[PrematureApex]

Originally Posted by Robin_NL

Well said, though I would not actually call our electronical M diff an E Diff, because the E82 135i had something called an E Diff at that time and that was more kind of torque vectoring as I recall.

McLaren also make use of TV 'diffs'. I though Porsche too(?), some models.

Cheers
Robin

The "ediff" in a 135 is an open differential. Meaning torque is ALWAYS split 50/50, no matter what...absent things like clutches on the outputs, etc.

There is no torque "vectoring" side to side with an open diff. With an open diff, output torque to either side is limited by the wheel with the least grip. For example, in the classic case of one wheel on ice and one on dry ground, the wheel on ice slips easily, limiting the torque provided to the wheel on dry ground (always 50/50, remember).

In that situation, the "ediff" function grabs the brake on the slipping wheel (ice wheel), ramping up the tractive torque "taken" by that wheel. Since it's a 50/50 split, that correspondingly increases the torque provided to the wheel with grip...and off you go. Mimics a LSD, but no true vectoring.

Cars like the focus RS don't technically have a rear diff. It uses a spool to split torque, with clutch packs on either sides output. So it can truly move torque side to side, or "vector" by controlling the clutches.

Car companies have expanded the term "torque vectoring" pretty ridiculously as a marketing tool.

A good read on the "myth" of an open diff, one-wheel drive, etc.

http://oppositelock.kinja.com/your-d...rks-1661277563

The "Engineering Explained" videos do a good job too.

It's one of the most misunderstood concepts out there in the car world. That and "you need backpressure to make low-end power" (no!)