# Definitive word on whether to turn "off" DSC.



## rumratt (Feb 22, 2003)

After reading the "Technology" booklet that came with my car, my conclusion is that pressing the DSC button is really not such a big deal! There have been quite a few posts on this (such as in this thread http://www.bimmerfest.com/forums/showthread.php?t=16533&) and reading this Technology booklet seems to contradict many of them. I scanned the two pages and posted them below. My conclusions after reading are the following:

- Pressing the button to "disable DCS" doesn't really switch anything off! It just uses higher thresholds regarding slippage before activating. (Bottom right of page 25). Conclusion: Turning off DCS puts you closer to the edge, but still kicks in if you really screw up.

- ADB (Automatic Brake Control: using the brakes to compensate like a limited-slip differential) is NOT active unless you disable DCS. (again, bottom of page 25) Conclusion: If you want a LSD, turn off DCS!

- ASC+T is a component of DCS, as oppossed to two different systems (not really relevant, but contradicts previous posts).

Sounds to me like hitting the DCS button is no big deal. You just raise the activation threshold and give yourself a LSD. Seems like a reasonable thing to do when you're in the mood to be sporty. Comments in this thread (http://www.bimmerfest.com/forums/showthread.php?t=31143&highlight=dsc)make it sould like turning it off foolish and irresponsible.

What gives? :dunno: Is this mass confusion due to BMW's poor documentation?


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## nate (Dec 24, 2001)

I don't have ADB


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## bmw325 (Dec 19, 2001)

Interesting. I didn't get a booklet like that w/ my 01. The explanations in my ownerss manual of DSC and ASC are much more terse. Judging by the illustrations of an e65 and the section on dynamic drive, I assume this is a generic booklet meant to apply to the whole BMW line. 

I didn't know that by pressing the DSC button you actually activate ADB-- I had thought that it was always on in low speed situations. I wonder if this was changed-- or if this has always been true. Also, the description you scanned fails to mention the ability to completely deactivate DSC and ADB by holding the DSC button down for 5 seconds. Can you still do that on 03 models (they introduced this 2 tiered DSC sometime during the 01 model year).


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## rumratt (Feb 22, 2003)

robg said:


> Also, the description you scanned fails to mention the ability to completely deactivate DSC and ADB by holding the DSC button down for 5 seconds. Can you still do that on 03 models (they introduced this 2 tiered DSC sometime during the 01 model year).


Yes, this is mentioned in the owners manual that pressing and holding the DCS button turns off everything. I guess they didn't include it in the technology guide because when it's off, it's not technology!

Just to be clear, the owners manual reiterates that there are basically 3 modes:

1) Default mode: DCS enabled, DTC disabled

2) Press once: DCS disabled, DTC enabled (from technology manual, DTC is ADB (LSD) + increased thresholds for DCS.)

3) Press and hold: DCS disabled, DTC disabled

EDIT: Note that 1) above is this is in direct contradiction to this web site: http://www.my330i.com/dsc.php which says "Press the DSC button to disable DSC while leaving ABD active." (obviously implying that ABD was on by default.


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## rumratt (Feb 22, 2003)

And not to beat a dead horse... but the manual also states:



> Press the DCS button briefly; the indicator lamp comes on and stays on. DCS is deativated; DTC is operational. In the following rare situations, it may prove useful to activate the DTC for a brief period:
> 
> - when rocking the vehicle or starting off in deep snow or on loose sufaces
> - when driving on snow-covered grades, in deep snow, or on a snow-packed down from being driven on
> ...


I'm fairly convinced that ADB is off by default. This also makes sense based on everyones comments that you need to turn off DCS to get started in snow or you're screwed.

Could all this b!tching and moaning about how bad BMW's are in snow be because people didn't know to turn ON their LSD by turning OFF DCS?

At this point my conclusion is: when it's dry, turn off DCS so you can have fun (but still be safe if you screw up). and when it's wet/snowy, turn off DCS so you get a LSD. WTF.. can this be right?


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## bmw325 (Dec 19, 2001)

rumatt said:


> when it's dry, turn off DCS so you can have fun (but still be safe if you screw up). and when it's wet/snowy, turn off DCS so you get a LSD. WTF.. can this be right?


Yes-- I think you're definitely right. I don't really understand why ADB isn't active in "regular" dsc mode as well. It doesn't seem like it would be mutually exclusive. Anyway- BMW should stop messing around w/ ADB, and start using real LSDs again. If there's some technical reason why they couldn't implement ADB along with full DSC that's even more reason to ditch ADB and go w/ a real mechanical solution.

Also, if i'm reading it right, it sounds like the only differnece between ASC+T and ADB is that ADB has a higher activation level. Functionally, they're the same thing (brake one dirve wheel to transfer torque to the wheel w/ more traction). Or, is there more to ASC then that?

Nate-- I guess this means that you do have a form of ADB on your 328 since you have ASC+T.


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## rumratt (Feb 22, 2003)

robg said:


> Also, if i'm reading it right, it sounds like the only differnece between ASC+T and ADB is that ADB has a higher activation level. Functionally, they're the same thing (brake one dirve wheel to transfer torque to the wheel w/ more traction). Or, is there more to ASC then that?


I have no idea. The description in the technology book is better than the owners manual, but it's still not very clear.

If turning off DCS provides a substantially better LSD simulation, I'm suprised nobody figured this out sooner. Maybe the booklet is just worded wrong? :dunno:

I'm also suprised so many people are worried about turning DCS off when it actually doesn't turn anything off.


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## joema (Aug 28, 2002)

I think some inconsistent and maybe model-specific wording 
in the Technology booklet is creating some confusion.

E.g. on page 24 it discusses Dynamic Drive, only available on the 
new 7 series. When discussing ASC+T on page 25 it mentions the 
"data bus system", also unique to the new 7 (as of 2002).

There's also confusion because the DSC button logic has changed 
within the past few years on the 3-series.

For non-M3 2WD e46 2002 (maybe 2001) and later, I think ADB is
normally active, and is only deactivated by a > 3 sec DSC button 
press. The booklet does say that switching off DSC/ASC "activates"
ADB/DTC. However other sources indicate ADB is on, but the more
sensitive DSC threshold intervens first via engine power reduction,
before ADB is triggered.

So in a sense disabling DSC "activates" ADB/DTC, not by turning it on,
but by removing the more sensitive DSC intervention threshold that
normally would kick in first.

To review, in > 2001 model year non-M3 2WD e46s normally DSC, 
ASC, ADB, DBC are all active.

A short press of the DSC button disables the DSC yaw control and
engine intervention. This effectively allows more wheel slip in slippery
conditions, thus triggering ASC/ADB. The other functions remain active.

A long press (> 3 sec) deactivates everything except ABS. According to
the BMW 3-series "Guide to Features and Operation" CD-ROM, it's
intended mainly for use on dynamometers and other diagnostic
situations. Below is some more info:

http://www.bmwworld.com/models/years/2002/3er1.htm

"For 2002, the 3 Series' Dynamic Control System (DSC) has been 
refined. DSC has been standard since mid-'99 and it was upgraded 
in September 2000 with the addition of Dynamic Brake Control (DBC)"

"A function called Automatic Differential Brake, which via a brief 
push of the DSC button on the console de-activates the system's 
engine intervention but leaves the brake intervention functional, 
was already present; this "softens" the traction-control effect of 
DSC and is useful on certain very slippery surfaces, such as gravel 
or packed snow. In this mode, when the drive wheels begin to slip, 
individual wheel brakes react to control the slip but the usual 
reduction of engine power does not occur."

"New for 2002 is a phase-in of engine intervention with increasing 
vehicle speed, adding stability at higher speeds while leaving the 
moderated traction-control effect at low speeds. BMW calls this 
Dynamic Traction Control. As before, pressing the DSC button for 
a longer period (2 seconds) completely de-activates all DSC functions 
except antilock braking."

http://www.bmwnation.com/ARTICLES/e46_2002details_01.html

"It is already well-known that DSC prevents the car from swerving out
of control even in abrupt manoeuvres, especially on slippery roads, and
keeps the driver in control even in bends he has falsely assessed or 
takes at an excessive speed by applying the brakes individually on 
the right wheels. The overall DSC system comprises ASC + T traction
control and, as of September 2000, the electronic differential lock 
(ADB) and Dynamic Brake Control (DBC) particularly beneficial when 
applying the brakes in an emergency."

"An option remaining at the driver's disposal also in the 2002 model 
year is to briefly press the DSC button in order to switch to a 
drive-oriented operating mode in which the differential lock function 
remains active through intervention of the brakes, without however 
the usual reduction in engine power otherwise provided by restricting 
the throttle butterfly opening whenever a wheel is about to spin. 
With this new feature the car is now stabilised also in this mode 
when threatening to swerve out of control by selective application 
of the brakes as a function of road speed. The system intervenes in 
the position of the throttle butterfly only at higher speeds, ie, 
only when really necessary."


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## wrwicky (Jan 17, 2003)

Great Info. Time to give the technology book a thorough reading.


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## gmlav8r (May 28, 2003)

Yeah, basically what everyone else said

I'm glad I am not the only one slightly  with that little DSC button. I found my manual a little vague too. I just got my 2004 330ci. I have reread page 78-79 and page 109 of my manual and that technology guide page 24 thru 26. I have discovered pressing the DSC button only turns off portions of the DSC system. It is as clear as mud.


DSC: Dynamic Stability Control
DTC: Dynamic Traction Control
CBC: Cormering Brake Control
DBC: Dynamic Brake Control
ABS: Antilock Brake System
EBV: Electronic Brake-force Distribution
ADB: Automatic Differential Brake
MSR: Engine Drag Torque Management
ASC+T: Automatic Stability Control Plus Traction

Here we go:

For math oriented folks:enjoy
DSC=ASC+T(ABS+CBC+EBV+ADB+MSR)+DTC+DBC :tsk:


DSC includes:
ASC+T=(ABS+CBC+EBV+ADB+MSR)
DTC
DBC


HERE IS MY ABBREVIATED CONCLUSION:

ABS: always on

NORMAL MODE:
All systems on

PRESSING DSC BRIEFLY:
Caution grey/gray area!
OFF: ASC+T
ON: DTC and DBC

PRESSING DSC FOR MORE THAT 3 SEC:
All OFF


Please Discuss:


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## bmw325 (Dec 19, 2001)

joema said:


> I think some inconsistent and maybe model-specific wording
> in the Technology booklet is creating some confusion.
> 
> E.g. on page 24 it discusses Dynamic Drive, only available on the
> ...


This is a much clearer explanation. Although, it says that as of 2002 a brief press of the DSC button triggers a "more driver operated mode" where only the brake intervention is maintained. My understanding was that this was introduced during the 2001 model year. Or, is it that on 2001s the single press raises the threshold for engine intervention-- but its still possible whereas for 2002 a single press of the DSC completely shuts ofthe engine intervention portion of the program...


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## Matthew330Ci (Sep 9, 2002)

TMI...


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## fkafka (Mar 12, 2002)

Thanks for posting that rumatt. That's the best description of the system yet.

One implication here is that the yaw control portion of DSC will stay active, but be less intrusive after a single push of the deactivation button. 

And the obvious test of this assertion is that I ought to be able to go to a go to a snow covered parking lot, "one push" the deactivation button, and still get yaw control DSC to kick in with oversteer or understeer.

Do I understand that part correctly?


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## joema (Aug 28, 2002)

fkafka said:


> One implication here is that the yaw control portion of DSC will stay active, but be less intrusive after a single push of the deactivation button.


I think a single press fully deactivates the yaw control portion of DSC, plus allows a higher threshold for tire slip. That way if trying to get moving in snow or ice, DSC won't reduce engine power and ADB will help rear wheel traction.


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## JetBlack330i (Feb 8, 2002)

rumat said:


> Definitive word on whether to turn "off" DSC.


:blah: So, do I turn DSC off or not?


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## suzer (Jan 4, 2002)

And how does this work if you have an X5? :dunno:


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## rumratt (Feb 22, 2003)

joema said:


> I think a single press fully deactivates the yaw control portion of DSC, plus allows a higher threshold for tire slip.


Why do you say that? The technology manual doesn't confirm the first part of your statement, and in fact it strongly implies that your statement is not true (it defines DTC as higher thresholds + ADB; no mention of subtracting yaw control). So either the booklet or bmwworld.com is wrong. Are you sure it's not bmwworld that is wrong?

I agree with fkafka. We should get these cars out on the ice/snow and try to assess for ourselves whether the yaw correction is on or off.

By the way, it's ridiculous that we can't figure out what pressing the DCS button does. It's not like this is a minor detail. :tsk:


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## joema (Aug 28, 2002)

rumatt said:


> Why do you say that?


Because I had the opportunity to look at the factory service manual for the car and that's what it said.

You're right it's sad there's not more open technical information on this. BMW owners aren't like Buick drivers -- we tend to be fairly technical people and want to know lots of internal details about how our cars function. It's too bad BMW doesn't provide more information.


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## dlloyd1975 (Sep 8, 2002)

rumatt said:


> Hmmm. That's a pretty good reason.  But it would still be nice to confirm this in a snow covered parking lot.


I usually try to find an empty lot the first time it snows every year to keep my winter driving skills sharp. This year, though, will be the first time I've driven a rear wheel drive car (my wife's 4WD Ranger doesn't count) in the snow in quite a while. The last RWD car I drove in the snow was my '79 Corolla wagon. Really light (in part due to the completely rusted floorboards and body panels), so easy to get going if you put a bag of tube sand in the back, but you could still slide sideways or do donuts all day. And it had the best snick-snick transmission. I remember I scared the crap out of an ex girlfriend doing donuts in and empty mall parking lot one time. Ah, memories. I expect that the new car, with winter tires on it, of course, will handle far differently.

So, has anyone actually tried sending e-mail from the owners circle or calling BMW for the definitive answer? You'd figure that they would probably know.


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## Moderato (Nov 24, 2003)

Anything new on this subject? I've followed everything so far and I understand how all the individual systems work, but I'm still trying to figure out EXACTY what systems are active when you press the DSC button once and deactivate DSC and activate DTC? The owner's manual and technology guide is very vaque on that subject.


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## Moderato (Nov 24, 2003)

rumratt said:


> Well, I can comment on my experiences with my '03 330i.
> 
> One observation I've had is that when I press the DCS button once, I do get the simulated LSD, but if I spin the wheels enough the gas will cut off (ala traction control). But if you turn the DCS all the way off, you have the wide open rear diff. So there is really no "aggressive" setting, where you get the simulated LSD, but without the cuttoff-the-gass-traction control.
> 
> Also, I've confirmed that the yaw controll is still on when the DCS is pressed once. Well, to be precise, I've observed that it won't let me get the tail out TOO far when going around a wet corner, now matter how hard I try. :fingers:


Ok, so basically if you're not one of those "I don't like to drive" people, then press the DSC button once and have some fun, but you still have the protection of DSC , just at a higher threshold. If you want to get really crazy press the DSC button for 5 seconds and beware! Right or Wrong?


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## Moderato (Nov 24, 2003)

rumratt said:


> I do believe this is true. But be careful risking your life based on what some dumbass on a message board says.  I could be wrong.
> 
> At an autox someone mentioned that pressing DSC button once on the 325/330 might give you the same DSC that you normally get on the E46 M3. I have NO idea if this is even close to true though.


Isn't there SOME way we could find out for sure? I mean this information must be available somewhere. Is it to much to ask? We E46 owners want to know, "Exactly what gets turned off and turned on when you press the DSC button once?" :banghead: I've been reading posts, and searching and can't find an answer to this question!!!


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## RKT BMR (Sep 7, 2002)

Moderato said:


> Isn't there SOME way we could find out for sure? I mean this information must be available somewhere. Is it to much to ask? We E46 owners want to know, "Exactly what gets turned off and turned on when you press the DSC button once?" :banghead: I've been reading posts, and searching and can't find an answer to this question!!!


You might try a one-day subscription ($25) to the BMW tech site, www.bmwtis.com, poke around, and see if you find the answer there. There is all kinds of training, theory of operation, and repair docs on the site. I've used the site several times to get information necessary to troubleshoot and solve problems.


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## kriss (Jan 1, 2004)

*definitiviw word on whether to turn off dsc*

speaking to my bmw service advisor(2004 325i) he indicates the dsc on will prohibit wheel slip so that if you are stuck in snow / ice you want to turn off dsc to allow wheels to spin and get out of the mess.otherwise driving along on a snowy surface you would not want to have wheel slippage but rather maximize traction so you would leave dsc on.


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## Jim in Oregon (Dec 23, 2001)

On my 2003 M5, the DSC button seems to only work as an on/off swithch of everything except of course ABS.

My wife and I went to the M5 driving experience in South Carolina at the Performance center. On a wet skidpad with DSC on, the car will not allow spining of the car or even spinning of the tires. The car will go where it is pointed no matter what the throttle position is, including floored.

With DSC turned off (one quick push, dash lights up) wheter in a straight line or curve, the car doesn't intervene at all. If floored in a straight line, the car will spin to redline. If floored on a curve, the car goes into a violent spin off the skidpad.

As much as people try to read manuals about on and off switches or holding the button for longer than 3 or 10 seconds, the fact remains (at least to my testing) that the DSC is off or on....nothing in between.

I further tested my M3 in the dry at night in an empty parking lot and with DSC on, no spins, no tail out...no matter how hard I try, can't mess up the travel of the car.

With a quick push of the button....I spun both tires (limited slip diffy) all the way through 1st, 2nd, and halfway through 3rd when I let up. If I gunned the car while turning, I could do a tailout all across the parking lot by modulating the throttle. The car did not intervene at all at any time.

As a note....I was getting my track tires scuffed up for the new season. I would never do that test with my regular tires....way too much tire wear.



rumratt said:


> After reading the "Technology" booklet that came with my car, my conclusion is that pressing the DSC button is really not such a big deal! There have been quite a few posts on this (such as in this thread http://www.bimmerfest.com/forums/showthread.php?t=16533&) and reading this Technology booklet seems to contradict many of them. I scanned the two pages and posted them below. My conclusions after reading are the following:
> 
> - Pressing the button to "disable DCS" doesn't really switch anything off! It just uses higher thresholds regarding slippage before activating. (Bottom right of page 25). Conclusion: Turning off DCS puts you closer to the edge, but still kicks in if you really screw up.
> 
> ...


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## Moderato (Nov 24, 2003)

I'm fairly certain thought, at least with the 330i, that when you press the DSC button once it deactivates DSC, and activates DTC. DTC allows more wheel slip before activating the brake differential system, but DTC will NOT prevent the car from oversteering or understeering. It's still safer then turning it off completely though because with DTC you still have electronic brake distribution and some other saftey features. When you press the DSC button for 3 seconds you are completely on your own.


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## wrwicky (Jan 17, 2003)

It's not supposed to kill the gas after one short push on a 330i, only differential braking at an elevated threshold.


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## MantisMan13 (Jun 27, 2004)

*330xi will Donut in Snow sans DSC*

Like all here, I too am seeking clarification on what exactly the car does or doesn't do depending on the DSC button. While I cannot offer any further technical explanation to what has been previously posted, I have a few observations from my own experience I will happily share.

Firstly, my car is a 2004 330xi. I took delivery at the end of January during very heavy snow. The car came equipped with the Goodyear Eagle RS-A Run Flat tires. Even with the AWD, the car was chopping at ABS and I would get a real sense of engine power loss on almost any turn where I would normally let a car get just a bit sideways to slide through the slush and then pull out straight with a little push of power. However, even with no power to pull out and breaks dragging that seemed to hold me back, directional control was perfect, just not as fast as I was wanting and thus forcing me to come off the gas before power was returned. Letting to car go sideways just a bit and powering out was my expectation and intention, but this - the DSC system was clearly not going to allow. One problem was obvious to me immediately. The Goodyear tiers simply allowed way too much tire slip in the slush and they had to go. Replaced with a set of Bilzzaks LM22 a few days later, but not before we got hit with about 2-3ft of snow overnight. With 2ft of snow in my driveway and the plow guy running late, seemed like a good test of how my new AWD sedan would do in deeper snow, so I tried backing out of my garage and backwards down my driveway. I got about 50ft backwards when the car had managed to compress enough snow under it to come to a complete stop aided by un-wanted breaking action. Rocking the car from 1st to R wasn't getting me anywhere, just fighting with the ABS system. Guess I was not used to a car with all this gadgetry trying to do my job for me. This is when the idea of turning off the DSC by way of that button (quick button push) finally hits me. Till that point I had gotten the idea backwards, thinking that DSC would help me maintain traction, even in these extreme conditions. A quick check of the manual now got my thinking somewhat corrected. Wow, what a difference. All of a sudden my tires were allowed to spin as I revved the engine just a bit, throwing the snow and eventually finding the driveway blacktop, and once I got the motion going again, I was able to power out the rest of the way to the street in one fluid motion of flying snow spitting out from the front and sides of the vehicle. Now that was the kind of fun I bought the car for. Next day, with good snow shoes now fitted, cornering on slushy city streets did not lead to the upsetting ABS and power loss without a good bit of effort. Disabling the DSC with a single button push (I've never heard of this >3 mode till I read this forum) I was able to let the back end swing a bit sideway and then let the front wheels pull me out with a slight ease off of the throttle to stop the rear end swishing followed by a reapplication of power as I straightened the wheels. My conclusion at that point was that the DSC normal mode was good for most driving but if I want to play, disable it. So play in a snow covered parking lot I did. After years of driving Saabs and only knowing the joy of backward donuts under power, this was a new love in life. With DSC disabled, the 330xi doesn't need much power to dance in a circle in light power snow over packed snow and ice. Back off slightly on the power and full traction returns letting you drive out at will. Really fun! All in all, the car has amazing winter driving controllability, but I still get the feeling at highway speeds when the roads are icy and sleet covered that if I'm not careful, the rear power bias might let me go sideways faster than in a FWD (thankfully I haven't put the DSC to this extreme a test yet), but nothing as scary as driving a 95 Mercury Grand Marquis in a lake effect storm back last fall that turn a 2 1/2hr trip into an 8 hour test of nerves, passing scores of cars and suv's stranded off the road. On ice, nothing is going to keep you on the road if your going too fast. The 330xi is about the best I've ever driven under adversity. Easily besting an embarrassing experience I had with a WRX on ice a few years back that let under-steer lead to an over-steer correction getting me turned around and stuck in a ditch. There was a driver error on my part I believe a DSC like system and perhaps better tires would have kept in check and in general the 330xi is simply far better mannered, all in all, justifying the cost deferential in my book.

So, now it's summer and I've put a nice set of sticky BF Goodrich GForce-TA KDW's on the car. These are so sticky; they tease you to see what you can do to get the DSC system to kick in. It's tough, but on quick rally style turns, where you'd normal expect a bit a soft tire scrub with a front wheel drive car, or a bit of scuff at the back from a rear wheel drive, here I sense a light bit of power loss, but no break action (did I just imagine that there should have been more power?). Ok, same quick, low gear under full power turn with DSC off rewards me with just the slightest bit of tire chirp as the tires find their grip in the pavement and launch you forward along your new path. It's subtle, but the latter seems a bit more fun. Again with DSC off, on a parking lot with fresh flat blacktop, I cranked the wheel all the way to the left and floored it in second. The tire spin made a glories high screeching noise issued out as the xi moved in a semi circle a good deal tighter than the normal turning radius allows. A bit of embarrassment for my age in pursuit of adolescent joys and a desire to not solicit un wanted attention cause be to quickly put end to this experiment, satisfied that I could break my tires free to at least some degree on dry pavement. Can I smock them up as one poster described his M5, I doubt I have the power plant for the job, but given my experience in snow and more recently on dry, DSC does not seem to restrict tire spin under power when disable - at least at low velocity. This all seems expected, but what makes me wonder further is when I enter a sharper curve from a bit more speed. Here, without DSC, I sense much more body roll than normal - Did I really enter that curve so much faster that time? So, what am I really loosing when I turn DSC off. In low speed it is very fun to play with disabling it and I'm sure that on the parking lot Auto Cross tracks that will give me the most fun, but at the high speeds which I might be able to run the car at on say Watkins Glenn, how much of the cars' handling and stability am I really sacrificing for a bit of tire play? I'd love to see some skid tests set up with the various E46 models that would show the lateral acceleration tolerances for various DSC modes, tire and suspension set ups. (See R&T for '02 330i base line stats) I'm somewhat confidant that at highway speeds, the ABS and/or ADB retardation and other managed systems used to perform stability correction is far less noticeable and much more useful at keeping the car from being over driven. But to take full advantage of the car, tuned or un-tuned, one should be fully aware of just where the performance boundary and in there being what the driver and tuner are working to compensate for. I wholly agree that BMW needs to disclose a better explanation of how these systems physically affect their vehicles. The high level explanations offered thus far are IMO total inadequate beyond a marketing scope. I'd love to read more from others who can share their thoughts on this, so please keep this thread going. Maybe someone in the know from BMWNA will take notice and contribute some definite info.


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## ·clyde· (Dec 26, 2001)

I think someone has been having a bit too much rum with the ratts. :eeps:


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## MantisMan13 (Jun 27, 2004)

*Short Version for Ratt*



rumratt said:


> :wow:
> 
> Wow, you need some paragraph breaks in there. I made it through only 1 line before I gave up reading. Sorry.


Ok, short version:

Sure.. Turn off DSC with a single press, do all the donuts your local cops will let you.... :angel:


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## Moderato (Nov 24, 2003)

rumratt said:


> :wow:
> 
> Wow, you need some paragraph breaks in there. I made it through only 1 line before I gave up reading. Sorry.


I'd bet $5 that you really did read that whole post! :stickpoke

MantisMan13 - So the moral of your story is for low speed drifting and poor traction situations, shut off DSC and at high speeds leave it on, right?


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## MantisMan13 (Jun 27, 2004)

Moderato said:


> I'd bet $5 that you really did read that whole post! :stickpoke
> 
> MantisMan13 - So the moral of your story is for low speed drifting and poor traction situations, shut off DSC and at high speeds leave it on, right?


It's easy to see what happens at low speed, and fun is fun... The point is, at track speed, I want to have some way of predicting how the car will behave and right now I have to be over cautious, and that is why I was reading this thread in the first place. There are too many under explained control management systems at work and when they give us a button to disable part of it, they should bloody hell tell us exactly what we are messing with... I think people here have come to perhaps the best guess possible given the current documentation but I personally am not completely comfortable with a best guess and would truly appreciate some word of god (BMW) explanations as to how our cars are engineered and programmed. The key to safe driving is predictability. I'm just hoping to get a bit more information before I start testing the limits of my car out on a track at speed. But a collective exchange of experience may help shed more light if not perhaps make the wheel squeak loud enough for BMW to take notice


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## Pinecone (Apr 3, 2002)

Again there are two levels of DSC in non-M cars, and only one in M cars.

So a single button push on a non-M car makes it behave like an M car with DSC on. The long push on a non-M and a single button push on an M turns it pretty much off.

I am against turning the DSC totally off on the street. However in certain circumstances, dropping the non-M DSC to the lower level is desireable.

I wrote this in the M section a while back on the differences of what a car does at the limit with and without DSC tyep systems for FWD, RWD and a little on AWD.

http://www.bimmerfest.com/forums/showthread.php?t=56870

Bottom line, if you spent much time in a FWD car without LSD, and move to something like an M3 the reaction of the car at the limit is very different than what youare used to, and may lead to an accident if you turn DSC off.


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## Moderato (Nov 24, 2003)

MantisMan13 said:


> It's easy to see what happens at low speed, and fun is fun... The point is, at track speed, I want to have some way of predicting how the car will behave and right now I have to be over cautious, and that is why I was reading this thread in the first place. There are too many under explained control management systems at work and when they give us a button to disable part of it, they should bloody hell tell us exactly what we are messing with... I think people here have come to perhaps the best guess possible given the current documentation but I personally am not completely comfortable with a best guess and would truly appreciate some word of god (BMW) explanations as to how our cars are engineered and programmed. The key to safe driving is predictability. I'm just hoping to get a bit more information before I start testing the limits of my car out on a track at speed. But a collective exchange of experience may help shed more light if not perhaps make the wheel squeak loud enough for BMW to take notice


This is why I've decided to forget about DSC and just leave it on all the time. I've accepted the fact that my 330i is not a sports car and merely one damn fine everyday driver. In a couple of years I will buy a C6 Z06, for track driving (hopefully....are you listening wifey-poo?  ). When I want to drive with DSC on I will take the 330i and when I want to drive with DSC off I will take the Z06.


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## MantisMan13 (Jun 27, 2004)

Pinecone said:


> Again there are two levels of DSC in non-M cars, and only one in M cars.
> 
> So a single button push on a non-M car makes it behave like an M car with DSC on. The long push on a non-M and a single button push on an M turns it pretty much off.
> 
> ...


Pinecone, thanks for pointing me at that older thread. Your write up on the various differential combos is exactly the sort of thing I'm looking for.

And that brings me to another one of my areas of confusion in my quest make some reasonable predictions regarding my xi's handling.

I had originally assumed that the car would be LSV on both axels and that this was governed by the ADB-X system (Automatic Differential Break). In doing some research I came across one article on the BMWNATION website ( http://www.bmwnation.com/articles/3er_xi.html ) that seems to indicated that ADB is simply another re-use of ABS breaking and thus is not a true LSD.

"ADB-X replacing all lock differentials
As soon as ADB-X recognizes that a wheel is about to spin, it slows down the wheel by activating the brakes. At the same time available power is diverted to the wheels which still have traction, while the wheel which otherwise would have gone on spinning is able to regain its grip on the ground. ADB-X thus offers the same effect as a conventional differential lock without its disadvantages. A telltale flashing on and off on the dashboard informs the driver whenever DSC is about to become operative, telling him that the car is approaching its traction limit. While the ADB-X and DSC are excellent, drivers are advised that the laws of physics do still apply."

Another article that I found from 2001 by Mike Wan for Autozine ( http://autozine.kyul.net/html/BMW2.htm ) talks about what sounds like ADB under the term EBD for electronic brake differential and more specially claims that the xi system does not use LSD.

"Therefore BMW employs electronic brake differential to get out of trouble. What is that? As you might already learned that in my Technical School article about Porsche EBD, it is not actually a real differential. EBD employs ABS hardware to detect wheel spin, then apply braking to the spinning wheel so that the differential will transfer more power to other wheels. The same goes for the torque split between front and rear - apply brake force to rear wheels will lead to the transfer of more torque to front wheels by the center differential. Using EBD instead of LSD saves a lot of money."

He make sense, but I'm hoping that somehow he's got it wrong.

I found a BMW site for the Russian market, in English that has some of the better BMW Technical descriptions. ( http://www.bmw-lahta.ru/English/Technologies/index.html )

Here, BMW describes ADB-X as "ADB -X is an automatic differential lock, connected and controlled by DSC". They never come out and claim that DSC utilizes ABS or the wheel breaks for this operation. So I am left wondering if there is some other mechanical means built into the differential that is responsible for the ADB function. If there isn't one, then it seems that the ADB and the ASC+T systems are redundant.

The M class clearly has this covered with the use of "M Variable Differential lock". Described in this article by Jim Kerr for Canadian Driver, http://www.canadiandriver.com/articles/jk/at_011219.htm , I find my self hoping that the xi has quietly incorporated this style differential into it AWD system.

So, since I can't get out of the car to actual see what is happening when I'm spinning my tires in the snow after hitting the DSC button to raise the bar on wheel spin. Is one tire spinning faster and another not at all? Is it a full lock with both tire spinning in sync? It seems that there must be some way of letting wheels on both side of the car spin a bit, otherwise there would be a lot of torque pull that would make it hard to go straight if wheels were only spinning on one side or the car or the other as I think would be the case with a fully open deferential. Also of note, for the xi models, ADB-X is said to never be disabled, rather it reverts to its 'maximum torque-transfer mode' when pressing the DSC button to deactivate. Unfortunately, no further explanation or any description of what a 'maximum torque-transfer mode' truly is has been given. So I'm still at this guessing game.

These are my questions/guesses:

Does the xi use as part of the ADB-X,

A: Older M-class 25% LSD 
OR
B: New M-class Variable Differential lock
OR
C: Just some action taken via the ABS wheel breaks
OR
D: ADB can be switched from full open to full lock and perhaps some middle ( say 25% ) slip setting, and then ABS helps further regulate wheel spin

in order to limit wheel spin on any give wheel past a desired threshold, and if so, what is that threshold and how is it determined by the governing DSC if at all.

What physical mechanisms are used to implement ADB-X and what can we assume their mechanical reliability to be?

If ADB-X is simulating a LSD action via ABS, what impact might elemental and driving stress factors that influence breaking efficiencies play on AWD systems ability to normalize traction from side to side?

Could extended driving under conditions that solicit ADB-X assistance for traction adversely effect breaking efficiency where there would be noticeable break fade?

What is the likely hood of finding answers to these questions and maybe more if I buy myself a day pass on http://www.bmwtis.com/. Does anyone know how up-to-date they are with current models and how deep do they go into the physical mechanics?

Thaks All....


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## phrider (May 6, 2002)

Don't miss this post comparing DSC etc systems by model line, year, and class (M or not): http://bimmerfest.com/forums/showthread.php?t=54522&highlight=DSC

Pressing that button does different things in different years in different models.


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## Nick325xiT 5spd (Dec 24, 2001)

ADB is NOT equivalent to M DSC. All it does it use the brakes to limit wheel spin. (And pretty poorly, at that.) The only time it will touch the throttle is when the brakes are about to overheat. Rumratt's conclusions in this thread are quite thoroughly wrong and should be ignored by sensible drivers.


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## Moderato (Nov 24, 2003)

Nick325xiT 5spd said:


> Rumratt's conclusions in this thread are quite thoroughly wrong and should be ignored by sensible drivers.


 :yikes: 
: popcorn:

The M DSC is programmed with the M LSD in mind, so I don't think that it would be accurate to say that one press of the DSC on a regular car would be equivalent to leaving DSC active on an M car.


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## Pinecone (Apr 3, 2002)

a) AFAIK BMW uses differntial braking to simulate LSD on the AWD cars. No big deal with this for short time periods. For long durations of action, you could cause individual wheel brakes to overheat and fade.

b) From previous discussions and testing by various people, the one push on a non-M is VERY close to the response of an M with the system on. Also the M has been shown to not have two levels of DSC like the non-M cars do.

c) And yes, there does seem to be some difference from year to year. But until I see some side by side testing on te same surfaces, my opinion is still out on how much difference. Talking to Nick, it does seem his DSC has a higher intrusion factor than mine does (04 versus 02), but until we swap cars on the same piece of pavement, I can't rule out driver differences, ie Nick is just not smooth.


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## Moderato (Nov 24, 2003)

This is all BMW's fault for not fully explaining what pressing the DSC button once and activating DTC actually does. They explain a whole lot about DSC, but not much info is given about DTC.

Taken from the "technology guide" I received with the car:

DSC:

Sensors used:

- Wheel Speed
- Tendency to spin around its vertical axis
- Lateral acceleration rate as a reference in calculating curve radius
- Steering wheel angle
- Braking pressure
- Vehicle speed

Functions:

1. ABS

2. CBC - Cornering Brake Control - Extended version of ABS designed to furnish particular improvemnets in handling stability during braking and in curves, by neutralizing the tendency to gyrate by stabilizing counter-forces on one side of the vehicle during moderate braking

3. EBV - Electronic Brake Force Distribution

4. ASC - Automatic Stability Control - prevents the drive wheels from spinning, by braking the spinning wheel and transfering power to the other wheel. Because ASC is a part of the data bus system, it can also intervene in engine management functions

5. MSR - Engine drag torque control - inhibits the tendency of the rear wheels to lock when the driver downshifts or suddenly releases the accelerator on a slippery surface, by using wheelspeed sensors to detect incipient lock, and responds with a brief gentle application of the throttle to temporarily reduce drag torque.

6. a) DTC - Dynamic Traction Control - Compared to DSC, DTC allows greater slip at the drive wheels, with different objectives depending on the vehicle model:

On the 5 & 7 series, DTC is only active during straight-ahead driving to ensure maximum tractive power when driving in deep or slushy snow.

On the 3 Series & Z4, DTC is also active during cornering and enables not only improved tractive power, but also a sportier driving style. DTC first intervenes in critical situations at a relatively late stage. Compared to this, DSC offers optimum driving stability within physical limits.

b) ADB-X - Automatic Differential Brake (this takes the place of DTC on the xi models)
This imitates the function of differential locks with specific braking on individual wheels. If necessary, the engine output is also reduced. With DSC switched off , ADB-X provides maximum tractive power and engine intervention and stability control are no longer available.

7. DBC - Dynamic Brake Control - aid in panic stops

In the technology guide, as well as the owners manual DTC is said to be a part of the DSC system. On xi models DSC has ADB-X, and when you press the DSC button you deactivate DSC and ADB-X reverts to its maximum torque-tranfser mode. So as we can see, there is a big difference between DSC in _ and [xi] models. In  models pressing the DSC button once enables DTC, but in [xi] models pressing the DSC button once enables ADB-X. There are 2 distinctly different definitions of DTC and ADB-X and I don't think they are comparable.

In the owner's manual it says that "pressing the DSC button briefly will deactivate DSC and activate DTC." The owners manual also states: "in rare situations it *may* prove useful to activate DTC for a *brief* period when rocking or starting off in deep snow or on loose surface, on snow covered grades, in deep snow or on packed snow, when driving with snow chains. Under these special circumstances traction is increased by *deactivating the control systems which enhance traction under normal circumstances. In the owner's manual it makes no mention of pressing the DSC button once for a "sportier driving style" like it says in the technology guide.*

DTC greatly differs between the 3 Series/Z4 & the 5/7 series.

The definition of DTC doesn't include exactly what functions are active, and this is what is causing all this confusion. If you need straight ahead, low speed tractive power then you want to press the DSC button and enable DTC. If you want to enable a "sportier driving style"  (what *exactly* does this mean) then press the DSC button.

The owners manual says: "Whenever the DTC is activated, the DSC is switched off and DTC performs minor stabilizing intervention." It also says DSC incorporates DTC and CBC. Then it says if you press the DSC button once that DTC and DBC are operational. I think this is a typo and it ment to say "CBC" instead of DBC. *edit* - I was wrong about this being a typo. DBC is Dynamic Brake Control which helps in panic stops to achieve maximum vehicle deceleration, regardless of the actual pressure when the brake pedal is pushed rapidly enough to activate it.

*edit* - So DTC definitely leaves the DBC portion of DSC activated. But what about CBC, EBV, ASC (definitely no engine management we know that) & MSR. All the documentation I've read leads me to believe that DTC doesn't incorporate any of these systems except DBC and DTC's version of ADB. The only grey area is the section where it says "DTC first intervenes in critical situations at a relatively late stage." BUT how does it intervene? With DSC? With certain sub-systems of DSC? That is what we just don't know.

This is why we are all confused. They throw all this information at us, but they don't state clearly exactly what is going on with DTC.

edit - fixed a few typos & mistakes_


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## MantisMan13 (Jun 27, 2004)

*Great Summery!*



Moderato said:


> This is all BMW's fault for not fully explaining what pressing the DSC button once and activating DTC actually does. They explain a whole lot about DSC, but not much info is given about DTC.
> 
> ..EFSB...


Right on! That's about what I can make of it too. But I still want to know for the xi just how ADB-X is putting the power to the road in it's Max-Trac mode. It's hard for me to imagine that the system is really using wide open diffs and totally reliant on breaking for anti-spin.


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## 318-Bmw (Jan 15, 2004)

DSC OFF eventually kicks in?!?!? I'm able to hold the tail of my car out there pretty much forever if I wanted to.........


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## Moderato (Nov 24, 2003)

MantisMan13 said:


> Right on! That's about what I can make of it too. But I still want to know for the xi just how ADB-X is putting the power to the road in it's Max-Trac mode. It's hard for me to imagine that the system is really using wide open diffs and totally reliant on breaking for anti-spin.


It is using wide open diffs and is totally reliant on breaking for anti spin.

ADB-X

"ADB-X Automatic Differential Brake imitates the function of differential locks with specific braking interventions on individual wheels. This makes conventional differential locks in the front and rear differentials and the transfer case redundant. If a wheel tends to spin, it is automatically braked by ADB-X until it grips again and can transfer drive forces. If necessary, the engine output is also reduced. With DSC switched off (one quick press), the ADB-X function is designed for maximum tractive power. Engine intervention and stability control are no longer available."

So the way you are getting maximum power when you press the button, is because the car will allow you to spin the wheels without cutting engine power, while using the brakes to act like limited slip diffs.

There are two ways to look at this. First some will say that having limited slip diffs is better, and they are for certain situations but for an everyday street driver (no serious off road) there are some advantages to the open diffs set up in the xi's. For one thing, the open diffs have less drivetrain loss then limited slip diffs. This will allow you to get more power down to the ground (assuming good traction conditions) and it will also yield better fuel economy. It will also limit torque steer which is possible on AWD cars which use limited slip diffs, and that coupled with the set rear wheel torque bias, will give you more of that RWD BMW feel which is something they advertise about the xi cars. Even Audi, which is well know for it's AWD systems use open diffs front and rear and rely on braking to provide traction. Where the Audi system differs from the xi system is the fact that the Audi uses a Torsen Center LSD. This proves, my point. The Audi A4 doesn't have as good handling characteristics as the xi's (of course there are more factors involved in that then simply the differential characteristics but I want to stay focus on the point), and gets worse fuel economy. Keep in mind though that the Audi system is dedicated to AWD and makes no secret about it. The BMW AWD system is more of a system which tries to mimic the benefits of RWD, while providing non-heavy duty AWD traction. It's a good system once you understand what it is, and what it is not. Simple right!


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## Moderato (Nov 24, 2003)

rumratt said:


> BMW's aren't the most reliable cars out there, so they do plenty of breaking.
> 
> But to avoid wheel spin they use *braking* folks....


Ok, that was funny so I'm not going to edit out that typo :rofl:

I really did mean braking! :rofl:

I also edited that summary post I did with another point about DTC if you didn't read it, FYI.


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## MantisMan13 (Jun 27, 2004)

Moderato said:


> It is using wide open diffs and is totally reliant on breaking for anti spin.
> 
> ...EFBS...
> 
> Simple right!


I really am quite pleased with the drivability of the 330xi thus far and that is what really matters.  But as most things, the more I mess with it, the more I want to take it apart and see what every little bit of it does. I really had thought that the diff would be something more like what had been in the older IXers. They used some sort of viscous couplings for their LSD ( http://home.earthlink.net/~hainesinutah/iX/general/iXfaq.html ) and people have been driving those around for years proving the systems reliability and good functionality. Never occurred to me that this wasn't an evolution of that system till I really started looking into what was in mine. With luck, this new setup will prove out to be just as reliable maybe better. One can only hope.


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## MantisMan13 (Jun 27, 2004)

Moderato said:


> Ok, that was funny so I'm not going to edit out that typo :rofl:
> 
> I really did mean braking! :rofl:
> 
> I also edited that summary post I did with another point about DTC if you didn't read it, FYI.


Sorry folks, I'm one of those who are spell check challenged. If my typos make you laugh, all the better....


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## 16hr Day (Apr 17, 2004)

I am still confused. So which switch operates the booster rockets? I also read that if you hold the horn button for 10 seconds it puts the car in cloking mode so you can speed with out the chance of a ticket! :supdude:


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## wrwicky (Jan 17, 2003)

rumratt said:


> Well I don't know. :dunno: Can someone else confirm that they were able to do doughnuts in the snow/rain with the DTC on?
> 
> I will try again, but the last time I tried I was convinced that the car wouldn't let me.


Since it does still have differential braking, it makes sense that depending on how much yaw (rotation) whether the intermediate level will intervene. Perhaps the time it intervened you were getting enough rotation, speed?, cornering load? to engage the nanny. I don't know, but I don't think that your experience rules out my understanding of the manual.

edit: Just read my earlier post, whew, not very clear! I was trying to say the intermediate level disabled the power reducing function, but left differential braking active with a higher threshold.


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## MantisMan13 (Jun 27, 2004)

*New Twist on the tread - DSC sensor display?*

Here's a though I pulled out of my propeller hat. Does anyone know of a way to access all of the sensor data that DSC uses? I'd love to see the LA g's , YAW, 4 wheel spin rates and steering inputs displayed live on some sort of small LCD or HUD mounted just above the steering wheel on the dash. And if I could capture that data to a log using a connected laptop, all the better. Add a GPS (I think that's part of the BMW Assist module) and we can start plotting maps with segment time stats. This sort of data would be far more useful than an oil pressure gauge. I've seen these sorts of systems for race cars, but be nice to take advantage of the OEM sensors and just jack into an existing data port. Has anyone seen anything like that for the Bimmers?


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## rost12 (Dec 22, 2001)

So what conclusion did you guys reach? There's a definite TMI thing going on in this thread... DSC off for snow and or sporty driving?


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## Moderato (Nov 24, 2003)

MantisMan13 said:


> Here's a though I pulled out of my propeller hat. Does anyone know of a way to access all of the sensor data that DSC uses? I'd love to see the LA g's , YAW, 4 wheel spin rates and steering inputs displayed live on some sort of small LCD or HUD mounted just above the steering wheel on the dash. And if I could capture that data to a log using a connected laptop, all the better. Add a GPS (I think that's part of the BMW Assist module) and we can start plotting maps with segment time stats. This sort of data would be far more useful than an oil pressure gauge. I've seen these sorts of systems for race cars, but be nice to take advantage of the OEM sensors and just jack into an existing data port. Has anyone seen anything like that for the Bimmers?


I think you're going to have to fly to Bavaria to find someone who knows how to do that! :dunno:


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## Moderato (Nov 24, 2003)

rost12 said:


> So what conclusion did you guys reach? There's a definite TMI thing going on in this thread... DSC off for snow and or sporty driving?


Yes, for sporty driving press the DSC button once and enable DTC (not on xi models). Just be aware you're less protected from "losing it."


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## MantisMan13 (Jun 27, 2004)

*DSC live display*



Moderato said:


> I think you're going to have to fly to Bavaria to find someone who knows how to do that! :dunno:


It looks like scan tools like iScan can access the live data feeds via the the ODB-II interface. How much one of those tools are, I don't know. http://tools.baumtools.com/pdf/iscan_d91-1_apps.pdf 
But if the data is there, it should'nt be too hard to make a little display. Something like they do now with the avg MPH and MPG displays.


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## Moderato (Nov 24, 2003)

MantisMan13 said:


> It looks like scan tools like iScan can access the live data feeds via the the ODB-II interface. How much one of those tools are, I don't know. http://tools.baumtools.com/pdf/iscan_d91-1_apps.pdf
> But if the data is there, it should'nt be too hard to make a little display. Something like they do now with the avg MPH and MPG displays.


Get one!


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## rost12 (Dec 22, 2001)

Moderato said:


> Yes, for sporty driving press the DSC button once and enable DTC (not on xi models). Just be aware you're less protected from "losing it."


Okay.. I remember at the begining of the thread (and my attention span) it was said that deactivating DSC activates DTC. Unless you guys said it on the 2nd and 3rd pages, I'm gonna have to say it... From 2004 E65 manual:

"The DSC is operational every time you start the engine. DSC includes the functionality of the DTC Dynamic Traction Control and DBC Dynamic Brake Control."

The only benefit of deactivating DSC in snow (and only at low speeds, mind you) is that it allows you to get out of whereever you got stuck, since DSC would cut in too early and prevent any wheels spin that can help get you moving... Otherwise, I dare anyone who drove his bimmer in snow with DSC off to tell me with a straight face that it made the car handle better/safer. Fun, yeah :angel:

If you have reached this conclusion already, then disregard my ramblings.


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## Moderato (Nov 24, 2003)

rost12 said:


> Okay.. I remember at the begining of the thread (and my attention span) it was said that deactivating DSC activates DTC. Unless you guys said it on the 2nd and 3rd pages, I'm gonna have to say it... From 2004 E65 manual:
> 
> "The DSC is operational every time you start the engine. DSC includes the functionality of the DTC Dynamic Traction Control and DBC Dynamic Brake Control."


Please read the 2nd and 3rd pages because we went through all of this in quite some detail.



rost12 said:


> The only benefit of deactivating DSC in snow (and only at low speeds, mind you) is that it allows you to get out of whereever you got stuck, since DSC would cut in too early and prevent any wheels spin that can help get you moving... Otherwise, I dare anyone who drove his bimmer in snow with DSC off to tell me with a straight face that it made the car handle better/safer. Fun, yeah :angel:


Everyone should agree with this.


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## Moderato (Nov 24, 2003)

rumratt said:


> No, I don't think it's better/safer. But the question in my mind is whether entering the the intermediate phase on E46
> 
> a) costs you substantial safety because certain systems are not active, or
> b) it's all still there anyway, just activated slightly higher threshold.
> ...


rumratt, from all the reading I've done on this I'm in agreement with you. DTC will allow you to spin the wheels and not cut engine power, however it will still allow DSC to kick in at higher speeds and at a higher threshold. On the 3 series (with DSC III) and the Z4 DTC stays active in the curves, but on the 5 & 7 series DTC is only active when driving straight ahead. Read these articles which describe the differences between DSC and DTC

http://www.germancarfans.com/news.cfm/newsid/2021010.001/page/4/bmw/1.html

http://www.germancarfans.com/news.cfm/newsid/2021111.003/page/4/bmw/1.html

I would feel a lot better about it though, if BMW actually said this in the owners manual.


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## rost12 (Dec 22, 2001)

Moderato said:


> Please read the 2nd and 3rd pages because we went through all of this in quite some detail.


The amount of detail is a problem :angel: Noted...


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