Results 1 to 3 of 3

Thread: Surge on coastdown

  1. #1
    Tuner in Training
    Join Date
    Sep 2019
    Posts
    12

    Surge on coastdown

    Im new to tuning so I need some help figuring this out. Car will surge on deceleration. Goes away after driving for 10 minutes or so but will do it every time the car is turned off and restarted. It mainly shows up on my logs as engine torque swinging up and down wildly. Ive attached a log so you guys can see it. One clue I have is that when I step on the brake the surge goes away. Any advice would be greatly appreciated.
    Attached Files Attached Files
    Last edited by MurderV2; 07-01-2020 at 04:43 AM.

  2. #2
    Advanced Tuner
    Join Date
    Aug 2010
    Location
    Detroit, MI
    Posts
    926
    I see it downshifting, I wouldn't call that surging. But you may have too much torque in your closed throttle downshifts, which could come from a number of sources. Need to log brake pedal position, desired airflow, any engine torque control sources, desired engine torque, actual engine torque, etc. And don't pull them from the TCM...no need to get engine data double-relayed through via TCM. CAN is slow enough as is. And post the file itself.

  3. #3
    Tuner in Training
    Join Date
    Sep 2019
    Posts
    12
    Quote Originally Posted by smokeshow View Post
    I see it downshifting, I wouldn't call that surging. But you may have too much torque in your closed throttle downshifts, which could come from a number of sources. Need to log brake pedal position, desired airflow, any engine torque control sources, desired engine torque, actual engine torque, etc. And don't pull them from the TCM...no need to get engine data double-relayed through via TCM. CAN is slow enough as is. And post the file itself.
    I appreciate the help. I?ll add some parameters and upload the tune and scan logs. Only reason trans file is up front is because I?m doing some trans adjustments. More parameters are in the other charts there though. 👍🏻