? about my lean problem, tell me what you think...

98COBRA281 · Dec 9, 2009

well i talked to my tuner today, he said everything in the datalogging was perfect, he talked to SCT about what my problem could be, i have a 255 intank walbro, 9/16 edelbrock rails, -8 from rail to rail, and stock line from the tank to the rails, they think its the stock fuel line not being about to fee enough VOLUME to the bigger rails and -8 line, he said its not a pressure problem, but a volume problem, does that sould right? and can i run -8 line from the tank to the rails?

Rickyll7 · Dec 9, 2009

the stock fuel lines and rails for that matter are good to your hp level. im running stock lines and rails at 427 rwhp.

maybe your tune is off, maybe your walbro is sucking your basket dry, maybe your maf is pegged.

BurningRubber · Dec 9, 2009

What injectors are you running?

If you're still on the factory 19's I wouldn't be surprised if they are near or beyond 100% duty cycle at your power.

Mr. Rustypwnz · Dec 9, 2009

im pretty sure you went with 30's right? are they scaled in right to the computer (tune) that can **** you bigtime..

98COBRA281 · Dec 9, 2009

no im running brand new FMS 30lber's, and brand new 255 intake pump!

i know the stock lines are good to 400+rwhp, but think on it like this, a garden hose on full blast, going into a sewer pipe, it has plenty of plessure, but cannot move enough volume to keep the sewer pipe full becasue of the size difference

98COBRA281 · Dec 9, 2009

Mr. Rustypwnz said:
im pretty sure you went with 30's right? are they scaled in right to the computer (tune) that can **** you bigtime..

yes everything is in the tune, including the 90mm LMAF........

Mr. Rustypwnz · Dec 9, 2009

im really thinking that the stock lines are not the case, you got guys running 400+ hp with turbo's/blowers that need alot of gas up top and are fine with a 255lp.

if your thinking it, there is only one way to find out, put and gauge on it, and go drive it, and watch for it to drop..

if not that, something in the tune is killing you, most sct programs, run on the leaner side of things..

or do you have a xcal3? if so i would put a 87 tune on it, and program it for your maf and all, and go try it out, pretty much like a stock tune for your mods.. if all is well up some timing.. but thats just me, i constantly am treaking little things on my car..

Rickyll7 · Dec 10, 2009

98COBRA281 said:
no im running brand new FMS 30lber's, and brand new 255 intake pump!

i know the stock lines are good to 400+rwhp, but think on it like this, a garden hose on full blast, going into a sewer pipe, it has plenty of plessure, but cannot move enough volume to keep the sewer pipe full becasue of the size difference

That's a good analogy, but you forgot one thing. The sewer pipe is full and at 40 psi and the flow out of the sewer pipe isnt enough to drop it from its 40 psi.

Even if you were right, the answer would be to get rid of the sewer pipe, not enlarge the garden hose.

its either your tune, maybe your sucking the basket dry with that big pump, your maf, or a vacuum leak.

it could even be that your tuners wideband sensor is bad or not calibrated correctly.

Rickyll7 · Dec 10, 2009

could also be an exhaust leak.

98COBRA281 · Dec 10, 2009

Rickyll7 said:
could also be an exhaust leak.

i do have a little leak around my collector......

im going to try the fuel filter and maybe drill some holes it the basket in the tank to get more fuel to the pump........

Rickyll7 · Dec 10, 2009

98COBRA281 said:
yes everything is in the tune, including the 90mm LMAF........

That MAF shouldn't be pegged at this power level (contrary to my earlier suggestion). I would check the fuel pressure while the lean condition is taking place before messing with the fuel filter or basket.

If the pressure is low, you probably have a basket or fuel filter issue. If the pressure is good, you have a tune issue or a bad o2 reading from a bad o2 sensor or you could even have contaminated exhaust from the exhaust leak giving a bad o2 reading.

You could also have a combination of the above which will complicate this diagnosis further.

98COBRA281 · Dec 10, 2009

Rickyll7 said:
That MAF shouldn't be pegged at this power level (contrary to my earlier suggestion). I would check the fuel pressure while the lean condition is taking place before messing with the fuel filter or basket.

If the pressure is low, you probably have a basket or fuel filter issue. If the pressure is good, you have a tune issue or a bad o2 reading from a bad o2 sensor or you could even have contaminated exhaust from the exhaust leak giving a bad o2 reading.

You could also have a combination of the above which will complicate this diagnosis further.

SCT went over the datalog and said everything was fine, so i dont think its a sensor problem, i have a fuel pressure guage on the regulator, i wish i would have watched it during a dyno pull

Rickyll7 · Dec 10, 2009

98COBRA281 said:
SCT went over the datalog and said everything was fine, so i dont think its a sensor problem, i have a fuel pressure guage on the regulator, i wish i would have watched it during a dyno pull

No one can say if the wideband is bad/miscalibrated by looking at the datalog unless its just that far off and even then they couldn't say conclusively why its off.

i would look at the fuel pressure.

98COBRA281 · Dec 10, 2009

im going to change the fuel filter and mess with the fuel basket in the tank, i remember the filter screen not fitting just right in the basket, do i have to run that?

the AFR is getting to the mid 13's @ 6k, and im planning to rev it to 6500+ if the MHS cams work out, so i have to fix this problem

bhuff30 · Dec 10, 2009

I agree with monitoring the fuel pressure when it is going lean before digging in deep. If the pressure drops, then it is related to the supply side. If it holds well, then you should be able to adjust the tune.

Also, pressure and flow are related... demanding more pressure reduces the flow. If your pump can supply the required pressure, then it is obviously supplying enough volume. If it couldn't keep up with the flow, the pressure would drop.

Notchbck93 · Dec 11, 2009

Post up your A/F ratio chart that your tuner should have given you!

It would be nice to have a recorded cycle of the injector duty cycle and maf load at that given RPM where you are running lean.

Also, ANY leaks before the exhaust reading zone need to corrected before any tuning is done. I wouldn't even accept a car on a dyno with an exhaust leak up stream of where I am gathering a reading.

While your comp will go into open loop and use a preset table under WOT, your tuners wide bands won't. Your tuner should know better than to tune a car with an exhaust leak, but you probably signed a waiver of liability so if you go out and melt your piston, it certainly isn't his problem.

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