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Thread: Off idle timing dump - LNF

  1. #1
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    Off idle timing dump - LNF

    Looking to see if anyone else has experienced this kind of off-idle timing dump. It only occurs when trying to take off from a dead stop in 1st gear. Is even worse after a long DFCO and the lambda is targeted for .95 (I've always assumed this was another form of catalyst protection that we don't have access to adjust) and I try to take off before it has returned to targeted command of 1.0. In both cases, the car literally falls on it's face and then recovers rather wildly, almost like the car is fighting a limiter.

    Here's a list of things I've tried to remedy this problem:
    1 - I've tried bumping up my MS in the off-idle cells, no change
    1.1 - I then tried lowering the timing in the same areas, no dice
    2 - I bumped the OS in the same areas as the MS changes, still the same
    3 - I tried adjusting the DALs to see if that would help, nadda


    The only other table I can think of to adjust to try and remedy this situation would be the optimum torque table. However, in the past when I would try to adjust this table, it seems I needed to go back and crank MS timing through the roof and it didn't seem to allow for smooth drivability.

    Any thoughts?

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    09 RY Cobalt SS Coupe - 19K miles - Bolt ons + 7163 ZFR, HP tuned on ethanol

    Sold - 09 SRTC Cobalt SS Sedan
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  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    Did you look at your tip in?
    2000 Ford Mustang - Top Sportsman

  3. #3
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    Quote Originally Posted by cobaltssoverbooster View Post
    Did you look at your tip in?
    Yes, I have it zeroed out

  4. #4
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    in the picture attached from ETC Pdl PID it looks like you let off. From the picture to me it seemed like it cut spark because you let off. i guess it's kinda hard to figure out which is the cause and which is the effect?
    Could you help me better understand the problem?
    Not that i'll be able to help, just curious to learn.
    Edit: what is a "timing dump", i assumed its low spark advance?
    Last edited by TurboCobalt; 10-13-2015 at 03:49 PM.

  5. #5
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    I was fighting the same thing when I spun a bearing, so I am no longer able to investigate this. I noticed the exact same conditions you talk about, but what I noticed first was my AFR dropping to 0.88-0.95 after DFCO. I have never gotten my commanded ignition advance though

    I am not sure what is causing it, the only progress I made on it was to disable DFCO by zero'ing out the table, but it still did not completely solve the issue and I don't know what effect it had on timing.

  6. #6
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    Quote Originally Posted by TurboCobalt View Post
    in the picture attached from ETC Pdl PID it looks like you let off. From the picture to me it seemed like it cut spark because you let off. i guess it's kinda hard to figure out which is the cause and which is the effect?
    Could you help me better understand the problem?
    Not that i'll be able to help, just curious to learn.
    Edit: what is a "timing dump", i assumed its low spark advance?
    I can definitely see how it could be confusing. I had blipped the throttle just before letting the clutch out. Timing dump meaning commanded spark advance plummets from 20 degrees or so down to negative advance (-3 and as much as -7). Essentially, the car will literally fall on it's face as I'm trying to accelerate from a dead stop. Sometimes it's abrupt enough to slightly throw me forward in my seat, almost as if I got rear ended.

    Quote Originally Posted by mkriebs View Post
    I was fighting the same thing when I spun a bearing, so I am no longer able to investigate this. I noticed the exact same conditions you talk about, but what I noticed first was my AFR dropping to 0.88-0.95 after DFCO. I have never gotten my commanded ignition advance though

    I am not sure what is causing it, the only progress I made on it was to disable DFCO by zero'ing out the table, but it still did not completely solve the issue and I don't know what effect it had on timing.
    Sorry to hear about the bad news Kriebs! I like my DFCO and don't want to disable it. I would much rather gain control of the table associated with it, baring it's not some proprietary GM deal that would get HPT in trouble.

    Here's a better back to back comparison of what I'm experiencing, from the same log this AM

    No timing dump


    Dump
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    09 RY Cobalt SS Coupe - 19K miles - Bolt ons + 7163 ZFR, HP tuned on ethanol

    Sold - 09 SRTC Cobalt SS Sedan
    Totaled - 09 VR Cobalt SS Sedan
    Sold - 09 RY Cobalt SS Sedan

  7. #7
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    Thanks to some off-line help and referring back to some other notes from CBD, I've alleviated the problem, for the most part. My MS to OS difference was okay, it just needed a little more MS in certain off-idle areas.

    So far so good. Now I can go back to having fun with the PIDs and my 7-bladed compressor K04R
    With the stock turbo I was seeing 0-20lbs in 0.7-0.8 seconds and now I'm seeing 0-20lbs in 0.81
    09 RY Cobalt SS Coupe - 19K miles - Bolt ons + 7163 ZFR, HP tuned on ethanol

    Sold - 09 SRTC Cobalt SS Sedan
    Totaled - 09 VR Cobalt SS Sedan
    Sold - 09 RY Cobalt SS Sedan