Quote:
Originally Posted by footie
No, Audi's system isn't supplied by ZF ( by the way it was ZF and GKN that co-developed the TV diff in the X6) they chose someone else for their system, I think it was Ricardo (the company behind the DSG in the Veyron) though I am not sure if the one in the S4 is indeed this one or maybe this is a future offering. But I honestly though that the Audi setup was the only one to still work it's magic without load, if I am wrong then sorry BMW for doubting you.
It's great to get to talk to another car nut that seems to know his stuff.  |
I forgot about the GKN stuff... they make the guts! From what I know BMW also has a hand in developing stuff with ZF and is part of the R&D budget...
I think most manufacturers will start using planetary gears with some form of electromechanicals it is more efficient and cost effective, that is what ZF and Ricardo use.
Here is the rest of the nonsense on the rear diff...
ZF Speak:
Vector Drive rear axle drive: intelligent torque distribution
As the drive torque is distributed to the left or right-hand wheel individually, the Vector Drive rear axle drive generates an additional yaw moment. This screwing motion lends support to the vehicle steering and stabilizes the car during sudden swerving without having to apply any of the wheel brakes. Vector Drive therefore results in better driving dynamics and enhanced safety. And, with its planetary construction, the rear axle drive even delivers when the engine has no traction, i.e. in cases where the driver is not accelerating, such as when descending winding mountain roads. It also prevents tire slip when moving off on all kinds of road surfaces, which reduces wear and tear and improves the vehicles traction.
BMW Speak:
Dynamic Performance Control switches power between the left and right rear wheels to stabilise the vehicle within milliseconds and help increase traction and lateral acceleration. Handling is lighter and more precise during normal as well as difficult driving conditions.
How Dynamic Performance Control works can best be described in canoeing terms: if you want to turn right when canoeing in the main current, you can brake using the paddle on the right side of the canoe. This is how most common electronic stability programs work. Alternatively, you could use the paddle powerfully on the left side of the canoe in order to have more control in progressing forwards and turning right. This is the principle behind Dynamic Performance Control.
It links the standard rear differential with a mechanical planetary gear set and an electronically controlled multi-plate clutch for each rear wheel. Its mechatronical system combines informatics, electronics and mechanics to process complex data such as the yaw rate, wheel speeds, steering angle and engine torque so that it can react immediately: when required, the system ensures that drive power distribution to the rear wheels can be freely varied and increased on either side as needed. The power distribution can also be displayed on the onboard computer.
Dynamic Performance Control increases directional stability when accelerating out of bends and provides the driver with extra support when dealing with difficult driving conditions. Before under- or oversteer can take place, lateral guided force is used to keep the vehicle on track. Precise steering significantly increases driving comfort and safety.
Dynamic Performance Control is also effective when the vehicle is coasting - when the driver removes their foot from the accelerator - or when they have pressed the clutch pedal. If the rear wheels are on different types of surfaces, Dynamic Performance Control improves traction by supplying more drive power to the wheel with more grip. A wheel torque difference of up to 1,800 Nm can be actively created between the left and right rear wheels. This increases driving stability and allows for much faster acceleration.
As a logical progression to the xDrive all-wheel drive system, Dynamic Performance Control can be matched to all drive concepts and engines. Whereas xDrive variably controls the power distribution between the front and rear axles, Dynamic Performance Control intelligently distributes power between the two rear wheels. This results in precise handling whatever the driving conditions.