FAST XFI fuel injectors

[J-440]

I have a 440 naturally aspirated motor that was built for a supercharger in the future but want to drive the car right now. I have a 2000cfm throttle body and 83lb. injectors pushing 8.5:1 compression. Obviously this is overkill for a non-blown motor but I want to drive the car as is on 89 octane. I had an EFI expert troubleshoot my car, and he explained that if I were to run the car as is, I would lock up the motor because of excessive fuel wash. Now, with the FAST ecm could'nt I just play with the pulse width/timing of the injectors and run the car with no harm or do I need smaller injectors? Thanks for the help.

[David Pozzi]

I moved this thread to the fuel injection section for you.
I'm no EFI expert but there is a limit to how short you can go on injector pulse width. I would ask about how low you could go on your fuel pressure setting to reduce flow and get the pulse width in a better zone. Using a vacuum referenced fuel pressure regulator would help for example because it would lower pressure at idle, but setting your base pressure lower would help too.
David

[J-440]

Dave, talked to a FAST tech guy and because of the size of the injectors, there is no way the pulse width will go low enough. I'm new at all this and am still learning. I've been working on this car for 12 years and am not about to screw up anything internally. Thanks for the input bro. Keep the advice coming.

[Mike Norris]

I posted this on the other board also and figured I would post up here.

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.

If you like you can send me the program you have and I look it over.

Mike Norris

[J-440]

Mike, I have the boost referenced fuel pressure regulator from Aeromotive and have it set around 45psi. Also, are those LS engines supercharged with those big injectors? As far as sending you the program, I would not no where to begin on that. I did not realize I could send you my data from the ECM to your computer.

[Mike Norris]

Yes, the LS engines were all FI setups and the largest injectors I use on an NA setup on gasoline is 42lb's.

And yes again, we can send programs and data log files back and forth via e-mail.

Do you have a base program someone made for you, or are you starting from scratch? There are a few base start up programs that come with the software and I have one for a 440ci NA package with 65lb injectors and then there is another for a 347ci SC package with 83lb injectors. These two should be able to be modified to get you running.

Of course all of this will depend on if you have all of the basics correct as far as fuel pressure (which you mentioned as 45 PSI which is the norm) and distributor setup and phasing. And throw proper electrical connections, both powers and very good grounds. We usually run several redundant grounds.

So if you have a base file someone built for you, you can just send me an e-mail with it attached. My e-mail address is [email protected]

You could also check with FAST to see if there is anyone in your area they would recommend you to go to for tuning.

Let me know.

Mike Norris

[J-440]

Yes I am using the basic FAST file for the 440 that's pre-programmed. As far as grounds are concerned and the distributor phasing, everything is set. I've even gotten the dash sensor screen all set up with the right parameters. It's basically ready to start except for this whole fuel wash situation. Which "screen" on the FAST setup do you need and I'll see if I can send it to you this weekend. Thanks for your time Mike.

[Mike Norris]

If you have that base file, you can change the injector size and the MAP sensor setting (1,2 or 3bar) and if all is good it should at least start.

I went ahead and built a base program using a 2bar MAP setting that should be close. If it is a 3bar MAP I would have to redo a lot.

Mike

[J-440]

Not to worry, it is a 2 bar. And my tech guy said that I couldn't "lie" to the ECM by telling it that I had smaller injectors when I don't. Heck that's what I was thinking when I went and bought the 83lbers in the first place.

[J-440]

Hey Mike, I found that screen where you enter the correct size injector. I'm assuming I need a pulse width adjustment screen where I can enter settings to control the 83lb injectors? Thanks again for your time.