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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > DSC



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      06-10-2008, 08:20 AM   #1
Appropriate
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DSC

Can anyone explain to me what this button does in my 335xi? I did a quick search and didn't find as simple a thread as I would like. As I understand it, there are three ways to use this button:

1) Don't press it at all.

2) Press and release (dash says "DSC" after this I think).

3) Press and hold until the little crazy icon appears on the dash.

I would welcome a simple explanation. Thanks!
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      06-10-2008, 09:17 AM   #2
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The car normally drives in DSC.

If you press it once you go to DTC mode which is a more generous type of traction control. Used for tracking a car or winter driving with loose snow. Also good for hard street drving if you are into that sorta thing. Don't kill anyone.

Press and hold for 5 seconds, the traction control is off. You have total control of the car, but no bail out if you f'up. Its gonna hit the wall/curb of your choice if you push it and loose it.

I never use the DTC for my AWD, not really needed on the street at. all. One the track the DTC is faster but we are not talking about 10's of seconds here but it adds up.

That is as aimple as I can get it.

I am pretty sure ont he DSC/DTC thing but anyone back me up?
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      06-10-2008, 12:10 PM   #3
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So when you say "you have total control of the car," all-wheel drive is still active right? It doesn't switch to RWD only, it just eliminates shifting of power from wheels that slip to wheels that grip, right?

Good summary though.
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      06-10-2008, 12:14 PM   #4
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From BMW...

DSC -

Dynamic Stability Control (DSC) adds to safety by facilitating vehicle control even in adverse driving conditions or on tough surfaces.
Dynamic Stability Control (DSC) is the nucleus of the chassis control systems in BMW vehicles. It ensures the highest possible levels of stability when driving, and it maximizes traction of all wheels when setting off or accelerating. It is able to detect the first signs of oversteering or understeering and helps keep the vehicle safely on course, even if the tyres have varying levels of grip.
Sophisticated sensors permanently check how the vehicle is driving. Information comes a range of sensors monitoring wheel rotation, steering angle, lateral forces, pressure and yaw (degree of rotation around the vertical axis). A simulation model stored in the DSC control unit to ensure stability ("one-/two-track model") and can be compared information coming from the steering wheel and accelerator: if there is too great a difference between the model and how the vehicle is currently travelling, DSC acts to increase stability or traction.
The engine and brake management systems are targeted specifically; xDrive is also included in all-wheel drive vehicles. Reducing or increasing the engine torque or braking individual wheels can improve stability and traction. Active Steering’s integrated yaw regulation system can even help significantly reduce steering effort and the extent of DSC’s contribution to stability.



DTC -

Dynamic Traction Control (DTC) allows for sports-style driving dynamics even when DSC is controlling stability and when wheel traction is higher.
Dynamic Traction Control (DTC) is a sub-function of the Dynamic Stability Control (DSC) system that can be turned on and off. DTC has two major uses: to regulate traction and to enable sports-style driving while providing active stability control.
If the front wheels are stuck in snow and cannot spin properly, this leads to slip on the rear wheels (when they spin faster than the front wheels, generally a sign that performance has been exceeded) and DSC acts to change engine output: the power needed for forward movement is reduced. Switching to DTC has a positive effect on this situation, as traction is improved without a loss of power.
When DTC is on, it helps the driver alleviate the situation enough for DSC's measures to become effective. The driver retains complete control over the vehicle
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      06-10-2008, 04:58 PM   #5
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In simple terms as I understand the system
DSC, the car can apply the brakes individually to either wheel without you having to touch the brake pedal. It does this to keep you out of trouble and avoid you hitting the curb. It detects wheelspin and prevents it by applying the brakes to whatever wheel is spinning

DTC, the car can send from 0 to 100% torque to either wheel depending on available traction. It will not apply the brakes to the spinning wheel, it will just send more torque to whatever wheel(s) have the most traction.

DSC and DTC off, you dont have a baby sitter to get you out of trouble. If you are driving to hit the curb, you will hit the curb, no braking of the spinning wheels or re-routing of the torque to the wheels that have the most traction.

If I am wrong, please corect me.
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      06-10-2008, 05:11 PM   #6
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Quote:
Originally Posted by Appropriate View Post
So when you say "you have total control of the car," all-wheel drive is still active right? It doesn't switch to RWD only, it just eliminates shifting of power from wheels that slip to wheels that grip, right?

Good summary though.
Sorry, it still sends the power to all the wheels but the stability control is disabled so if you come into a corner too hot, get on the brakes and then steer and then the front starts to plow, the inside rear tire is not going to brake to help avert the understeer problem. You are going into the wall/curb etc.

The AWD system will still work but the DSC/DTC sytem of braking individual wheels to control vehicle motion is off.
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      06-10-2008, 05:19 PM   #7
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Quote:
Originally Posted by sparkyg View Post
The car normally drives in DSC.

If you press it once you go to DTC mode which is a more generous type of traction control. Used for tracking a car or winter driving with loose snow. Also good for hard street drving if you are into that sorta thing. Don't kill anyone.

Press and hold for 5 seconds, the traction control is off. You have total control of the car, but no bail out if you f'up. Its gonna hit the wall/curb of your choice if you push it and loose it.

I never use the DTC for my AWD, not really needed on the street at. all. One the track the DTC is faster but we are not talking about 10's of seconds here but it adds up.

That is as aimple as I can get it.

I am pretty sure ont he DSC/DTC thing but anyone back me up?
THERE IS NO SUCH THING AS COMPLETELY CONTROL OF THE DTC. ONCE YOU TURNED OFF THE DTC. THE DSC WILL HAVE ABOUT 25% CONTROL OF YOUR CAR. THIS IS PART OF THE SAFETY AND PLAUSIBLITY CAUSE MODE.
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      06-10-2008, 07:59 PM   #8
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OP. Find an empty parking lot and experiment. Thats the best way to explain it. Hit the button, drop the clutch (if you have one) and floor it. Then, when you reach a comfortable g-producing turn speed, crank on the wheel and keep the vehicle under control.

Next, hold the button for a few secs and do the same maneuver. (feel free to take a couple runs at this, just bc, and remember the goal is to keep control)

Im sure you will quickly feel the difference
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      06-10-2008, 09:02 PM   #9
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I'm sure most of us are thinking along the same lines, but the message is getting hazy with some of the explanations.

First, if you DON'T push any buttons on the dash (i.e. start & drive), DSC is fully engaged. It does a number of things to control under/over-steer and adjust yaw, among them distribute power to the appropriate wheel(s) *actually X drive is doing this* as well as apply brake(s) to the appropriate wheel(s). DSC also cuts power (at the engine)

DTC is a SUBSET of DSC, and is activated by a quick push of the button. This allows for more aggressive driving (allows for more slippage). Great for keeping power to wheels in less than ideal conditions *you can drift the back end out in the snow*. Also better for more aggressive driving thru hot corners (i.e. tracking the car). Engine power / wheel braking is not applied as aggressively as it is in full DSC mode.

Last mode is DSC OFF (which actually doesn't shut off DSC, just limits it significantly). This mode is actuated by pressing and holding DTC button for approx. 5 seconds. In this mode, DSC activates power cut / applies braking only when the car is nearly out of control. For most drivers, this would be too late.
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      06-10-2008, 09:56 PM   #10
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+1

The DTC one push is the best setting for summer sport driving or winter driving.

Without it, in the winter DSC intervenes too readily to cut power when you don't want it to and keeps you from accelerating properly.

In the summer, for best launches, do not fully disengage DSC. xDrive behaves weirdly shifting torque to the front and back tires and slowing your time. Once again the DTC one push gives the best results.

One push and DSC/DTC cuts you some slack in a controlled fun zone. It intervenes just at the right time by doing things that you cannot on your own like braking individual tires.

With DSC off (5 sec push), as said above, intervention comes when you are already done for.

Seen in this light, in my view, DSC with the DTC one push is an effective driving tool.
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      06-11-2008, 09:18 AM   #11
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Quote:
Originally Posted by Calgary Agent View Post
I'm sure most of us are thinking along the same lines, but the message is getting hazy with some of the explanations.

First, if you DON'T push any buttons on the dash (i.e. start & drive), DSC is fully engaged. It does a number of things to control under/over-steer and adjust yaw, among them distribute power to the appropriate wheel(s) *actually X drive is doing this* as well as apply brake(s) to the appropriate wheel(s). DSC also cuts power (at the engine)

DTC is a SUBSET of DSC, and is activated by a quick push of the button. This allows for more aggressive driving (allows for more slippage). Great for keeping power to wheels in less than ideal conditions *you can drift the back end out in the snow*. Also better for more aggressive driving thru hot corners (i.e. tracking the car). Engine power / wheel braking is not applied as aggressively as it is in full DSC mode.

Last mode is DSC OFF (which actually doesn't shut off DSC, just limits it significantly). This mode is actuated by pressing and holding DTC button for approx. 5 seconds. In this mode, DSC activates power cut / applies braking only when the car is nearly out of control. For most drivers, this would be too late.
This is basically correct, but I have just one (very minor) tweak:

DSC/DTC actually does have the ability to redistribute power between driven wheels on the same axle, which it accomplishes by braking one of the wheels on that axle. In a car with an open diff, braking one wheel on a driven axle will have the effect of sending power to the other wheel. xDrive only handles the front-rear power distribution (unless you drive an X6).
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      06-11-2008, 09:34 AM   #12
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Quote:
Originally Posted by Lassaxi View Post
This is basically correct, but I have just one (very minor) tweak:

DSC/DTC actually does have the ability to redistribute power between driven wheels on the same axle, which it accomplishes by braking one of the wheels on that axle. In a car with an open diff, braking one wheel on a driven axle will have the effect of sending power to the other wheel. xDrive only handles the front-rear power distribution (unless you drive an X6).
Correct The X6 X-drive features torque vectoring
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      06-13-2008, 12:56 PM   #13
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Is there any reason to disable DSC/DTC for normal daily commuting/normal street use? That is, does it increase gas mileage or anything like that?
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      06-14-2008, 06:38 AM   #14
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Quote:
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Is there any reason to disable DSC/DTC for normal daily commuting/normal street use? That is, does it increase gas mileage or anything like that?
It shouldn't make much difference, unless you break traction or spin your wheels a lot.
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      06-14-2008, 07:40 AM   #15
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Doesn't DSC help me to not break traction or spin my wheels. I think if I wanted to break traction or if I wanted to reduce the life of my tires, then I would turn it off - but for normal everyday driving, why would i want to turn it off?
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      09-02-2008, 02:42 AM   #16
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i love how these heated convos just sorta terminate randomly. lol.
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