DSC and DTC

I have been driving my 745 LI for a while now. I am getting confused by the DSC and DTC functions, not so much for what they do but rather "when" they are activated .

The manual says DSC (Dynamic Stability Control) is on by default as soon as your start the car. However, it appears that DTC (Dynamic Traction Control, which limits wheel spin on slippery road conditions like ice and snow) is by default off.

If you go to the iDrive car setting menu, the DSC will turn off if you press and select that, but strangely when you press the DTC button, the screen says now its ON. This means it was off by default when you start the car.

I am confused because I thought DTC would be on all the time, just like on other cars with DTC. I have a Volvo XC-90 and the DTC is on by default.

An commettns would be appreciated.

A good example of the difference is driving the car in the snow. DSC will keep the car from spinning out. In fact you cannot pull donuts in a 745 with DSC on. It will do everything it can to keep the back end from spinning out.

DTC in the snow acts more like a limited slip differential trying to keep equal power to both wheels. My understanding is DTC is off when DSC is on so that there is no fight between the systems to keep the car in control.

pan,

Thanks for your insightful response. It seems the DSC is more useful when the car is already in motion whereas DTC is activated manually only if you get stuck in the snow ? That is why DSC is on by default and DTC is driver activated only when needed.

In the three years I've had my 745i I've used DTC only for experimenting. I never had to use it specifically for traction. I just left DSC on all the time.

A few years ago I attended a driving course at BMW in North Carolina. As part of the course we drove on a donut shaped skid pad. The purpose was to learn how to manage over and under steer which is actually difficult to do with any precision. After spinning out a number of times trying to go around the skid pad as fast as possible the instructor engaged DSC. With DSC the car stayed on track without spinning out at a much faster speed than I could manage without DSC. I learned to trust it and depend on it.

By default, when you start your car, Dynamic Stability Control is on and Dynamic Traction Control is off. DSC will not allow any wheelspin at all. So, in snow for example, when you might need a little wheel spin to get going, you can turn on DTC to allow this. DSC is still on, but with DTC turned on, the wheels are allowed to spin a bit.

If you turn DSC off, everything is off and you can spin the wheels, fishtail, just like a car with no DSC.

I was surprized at how effective the system really is. It's really tough to make the car slide in snow with DSC on. With it off, you can slide at will.