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Thread: cammed scat stalls too easy. TPS voltage dropping when it should be increasing.

  1. #1
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    cammed scat stalls too easy. TPS voltage dropping when it should be increasing.

    tuning a 6.2 based 426 with a decent sized cam, ported heads, ID1050's and kenne bell. Car runs pretty good so far just need to iron it out.

    I'm noticing as I let the clutch out the car wants to stall if rpms get blow 700 ish rpm. I'm noticing the throttle voltage isn't even trying to increase or prevent stalling. In the attached scan what I'm doing is letting the clutch out with the brakes applied to create the situation. You can see at 42 seconds once the rpms drop below about 725 the throttle voltage drops as well. I would expect the ecu to try to add tps voltage to prevent the rpms from being below target. Also, at 1:06 you can see I did it again but this time it wasn't able to recover.

    Any ideas how to bump up tps voltage at low than idle rpms? I have idle set to 775.

    Also, does anyone know of any good ADVANCED reading material I can buy to explain the proper way to tune the torque model on these newer mopars?


    editor.hpt
    stalling 2.hpl
    2018 Camaro SS, Maggie 2650, 103 TB, Big Gulp, E85

  2. #2
    Bring the idle up to 850-900 until you get some stability. 725 will likely be to low period.

    First off, you must ensure idle airflow is correct.... then you use the Idle Torques to stabilize the idle. This takes a fair amount of trial and error. Best case, you want your throttle position very stable and then let the timing control everything.

    When you get idle airflow dialed in, this becomes relatively easy to do.

    I'm sure the blower drag adds additional elements that I haven't dealt with.

  3. #3
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    Hey thanks for the reply. Idle is actually very stable, it just doesn?t want to recover if I load the engine below 700, figure it should at least attempt to recover and be able to above ~500.

  4. #4
    Quote Originally Posted by GPGTP View Post
    Hey thanks for the reply. Idle is actually very stable, it just doesn?t want to recover if I load the engine below 700, figure it should at least attempt to recover and be able to above ~500.
    The PID system in the idle torques can help with this.

    If the idle is very stable, try setting the throttle proportional in Drive to 20 at -100 and ramp it up maybe 44 at -500.

    For the time being, I would zero out any correction in the throttle PID under +/- 100 rpms.

    If the airflow is right, the spark PD will do a good job, but the throttle PID will save it from stalling during big movements (coming to quick stop).

    Use proportional and the gradually bring in Integral. I actually don't have to use any derivative, but it can be used for fine tuning.

  5. #5
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    so I decided to try something. Put the VE table back to stock and skewed the fuel injector data to lean it out. It now starts idles and drive perfect. Issue is now it is doing the oscillation thing where the throttle jumps around. Is there a way around this?
    Attached Files Attached Files
    Last edited by GPGTP; 07-15-2019 at 06:05 PM.
    2018 Camaro SS, Maggie 2650, 103 TB, Big Gulp, E85

  6. #6
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    Quote Originally Posted by GPGTP View Post
    so I decided to try something. Put the VE table back to stock and skewed the fuel injector data to lean it out. It now starts idles and drive perfect. Issue is now it is doing the oscillation thing where the throttle jumps around. Is there a way around this?
    I'm gonna lower the airflow values in the Large range demand table. I've had a similar issue on other cars where the throttle wouldn't open but then snap open but never an oscillation.
    2018 Camaro SS, Maggie 2650, 103 TB, Big Gulp, E85