Results 1 to 7 of 7

Thread: m157 knock retard

  1. #1
    Potential Tuner
    Join Date
    Jun 2019
    Posts
    4

    m157 knock retard

    During logging, i logged all cylinders knock retard.

    Does the same hold true in mercedes world that a negative knock retard # is adding timing and not a bad thing?

  2. #2
    Senior Tuner BackyardTurbo_FTW's Avatar
    Join Date
    Jul 2009
    Location
    East Suckburg, PA
    Posts
    1,150
    no, thats the amount of timing it is pulling back. Should be easy to compare your actual timing to the timing table and see you aren't getting the commanded timing amount

  3. #3
    Potential Tuner
    Join Date
    Jun 2019
    Posts
    4
    Quote Originally Posted by BackyardTurbo_FTW View Post
    no, thats the amount of timing it is pulling back. Should be easy to compare your actual timing to the timing table and see you aren't getting the commanded timing amount
    Thanks.
    Im learning slowly, but here is log put on a graph from VCM scanner. Im not sure how to pull the timing table. Even on 93cotane and stock setup, my knock retard is going off a bit in each cylinder.

    Knock retard i can log cylinders 1-8, but im assuming the 'timing advance sae' is for cylinder 1 only.

    https://datazap.me/u/5soko/e63-0?log...zoom=1097-1191

  4. #4
    Senior Tuner BackyardTurbo_FTW's Avatar
    Join Date
    Jul 2009
    Location
    East Suckburg, PA
    Posts
    1,150
    Its not uncommon for stock tunes to be set at a higher timing amount and then they rely on the knock sensor to adjust the timing for different qualities of gas, air, etc. BUT, OEM's will also set the decay rate to be very slow when knock correction is applied as well. This way if it senses any knock it will pull timing and hold that amount of retard for an extended period of time to try and keep the car safe. Also, they typically pull more than required and you are likely having timing pulled in areas it doesnt need it because of that slow decay rate.

    This is why custom tuning yields great results, you are fine tuning the car for your fuel quality, air quality, elevation, parts upgrades etc etc etc.

  5. #5
    Potential Tuner
    Join Date
    Jun 2019
    Posts
    4
    Quote Originally Posted by BackyardTurbo_FTW View Post
    Its not uncommon for stock tunes to be set at a higher timing amount and then they rely on the knock sensor to adjust the timing for different qualities of gas, air, etc. BUT, OEM's will also set the decay rate to be very slow when knock correction is applied as well. This way if it senses any knock it will pull timing and hold that amount of retard for an extended period of time to try and keep the car safe. Also, they typically pull more than required and you are likely having timing pulled in areas it doesnt need it because of that slow decay rate.

    This is why custom tuning yields great results, you are fine tuning the car for your fuel quality, air quality, elevation, parts upgrades etc etc etc.
    Excellent info! Thanks for that!

  6. #6
    Potential Tuner
    Join Date
    Jun 2019
    Posts
    4
    Quote Originally Posted by BackyardTurbo_FTW View Post
    Its not uncommon for stock tunes to be set at a higher timing amount and then they rely on the knock sensor to adjust the timing for different qualities of gas, air, etc. BUT, OEM's will also set the decay rate to be very slow when knock correction is applied as well. This way if it senses any knock it will pull timing and hold that amount of retard for an extended period of time to try and keep the car safe. Also, they typically pull more than required and you are likely having timing pulled in areas it doesnt need it because of that slow decay rate.

    This is why custom tuning yields great results, you are fine tuning the car for your fuel quality, air quality, elevation, parts upgrades etc etc etc.

    So, i did another datalog, on 93 octane with my rentech tune.

    All my knock retard values for all 8 cylinders at wot above 5K RPM, are at -3 or -5/6
    I am not getting any CEL or codes, car runs fine and all other values are good, AFR and boost etc.

    My timing advance is hovering around 0 at this point.

    Is this bad?

    Here is a link to my datalog graph:

    https://datazap.me/u/5soko/e63-s-ren...0&zoom=214-269

  7. #7
    Potential Tuner
    Join Date
    Jul 2016
    Posts
    1
    That just looks like too much boost for the fuel quality you're running. Timing is very low as a result. A bit less boost with more efficient ignition and lower IATs would yield a faster car IMO.