I'm singin' the over-injected blues!

[mysweetlx]

Hey all.......I've been in denial for quite some time. I've finally come to grips that I've got a problem - I'm over-injected. I was hoping that an AFPR would set my stang straight if it was set at about 22-24 psi, but I can't seem to find one that adjusts that low. Also, I'm told that wouldn't even fix the situation. I guess I need to drop dow to 24#'s even though I plan on spraying 150 horse shot of N2O next year. Any ideas..........does this see to be the best solution? Anyone wanna buy my 30#'s? How much could I get for the?

[gtsr515]

There's no way in God's green 5.0 world that you are OVER-INJECTED, whatever your problem is?, which you need to address for us to help? is, something else.

What's up??????????????

[ArtMan]

I agree - you're not overinjected. In fact I say that if you are stepping up to a 150 HP NO2 shot, you'll wish you had 36#s.

Without knowing why you believe you're over injected, I'll bet your idle isn't so great and the engine runs somewhat sluggish unitl higher RPMs. This is due to your cam. The higher lift of the F303 is confusing the EEC at low RPM and idle.

What you would benefit from is a burnt chip, or better yet, a programmable piggyback computer. Keep your fuel pressure at 40 psi +/- and calibrate the EEC for the large injectors. You'll thank me in the morning.

Just my 2 cents.

[red82gt]

Run your fuel pressure at at least 33psi (probably even a bit higher), anything lower and the injector will be drizzling rather than spraying. The computer is able to adjust the pulse width to change the A/F ratio but you may need a chip or an air adjuster to run just right. I think you made a good choice for the nitrous combo, the 30's can provide plenty of fuel. At 55psi fuel pressure they can fuel 560hp so they definitely have you covered.

[mysweetlx]

Well, first off, artman is correct, it's felt a little slugish in the lower rpm's, but it does wake up after 3k. I then checked on the analyzer on this site and it tells me I'm over-injected and w/ 30#'s I should be running them at 24psi.........I checked all over and can't find an AFPR that will adjust that low. Don't you guys think that running my current set up at 33psi would be too much? I am switching to a AFM cam soon too. I also plan on getting dyno tuned after my next few mods too.

[sn95gt19]

i would never even think of running my fuel pressure under 35, i would look into the afm PMS its a programmable computer, for 780 bucks i think its well worth it

[mysweetlx]

When I spoke to a tech at Jegs, e told me that I needed to go w/ 24 #'s too........said that I'd need to run below 30psi, on the 30#'s that wouldn't work though because it would throw off the spray pattern and it wouldn't work w/ the 30's pulse width. He said running over 30psi on the 30#'s would make my car run too rich and I'm fouling my plugs whenever I drive. What's up w/ all the different info I'm getting?

[red82gt]

The spray pattern is why I was saying not to go below 33psi. So far I don't see a lot of conflicting info, your computer can adjust the pulse width somewhat but you'll still run rich until you use a chip or something else to electronically fix this problem. For your N/A combo you'd be better off with 24# injectors, but the 30's can work with electronic tuning.
Set your fuel pressure up to about 33-35psi and give the computer a couple of days to adjust, I think you'll find that it will not be fouling plugs as bad and the better spray pattern will make your motor run better.

[ArtMan]

Lowering the fuel pressure for idle quality could result in fuel starvation up top. Yes, maybe for your naturally aspirated combination 24s would be fine. But you mentioned the NOS shot. You would need at least the 30s at that point.

A programmable computer would give you the flexibility to tune for idle and WOT, and allow you to grow with combination changes. I run an EPEC and I know its alot of coin, but you can adjust with combo changes, smooth the idle and pass emissions inspection.

You hit the nail on the head though. Your dyno session will tell the story. Never mind what I say, the truth will come out on the dyno (with wide-band O2 sensors). Here's what you'll discover:

You can't lower the fuel pressure enough to obtain decent idle quality. Why? Because its not the injectors alone - its the cam.

When you lower the fuel pressure, you'll find your getting a bit lean up top. When you tell the mechanic you'll be adding a 150 hp nitrous shot to this, he'll just laugh.

Good Luck!

[mysweetlx]

Thanks guys.....VERY helpful. Artman, you're in Ossining? I'm up in Mahopac.....we're almost neighbors.

[ArtMan]

Hey, I didn't realize that. If you ever head to the track give me an e-mail.
artcaley@email.com

[gtsr515]

Whats with all this low pressure stuff?, 24psi and 33 psi being to much? The system is designed to run STOCK at 38-42psi, every car seems to likes it's own settings, but in 16 years of tuning SEFI, I have never seen a package that needed to run that low, the injector is what supplies the fuel, it NEEDS that pressure to run accurately and properly, 33psi is just plain to little. Switching from 30's to 24's would do almost nothing in the grand scheme, it's only a 6lb. difference anyway. And 24's are notoriously finicky.

In all truth be told, if I had your iron and was planning on spraying soon I would go to 36lb injectors from Motorsport, a 190 in-tank pump (or more) and a T-Rex in-line pump. Your definetly going the wrong way with the injectors, just trying to help.

[mysweetlx]

Thanks for all the responses. I think I'm gonna stay w/ the 30#'s for now.......the MW analyzer told me it should be lower (I'll try it at about 34 and work from there). I also think that my F cam is respnsible for my low rpm bogging. Artman, do you go to E-town or Lebanon Valley? I'll let you know next time I go to either, and it'd be cool if you did the same.

[ArtMan]

I've always gone to E-town, but met a guy at work who goes to Lebanon Valley often so I want to check it out.

My Stang is garaged now while I wait for 50# injectors I need. Next time I go I'll let you know.

[mysweetlx]

Yeah Art, that sounds cool. I checked out your car on user rides.....love the stock look, but you can't fool too many w/ that S-trim blower howl!
50#'s???? Wow, and I'm worried about 30#'s. LOL
Hopefully we'll meet up one day soon. Later

[jimberg]

Set your pressure to 39psi as already suggested. If your MAF sensor is calibrated correctly you should be getting the correct amount of fuel when it matters. Dropping your fuel pressure so low will definitely mess up the injectors' ability to atomize the fuel which will just make your problem worse. Remember that when you set your fuel pressure that it is the high limit. If you set it to 24 psi it could go as low as 18 psi which would be ridiculous.

After setting your pressure, you also need to give the computer plenty of time to adapt so that it can deliver the correct amount of fuel. Start by resetting the computer when the car is warm and then let the car idle for about 10 minutes with accessories off. Shut it down, wait a couple minutes and the start it up with all accessories on and let it idle for another 10 minutes. When that's done, go for a long drive. Drive 50 miles or so before you try to got at WOT. This will keep the computer in closed loop giving it time reconstruct the fuel tables.

[Mach 1]

24lbers are better for your combo, and they can be run with nitrous safely, especially a wet kit.

Lower fuel pressure usually runs stronger, I had good results around 35 psi.

the Kirban FPR does go down to around 22 psi or so if you wanted to try that route.

24 lbers are better for your combo., but might not be the answer to your problem.

a lot of cammed stangs dont start screaming until 3000 rpm.

what gear ratio do you have?

[mysweetlx]

3.55's currently, but i'm putting in 3.73's soon.