Procharged Xtreme

[Devonsz]

Im working on tuning a 2001 S-10 Xtreme 4.3 that is Procharged pushing around 14lbs of boost. The problem is that under light throttle/decell it will load up very bad. Sometimes you can clear it out (wot) but other times it will just die. Does any one know what it could be causing this.

Here is his current tune, and a short log.

Thanks in advance for any help!!!

[Bill@HPTuners]

Im not sure about the light throttle/decel issues but you are severly out of injector with as much boost as your pushing and are going super lean at wot.

[Devonsz]

Are you just saying its lean because of the injector duty cycle being 150%? I already talked with my friend about that but we set the afr using the stock o2's to about 11.9.(I know the stock o2's can be way off but it's all we have for know) And the truck pulls fine up to 5600rpm or so.

Not sure what stock fuel pressure is but my friend is running about 85lbs at wot.

[Bill@HPTuners]

If your running an FMU its not uncommon to see ~100psi fuel pressure in those things, but look at your stock o2's they go to 30mv at 5000-5400 rpms...how exactly did you guys determine that was 11.9:1 a/f ratio?

[Devonsz]

If your running an FMU its not uncommon to see ~100psi fuel pressure in those things, but look at your stock o2's they go to 30mv at 5000-5400 rpms...how exactly did you guys determine that was 11.9:1 a/f ratio?

We got that using the stock o2's on the table view it showed 11.9, but I wasnt paying any attention to the inj. mv reading. Why would that drop like that? Is it just shutting the injectors off or what? I dont know much about tunning as i've only messed with my car alittle. We are just trying to get the s-10 to not load up. The majority of his tune was mailorder and i've just changed afew things.

Thanks for the help

[BTLD_LS1]

I have to agree it does look like you are running VERY lean at WOT, the injecotrs appear to be maxed out. I was going to suggest possibly chaning the MAF/ VE tables, but even that will not help as it looks like a fuel delivery issue.

You are looking at O2 mV, not injecotr mV. the dropping voltage means there is an EXCESS of oxygen in the Exhaust system, which is a VERY bad thing....

[BTLD_LS1]

this is a log file of a drive in my car, notice how in frames 1009 to 1032 and 2816 to 2834 the mV is over 900 at WOT? it should look something like that when in PE.

[BTLD_LS1]

Just thought I would add that the MAF table is pretty much the same on your mail order tune as a stock tune.
VE was increased in lower parts significantly, but in the higher MAP ranges only slightly increased.
Spark tables are increased over stock when usually with boost you want to decrease them.
also the last colum of the force current motor table generally gets zeros out yet their tune retains the normal 1245 setting, very unusual.....

[5_Liter_Eater]

It seems to me like you're looking at the PE table and assuming you're getting what you're commanding. Narrow band O2 tuning is a no no but if you're going to do it at least do it right. 13:1 is ~890mV. 12:1 is ~910-920 mV. You're nowhere close to that in the short WOT burst in the log. Like off the scale lean. Regardless of your fuel pressure your stock/narrow band O2's should still be ~900 mV at WOT.

[Bill@HPTuners]

Pushing 14psi I wouldnt even risk listening to what the stock o2's are telling you 900mv or otherwise. My gtp pushing 12psi shows anywhere from 860-940mv and its rock solid at 11.8:1 so theres no way I would trust stock o2's knowing widebands are $200-250 new.

I assume thats a Mach performance kit which probably cost $5000 on top of what the motor would cost if you need to replace it if you melt a piston and ultimately destroy the block...risking that to save a couple hundred bucks isn't worth it IMHO.

[Devonsz]

Thanks for all the help guys. I just forgot all about watching the injector mv reading. I trying to track down a wideband right now to use, and if that doesnt work we'll just buy one because I could use it for my car when done with the truck.

But we are injecting fuel into pre throttle body using a pump right now that is on a switch and getting some better #'s.

Thanks again!

[Hauss]

kinda like an accelarator pump? how do you meter that extra fuel? is it on a wot switch?

[Frost]

if it were my truck I'd be doing a compression test already... that lean even a few times can tear up a bottom end quick.