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Thread: Is the 14.7:1 cruise AFR target on M156 REALLY hard coded?

  1. #1
    Tuner in Training
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    Is the 14.7:1 cruise AFR target on M156 REALLY hard coded?

    Is the 14.7:1 cruise AFR target on M156 REALLY hard coded or is it just a flag or table that has not yet been discovered by HPTuners?

    This large capacity high compression engine has huge pumping losses and I'm desperate to get the light load stuff to around 15.5:1 to reduce pumping losses. I've had great success with doing the same on other vehicles.

  2. #2
    i have yet to try this or lean burn for the M156, but from what I've experienced with my Audi A4 B6, the Motronic ECU has this hard coded as a safeguard for that vehicle.

  3. #3
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    I've had a reply to my old ticket and there are some new tables to try in the latest beta

    They only work for one ROM firmware by the looks. Only a 2014 example file I have shows them so they're working on adding them to the others.

    I can't wait to try them. If we can target 1.04:1 at idle and 1.08:1 at light driving loads and cruise, economy should improve substantially and no more catless smell and black stuff. I've seen big improvements on even much smaller and lower compression engines. The gains should be even more profound on an M156. Timing will need to be added to suit as the leaner you go, the slower the flame front speed.

    Target Lambda Adder.jpg

  4. #4
    hi bradsm87, happen to have any updates to the latest beta and the new maps?

  5. #5
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    Quote Originally Posted by hachiroku View Post
    hi bradsm87, happen to have any updates to the latest beta and the new maps?
    No unfortunately by the time these maps were defined, I lost motivation in tuning the C63 and am busy with other things but I'd like to re-visit it hopefully in a few months after doing decat and X-pipe.

  6. #6


    Thank you for contacting support, IF the M156 computer supports the ECM 34035 and ECM 34036 parameters it will populate for them. If you can find a Table ID for the rev blip I can forward that information to our engineer and see if he can add the requested parameter.

    Christopher Martinez
    HP Tuners LLC
    www.hptuners.com