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Thread: Timing ? on hard launch

  1. #1
    Tuner in Training
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    Timing ? on hard launch

    I have an 02 ls1 that I drag race . I logged a few runs and noticed when I am stalling the car at 2100 rpms on the starting line my timings is 42. When I launched the timing dips to 15.5 then comes right back to 26.5 and stays there. The tune is olsd. What is causing this dip? What tables should I be looking at? I can send someone my logs or tune to help me figure this out. Thanks.

  2. #2
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    Quote Originally Posted by nj02z View Post
    I have an 02 ls1 that I drag race . I logged a few runs and noticed when I am stalling the car at 2100 rpms on the starting line my timings is 42. When I launched the timing dips to 15.5 then comes right back to 26.5 and stays there. The tune is olsd. What is causing this dip? What tables should I be looking at? I can send someone my logs or tune to help me figure this out. Thanks.
    Posting log and tune here would be a good start. Without seeing either, I would guess that when you launch you are venturing to a portion of your timing table where your timing is set to that amount.

  3. #3
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    Current tune and log from Friday.
    Attached Files Attached Files

  4. #4
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    Quote Originally Posted by nj02z View Post
    Current tune and log from Friday.
    I don't see anything that stands out on the launch (no knock, high IATs or ECTs, etc) from the quick look I gave the log, and the high/low octane tables look legit in the tune. Personally, I would probably lower the 42* cells to something in the mid/high 30s to keep from jumping too many degrees at once (ex. 42* to 27*).

    The first thing that caught my eye in the log is sporadic timing while idling - the overspeed/underspeed timing tables definitely need some work in the tune. The idea is to make smaller timing changes when the RPMs are slightly off of the target idle RPMs; larger timing adjustments when the RPMs are farther away from the target idle RPMs. Currently, you are removing 15* when it is over any amount and adding 10* when it is under any amount.

    Hope that helps at least some.

  5. #5
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    Ok I will start there. Do you have any suggestions for a starting point to change them to? Any help or suggestions is greatly appreciated. Thanks, PS the car is cam only 233/239 TSP cam.
    Last edited by nj02z; 11-29-2015 at 05:28 PM.

  6. #6
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    Is it possible the original tuner set the overspeed /underspeed values to there current values to try and combat the stalling issue the car had? Should I set these tables back to stock or stock minus 50%? I always noticed that sawtooth idle but was not sure why. Thanks.

  7. #7
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    Torque Management zero out TCS Method( Retard vs. RPM and Aggressive Retard vs. RPM ), Spark Retard and Torque Loss.

  8. #8
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    Quote Originally Posted by nj02z View Post
    Ok I will start there. Do you have any suggestions for a starting point to change them to? Any help or suggestions is greatly appreciated. Thanks, PS the car is cam only 233/239 TSP cam.
    The stock values might be a good place to start -

    Overspeed
    0* at 0 deltaRPMS
    -16* at 300 delta RPMS
    Interpolate between

    Underspeed
    0* at 0 deltaRPMS
    3* at 12.5 deltaRPMS
    7* at 25 deltaRPMs (I could probably lessen this to something closer to 5)
    9* on up

    Quote Originally Posted by nj02z View Post
    Is it possible the original tuner set the overspeed /underspeed values to there current values to try and combat the stalling issue the car had? Should I set these tables back to stock or stock minus 50%? I always noticed that sawtooth idle but was not sure why. Thanks.
    Always possible.

    Quote Originally Posted by C5 2000 View Post
    Torque Management zero out TCS Method( Retard vs. RPM and Aggressive Retard vs. RPM ), Spark Retard and Torque Loss.
    Doh! I completely forgot about those since I thought they went away with a TH350 as the tune file states. Good call.

  9. #9
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    Thanks for the help. I deleted the rest of the TM and also set my overspeed/underspeed back to stock. Now long wait for winter to end and track to reopen. Thanks again.