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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 02-06-2011, 11:07 PM   #41
dephantn
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first, please do not make statement if you don't ( or didn't) have driven an Xi on snow zone.
Second, if your Xi does not have winter tires.
Third, if you don't or never driven others brand AWD/4WD to compare with XI ( no "I heard that", I read that, people said that "....)
If your Xi stuck in snow, either it does not equip with winter tires, or DSC turn off, or DSC bad ( you assume it works, but it died ).
If you drive a Xi, do not let people see that you are thinking " the grass on other side the hill always greener".
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Old 02-07-2011, 06:53 AM   #42
Kubica
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Quote:
Originally Posted by dephantn View Post
first, please do not make statement if you don't ( or didn't) have driven an Xi on snow zone.
Second, if your Xi does not have winter tires.
Third, if you don't or never driven others brand AWD/4WD to compare with XI ( no "I heard that", I read that, people said that "....)
If your Xi stuck in snow, either it does not equip with winter tires, or DSC turn off, or DSC bad ( you assume it works, but it died ).
If you drive a Xi, do not let people see that you are thinking " the grass on other side the hill always greener".
+1.

Most of these kids can't drive. They blame their lack of snow driving abilities on their car.

These cars are miraculous in the snow with the right tires.
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Old 02-07-2011, 07:19 AM   #43
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+1.

Most of these kids can't drive. They blame their lack of snow driving abilities on their car.

These cars are miraculous in the snow with the right tires.
I don't care what car/truck you are in. If you can't drive in the snow nothing will help you. I luckily have had the chance to have snow and ice twice since I bought my XI. That's a rarity in North Carolina. It handled superb even without snow tires. I grew up in the mountains of Pennsylvania and took my first drivers test there in the snow. I actually enjoy driving in the snow except for the idiots. And my usual vehicle is my '79 GMC pick up with the Pontiac 400ci V8. Lots of fun and never an issue.
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Old 02-07-2011, 08:16 AM   #44
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Originally Posted by dephantn View Post
first, please do not make statement if you don't ( or didn't) have driven an Xi on snow zone.
Second, if your Xi does not have winter tires.
Third, if you don't or never driven others brand AWD/4WD to compare with XI ( no "I heard that", I read that, people said that "....)
If your Xi stuck in snow, either it does not equip with winter tires, or DSC turn off, or DSC bad ( you assume it works, but it died ).
If you drive a Xi, do not let people see that you are thinking " the grass on other side the hill always greener".
1) I live in VT
2) New studded Artic Altimax
3) Have owned an 83 Audi Ur Quat, 2 87 VW Quantum Synchro Wagons, 1 2004 Subaru WRX, 1 2005 Subaru Legacy GT Wagon and finally my 325XIT.

I feel I meet your criteria to comment.
BMW has used a reliable first generation AWD system and put brake technology on top of it to replace the manual diff locks found in all my older german cars. Its a solution, but the best no way! Does the car handle awesome, it sure does and you would never know the difference unless you were stuck in a snow bank or in a driveway with two feet of snow. As a test I tried to get out of my driveway with DSC on , not happening so much braking there was no power to get out of the snow holes my tires created, no slipping but also no going. I turn off the DSC and gave it a go and I got out. In my wife's Outback there was no hesitation it just rolled right out.


The Subarus I owned were the most stable cars I have driven in the snow. That being said the BMW is more fun because of its over steering nature, where the Subaru's under steer to a fault.

Kubica I commend your loyalty to our cars but understand they are not the latest and greatest. I am sorry to hear about your name sake Robert Kubica had a terrible Rally accident in a Skoda and might lose his hand.
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Old 02-07-2011, 10:15 AM   #45
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Yeah. To this point, we all need to realize what BMWs design goals and limitations were when the e46 XI came out.

The e46 XI was an after-thought. Pure and simple.

Audi was gaining market share on BMW rapidly in the late 90s due to their quatro system, and many other luxury brands also had AWD options.

BMW quickly devised the e46 XI using existing hardware and technologies adapted for the already in production e46 platform.

In short, they pulled it off on a shoe string budget with short design window timelines and a little time for in depth testing. That said, it explains why it is not the most stoudt or all-conquering system out there. However, it certainly does very well.

Those engineers once done with the e46 XI project were unleashed with fewer constraints and longer time frame to develop the new X drive systems found on the e90, X5, X6, and others.

Lesson - the resulting end design is all about the constraints you are under.
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Old 02-07-2011, 10:31 AM   #46
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Quote:
Originally Posted by Kubica View Post
The front diff can go into what I call 'TC preservation mode' when the rear wheels are spun too much.

When this happens, the front driveshaft is spinning but the front axles are not.

I just blew all your minds.
wut... that doesn't sound like something i'd want out of my awd system... hmmm.
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Old 02-07-2011, 11:27 AM   #47
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Originally Posted by TCSKIBIKE View Post
1) I live in VT
2) New studded Artic Altimax
3) Have owned an 83 Audi Ur Quat, 2 87 VW Quantum Synchro Wagons, 1 2004 Subaru WRX, 1 2005 Subaru Legacy GT Wagon and finally my 325XIT.

I feel I meet your criteria to comment.
BMW has used a reliable first generation AWD system and put brake technology on top of it to replace the manual diff locks found in all my older german cars. Its a solution, but the best no way! Does the car handle awesome, it sure does and you would never know the difference unless you were stuck in a snow bank or in a driveway with two feet of snow. As a test I tried to get out of my driveway with DSC on , not happening so much braking there was no power to get out of the snow holes my tires created, no slipping but also no going. I turn off the DSC and gave it a go and I got out. In my wife's Outback there was no hesitation it just rolled right out.


The Subarus I owned were the most stable cars I have driven in the snow. That being said the BMW is more fun because of its over steering nature, where the Subaru's under steer to a fault.

Kubica I commend your loyalty to our cars but understand they are not the latest and greatest. I am sorry to hear about your name sake Robert Kubica had a terrible Rally accident in a Skoda and might lose his hand.
Robert will be ok. He's a tough guy. We'll see him back for the 2012 season.

I live in northern Vermont half the time in the winter too.

I run studded Nokian Hakkas and also non-studded Nokian Hakka R's in the winter. You can often find me in the unplowed right lane on I-91 passing cars, on my way to/from Boston.

Either way, I'm referring to high-speed driving in the snow. 75-100 mph in the snow. This is a BMW, not a pickup truck. Of course some other cars can get through some more unplowed snow better than an xi, or free you from the snow bank you shouldn't have driven into anyway. However, I have yet to get stuck in my xi.

I've owned and driven Audi A4's, S4's, VW passat 4motion, 325ix, and more than a few Subarus. Nothing approaches the high speed stability and inspires more confidence (for me) in serious snow driving like the xi.

I'm speaking for advanced driver's here: if you often get stuck, drive without snow tires, can't get through 8 inches of unplowed snow, or have ever rear-ended someone, you'd proabably be better off in a Subaru. Have fun guessing what wheels are getting power when you get on the gas.

And for the record, my DSC has kicked on maybe 3 or 4 times this winter in several thousand miles of snow driving. If any of you have kicked it on much more than that, you just aren't a good snow driver. Sorry. Kind of makes the DSC argument moot- it's the driver and the tires, not the car. So stop trashing the xi and learn how to drive.
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Old 02-07-2011, 11:29 AM   #48
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wut... that doesn't sound like something i'd want out of my awd system... hmmm.
It's better than blowing your TC to pieces if the rear wheels are off the ground.
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Old 02-07-2011, 11:50 AM   #49
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C'mon I let the DSC kick on in side streets to see how far the electronanny will let me go! It is fun to let otherwise experienced RWD drivers (my e34 driving brother) try to make the car skid with snows and DSC on.

That is my only "feature request" on the xi, a locking center. Could even have a pull knob like the old VW/audi system.
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Old 02-07-2011, 12:45 PM   #50
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so if the center is an actual diff, what's stopping one from running different ratios on front and rear diff ? it's all gear-based, so there's nothing rubbing and generating heat.
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Old 02-07-2011, 01:12 PM   #51
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so if the center is an actual diff, what's stopping one from running different ratios on front and rear diff ? it's all gear-based, so there's nothing rubbing and generating heat.
That is a good question...

Also, because it is gear based, there are things rubbing and generating heat. Hence the TC fluid to lubricate the gear set.
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Old 02-07-2011, 01:14 PM   #52
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It's better than blowing your TC to pieces if the rear wheels are off the ground.
just FYI, your namesake seems to be doing better.

http://www.miamiherald.com/2011/02/0...ing-after.html
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Old 02-07-2011, 01:51 PM   #53
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C'mon I let the DSC kick on in side streets to see how far the electronanny will let me go! It is fun to let otherwise experienced RWD drivers (my e34 driving brother) try to make the car skid with snows and DSC on.

That is my only "feature request" on the xi, a locking center. Could even have a pull knob like the old VW/audi system.
I just turn it off when it's time to play.

I guess I'm not following here: what does your car not do in the snow, or what do you need it to do better? I'm just still at a loss that anyone needs anything more in a sports sedan in the snow. I got up and down my buddy's unplowed driveway (uphill with two turns) yesterday morning at Jay Peak in 12 inches of fresh snow.

The simplicity of the AWD system makes it better, not worse. If an electronics module and brakes can take the place of expensive AWD components that require big maintenance and often wear out, what's the problem?

The TC is essentially locked all the time anyway- not sure why you would want to unlock it?

Quote:
Originally Posted by gurov View Post
so if the center is an actual diff, what's stopping one from running different ratios on front and rear diff ? it's all gear-based, so there's nothing rubbing and generating heat.
It's not a diff, it's a TC with a fixed TORQUE split. The front and rear driveshafts spin at the same speed.

Quote:
Originally Posted by SamDoe1 View Post
That is a good question...

Also, because it is gear based, there are things rubbing and generating heat. Hence the TC fluid to lubricate the gear set.
Again, torque is split at a fixed ratio. Driveshafts need to spin at roughly the same speed, or the TC will be damaged. Different diff ratios or tire diameters front/rear will cause slipping/grinding/binding which breaks down the fluid and ruins your TC eventually.

Quote:
Originally Posted by scottz View Post
just FYI, your namesake seems to be doing better.

http://www.miamiherald.com/2011/02/0...ing-after.html
Yeah, I was very happy to read that when I woke up this morning. I had front row seats for his crash in Montreal a few years ago. I actually thought he was dead it was such a violent collision- his feet were actually hanging out the front of his BMW just dangling there. The following year he came back and won the race in Montreal- I've been a massive fan ever since.
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Old 02-07-2011, 04:02 PM   #54
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No it is just a paranoia feature like my brother's old VW quantum synchro had. Even with nokians, locking diffs helped get it out of some sticky spots.

As i understand it, the t-case should function like the NP242 in a selec-trac jeep in 4wd full time. Meaning it has a built in bias, but the center isn't locked, otherwise the tires should hop around corners like the NP242 in "part time" or an NP231 in "4wd high" If it were "locked" , the test earlier in the thread should have resulted in both output shafts spinning regardless of whether they were held stationary.

I agree the simplicity is nice, nothing mechanical to really break. I do wish BMW would have been more honest with folks regarding changing the t-case fluid.
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Old 02-07-2011, 04:40 PM   #55
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No it is just a paranoia feature like my brother's old VW quantum synchro had. Even with nokians, locking diffs helped get it out of some sticky spots.

As i understand it, the t-case should function like the NP242 in a selec-trac jeep in 4wd full time. Meaning it has a built in bias, but the center isn't locked, otherwise the tires should hop around corners like the NP242 in "part time" or an NP231 in "4wd high" If it were "locked" , the test earlier in the thread should have resulted in both output shafts spinning regardless of whether they were held stationary.

I agree the simplicity is nice, nothing mechanical to really break. I do wish BMW would have been more honest with folks regarding changing the t-case fluid.
Yup, I've been changing TC fluid with every oil change.

The tires (front vs. rear) don't hop because it's not "locked" 100%. The TC can slip a bit, so for example, it doesn't grenade when your rear tires have a few more 32nds of an inch of tread.

If the TC were a diff, which it is not, and if it was an "open" diff, which it is not either, only one wheel would ever get power. We know in almost all situations that a front and rear wheel will get power. It's not "open", it has a "fixed" torque split. The only time a front wheel doesn't get power is if there is zero rear traction at both rear wheels (like when you have the car up on jack-stands). The front driveshaft will be spinning in this situation, at the same speed as the rear driveshaft. The front axles won't spin though, and no power reaches the front wheels, because the front wheels would spin much slower than the rear wheels, creating a speed difference at the TC, which would then grenade itself.

Differentials are meant to allow outputs to spin at different speeds while splitting power.

Transfer Cases allow the power to be split while the outputs rotate at the same speed.
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Old 02-07-2011, 04:57 PM   #56
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The front driveshaft will be spinning in this situation, at the same speed as the rear driveshaft. The front axles won't spin though, and no power reaches the front wheels, because the front wheels would spin much slower than the rear wheels, creating a speed difference at the TC, which would then grenade itself.

Differentials are meant to allow outputs to spin at different speeds while splitting power.

Transfer Cases allow the power to be split while the outputs rotate at the same speed.
I understand the concept of a differential and a transfer case, BUT, what I don't get is if the front drive shaft is spinning, why isn't the axle spinning. Where is that rotational force going? It has to go somewhere, doesn't matter if it's one wheel or both but it has to go somewhere. There is a mechanical joint between the driveshaft and the differential that is not disconnectable by the car or the driver so that spinning driveshaft must connect to and spin something else. Otherwise you have a magical differential that can somehow disconnect itself from the drivetrain. If there is no traction to the rear wheels at all, the front wheels should still be receiving some amount of the engine's torque output (by your statement that it is a transfer case not a center diff) no matter what happens at the rear. Can you explain more because the farther this goes on, the more confused I'm getting.
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Old 02-07-2011, 05:23 PM   #57
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Quote:
Originally Posted by SamDoe1 View Post
That is a good question...

Also, because it is gear based, there are things rubbing and generating heat. Hence the TC fluid to lubricate the gear set.
i meant versus clutch-based.
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Old 02-07-2011, 05:33 PM   #58
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I understand the concept of a differential and a transfer case, BUT, what I don't get is if the front drive shaft is spinning, why isn't the axle spinning. Where is that rotational force going? It has to go somewhere, doesn't matter if it's one wheel or both but it has to go somewhere. There is a mechanical joint between the driveshaft and the differential that is not disconnectable by the car or the driver so that spinning driveshaft must connect to and spin something else. Otherwise you have a magical differential that can somehow disconnect itself from the drivetrain. If there is no traction to the rear wheels at all, the front wheels should still be receiving some amount of the engine's torque output (by your statement that it is a transfer case not a center diff) no matter what happens at the rear. Can you explain more because the farther this goes on, the more confused I'm getting.
yes, i'm curious about this as well, sounds like the front differential is a bit more than a simple differential then. if the driveshaft is rotating, at least one of the front wheels should be turning.

i agree that there's something else going on when taking the corners, and pretty much every single wheel is moving at a different speed.

could the person with the NV124 on the bench please perform a few more tests, such as actually counting the number of rotations free output shaft performs when the other output shaft is held stationary versus number of rotations when the shafts are let spin freely.
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Old 02-12-2011, 03:17 PM   #59
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While under my XI this morning I made an interesting observation.

Back wheels off the ground, if you spin one wheel, the other spins the opposite direction. This means the rear is a standard open differential as we all know. Now for the odd thing. If the front is also an open differential we'd expect the same results right? Wrong. With the front axle off the ground, I spun the passenger wheel and the driver's wheel did not move, but the driveshaft to the TC was spinning. I then went over and spun the driver's wheel, but the passenger wheen did not move, although again the driveshaft to the TC was spinning.

It would almost seem that the front differential is an unusual form of an open diff. Perhaps the front diff is Vicious and not gear driven?? Anyone ever seen inside one?

Also, regarding the TC, why does it have a vacuum line feeding into it? If it were just a vent pipe there would be no need for a hose right? However there is a vacuum hose that comes off the TC and goes up over the trans tunnel. Why?
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Old 02-12-2011, 03:42 PM   #60
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Not sure i have a vac line coming off my transfer case. Jeeps have a vent that goes into the engine bay, near the firewall. The idea is to keep the vent free from ingesting any water if you submerge the case. Maybe that is what BMW is doing there?
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