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Thread: Throttle Cracker Tuning Question {B4309}

  1. #11
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    I got a log with the PIDs in my last log and the ones you wanted, Statesman.

    I looked at it a bit, I'm at lunch now. Frame 3950 is a pretty good spot to look at for what I'm trying to smooth out. I let off the throttle on the highway and coasted for a bit. My RPM was nice and smooth around frame 3833, then around 3950 it started bucking. Timing is steady at 24*, IAC is steady, but my STFTs start to creep up. I did get my new wideband sensor, my goal is to get that in the car this weekend so I can get back on tuning fueling.

    Doc, I did copy the lower airflow portion of the B5913&B5914 tables from the ASA tune in the tune DropBox (what used to be holdencrazy.com). From what I found, the ASA cam that Speedway Motors sells has almost identical specs to my cam, Summit's SUM-8700. That lead me to believe that, along with some threads I've read that big cams need more advance, the tables in the ASA tune should work well for my setup. Since I'm off throttle, my timing goes back to my base spark table, and like I said in the previous paragraph this is 24* off throttle at speed.

    Any other thoughts? My tune and its log from this morning are below. Thanks for the help, by the way!

    Tune:
    Garrett_GTO_tuned_20181220_1.ctz

    Log:
    GTO Dec 21 2018 home to IBC.efi

  2. #12
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    I'm making some changes to your fueling... most notably, your injection timing. You were spraying really late... this is unwarranted with your cam.

    Do a log for me with exactly the same pids you logged last time... and make a note of where it's bucking (like you did last time).
    Attached Files Attached Files

  3. #13
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    I finally got a good log. I flashed your tune Statesman, and got my wideband fixed and included its PIDs as well in this log.

    All my injector tables are still stock, but it seems like your tweaks helped out. I notice less bucking when off throttle in general.

    Here are a few places to look in the log:

    On throttle bucking:
    1. Frames 3100-3128, IAC is steady, STFT aren't bad, LTFT are about -9% which shows room for improvement.
    2. Bad around frames 5435-5450, STFT goes from positive to negative, WO2 goes lean/rich/lean, IAC steps are steady but seem to suddenly increase midway through this portion of the log and plateau.

    Off throttle bucking:
    1. Frames 5154-5302, IAC is steady, STFT average around 1%, LTFT is around -4.5%, spark is steady, WO2 average is a hair lean. I'm decelerating in gear smoothly, then I get the herky jerkies.
    2. Frames 6446-6501, IAC is steady, STFT are rich then go a bit lean, LTFT is about -3%, WO2 is rich then goes a bit lean. Same RPM action as above.
    3. Frames 7347-7431, IAC is steady, STFT goes rich then bounces rich/lean, LTFT looks fine, WO2 has a couple lean spikes, RPM does the same as above.

    Later in the log there are a couple more areas where WO2 shows a couple lean spikes, but the spots in the log above are good examples of the bucking I'm getting.

    Log:
    GTO Dec 27 2018 IBC to home.efi

  4. #14
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    Quote Originally Posted by pinstripebob View Post
    All my injector tables are still stock, but it seems like your tweaks helped out. I notice less bucking when off throttle in general.
    Stock injector data isn't always the best injector data.


    Quote Originally Posted by pinstripebob View Post
    1. Frames 3100-3128, IAC is steady, STFT aren't bad, LTFT are about -9% which shows room for improvement.
    I'm not overly concerned with some wild trims in that log. The first change was just a 'rough cut'... it was never meant to be perfect, it was just to straighten a few things out so I can see what's going on a bit better. The changes I'm making now should start to bring your fueling back into line.

    Do a log on this tune file like you've been doing... but try taking the long way home next time, so I get a bit more of the log at full operating temperature. Taking such detailed notes of where it's bucking saves me a lot of time, so try to do the same again.
    Attached Files Attached Files

  5. #15
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    Statesman, your changes do seem to be working well! It's too bad stock data isn't always the best, but the improvements are great!

    I flashed your tune and took some country roads home. Unfortunately one that I chose was pretty low speed, but I think overall I got good data. Overall the car seems smoother, bucking is greatly reduced off throttle. There is still some under light throttle.

    Below are the areas where I noticed this bucking. Thanks for looking into this and helping out! I'm enjoying going through and noting areas of concern, so if that helps you I'll keep doing it.

    Unfortunately, I must have gotten comfortable and selected the wrong PIDs! I'm missing IAC, voltage, and STFT data. Sorry about that! I should be able to get another log tomorrow WITH those PIDs, if not tomorrow then probably Monday or Wednesday. If this log doesn't help and we need the STFT/voltage/IAC data, that's not a problem, I'll get a log with the correct PIDs. I did some steady throttle pulls as well in case that helps.

    Coasting in gear, no throttle, no bucking:
    Frames 4996-5130

    Coasting in gear, no throttle, some bucking toward end:
    General note, off-throttle bucking is almost gone. Comes on around 1100RPM, but if I stab the clutch the engine seems to be idling around that RPM anyway.
    Frames 5385-5836. WO2 looks good, LTFT are a bit off but seem okay in the bucking and pre-bucking area. Spark looks steady/smooth. This has the worst off-throttle bucking of the log, but it wasn
    Attached Files Attached Files
    Last edited by pinstripebob; December 29th, 2018 at 09:55 AM. Reason: Attached the wrong log file

  6. #16
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    wasn’t bad and was at a pretty low RPM.
    Frames 6032-6454. WO2 looks fine, maybe a bit lean in general but not bad. Spark is smooth, had very light bucking around 1100-1050 RPM.
    Frames 10677-10825. WO2 looks okay, LTFT are fine, spark is smooth. RPM was low, bucking was probably caused by the throttle cracker, just my guess.
    Frames 15626-15733. I was using throttle, lowered throttle, then went off throttle. Off throttle bucked the whole time, might be a good little area to look at in the log. WO2 went rich then lean, might be an indicator of the cause.
    Frames 16764-16940. WO2 looks okay, LTFT are fine, spark is smooth. RPM was low, bucking was probably caused by the throttle cracker, just my guess.

    Light throttle in gear, some bucking:
    Frames 8424-8583, WO2 looks alright, spark is smooth, LTFT isn’t bad.
    Frames 8772-8973, WO2 looks alright, spark is smooth, LTFT is low, RPM is around 1350.
    Frames 9148-9222, I think I shifted into 5th or 6th gear here and had some rough bucking. Spark actually got choppy around frame 9200.
    Frames 12868-13276, WO2 looks fine, spark is smooth, LTFT look great, had some RPM choppiness with a spot of rough chop near frames 13181-13199.
    Frames 13550-13769, I think I was going up a hill in a higher gear and kept TPS low with some bucking. WO2, LTFT, and spark advance look alright.


    NOTE: I'm not sure why I can't fit all of this in one reply.

  7. #17
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    Forum web software seems to somtimes truncate responses.

  8. #18
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    Quote Originally Posted by pinstripebob View Post
    Overall the car seems smoother, bucking is greatly reduced off throttle.
    The engine will run smoother as the tune gets better... that's normal.


    Quote Originally Posted by pinstripebob View Post
    Unfortunately, I must have gotten comfortable and selected the wrong PIDs! I'm missing IAC, voltage, and STFT data. Sorry about that! I should be able to get another log tomorrow WITH those PIDs, if not tomorrow then probably Monday or Wednesday. If this log doesn't help and we need the STFT/voltage/IAC data, that's not a problem, I'll get a log with the correct PIDs. I did some steady throttle pulls as well in case that helps.
    Yeah, that log is useless to me.... I need you to log everything that I asked for.

  9. #19
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    Double check your pids.

  10. #20
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    Alright finally got a log and had time to sift through it. Car has been pretty consistent, so no new notes. Overall it's smoother, bucking off throttle is mostly gone, bucking under 5% TPS is still there but not as often. ECT hits 80C at frame 700, pretty early in the log. Below are the areas where I logged bucking:

    On throttle bucking:
    Frames 1338-1446, STFT goes a bit positive, LTFT are about -6.5, everything else looks fine, some bucking here but it isn
    Attached Files Attached Files

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