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      11-27-2012, 03:37 PM   #53
ovekvam
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Norway
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Drives: F20 LCI 118i M-Sport B38
Join Date: Jun 2012
Location: Bryne, Norway

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The e-diff is just a regular open diff, but the car uses the ABS brakes to slow down spinning wheels individually. Since it usually is the inner wheel that wants to break traction, the braking will also take place on the inside. The resulting torque from the rear wheels will be unbalanced in a way that tries to rotate the car into the corner. The side effect is that it reduces understeer under power out of corners. It is quite noticeable on my 116i, and I would assume it is even more so on the M135i, which I haven't driven.

My experience from ice driving is fairly limited so far, but the overall traction seems to be the same in traction mode and DSC off. It is better than a car with open differential, but not quite as good as a car with a real limited slip differential.

In slippery conditions, the car is faster in DSC off mode than traction mode, as the car cuts in rather frequently with various braking to keep the car stable. The throttle response is however better in Sport+ mode, so that might be the fastest choice on dry tarmac. I'll have to test this more scientifically next summer.