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Thread: Fuel trim question

  1. #41
    Senior Tuner eficalibrator's Avatar
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    I'm surprised everyone missed my point (also shown in the DVD) that I usually set the stoich point in the calibration BEFORE I begin doing open loop calibration based on wideband feedback. It's not that difficult to get a good indication of your ethanol content before starting. As mentioned above, graduated cylinders are available for dirt cheap. GOOGLE LINK SUMMIT LINK

    Once you know what the fuel really is, why not just pick your actual stoich point as the stoich point in the PCM calibration before you start? If you do this, then all of your open loop work will be based around the right balance point and closing the loop should not have any affect as long as you did everything right and the O2's a in good working order.

    Don't make this any more difficult than it has to be.

    Quote Originally Posted by DSteck View Post
    Greg Banish would have a stroke if he saw this thread.
    Just for that, I'm getting the hell off this continent and going to Oktoberfest. You guys can argue without me.

    Quote Originally Posted by edcmat-l1 View Post
    He probably hasn't posted yet cause he read it, and now he's done locked up!
    No really, I'll be near the Paulaner tent on Sunday if anyone needs me. After that, I'm still wandering Bavaria for the rest of the week to give you guys time to come to your senses.

    Auf wiedersehen!

  2. #42
    Senior Tuner Higgs Boson's Avatar
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    Greg, enjoy Europe!

    One of the first things I tried was changing the stoich box, then tuning in OL. However, I couldn't get the results right but I still don't know why. So of course, I did some more "research" and found that I should change the slope in HPTuners to match the fuel stoich.....Again, didn't seems to come out right.

    It was only when I left the stock stoich setting and just used the built in formula in the scanner for stoich that it seemed to line up right so my conclusion was that 14.68 that shows in the old ECUs doesn't really mean 14.68, but 1.0....and I also concluded that it is really only a number that shows up in the scanner to base you AFRError on as it did not seem to affect CL trim tuning....

    Can you give some insight on my delusions?

  3. #43
    Senior Tuner IDRIVEAG8GT's Avatar
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    ttt....... At least everyone here drives General Motors products.
    Gray Ghost- The abomination. 2007 Chevrolet Silverado CCSB. 98mm turbo, nitrous, 428LSX, Rossler 80E with a brake. Finally finished. 23 psi, no numbers, Slow as hell.

    PBM G8- Aluminum 364, twin Precision 67/66 turbos, 6L90 trans swap, CTS-V/Vaporworx fuel system, slowly making progress.

    Dads 2011 CTS-V- Stock bottom end, stock heads, LS9 cam, pullies, ported blower, ported TB, D3 goodies, and lots of nitrous.
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  4. #44
    Senior Tuner eficalibrator's Avatar
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    Quote Originally Posted by Higgs Boson View Post
    It was only when I left the stock stoich setting and just used the built in formula in the scanner for stoich that it seemed to line up right so my conclusion was that 14.68 that shows in the old ECUs doesn't really mean 14.68, but 1.0....and I also concluded that it is really only a number that shows up in the scanner to base you AFRError on as it did not seem to affect CL trim tuning....
    The sooner you start working in units of LAMBDA instead of AFR, the better off you'll be. Too many people start confusing what their exact correction should be when they take a measurement in ASSumed AFR (based on the wideband's multiplier from lambda=1.00) and correct against another AFR based on the ECU's ASSumed stoich point, which may in turn be different than the fuel's actual stoich point.

    If you measure fuel composition and set the ECU's stoich point to match, you're done. Just work exclusively in lambda from there out and you'll be fine.

  5. #45
    Tuner in Training
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    Awesome thread, much learned, thanks to all who posted :-)