Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Please follow the links below to help get you started!

Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series

3 Series / 4 Series
The 3 Series / 4 Series Forum. If you would like to see all new posts in all the forums, click here.

 
 
Thread Tools Display Modes
  #1  
Old 03-16-2004, 09:34 AM
jason929 jason929 is offline
Registered User
Location: california
 
Join Date: Mar 2004
Posts: 2
Mein Auto: impreza
Automatic Differential Brake (ADB) + DSC

I'm doing my research into the purchase of a new car. I'm looking at the BMW 330xi. All wheel drive is a must for my choice.

I was interested in how BMWs DSC system works exactly. Here's how I understand it: the DSC system is composed of several individual systems, one of which is the ADB. and via its use of ADB, the 330xi gains the benefits of a hypothetical limited slip differential on both the front and rear axels.

question: if I choose to deactivate DSC, a yellow light comes on in the control panel to indicate such. But this yellow light only indicates that DSC is no longer using engine power to control the car. In other words, ADB (selective braking on each individual wheel ) is still operating. Now if I hold down the DSC button for like 5 seconds, then it lights up a solid red and this indicates that ALL DSC functions (except ABS brakes) are turned off--i.e., the ADB system among others is now no longer functioning. Is this correct?

Last question: I've read some comments online from a guy who has a driveway with an uphill steep that when it is snow covered he can NOT drive up it without turning off the DSC. What I was unable to determine was whether he meant turning off the DSC entirely (i.e., red light) or just partially (i.e, yellow light). Would having the ADB operational hurt one's ability to ascend a snow covered driveway? It shouldn't right? it just operates like limited slip differentials--it should help it.

Any comments/corrections I would greatly appreciate. Thx all
Ads by Google
  #2  
Old 03-16-2004, 11:25 AM
dlloyd1975's Avatar
dlloyd1975 dlloyd1975 is offline
IRIX Rocks!
Location: St Louis, MO
 
Join Date: Sep 2002
Posts: 742
Send a message via Yahoo to dlloyd1975
Mein Auto: 325iT Schlampenschlepper
Quote:
Originally Posted by jason929
I'm doing my research into the purchase of a new car. I'm looking at the BMW 330xi. All wheel drive is a must for my choice.

I was interested in how BMWs DSC system works exactly. Here's how I understand it: the DSC system is composed of several individual systems, one of which is the ADB. and via its use of ADB, the 330xi gains the benefits of a hypothetical limited slip differential on both the front and rear axels.

question: if I choose to deactivate DSC, a yellow light comes on in the control panel to indicate such. But this yellow light only indicates that DSC is no longer using engine power to control the car. In other words, ADB (selective braking on each individual wheel ) is still operating. Now if I hold down the DSC button for like 5 seconds, then it lights up a solid red and this indicates that ALL DSC functions (except ABS brakes) are turned off--i.e., the ADB system among others is now no longer functioning. Is this correct?

Last question: I've read some comments online from a guy who has a driveway with an uphill steep that when it is snow covered he can NOT drive up it without turning off the DSC. What I was unable to determine was whether he meant turning off the DSC entirely (i.e., red light) or just partially (i.e, yellow light). Would having the ADB operational hurt one's ability to ascend a snow covered driveway? It shouldn't right? it just operates like limited slip differentials--it should help it.

Any comments/corrections I would greatly appreciate. Thx all
I believe that the 'yellow light' is what he was talking about for steep hills. It specifically mentions in the owners manual that sometimes it is necessary to turn of DSC when negotiating such situations.

I believe that if you just click the DSC button once, DSC is stil active, but the limits are much higher. This may be a different situation on the xi's since the brakes are used to redirect torque in the AWD system. Holding it down does turn off everything but ABS. Again, this may be very different on the xi's due to the AWD system.

I believe that there was a pretty detailed discussion a while back if you search through the archives. Unfortunately, IIRC, it was pretty inconclusive.
__________________
--dlloyd1975



The Shaggin' Wagon
2003 Gray Green 325iT, PP, SP, CW, HK, Sand 'Ette
  #3  
Old 03-16-2004, 11:42 AM
jason929 jason929 is offline
Registered User
Location: california
 
Join Date: Mar 2004
Posts: 2
Mein Auto: impreza
Quote:
Originally Posted by dlloyd1975
I believe that there was a pretty detailed discussion a while back if you search through the archives. Unfortunately, IIRC, it was pretty inconclusive.
I tried doing a search but the engine isn't working.
  #4  
Old 03-17-2004, 03:06 PM
RKT BMR's Avatar
RKT BMR RKT BMR is offline
Banned
Location: Scotts Valley, CA
 
Join Date: Sep 2002
Posts: 9,926
Mein Auto: 5/01 production 330Cic
Quote:
Originally Posted by dlloyd1975
I believe that if you just click the DSC button once, DSC is stil active, but the limits are much higher. This may be a different situation on the xi's since the brakes are used to redirect torque in the AWD system. Holding it down does turn off everything but ABS. Again, this may be very different on the xi's due to the AWD system.
Not quite right. Partial disabling of DSC (the yellow indicator mode) completely disables several of the DSC functions (traction control, torque control), while leaving some others (ADB) enabled.

Torque control is simply moderation of the engine throttle. This is an effective strategy to improving traction when there is significant traction at one of the rear wheels. ADB will keep the other wheel, with little traction, from spinning, causing the differential to transfer power to the wheel with traction. However, under those circumstances it is easy to break the traction wheel loose, so the system overrides your throttle inputs and moderates engine power when it detects a loss of traction on the one good wheel.

This, of course, is disasterous if neither wheel has good traction.. Basically, you won't be able to get anything spinning at the back end with DSC on. In some low traction circumstances, like a packed-snow covered road surface, some wheel spin is instead an effective means of gaining traction, so DSC gets in the way. However, ADB may still be very helpful.
  #5  
Old 03-17-2004, 03:27 PM
Nick325xiT 5spd's Avatar
Nick325xiT 5spd Nick325xiT 5spd is offline
Registered User
Location: Bethesda, MD
 
Join Date: Dec 2001
Posts: 10,861
Send a message via ICQ to Nick325xiT 5spd Send a message via AIM to Nick325xiT 5spd Send a message via Yahoo to Nick325xiT 5spd
Mein Auto: M3 & 323i/999 KP
The guy who couldn't get up his driveway is Dougdogs. And he didn't turn off ADB because he CAN'T. He and I have both discovered that DSC does a nice job of stalling the engine in slippery conditions. If it's snowing, the first thing I do before I start driving is kill DSC. It's more dangerous to leave it on than off. (Assuming you know what countersteering and throttle modulation are.)
__________________
2006 GMC Sierra 2500HD 4WD Duramax LBZ/Allison 6-speed
2002 BMW M3 Alpinweiß/Black
1999 323i KP/GTS2 Alpinweiß
1990 325is Brilliantrot/Tan
1989 325is S50B30US Alpinweiß/Black
1989 M3 Alpinweiß/Black S50B32 (321hp, ITBs)


  #6  
Old 03-17-2004, 03:33 PM
fkafka fkafka is offline
Officially Welcomed to the 'Fest
Location: o
 
Join Date: Mar 2002
Posts: 366
Mein Auto: '02 330xi
Quote:
Originally Posted by jason929
I'm doing my research into the purchase of a new car. I'm looking at the BMW 330xi. All wheel drive is a must for my choice.



question: Is this correct?

Last question: Would having the ADB operational hurt one's ability to ascend a snow covered driveway? It shouldn't right? it just operates like limited slip differentials--it should help it.

Any comments/corrections I would greatly appreciate. Thx all
1) On an xi, you get DSC-X, and you only get *one* level of DSC-X deactivation. BMW has been purposfully vauge about what this does, but consensus is that is dissables yaw control entirely, and diables traction control partially.

2) When the wheels start to spin, traction control shuts down wheel spin by applying the brakes. If traction control is set to be very sensitive on a a slippery slope, then you can't move forward at all because TC shuts your power down too quickly. Making TC less sensitive allows you to go forward.
 

Bookmarks


Forum Navigation
Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



Forum Jump


All times are GMT -7. The time now is 09:49 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
© 2001-2011 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms