Update on my tune since swapping to larger injectors..

So I'm sure some of you have seen my other thread of frustration since swapping from a set of stock 2000 injectors to my 'supposed' Accel 42# units. I've since ditched my old map and decided to start as fresh as possible by obtaining a stock '00 TA map and working from there. I've made the usual changes (EGR/AIR/CAT/CAGS delete, fan turn on points) but have kept the meat of the tune 100% stock. I then went ahead and started by altering IFR to the predicted 42# values, the result was a VERY heavy 25% LTFT for much of the driving I was doing. I then progresivley went smaler on the IFR scale till I arrived at the scale for a set of '31#' injectors. The current result is approx. 0% LTFT at crusing with some slight deviation at low MANVAC (-5 to 6% LTFT) and higher MANVAC (+4 t 6% LTFT). I devised a LTFT log map and observed the most notable 'switchpoints' for higher trim and lower trim values and will make slight tweaks to the IFR as such, but I'm VERY happy to have finally arrived at this point where the vehicle is finally driveable without feeling like I'm behind the wheel of a bucking bronco!

From here it's AutoVE, RAFIG adjustment and some WOT PE adjustments. I'd like to delve into MAF adjustments but I feel I still need alot of brushing up to do in that area before I even attempt to run MAF-only.

Attatched is a log of my last pass with the 31# IFR, observations and input is GREATLY apprieciated :good:

You could have just entered the IFR values for the new 42 lb injectors , then re do the VE table with auto VE, that would have bought your fuel trims back into line, rather then fudging the IFR table to do so.

I would've gone that route if I was 110% sure of the size of these injectors. As stated in the previous thread however, after installing the injectors and rescaling the IFR to 42# I was getting some REALLY lean AFR's with the PCM maxing out LTFT just about everywhere. I made some rather large changes to the VE tables with relativley minor results, mind you this was built off a tune already so there really should've been little if any changes made to the VE tables since the engine's ability to flow air has not been altered. All roads pointed (at least to my primative understanding of the GM PCM) to the injectors being far smaller than I belived they were.

Of course now I'm rebuilding a map from a stock '00 unit so my intention is to draw as close as possible with IFR adjustments and fine tune it via VE tweaks.

Not easy when your knot sure what your working with:bash:

But there is more then one way to skin a cat !
and your method will still end up giving you the desired result .

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Originally Posted by johnv

Not easy when your knot sure what your working with:bash:

But there is more then one way to skin a cat !
and your method will still end up giving you the desired result .

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Yea looks like that's the case. I'm happy to report that after alot of frustration I appear to have finally 'gotten it' with regards to PCM function and fueling. I've taken SS's MAF tuning advice and applied it to my car with terrific results. After only 3 or 4 trimmings I've got the IFR down to within 2-3% at most MAVAC points. With a few more tweaking session I should be able to finally nail down the right IFR for my car and I'll be able to re-enable the transition fuel table (MAP/VE) and perform an AutoVE and so on..

Ahh the joys of modifying a vehicle :notacrook:

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Originally Posted by VTC_WS6

...Ahh the joys of modifying a vehicle :notacrook:

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Way to go... :cheers:

If it all went perfectly the first time, then we'd all be bored and we'd not have learned anything...:laugh: