Recently COBB has come to understand a bit more about the N55 DME and how it reacts differently when Traction-Control is left on. We had an experience with a customer who had a 335xi on the dyno and was noticing power output was a bit disappointing. Traction control was left on, as the AWD car would not be likely to loose traction when strapped down to a dyno. Though traction was not lost, the car made less power than expected.
As it turns out, even without loosing traction, the DME will target a lower amount of load (equating to torque and therefore horsepower). This caused the reduced power, as soon as it was disabled the car ran as expected.
What this means for you, is that if you expect to get the most out of either your performance tune, you will want to disable traction control. Though this is probably nothing new for most of us!
If you are in adverse conditions or otherwise limited in your driving ability, please leave traction control on. It is more important to make it home safe.
Please see the following document to see how the car runs differently with Traction-Control both engaged and disengaged.
If you have any further questions please email us at firstname.lastname@example.org!