NWS4Guy

This is false.

I encourage you to read the link in my post above, there is a link and explaination to an article showcasing the Acura SUV with SH-AWD (which is Acura's Sport Diff) against 2 other OEM SUV's without this type of feature.

The short of it is that without a Sport Diff type feature, ABS kicks in to stop the wheel slipping to match speeds with the wheel not slipping. These 3 SUV's were sent up a hill where the wheels on the left were on ice, those on the right were on clear pavement, and as a result the only one making it up the incline was the Sport Diff equipped car.

Why? Because the wheels slipping on the other's were stopped to match the speed of the wheels not slipping, which was a standstill. The Sport Diff SUV enabled it to move torque from the wheels slipping to those with grip. Expand this to ANY situation where you might have wheels on one side slip and you can see it is a huge safety feature as well. This would go for any situation with snow, ice, water, oil, sand, gravel - any type of event where you need control of the car on anything other than dry pavement.

AlA4

I would have to think this would also apply on dry pavement when near the edge of traction such as a hard accelerated turn.

NWS4Guy

Yes, in any situation where you might be losing traction to one or the other rear wheel (the fronts still will use ABS to slow whatever slips, as they don't have a Sport Diff). What makes it get the name Sport Diff, is that in a hard corner, weight would shift to the outside wheel, causing the inside to have less downward force on it and begin to slip - where the Sport Diff reacts.

Apparently this system is working so well the currently planned RS5 due to be officially unveiled in a few weeks at the Geneva Auto Show will have this type of electronic clutch driven system applied to the center diff, enabling the RS5 to shift torque between the front and rear sets of wheels. Current press release for the RS5 (which Audi released after the brochure for the RS5 leaked) shows that as much as 70% to the front, and 80% to the rear, with default of a 60/40 split like the S4 has. Of course the RS5 will have the Sport Diff as well.


I fully expect to start seeing the Sport Diff installed on the SUV segment in 2012, likely tweaked more towards safety than performance and perhaps given a different name for the use there, but it will be the same general system

westwest888

Another good example of loss of traction on a particular wheel is when you're making a turn on a racetrack. With the car at speed, nearly all of the weight transfers to one side of the car. If you make a left turn, the right suspension takes 95% of the load. If you make a right turn, the left side takes the cornering load. That's why you can hit the curbing at the apex at 100 mph and not lose control of the car - those tires are barely making contact with the road. With an open differential, a lot of power ends up flowing out of the inside wheel, which will spin freely while it barely touches the road. With the Audi system, this power will be rerouted to the outside wheel. This will propel the car through the turn and make use of of the near 300 whp.

Audicted2quattro

On the S4's the torque transfer occurs btw the rear wheels only correct? Not front to back as the RS5.

NWS4Guy

Correct.