Along with all of that, when I switch to E85, the 120's would "barely" reach my HP goals.

He recommended getting the new 2200cc injectors from Injector Dynamics. Since thoughs injectors are a high impedance injector, they are way more linear at very low pulse widths and he could "very easily" make idle with these, and they are larger injectors (210 lbs/hr) so my HP goals would be easily attainable. Then for a computer, he sells an AEM unit for about $1100 that get me where I want to be. This would be a more expensive route, but maybe I should bite the bullet and save for it?

Any thoughts on this? and where do I find a 2:1 boost referenced fuel pressure regulator?

C5kid

iTrader: (12)

There is a guy on the corvetteforum, I will try to find is info on my lunch break, but I know he has 120lb's in his car.

It's a Maggie setup w/ a pretty stout fuel system & bottom end.

As soon as I find his name and stuff I will let you know, I am sure he can give you some advice.

Texas_WS6

iTrader: (9)

I am not sure if anyone makes a 1.5:1 or 2:1 boost referance fuel pressure regulator. Its just an idea, I think it would work because you could run the same boosted fuel pressure but a much lower fuel pressure at idle, making the large injectors small under vacuum, it should make it tuneable, of corse the entire VE table would have to be redone as well as a few other things. It would be cheaper too I would think. Call FIC or some of the other sponsors, they might know of a regulator out there that will do this. If you find one please post up and tell us about it. I will try and take some time today and see if I can find one too.