# traction control dsc question



## HankM3 (Nov 5, 2002)

first of all

Why do you have your parents cars in your sig?



KwlAznKid said:


> first of all
> this is my car
> 2nd of all what makes you assume that i am bad driver? i'm not saying im good or anything, but you shouldn't make smart remarks like that to me before you even know me, i just posted this because i was curious and wanted to learn more and thanks to the people that actually want to help me i got some more information, i never said anything about doing anything crazy. I was just curious on how it works.


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## surewin (Jan 9, 2004)

tierfreund said:


> By the way, don´t be fooled by marketing gooble. The LSD DTC is supposed to emulate is no very helpfull. It might help you from a standing start, but the brake usage to shift power to the driven wheel with more grip is only active at low speed. Beyond 20 or 30mph the function is no longer active (It would overuse the rear brakes otherwise). A real LSD will give you better traction in fast cornering. Something DTC can not. Thats why all E46 M3´s have a very advanced electronically controlled mechanical LSD.


DSC's primary job is it stabilize the car when it's turning. It cuts off power/ applies brakes to individual wheels when it detects oversteer or understeer. It's a saftey mechanism, not a performance mechanism.

LSD, however is a performance mechanism, distributing torque to the drive wheels where it's needed. Instead of cutting away torque from a spinning wheel like DSC, an LSD will just distribute more torque to the non-slipping wheel. This improves handling and stabilzes the car in turns, elimitating torque steer and one wheel slippage. LSD has nothing to do with car saftey, and therefore isn't a primary concert for the regular line of BMVs. The M cars have an LSD since performance is its main concern.

An LSD is more than just a hunk of metal with 2 gears. There are different kinds of LSDs and I'll explain a few examples: the clutch type, the viscous coupling, and the locking.

The clutch type LSD uses a series of clutches and spring plates to makes sure that both wheels are moving at the same speed the whole time. In order for the wheels to spin at different speeds, one of the wheel must overpower the heavy clutch that is keeping both wheels spinning at the same speed.

A viscous coupling LSD has two sets of plates, each set connected to an output shaft and is filled with thick fluid. When one wheel spins faster than the other, the fluid moves the slower wheel faster in order for it to catch up with the faster moving wheel. The disadvantage of the viscous LSD is that it won't operate until one of the drive wheels starts to slip.

The E46 M3's LSD is a locking LSD, where a pump is activated when a difference in torque is sensed, closing the series of clutches that connects the two half shafts. It's different than a clutch type LSD because the clutch isn't activated until a difference in speed in the drive wheels is sensed by the system.

I think the 3 types of LSDs I've mentioned gives a clear look of how an LSD works and how it's only used as a performance mechanism, not a safety mechanism.


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## MicahO (Apr 19, 2004)

undien717 said:


> It says right there when you press the dsc button it deactivates DSC and activates DTC.
> 
> The braking mechanism that activates when oversteer or understeer is sensed is CBC. DBC and CBC are still on when DTC is activated. To turn everything off you have to hold down the DSC button for 3 sec. Hope this clears it up-


The third paragraph also states that DSC incorporates DTC and CBC. From using the car hard on a track with full dsc enabled, I can state categorically that full DSC leaves the advanced braking stability functions intact, and adds the extra throttle-nanny functions as well. You should have seen the inside (right) rear brake pads after a day at Lime Rock.

The language "activating the DTC" is definitely confusing. In my experience with the system, the throttle cut-outs happen at an earlier stage than the per-wheel braking inputs. But if you are pushing the yaw past the point that the car thinks cutting the throttle's going to help, it starts applying brake as well. The reality is that deactivating the DSC (disabling the throttle control) allows the DTC (braking functions) to be the first items activated in a low-traction or imminent-spin situation. Nonetheless, they are active all the time until the three-second push and hold.

And as Nick noted - all of these systems cut in long before the car is actually ready to swap ends (particularly the Sport and Performance models). They are great for brainless daily driving, and reasonable for a learner on a track. But they're much too conservative for truly hard driving. Put a real LSD in the car, turn off the various controls, and use the car for what it is capable of acheiving.


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## grimreapa (Jul 5, 2004)

KwlAznKid said:


> first of all
> this is my car
> 2nd of all what makes you assume that i am bad driver? i'm not saying im good or anything, but you shouldn't make smart remarks like that to me before you even know me, i just posted this because i was curious and wanted to learn more and thanks to the people that actually want to help me i got some more information, i never said anything about doing anything crazy. I was just curious on how it works.


cant some people really be jackass', listen up kid your had good question cause i was wondering about it to. this other guys manual is telling you totally something different than what your car will do. Best bet is to just check your owners manual. Description is pretty good and at least you will know what happens when you press that button. :thumbup:


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## Bob330Ci (Oct 15, 2002)

Just came back in from the freshly falling snow and ice and a little experimenting in some low traction scenarios with my 2003 330Ci. Conditions were about 3" of wet snow with patchy ice underneath, so some spots were really slick.

No button push, normal mode, I can feel the brakes getting applied as I under- or oversteer, even without power. Throw some power into it and the car first seems to try to limit wheelspin with the brakes, then it cuts engine power. It only allows a minimal amount of slip and my attempts to power oversteer resulted in a few degrees out of line for the tail. The cars does not stray very far from the line intended by the steering wheel. (Unless of course you do something dumb, but even flooring the gas mid corner is uneventful.)

Single button push gets much more entertaining. It seems wheelspin is unlimited, allowing me to freely rev the engine while in gear. In such low traction, it revs almost like it's in neutral. Excessive oversteer is allowed, even extended drifting. I did not feel individual brakes attempting to correct my course, which is counter to how the manual reads. My snow tires are same size front and rear, 225 width Blizzak LM-22's, and my suspension is stock. Oversteer was a lot easier to produce than understeer. 

I did not have excessively large runout areas so all this was done at low speeds (below 25).

The entertaining thing was trying to get back up my driveway into the garage. Not a steep slope, but steeper than most subdivision driveways. I came at it kinda slow with DSC on. DSC of course kicked in as the tires started to spin with a bit of braking and it reduced engine torque to the point I almost stalled and my forward progress stopped. DSC would not allow me to get moving again. Turned off DSC and was able to spin the tires to get moving, but came up the drive going about 5 or 10 degrees sideways.

With DSC on, I did not even have to countersteer. With DSC off, I probably could've done donuts if I had the room and didn't counter steer. That'll be worth trying if get a good 2" coating of powder and I can find a large parking lot to do it safely.

My conclusion is that in snow I'll leave the DSC on until I get stuck.

B.


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## tierfreund (Nov 12, 2004)

@undien717

I agree with all of your posts. I just sometimes use different words for the same things


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## Nick325xiT 5spd (Dec 24, 2001)

SonTon2003 said:


> so it's a good idea to turn the DSC off all the time but leave DTC and the others on. thx.


 Given how little understanding you apparently had of the systems before this post, I'd have to say no. I have this sneaking suspicion that you have no idea how to handle under or oversteer.


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## KwlAznKid (Nov 22, 2004)

grimreapa said:


> cant some people really be jackass', listen up kid your had good question cause i was wondering about it to. this other guys manual is telling you totally something different than what your car will do. Best bet is to just check your owners manual. Description is pretty good and at least you will know what happens when you press that button. :thumbup:


thanks 
also thanks to everyone who tired to explain to me


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## KwlAznKid (Nov 22, 2004)

HankM3 said:


> first of all
> 
> Why do you have your parents cars in your sig?


why are you trying to mock me?as for you question... cause... i felt like putting it in? cause i live with my parents still and i drive their cars sometimes... yea
if that was suppose to be a comeback or something please don't reply again your wasting my time trying to sort things out with you and just because you didn't have a good day don't try to say junk to me to make me feel bad too okay? :thumbup: thank you!


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## tierfreund (Nov 12, 2004)

KwlAznKid said:


> why are you trying to mock me?as for you question... cause... i felt like putting it in? cause i live with my parents still and i drive their cars sometimes... yea
> if that was suppose to be a comeback or something please don't reply again your wasting my time trying to sort things out with you and just because you didn't have a good day don't try to say junk to me to make me feel bad too okay? :thumbup: thank you!


Kiddo (and I mean that kindly and use it cause you seem young and I know I´m old),

I like your stile. Nobody is born knowing everything (especially about driving). The important thing is to make sure you learn and proceed carefully while doing so.

Youre doing that, you ask and then you experiment. One thing this thread goes to show is that most people are not completely clear on all functions of DSC or on how to explain them (me certainly included)...

So well done, but more than that you even react cool and kind when somebody tries to diss you (see above), so please send my compliments to your parents, they did a good job on bringing you up.

And my respect to you, because upbringing is only one part, character is the other.

So keep it up :bow:


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## KwlAznKid (Nov 22, 2004)

tierfreund said:


> Kiddo (and I mean that kindly and use it cause you seem young and I know I´m old),
> 
> I like your stile. Nobody is born knowing everything (especially about driving). The important thing is to make sure you learn and proceed carefully while doing so.
> 
> ...


thanks a lot, your reply made me smile


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