fuel running out at high RPMs b/c of stock fuel lines

[nightmare95stang]

Was wondering if anyone could help. I went to get my car tuned and put down some O.K. numbers...but only until 5500 RPMs. The 2 problems were:

1. My current fuel system starts to drop off between 5000-5500 RPMs and my tuner told me this is probably because of the stock fuel lines being too small....and...

2. He only revved the dyno pull to 5500 because my spark was dropping off too (I need an MSD).

The bigger problem to try to solve is the fuel management because the fuel delivery is somewhat greek to me, considering I never thought I'd be making the power where my fuel would start to run lean.

On my 95 mustang, I'm running a 255 lph in-tank plus a T-Rex external pump. It's all going to a 331 stroker motor with 8.5:1 compression, 42 lb injectors, 95 fuel rails, and just 10 psi at 5500 rpms (looking for more once I get the MSD hooked up so it controls spark a little better).

The tuner told me a quick fix, that instead of getting an ENTIRE new fuel system (which I do not wanna do) is to get two 6 or 8 fuel fittings and sending line. He told me the order of the fuel delivery should be: one fitting on the T-Rex flow-out side, then a short fuel line to the fuel filter, then the longer braided fuel line run under the car up to the fuel rails, then the other fitting on the fuel rail. He said not to worry about the return line...at least just yet.

Has this happened to anyone? Does anyone have a suggestion on what exact size fittings come out of the T-Rex and go into the Fuel Rails, while still fitting on an 8-size braided steel fuel line? Or maybe a place where I can direct that question to? If anyone can help, that would be excellent because I am just lost.

Thanks!!

[USMC302]

Those stock fuel lines can support up to 500hp. What cam are you running, and do you have any tuning device? With a PMS or FAST, you can alter fuel in the RPM range..Did your tuner say what % your injectors were at in the high rpm range and what was the air/fuel ratio? What is the fuel pressure set at? You mentioned boost but nothing about a blower or a turbo, more info? Boost will tend to blow out the spark as well, be sure to lower the gap on the plugs, MSD will work wonders as well.

[nightmare95stang]

USMC, I really appreciate your response and knowledge...here's a little more info to clarify:

I'm not sure the cam...mild to moderate. The tuner is just using the A9L computer and burning a Diablo chip. He didn't tell me the injector pulse or % they were at, but I saw the fuel curve on the dyno printout start to rise from 11.2:1 at about 5000 or 5100 RPMs and it kept rising gradually probably to about 14:1 at 5500 RPMs. At that point, the engine started conking out because I was losing spark, so I couldn't really see how much more fuel I was losing in the mixture.

Fuel pressure at full thottle is 45-47 psi....idle pressure is probably 39-40 psi. I am running a Paxton Novi-1000 with a 3.15" blower pulley and an 8" crank pulley.

When I did the 331 swap, I gapped all the plugs to .32-.33

Here's the two things I think I need:

(1) I just need an MSD (on the way) to fix the car losing it at 5500 RPMs and..

(2) I think I need to go with a "band-aid" set up by running an -8 AN fuel line from my T-Rex up to the 95 fuel rails.

Then have the tuner run the car. With the MSD controlling spark, he'll be able to rev the engine out further, and with that bigger fuel line, we'll find out if the pumps just can't handle it, or if I really just needed bigger fuel lines.

I can get almost all the stuff I need for the fuel fix-it. Fittings: no problem, fuel filter: easy. My BIG problem, is finding an -8 AN size fuel line the right length from the front face of the fuel tank, under the car, all the way up to the fuel rails. And I also need that fuel line with the -8AN fittings on each end. I know I can probably take a string and mark off the length, but if you (or anyone) happen to know the length off-hand , that would save me crawling around on my back and possibly miscalculating

[USMC302]

Def need the MSD to fix the spark problem first as you said.. I haven't upgraded my fuel lines yet but I've run a 150 shot on my 331 with the stock lines and rails, 255 pump and 30lb squirters with no problems running into the 10 second zone. I have a PMS with A/F meter and never ran lean..Does your Diablo chip remove the rev limiter? I agree your running lean at the end of the RPM range, but I don't think it's the lines or rails. I know your 42lbers aren't over there max % either, I think it's something else. Can your tuner program the chip to add fuel after 5000 RPM's?

[nightmare95stang]

I don't think the diablo chip gets rid of the stock rev limiter. Hmm, I don't think I've ever changed the fuel filter Think that might have something to do with it? Would my fuel pressure increase after I changed it as a sign that maybe it was restricting pressure?

I think he said he couldn't add fuel past the 5000 RPM mark; I think he said the fuel system just wasn't keeping up to what he set it for. And my 255 in-tank is probably at least 3 years old; the T-Rex is only a year and a half old. The car has been a daily driver, and every so often get up and on it. I've only been to the track twice with the blower, once with street tires, the other with slicks.

What do you think???

[USMC302]

MSD and fuel filter. Then let us know.