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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 09-14-2011, 02:26 PM   #61
chuckb
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Quote:
Originally Posted by xixixi View Post
The T case is "open" in the sense that the outputs can be moved at different speeds. (1 half shaft will spin while the other does nothing) Just like your "open" diff does on said corners. However in a straight line your "open" diff acts as a solid axle. When going in a straight line at a constant speed. The ABS manipulates how much torque is needed to spin each wheel. The power goes to the wheel that needs the least amount of torque to spin. This is where the DSC comes into play with your abs system. Your wheel speed sensors pick up that 1 wheel is spinning and 3 others are not. It applies the brakes to the spinning wheel allowing the other wheels to get the power/torque. The T case is "open" (don't get stuck on the word, just the meaning) If you take off your front half shaft the car refuses to move, why? B/c the part of the power train that takes the least amount of torque to spin will get the power. IE Your front half shaft. Apply the E brake put your car in the air and the front wheels spin. Hold the front wheels and the rears will spin. This isn't about "open/close" it's about what the abs will allow the drive train to do. It's all done with abs/wheel speed sensor out put/inputs. Thus the need for the planetary gears... Yes, the speed is very different on the out puts. One moves while the other does nothing. It's not what you're writing, it's how you are getting your information across.
BMW specifically states the power output is fixed between the front and rear.

"The transmission ratio of the planetary gear set provides a fixed torque transfer of 38:62 (front:Rear). The output speeds to the front and rear axle are the same (1:1)"

YOu say the speed is "very different". BMW specifically states it is "the same".
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Old 09-14-2011, 02:42 PM   #62
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Kubica's got it right. Chuckb, I think you confuse power "transfer" with a locking/limited slip differential. The power is "transfered" by locking or limiting the slip(difference on rotational speed) between the front and rear axels. Because of the locking or limiting slip, the transfer case is not open.
That's why you have to uncouple the rear driveshaft on an ix when towing. If you don't, you will burn up the VC in the transfer case.
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Old 09-14-2011, 02:56 PM   #63
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I don't think kubica is entirely wrong. I think the 3% openness he contributes to the tc are most likely failsafes designed into a closed system.

Clearly i don't think there are 3 or 4 gears in there driving everying with zero amount of forgiveness. THere has to be some forgiveness in the system. BUt it's still closed because the forgiveness doesnt change the fact that the outputs are fixed and don't change under normal operating conditions.

a vc never lock. ever. If you look up how a vc works ( i copied and pasted an explanation earlier you will see why it would crap out with the front wheels stationary and the back wheels driving down the highway.

a limited slip diff is an open diff with a locker built in. It's open until it starts slipping and then it locks. It's just a modified open diff.
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Old 09-14-2011, 03:04 PM   #64
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Originally Posted by Pierce1 View Post
The power is "transfered" by locking or limiting the slip(difference on rotational speed) between the front and rear axels.
Power is never transferred between front or rear ever. like i quoted from BMW, right before you posted that. All the outputs of the TC are FIXED.
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Old 09-14-2011, 03:04 PM   #65
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Yes. I guess the issue at hand is that we(whoever) have different definitions of what an open differential is.
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Old 09-14-2011, 03:12 PM   #66
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"When the differential is unlocked (open differential), it allows each wheel [output] to rotate at different speeds (such as when negotiating a turn)"

"By contrast, a locked differential forces both left and right wheels on the same axle to rotate at the same speed under nearly all circumstances"

http://en.wikipedia.org/wiki/Locking_differential:

Last edited by chuckb; 09-14-2011 at 03:14 PM.
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Old 09-14-2011, 03:13 PM   #67
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Here's an article describing all of the different transfer cases built by New Venture, including the NV 124, which it describes as a "type of open differential" with "varying torque splits":


Attached Files
File Type: pdf New Venture article.pdf (1.34 MB, 80 views)

Last edited by TiAgXi; 09-14-2011 at 03:19 PM.
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Old 09-14-2011, 03:20 PM   #68
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Originally Posted by chuckb View Post
Power is never transferred between front or rear ever.
Correct.

If the TC was open, along with both diffs, the inside front wheel would be getting all the power when you hit the gas on corner exit, because it has the least amount of grip. That's not what happens.

Also, open diffs TRANSFER equal torque to the ground through the tires on both sides. There can be more power on one side, it's just not being transferred to the ground. When a 325i does a burnout, one tire spins. The spinning rear wheel receives more power, but transfers and equal amount of torque to the ground as the stationary wheel.

http://farnorthracing.com/autocross/diffs.html
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Old 09-14-2011, 03:28 PM   #69
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Originally Posted by chuckb View Post
Power is never transferred between front or rear ever. like i quoted from BMW, right before you posted that. All the outputs of the TC are FIXED.
"Fixed" in the same way that power is fixed for the two wheels on an axle.
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Old 09-14-2011, 03:29 PM   #70
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Notice that article I posted doesn't say that one of the options is "locked" like you guys are asserting...
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Old 09-14-2011, 03:31 PM   #71
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That article looks to be talking about the entire 4wd system and what the TC is used in conjunction with to complete the system. That's why it says "Full time 4wd systems have the power going to all four wheels of the vehcile under normal operation. These systems feature some type of open-center differential". The e46 does use front and rear open diffs.

The article definately does not describe the nv124 as a "type of open differential." You are clearly taking it quite out of context.

Last edited by chuckb; 09-14-2011 at 03:50 PM.
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Old 09-14-2011, 03:41 PM   #72
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Originally Posted by chuckb View Post
That article looks to be talking about the entire 4wd system and what the TC is used in conjunction with to complete the system. That's why it says "Full time 4wd systems have the power going to all four wheels of the vehcile under normal operation. These systems feature some type of open center differential". The e46 does use front and rear open diffs.


You and I really can't communicate.
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Old 09-14-2011, 03:47 PM   #73
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notice the dash between "open" and "center" the term is NOT "center differential" it's open-center.......differential.
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Old 09-14-2011, 03:51 PM   #74
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The entire article is discussing nothing but the various transfer cases built by New Venture including the NV124 used in the e46. Those used in full time 4wd models have open center differentials that split torque in the ways the article describes.

reading comprehension. get some.
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Old 09-14-2011, 03:57 PM   #75
chuckb
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Originally Posted by TiAgXi View Post
The entire article is discussing nothing but the various transfer cases built by New Venture including the NV124 used in the e46. Those used in full time 4wd models have open center differentials that split torque in the ways the article describes.

reading comprehension. get some.
hah. I think you're wrong. It's clearly discussing the "4wd system", and the "system" sending power to the wheels. There are diffs between the transfer case and the wheels.

EDIT: That's why it ambiguously states "some type of open-center differential".

Last edited by chuckb; 09-14-2011 at 04:01 PM.
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Old 09-14-2011, 05:01 PM   #76
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"These systems feature some type of open-center differential and varying torque splits (in percentage, front axle to rear) including 48/52, 47/53 and 38/62."

^That's why in the same sentence it's talking about the torque splits going to the front and rear diffs.
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Old 09-14-2011, 05:14 PM   #77
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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.
I really think you've abandoned your own point and now you've resorted to trying to poke holes in my point. Not to help prove your point at all, but just because you want to argue and cant stand being wrong.

The fact is the outputs to the front and rear are CONSTANT. Whether you want to call it open,closed,Dan, or Ricki.

Since i've posted what i consider, irrefutable evidence, straight from BMW, saying this, you've now resorted to trying to poke holes in the terminology.

Honestly like i've already said, the terminology doesnt matter, it's the function of the transfer case that was in question. But all people want to talk about is whether it's open or closed.

The whole point to saying it was "closed" means that nothing changes, and the outputs don't differ speeds. "Open" does NOT mean two outputs with same speed that never differs. That's just not what "open" means.

Whatever the hell you want to think, it does not FUNCTION openly. It's as fixed as fixed can be. PERMANENT torque splits with constant 1:1 output speeds.

Last edited by chuckb; 09-14-2011 at 05:17 PM.
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Old 09-14-2011, 05:36 PM   #78
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Quote:
Originally Posted by TiAgXi View Post
The entire article is discussing nothing but the various transfer cases built by New Venture including the NV124 used in the e46. Those used in full time 4wd models have open center differentials that split torque in the ways the article describes.

reading comprehension. get some.
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Old 09-14-2011, 05:37 PM   #79
chuckb
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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.

even that article you posted has the same info on the nv124 as the link i posted on page one, http://www.xiftw.com/?page_id=16

It says the t case is SINGLE SPEED.

The case wont transfer power from front to back, or back to front.

All the outputs are constant.

Given such the transfer case doesnt even meet YOUR OWN definition of "open".
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Old 09-14-2011, 09:09 PM   #80
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Transfer cases cannot be open or closed. Some can be shifted into 2WD or 4WD, but are never open or closed

Differentials are open or closed. Limited slips offer some advantage to an open differential but are still open unless helped by brakes. A true closed differential require a Detroit Locker or similar in the differential.

Search Wikipedia for differential.
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