German Car Zone

Martinbro, my simple answer to your question is I don't think I feel the e-diff causes any notiecable "pulsations" (like ABS) when it is working. However, I'm not entirely sure, because I have not really pushed the car that hard when only the e-diff is active. Let me explain.

On the 135i, there are 3 levels of stabiliy/traction control.

1) The default and most intrusive mode is with DSC on. In this setting, it acts like any other stability and traction control system. The traction control feature will use individual brakes to stop excessive spin of any of the drive wheels and engine torque will also be cut back if necessary to get traction. The stability control feature will use individual brakes and cut engine torque if necessary to correct any understeer or oversteer.

2) When you press the DTC button once, the dynamic traction control mode becomes active. This mode works exactly the same as the standard DSC mode, except that the thesholds for intervention are all raised. In other words, individual brakes and cutting of engine torque are all used to increase traction of the drive wheels or to correct understeer or oversteer. However, the traction control feature will allow a certain degree of wheelspin of the drive wheels before cutting engine power, while the stability control will allow a degree of understeer/oversteer before intervening.

3) When you press and hold the DTC for 3 seconds, both standard DSC and DTC are deactivated, but the so called "e-diff" remains active. In other words, the system will still brake any drive wheel which is spinning excessively compared to the other to so that power will be transferred through the open differential to the other drive wheel which presumably has more grip (to mimic the actions of a mechanical LSD). However, there is no cutting of engine power in this mode, and there is also no stability control to correct any understeer/oversteer.

Although BMW has done very well in marketing this e-diff feature, it is by no means new. In fact, it was introduced back in 2004 when the C55 AMG was introduced, and it has been on all AMG models introduced since.

When I took the 135i on the track, I drove mostly in DTC mode (#2 above). It allowed for some good wheel spin and a degree of oversteer before any cutting of engine power kicks in. I didn't have the guts to drive with just the e-diff alone (#3 above).

But since the e-diff is simply a feature of the standard DSC and DTC, I am pretty confident there are no "pulsations" like you feel with ABS when it is working. Similarly, there are no pulsations I could feel with the C55's e-diff when I push ESP "off".

PC are you changing to a real meachanical LSD for your 135i?

Thanks PCV - you've given me some really useful insight based on your experience.

All the best with your 135i and enjoy those track days to the max you lucky bugger!

No plans to. I think I'm not hard core enough of a track driver to really benefit from one.