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E46 Xi Forum
The E46 XI was produced from 01-05 in sedan and touring body styles. Powered by either a 2.5L inline 6 in the 325xi or a 3.0L inline 6 330xi. Discuss all thing about BMW AWD E46 'Xi' here.

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Old 09-13-2011, 07:57 AM   #1
memo11
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Dsc off 4 wd on?

when DSC is turned OFF will the 4 WD still work?

Lets say DSC is turned off or malfunctioned, will the transfer case still deliver power to the front wheels on a slippery surface?

In case ABS system malfunctions will the front wheels get power from the transfer case?

Does the E46 XI system have an electronic control unit?
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Old 09-13-2011, 08:35 AM   #2
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It's mechanical. The AWD is on all the time unless you have a big problem.
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Old 09-13-2011, 09:01 AM   #3
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It's mechanical. The AWD is on all the time unless you have a big problem.
ok, so when we turn off DSC or when we loose ABS, the AWD still works. Thats good news.
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Old 09-13-2011, 09:36 AM   #4
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no, you still have ABS. it cant not be turned off.
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Old 09-13-2011, 10:53 AM   #5
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Originally Posted by chuckb View Post
It's mechanical. The AWD is on all the time unless you have a big problem.
That's not actually right. The transfer case splits power between front and rear wheels, but it acts as an open differential. DSC is required for the AWD system to work.
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Old 09-13-2011, 10:57 AM   #6
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That's not actually right. The transfer case splits power between front and rear wheels, but it acts as an open differential. DSC is required for the AWD system to work.
technically, the c-diff is permanent 38/62 split, what you dont have when DSC off is the side to side torque transfer in the front and back diffs (traction control).
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Old 09-13-2011, 11:10 AM   #7
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Exactly what did i say that was wrong?

"The NV 124 is a full-time, one-speed, four-wheel-drive transfer case. Unlike the chain driven transfer case in the BMW X-series vehicles, the 3-series cases are fully gear driven units. According to BMW, "The reason gears are used is to produce a compact low profile transfer case that could fit in the transmission tunnel of an E46 without excessively limiting the forward travel of the drivers seat." The gearing provides a permanent 38%F / 62%R torque split (discussed below) between the front and rear drive shafts."

http://www.xiftw.com/?page_id=16

EDIT: Emphasis on, "fully gear driven units", and "permanent 38%F / 62%R torque split".

Last edited by chuckb; 09-13-2011 at 11:15 AM.
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Old 09-13-2011, 11:16 AM   #8
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You guys really should read this thread:

http://forum.e46fanatics.com/showthr...highlight=open

The conclusion: the transfer case is "open" meaning that if the rear wheels spin freely (as they would on a sheet of ice) then the front wheels would stop unless traction control (i.e. DSC) kicked in to brake the rear wheels and force power to go to the front wheels. Thus, DSC is essential for our AWD system to work, or at least for it to work properly.

It's a half-assed system in my opinion. That's probably why BMW abandoned it. It still gets the job done, dont get me wrong. But it's not very sophisticated compared to torsen/xdrive/haldex/etc.

Last edited by TiAgXi; 09-13-2011 at 11:18 AM.
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Old 09-13-2011, 11:23 AM   #9
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Read how the transfer case works man. It's not open. It's the exact opposite of open. It's as closed as closed can be.

It's just gears and only gears.

"Rumors

Unlike many claims and rumors, the transfer case does not implement any use of viscous coupling or variable torque control, either passive or active. The torque ratio is 38%-Front / 62%-Rear."

http://www.xiftw.com/?page_id=16
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Old 09-13-2011, 11:38 AM   #10
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There's a picture book explanation of the power transfer to all the gears in the damn thing. Go look. It's quite a simple system.

http://www.xiftw.com/?page_id=16

I'm surprised you guys debated it so long in that thread..... I thought this was common knowledge.

If i'm not mistaken the E30 325iX did have a viscous coupling in the transfer case. Interestingly enough BMW did away with that in the e46.
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Old 09-13-2011, 11:53 AM   #11
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It's sort of funny you guys spent 4 pages throwing **** against the wall instead of just looking up the answer on google.

What you guys seemed to decide the e46 transfer case does is actually what the ix e30 transfer case did/does. It had a " viscous coupling integrated into the planetary gear center differential". The e46 does not.

It's gears and just gears. Nothing else.

For what it's worth my late 88 ix was better in the snow than my 01 xi too. I will regret selling that car until the day i die..... My new m3 at the time jaded me
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Old 09-13-2011, 12:17 PM   #12
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Quote:
Originally Posted by chuckb View Post
It's mechanical. The AWD is on all the time unless you have a big problem.
Yes.

Quote:
Originally Posted by jasonbimmer View Post
technically, the c-diff is permanent 38/62 split, what you dont have when DSC off is the side to side torque transfer in the front and back diffs (traction control).
Yes.

Quote:
Originally Posted by chuckb View Post
Exactly what did i say that was wrong?

"The NV 124 is a full-time, one-speed, four-wheel-drive transfer case. Unlike the chain driven transfer case in the BMW X-series vehicles, the 3-series cases are fully gear driven units. According to BMW, "The reason gears are used is to produce a compact low profile transfer case that could fit in the transmission tunnel of an E46 without excessively limiting the forward travel of the drivers seat." The gearing provides a permanent 38%F / 62%R torque split (discussed below) between the front and rear drive shafts."

http://www.xiftw.com/?page_id=16

EDIT: Emphasis on, "fully gear driven units", and "permanent 38%F / 62%R torque split".
Yes.

Quote:
Originally Posted by TiAgXi View Post
You guys really should read this thread:

http://forum.e46fanatics.com/showthr...highlight=open

The conclusion: the transfer case is "open" meaning that if the rear wheels spin freely (as they would on a sheet of ice) then the front wheels would stop unless traction control (i.e. DSC) kicked in to brake the rear wheels and force power to go to the front wheels. Thus, DSC is essential for our AWD system to work, or at least for it to work properly.

It's a half-assed system in my opinion. That's probably why BMW abandoned it. It still gets the job done, dont get me wrong. But it's not very sophisticated compared to torsen/xdrive/haldex/etc.
Naw. Confusing torque with speed again.
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Old 09-13-2011, 12:25 PM   #13
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"Full-time all wheel drive with all free differentials. 38% front / 62% rear torque distribution thru planetary gear. ADB-X (Automatic Differential Brake) electronic traction control performs functions of locking differentials."

http://www.awdwiki.com/en/bmw/
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Old 09-13-2011, 12:55 PM   #14
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http://auto.howstuffworks.com/differential2.htm

Full time AWD to ^free/open diffs
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Old 09-13-2011, 12:57 PM   #15
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There's a difference between splitting torque and being limited slip, open or locked. Your rear diff splits torque 50/50 between wheels, does it not? And yet it's open.

Explain this:

(able to stop one t-case output from spinning by hand, fully functional t-case)



and this:

(DSC off, front wheels off the ground, rear wheels on the ground, car doesn't drive itself off the jack stands)



Let me explain it for you: the transfer case is "open" just like the two differentials. KAratechop's video basically simulates what would happen if your DSC was turned off and your front wheels only were on a sheet of ice. With no DSC, the AWD system fails to function as it needs to.

This topic can be argued to death. People will never stop posting "naw man, power is split 32/68" as if that was ever in question. I give up.

Last edited by TiAgXi; 09-13-2011 at 01:02 PM.
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Old 09-13-2011, 01:07 PM   #16
jasonbimmer
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Quote:
Originally Posted by TiAgXi View Post
There's a difference between splitting torque and being limited slip, open or locked. Your rear diff splits torque 50/50 between wheels, does it not? And yet it's open.

Explain this:

(able to stop one t-case output from spinning by hand, fully functional t-case)



and this:

(DSC off, front wheels off the ground, rear wheels on the ground, car doesn't drive itself off the jack stands)



Let me explain it for you: the transfer case is "open" just like the two differentials. KAratechop's video basically simulates what would happen if your DSC was turned off and your front wheels only were on a sheet of ice. With no DSC, the AWD system fails to function as it needs to.

This topic can be argued to death. People will never stop posting "naw man, power is split 32/68" as if that was ever in question. I give up.
one or more wheels off ground is not really an ideal situation.
same for Torsen LSD on my RX8. if one wheel off ground, it wont limit the slip and send torque to the other wheel. its a worm gear configuration and one wheel off ground is not suitable for this set up.
in fact, any gear drive diff will act like open diff when one of the axle is completely load free.

Last edited by jasonbimmer; 09-13-2011 at 01:10 PM.
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Old 09-13-2011, 01:23 PM   #17
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Originally Posted by chuckb View Post
"Full-time all wheel drive with all free differentials. 38% front / 62% rear torque distribution thru planetary gear. ADB-X (Automatic Differential Brake) electronic traction control performs functions of locking differentials."

http://www.awdwiki.com/en/bmw/
This confirms what I have said. DSC performs the function of locking the diff when needed. And you link says that the e46 has "all free differentials" and it uses the term "differential" to include the center.
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Old 09-13-2011, 02:31 PM   #18
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Originally Posted by jasonbimmer View Post
in fact, any gear drive diff will act like open diff when one of the axle is completely load free.
+1


Quote:
Originally Posted by TiAgXi View Post
This confirms what I have said. DSC performs the function of locking the diff when needed. And you link says that the e46 has "all free differentials" and it uses the term "differential" to include the center.
No it is not referring to the transfer case as an "open differential" and there is nothing to get "locked" in the transfer case. Look at the link i posted earlier, it's just a set of gears. The page goes step by step through the power transfer of the transfer case. With pictures even!! It even dispels your specific notion as a "rumor". The system you have in mind is what was used in the e30 iX.

"Electronic traction control systems usually use the anti-lock braking system (ABS) roadwheel speed sensors to detect a spinning roadwheel, and apply the brake to that wheel. This progressively raises the reaction torque at that roadwheel, and the differential compensates by transmitting more torque through the other roadwheel—the one with better traction."

^the traction control doesn't control the transfer case in this system. It controls the differentials.
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Old 09-13-2011, 02:32 PM   #19
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e30 ix:

Full-time all wheel drive. Viscous coupling locking center differential with torque split 37% front / 63% rear. The viscous coupling is integrated into the planetary gear center differential. viscous coupling locks the differential when wheel slipping occurs and transfers up to 90% of torque to the axle that has traction. Viscous coupling locking rear differential distributes torque between the rear wheels.

^ This is what your thinking of.
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Old 09-13-2011, 02:41 PM   #20
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Automatic Differential Brake (ADB-X).
The Automatic Differential Brake (ADB-X) lets you make the most of your BMW's dynamic performance and sporting character on difficult road surfaces.

BMW's Dynamic Stability Control (DSC) system ensures that the vehicle remains stable when taking bends, speeding up or braking on uneven road surfaces or in poor driving conditions. The Automatic Differential Brake (ADB-X) is part of this system. Using sophisticated electronics, it offers the same function as a mechanical differential brake - without any disadvantages arising from weight and loss of efficiency.
If a wheel threatens to slip, it is individually braked: blocking momentum is directed to the wheel opposite, which thereby guarantees optimum drive power. When DSC or Dynamic Traction Control (DTC) is active, the engine power output is also adjusted.
If the sporting driver chooses to deactivate DSC or DTC, he still has the benefit of ADB-X, which then focuses on maximum forward drive and applies braking force only. A temperature control sensor ensures that the brakes do not overheat.

http://www.bmw.com/com/en/insights/t...ial_brake.html

^You could easily google this instead of me instead of blindly arguing.
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