Originally Posted by WAY
I don't know for sure, but I would have thought its the other way around? Ie. it comes on when you turn DSC off? It makes much more sense. But I can tell you from a driver's perspective, I was able to slide my Drexler equipped 135i with ease, where it wasn't so simple previously. I suspect it would be the same with my new car M135i.
When BMW launched the F20, they wrote in the ads that the e-diff now works with DSC off. I am pretty sure the earlier models worked differently.
Thinking about how it logically should work does not make much sense here. If it did, the modern BMWs would not select comfort mode when you disable DSC.
Our 116i can drift quite easily with DSC off in slippery conditions. Lack of power makes it difficult on dry tarmac. If the diff was open with no e-diff, it would have been more unpredictable.
You can feel the e-diff working on corner exits on dry tarmac as well in the 116i. When I don't have enough power to spin the outer rear tire at full throttle after apex, you would expect the car to understeer. After all, it has a weight shift to the rear tires. The e-diff brakes the inside rear tire, creating torque vectoring that tries to turn the car into the corner. This kills the understeer, and allows me to go very early on the throttle.