NWS4Guy

Check the video if you haven't already, the Sport Diff works all the time, whether on the gas, braking or coasting. It takes all the factors and sensors I mentioned into account and steps in at all times, the only difference is based on what you have the button for the ADS/ADS Lite set for:


Comfort - SP will not step in as eagerly and allow understeer to favor, which is easier for most people to control and wor with.

Dynamic - SP will be as present as possible, to the point where if you have disabled the nannies (ESP and ASR off) you can actually induce oversteer and step the back end out and around.

Auto - the ECU will attempt to decide what mode you are driving in based on how hard you are on the throttle, how fast you are going and hard you are cornering.


If you take a S4 with the SP and one without and put them through the same, high speed banked corner - like a sweeping on-ramp on a cloverleaf interchange - the SP equipped model will consistently be able to take this faster and safer. Here is what would happen and why, assuming ESP and ASR are on with both cars:

Non-SP S4: As the car approaches the limits of traction, ABS senses that the inside wheel(s) on the car are slipping, and will engage to slow these down, slowing the entire car down in the process, keeping traction with the road and the car and driver both safe from losing control and drifing into a wall.

SP equipped S4: As the car approaches the limits of traction, the SP will transfer torque from the inside rear wheel to the outside wheel, thus not slowing the car, but moving the power to where the wheel has grip. The feeling to an experienced driver who knows the feeling of over and understeer, this has a sensation like an invisible hand pushing the rear of the car around the corner to match the front wheel's track. It's almost a feeling like havingf 4 wheel steering, as it essentially is - since in a turn, inner wheels travel a shorter distance than outer wheels, this exaggerates the principle in the transfer of this torque.


The inner wheel will always start to lose traction first unless the banking on the curve is extreme, like on a racetrack, due to the weight of the car shifting to the outside - you can feel this on any hard turn, as your body and the car lean to the outside of the curve. This transfer of mass causes less weight to be on the inside tires, which is what causes them to loose grip first.

mellow_sparky

Has anyone actually tried this - can you actually get the rear to come out? I don't mean slip a little bit, I mean really break free and cause you to correct with steering?

mitche2010s4

how does dynamic mode change the sports diff? If it is always active and reacting to the input from the sensors than can it become more active? I understand what the different setting can do for engine steering suspension and shift points in the automatic but the sports diff?

mitche2010s4

whoops...while I was writing my post it appears someone else was answering it. thanks

NWS4Guy

I haven't just taking a turn, but if you give it a little Scandinavian Flick, it will most certainly step out - a standard A4 certainly won't do this.

http://en.wikipedia.org/wiki/Scandinavian_flick

Observe (and this is in a S4 AVANT!) -
http://www.youtube.com/watch?v=2mcmvkBkVeg


The SP can transfer as much as 100% of the torque in the rear wheels from one side to the other if needed. The settings between comfort and dynamic tell it how much is acceptible basically. In comfort it will never send 100%, but stop short allowing oversteer to kick in, which is easier for most drivers to control.

mitche2010s4

I miss my '07 avant! that video was great.

westwest888

I wonder how effective this part is, the "STaSIS Engineering Torsen Center Differential". Does it change the fixed 40/60 split to something variable?

westwest888

Here's the answer, from the S5 page:

westwest888

I wonder if the computer would get confused about 80% of the power being at the rear instead of 60%, and miscalculate. Or if it's completely variable and based on observed inputs (yaw, wheel speed) rather than measured inputs (steering angle, throttle).

Audicted2quattro

Yes, I have done this on a test car. It is much easier to do with the sports diff then without it. However, if you have an older quattro with a lot more horsepower it can also be done easily in dry conditions.