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Thread: What's the preferred method?

  1. #1
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    What's the preferred method?

    I have read a lot on this forum and methods are all over the place for tuning VE and MAF in regards to using STFT, LTFT and WBs.

    Some say use the STFT for tuning VE/MAF and use a WB for WOT.

    Some say use a WB for all of it.

    Some say you can't use the STFT/LTFT with a CAM'd car because of the overlap.

    And there are a few others.

    It seems to have changed with time and updates to HPTuners.

    My questions is, what is the current preferred/accepted method?

    Thx

    Sarge

  2. #2
    Senior Tuner eficalibrator's Avatar
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    If you have the wideband, why wouldn't you just use it?

    Remember that narrowband O2 sensors have a deadband of about 3% around stoich where they switch from "low" to "high". This means that you'll never really get inside this level of accuracy reliably. Although 3% sounds good on paper, remember that this is just one of many possible sources of error. So the more error source we can eliminate during the calibration process, the better. It will just make everything else easier down the road.

  3. #3
    Senior Tuner DSteck's Avatar
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    I use LTFTs and a wideband for WOT. Reasons:

    a) If a car is REALLY far off from where it should be, closed loop helps get it to a drivable AFR (really only applies at the start if you don't have a decent base to go off of).
    b) I trust the narrowbands and the LTFT algorithm to give me a fairly accurate representation of just how far off I am.
    c) I like to make sure there are no positive LTFTs so that they don't carry into WOT.

    That's my $0.02.

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  4. #4
    Advanced Tuner blownbluez06's Avatar
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    I use STFT's for cruising with LTFT's off. I will make sure that the wideband agrees within a reasonable percentage and investigate if it doesn't. Why use STFT's? Because when you tune with the wideband and then try to operate within closed loop, you're going to get constant adjustments made by the PCM (STFT's) anyways. I feel it's best when the PCM has to deviate the least amount from the VE table. When running SD OS's, you will also incur circumstances where you can hit the same cell, yet require differing amounts of fuel. This is because the cells aren't load based. They only offer MAP and RPM values.

    IMO, it's smart to temporarily turn on the LTFT's because it is more of a long-term value, but I would turn them off once the tuning is completed.
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  5. #5
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    Quote Originally Posted by eficalibrator View Post
    Although 3% sounds good on paper,
    That's an A on any engineering exam right?

  6. #6
    Senior Tuner Ben Charles's Avatar
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    Remember that narrowband O2 sensors have a deadband of about 3% around stoich where they switch from "low" to "high". This means that you'll never really get inside this level of accuracy reliably. Although 3% sounds good on paper, remember that this is just one of many possible sources of error.
    Greg would this not fix the problem? I still consider myself new to tuning, but something I just did was install a o2 bung behind my passenger o2 sensor to run CL the same time as I am running my WB. I'm using a filtered histogram to measure o2 MV compared to AFR (outside of PE mode). This allows me to modify the o2 MV airflow mode to what really stoich is on an engine or a desired AFR close to that (leaner cruise around 15.4AFR). Stoich on stock cars are aroun 450Mv, but this number can differ a lot on modded cars with dfferent exhaust configurations and EGT's.

    The idea of this is to make CL match the WB reading so in essence tuning in CL outside of PE mode will be the same as using a WB in my opinion. I think the problem most people have is trusting the STFT's when the Mv are not tuned to the airflow mode which makes for large percent differences between the two.

    Im a grad school student and I will be done with classes Tuesday, plan to play with this some then
    Last edited by Ben Charles; 12-11-2011 at 02:25 PM.

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  7. #7
    Senior Tuner DSteck's Avatar
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    Quote Originally Posted by blownbluez06 View Post
    When running SD OS's, you will also incur circumstances where you can hit the same cell, yet require differing amounts of fuel.
    The alpha-N table in the E38 custom OS was a pretty cool feature added just for this.

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  8. #8
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    Wideband for ALL if available.

    IF no Wideband use STFT/LTFT for anything other than WOT.
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  9. #9
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    Does anyone have an accurate information how reliable typical $200 wideband is at the same area where narrowbands are switching? Less or more than 3%?

  10. #10
    Senior Tuner LSxpwrdZ's Avatar
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    There was a huge test done not long ago and the NGK AFX was found to be the most accurate of the bunch... I would agree with that as well!
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