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Old 12-24-2008, 09:21 AM
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Mein Auto: '84 533i; '05 VNL 630 66K
Originally Posted by jcl10 View Post
That isn't what DTC is for. The confusion starts with the BMW labelling system for warning lights and the button.

In normal state, no lights, you have DSC (Dynamic Stability Control) and DTC (Dynamic Traction Control), by default. DSC helps with sliding, DTC puts a brake on to stop a wheel from spinning. There is a low system threshold for a spinning wheel, meaning the system (nanny) intervenes quite early.

Pushing the button once turns off DSC, but keeps DTC on. It allows more wheelspin than the standard setting (fewer nannies). This is designed to be used if you try to get going at slow speeds and the road is so slippery that you have no throttle response, ie the computer is limiting throttle because of wheel spin. Allowing some wheel spin can get you up a hill or get you moving sometimes when the system would otherwise stop you. Once you are moving, it is worth putting turning DTC off (back to normal state) for most drivers.

Holding the button for longer turns everything off. Good for track days, or playing around in parking lots to find out the limits of your car.
I think this is mostly right, except that I thought / think that rather than putting brakes on to stop wheel spinning, it reduces accelerator inputs to prevent spinning. Maybe both, I'm not sure, but it is clear that you have reduced power when you're trying to break the rear-end loose if you don't turn the system off.

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