CRAZYCUTER4.8

iTrader: (2)

I am on the verge of a serious mental breakdown! I am attempting to tune my fathers 03 SS with a p1sc, 8.1 injectors, cam, the normal bolt on's.
I am using the ifr & pe vs. rpm's tables & consistantly having no luck

We are still using the fmu just for ease of fine tuning. I have seen a few post about tuning forced induction using the volumetric eff. tables, not quite sure how that works. I have the ltft's sitting @ -2%, at WOT I can watch the O2 sensors drop out. This does not occur all the time. The injector pulse width sits around 33.0 at wot. I have the pe se @ 2.7 this seems really high to but I am comparing it to other files that are probably tuned by the ve table.

I have the edit file if anyone is interested in looking at it. If anyone has a forced induction 6.0 with the 8.1 injectors I would love to see it. does anyone have the max amount of pe multiplier I can program in? Is it better to tune using ve or pe tables? This **** is driving me nuts! I have a strong suspension the fmu is acting up giving us incosistant fuel pressure. The few times we checked it though it was around 100 with boost. Any help would be appriciated.

Black Blown 02

Are the injectors 8.1 or 8.1 marine(43lb)?

Black Blown 02

With a pulsewidth like 33ms, I assume the injectors are not the 43lb marine versions. At 33ms, your injectors are maxed at 3500rpm, so adding fuel via pe/rpm won't do anything. You'll have to rely on the FMU to add fuel.

I wouldn't mess with the VE table.

When you say your 02's drop out at WOT, do you mean they go lean? What are the 02's voltages at WOT?

If you've verified that fuel pressure is at 100psi at WOT, then the FMU is working correctly. Do you have the adjustment screw screwed all the way in on the FMU?

greentahoe

iTrader: (2)

With a setup like that I wouldnt want to rely on the FMU. If you can I would get a set of marine 43lb injectors from asm. Sounds like they would simplify you tuning.

Black Blown 02

Yeah, tuning is a breeze when you don't have to rely on that FMU. You can't really do anything with edit to your fuel if you're using that FMU.

Speartech

iTrader: (14)

If 33ms is the commanded injector on time, you're way past the useful range of the injectors! They are basically staying open all of the time once the revs climb. That's why you are having problems. They can't stay open any longer so you don't see any results from your programming changes.
You need much bigger injectors!

CRAZYCUTER4.8

iTrader: (2)

they are the normal 8.1 injectors, they are suppose to be 42lb injectors, I am starting to wonder if I have the pe tables so far advanced that the pcm is pegging the injectors out. the O2's drop to 600-700 mv when it starts missing. I was watching the O2's & it seemed like the more we screwed it in or the more fuel I added the worse it got.

Black Blown 02

The 8.1 truck injectors aren't 42lb. Where did you get the injectors?

BigTex

iTrader: (16)

Normal 8.1 truck injectors are closer to 30#. The marine injectors are the 42 pound ones. You didn't say so, so I'm going to ask. Did you change the injector flow rate to compensate for the bigger injectors? If not, that truck is drinking fuel.

Email me the file. richard (at) z71.net

Black Blown 02

I've never seen it happen, but I've heard injectors can lock-up at higher than normal pressures. That could be a possibility. I'd say spend the $400 on some 8.1 MARINE injectors from AS&M, and ditch that FMU. Otherwise, with 02 readings that low at WOT, you may be getting a new engine soon.