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      11-16-2010, 07:09 PM   #89
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Quote:
Originally Posted by cyphr View Post
The Bentley lists the fuses as controlling only the wipers.

Unfortunately, I only have diagrams from MY2006-2008. Have you referenced the diagram that's on the back of the fuse panel?
Ah yes that diagram...I will check!

If this works :|


I will be very very happy...I love RWD...and def do not need the traction control in the summer
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      11-17-2010, 04:38 PM   #90
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BUMP !!!! Come on Terry or Shiv, help us Xdrivers out
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      11-17-2010, 05:58 PM   #91
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One thing we need to check is if our brake lights still function after pulling this fuse....I just scanned my car and pulled/replaced the fuse on Monday.

I had an error with a description something like brake light input to ECU.

BTW FOR THOSE WITHOUT A WAY TO CLEAR CODES OFF YOUR CAR!!!!!!

THERE ARE TONS OF HIDDEN FAULTS STORED THROUGHOUT MULTIPLE MODULES!!!!!!

Last edited by fdriller9; 11-17-2010 at 06:07 PM.
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      11-17-2010, 06:03 PM   #92
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Quote:
Originally Posted by ajsalida View Post
Probably what remains is the 2WD version of the 4WD pseudo e-diff feature of xDrive (I know it does not have a true e-diff). There is some evidence that even with DSC/DTC completely off, you still have the brakes allocating torque by stopping wheel spin on all four wheels. So maybe with the TC disabled/running open, you have RWD-only version of this.

It would make sense, suppose somehow front diff blows up, front driveshaft breaks whatever, you'd want some kind of e-LSD left in RWD as a default.
I don't know if I'm understanding you correctly but I beleive (not sure) that the braking is applied by our ABS system....which is also disabled with pulling the fuse.

So I don't see how power would be traveling from side to side. Also I beleive the rear diff is always engaged and since it is electronically controlled, pulling the fuse disables the ability to disengage the rear diff.

That's my theory as to why the rear diff is "locked."

EDIT: So the xDrive system can only transfer power from the rear to front axles...not side to side. I beleive braking is applied to slow down a wheel so it can match torque on each side.

However, as per the BMW website:

"In addition, brake force courtesy of DSC is used when there is traction difference between the two sides of the vehicle and wheel spin is likely. "

So I think ABS is part of DSC and both are disabled by pulling the fuse. So no braking is applied and that's why we can spin both rear wheels.

Last edited by fdriller9; 11-17-2010 at 06:27 PM.
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      11-17-2010, 06:31 PM   #93
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Originally Posted by ********* View Post
So I think ABS is part of DSC and both are disabled by pulling the fuse. So no braking is applied and that's why we can spin both rear wheels.
No, with DSC and DTC off you still have ABS and the side-to-side e-LSD. I doubt you lose ABS by pulling fuse, but ABS and e-LSD may not be on the same circuit. Don't know. I doubt you'd get 2 strips of rubber with an open diff if e-LSD is not working.

With an open diff and no e-braking you'd just spin one wheel.
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      11-17-2010, 06:36 PM   #94
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Quote:
Originally Posted by ajsalida View Post
No, with DSC and DTC off you still have ABS and the side-to-side e-LSD. I doubt you lose ABS by pulling fuse, but ABS and e-LSD may not be on the same circuit. Don't know. I doubt you'd get 2 strips of rubber with an open diff if e-LSD is not working.

With an open diff and no e-braking you'd just spin one wheel.
Check out my video on page 3....ABS is listed as one of the malfunctioning modules on my iDrive screen.

We have open diffs but I don't think the diffs ever disengage a wheel....that's why the car uses the brakes to balance torque, hence side-to-side but not really lol.
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      11-17-2010, 06:38 PM   #95
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And here is our answer...

http://auto.howstuffworks.com/differential2.htm

This is why the guy who pulled a 180 turn thought the inside wheel was spinning at a different speed..

So in a STRAIGHT LINE our rear diff is indeed locked.
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      11-17-2010, 07:47 PM   #96
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Quote:
Originally Posted by ********* View Post
And here is our answer...

http://auto.howstuffworks.com/differential2.htm

This is why the guy who pulled a 180 turn thought the inside wheel was spinning at a different speed..

So in a STRAIGHT LINE our rear diff is indeed locked.
When I pulled the turn, both were spinning. Upon shifting to second (remember in an AT the power is continuous during shifts) the right wheel gripped and the left wheel kept wailing, which Im sure of. Left tire is slightly stripped, which led to the imbalance.

I think its in open diff mode.
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      11-17-2010, 07:50 PM   #97
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Quote:
Originally Posted by Peteypab2133 View Post
my buddy has an R32 and its as easy as pulling the big green fuse under the dash. here is a quick video in RWD mode...
Yes, that used to be very fun, too bad I dont have this feature in the R34.

Quote:
Originally Posted by ajsalida View Post
No, with DSC and DTC off you still have ABS and the side-to-side e-LSD. I doubt you lose ABS by pulling fuse, but ABS and e-LSD may not be on the same circuit. Don't know. I doubt you'd get 2 strips of rubber with an open diff if e-LSD is not working.

With an open diff and no e-braking you'd just spin one wheel.
I tested the ABS functionality and answer is NO.

Hitting the brakes will cause you to lockup like a mother. ABS is out.
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      11-17-2010, 08:27 PM   #98
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Originally Posted by ********* View Post
One thing we need to check is if our brake lights still function after pulling this fuse....I just scanned my car and pulled/replaced the fuse on Monday.

I had an error with a description something like brake light input to ECU.

BTW FOR THOSE WITHOUT A WAY TO CLEAR CODES OFF YOUR CAR!!!!!!

THERE ARE TONS OF HIDDEN FAULTS STORED THROUGHOUT MULTIPLE MODULES!!!!!!
Can these codes be cleared with procede?
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      11-17-2010, 09:10 PM   #99
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Quote:
Originally Posted by issabmw View Post
When I pulled the turn, both were spinning. Upon shifting to second (remember in an AT the power is continuous during shifts) the right wheel gripped and the left wheel kept wailing, which Im sure of. Left tire is slightly stripped, which led to the imbalance.

I think its in open diff mode.
Were you still in the trun when the right wheel gripped? I said in a straight line the diff is locked....that's how an open diff works. When you turn, the wheels can rotate at different speeds.

Quote:
Originally Posted by Alchem View Post
Can these codes be cleared with procede?
I'm not sure what a procede is.

Last edited by fdriller9; 11-17-2010 at 09:16 PM.
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      11-17-2010, 09:22 PM   #100
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Quote:
Originally Posted by issabmw View Post
Yes, that used to be very fun, too bad I dont have this feature in the R34.



I tested the ABS functionality and answer is NO.

Hitting the brakes will cause you to lockup like a mother. ABS is out.
Did you notice if your brake lights lit up?
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      11-17-2010, 09:29 PM   #101
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Did you notice if your brake lights lit up?
No, I need to check on that. Im almost positive they work though
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      11-17-2010, 09:31 PM   #102
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Were you still in the trun when the right wheel gripped? I said in a straight line the diff is locked....that's how an open diff works. When you turn, the wheels can rotate at different speeds.
No, I was driving straight when it gripped and the left kept spinning.

Btw, procede is the turbo tuner for 335 owners.
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      11-17-2010, 09:36 PM   #103
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Quote:
Originally Posted by issabmw View Post
No, I was driving straight when it gripped and the left kept spinning.

Btw, procede is the turbo tuner for 335 owners.
So the front wheels were aligned with the rears? My wheels both spin.

That's what I thought. (About the procede)
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      11-18-2010, 06:30 AM   #104
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Pretty clear neither e-LSD (for traction) or ABS (for slowing down) are working.
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      11-18-2010, 07:20 AM   #105
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SO, i tried this on a 2011 sedan yesterday, and it works the same. But my car is a lease, so can someone tell me the easiest way to reset the error codes that will show? whats the best scan tool to buy simply to read and reset codes on my car?
very interesting thread, the reason i registered. Thanks!
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      11-18-2010, 10:37 AM   #106
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What is this e-LSD you guys are talking about? I'm pretty sure our cars cannot disengage wheels on either side of the axle...especially the rear.

The xDrive system can ONLY transfer power from front to back and vice versa with a 40:60 split(rear bias). ABS (I think) applies brake to each wheel to balance torque on each side.

A mechanical wet clutch pack is used to transfer power from the front to rear...I think this is the e-LSD you guys are referring to. However with the fuse pulled, the e-LSD never engaged the front. An with the behavior of traditional open diff, the rear axle locks up, in a straight line....I think the front wheels have to be parallel with the rears for the diff to lock up.

Also our wheel angle sensor is disabled by pulling the fuse(hidden fault) so I don't know how the car knows we are turning. Maybe this is why the rear diff acts invariably.

Also because the wheel angle sensor is disabled, our turn signal does not automatically turn off after coming out a turn.

Last edited by fdriller9; 11-18-2010 at 10:51 AM.
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      11-18-2010, 03:06 PM   #107
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In certain situations, an open diff can be made to behave like a limited slip diff by applying the brakes to the spinning wheel. That is because an open diff will always send torque to the wheel with less traction and spin it. So by braking the spinning wheel, TQ gets sent to the wheel with more traction, electronically simulating a limited slip diff (LSD). Xdrive uses this feature on both the front and rear axles. RWD 335 cars have a similar feature for the rear diff only. It is not an optimal solution, a conventional LSD is better. M3 has a true LSD, and I think X6 gets an xDrive with true LSD ("torque sensing").

Xdrive has three layers of software, DSC, DTC, and then both off. DTC is a subset of DSC, lighter stability control and no engine power reduction, but traction control is still on though a bit more agressive, allowing a bit of oversteer. With DTC/DSC off completely, in xDrive you still have the front and rear e-LSD (via brakes) and the transfer case working. So IN THEORY as far as I can tell, with DTC and DSC off you may be able to spin all four tires on ice. Have not tested this yet as I have not had the car in winter.

As I have said in other threads, BMW is very cagey about how all this works.

BTW ABS and "e-LSD" both work through the brakes of course, but one works by modulating (cutting) pressure in the lines on lock up, the other actively applies the brakes based on sensors and electronics to stop wheel spin. So in theory they are totally separate systems, both of which act on brakes but no need for them to be in the same fuse circuit or even same control algorithm. They have nothing to do with one another as one works when you apply the brakes the other is when you give it gas. Then there's stability control which another system entirely. They all talk to one another of course.

I personally would not want to yank a fuse out of the middle of all this, disable ABS and all layers of DTC/DSC/e-LSD, and then push around dead rotating mass of front AWD system. But I admire the spirit of experimentation it represents. Proper solution is for Shiv or someone similar to do this w/o messing with the other sytems (if that even can be done).

edit: the above is as far as I have been able to figure out, reading a lot here and on other forums. Anyone has any knowledge to the contrary please chime in.
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      11-18-2010, 03:52 PM   #108
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Quote:
Originally Posted by ajsalida View Post
In certain situations, an open diff can be made to behave like a limited slip diff by applying the brakes to the spinning wheel. That is because an open diff will always send torque to the wheel with less traction and spin it. So by braking the spinning wheel, TQ gets sent to the wheel with more traction, electronically simulating a limited slip diff (LSD). Xdrive uses this feature on both the front and rear axles. RWD 335 cars have a similar feature for the rear diff only. It is not an optimal solution, a conventional LSD is better. M3 has a true LSD, and I think X6 gets an xDrive with true LSD ("torque sensing").

Xdrive has three layers of software, DSC, DTC, and then both off. DTC is a subset of DSC, lighter stability control and no engine power reduction, but traction control is still on though a bit more agressive, allowing a bit of oversteer. With DTC/DSC off completely, in xDrive you still have the front and rear e-LSD (via brakes) and the transfer case working. So IN THEORY as far as I can tell, with DTC and DSC off you may be able to spin all four tires on ice. Have not tested this yet as I have not had the car in winter.

As I have said in other threads, BMW is very cagey about how all this works.

BTW ABS and "e-LSD" both work through the brakes of course, but one works by modulating (cutting) pressure in the lines on lock up, the other actively applies the brakes based on sensors and electronics to stop wheel spin. So in theory they are totally separate systems, both of which act on brakes but no need for them to be in the same fuse circuit or even same control algorithm. They have nothing to do with one another as one works when you apply the brakes the other is when you give it gas. Then there's stability control which another system entirely. They all talk to one another of course.

I personally would not want to yank a fuse out of the middle of all this, disable ABS and all layers of DTC/DSC/e-LSD, and then push around dead rotating mass of front AWD system. But I admire the spirit of experimentation it represents. Proper solution is for Shiv or someone similar to do this w/o messing with the other sytems (if that even can be done).

edit: the above is as far as I have been able to figure out, reading a lot here and on other forums. Anyone has any knowledge to the contrary please chime in.
Holding the DTC button for more than 3 seconds to turn both off allows all four wheels to spin in snow....I've done it.

Have you ever jacked up your car on all 4 wheels? The front wheels can spin freely while the back is locked up. I think because the front can spin freely, it is disengaged from the rest of the drivetrain. When the car is on, the wet clutch pack in the xDrive system engages the front diff. and the axles can only go in a 40:60 split with rear bias.

I wonder if you can spin the front wheels with the car on, off the ground in neutral? Obviously in drive the wheels would be spinning and the front diff would be engaged.

Also when you reach highway speeds, no power is going to the front so I would assume the xDrive system disengages the front axle so less parts are moving and the front wheels are just rotating because the rear wheels are pushing the car.
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      11-18-2010, 04:19 PM   #109
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Holding the DTC button for more than 3 seconds to turn both off allows all four wheels to spin in snow....I've done it..
Good to know, that is what I thought. That means the e-LSD things still works AND the transfer case is operating as intended.

Quote:
Have you ever jacked up your car on all 4 wheels? The front wheels can spin freely while the back is locked up. I think because the front can spin freely, it is disengaged from the rest of the drivetrain. When the car is on, the wet clutch pack in the xDrive system engages the front diff. and the axles can only go in a 40:60 split with rear bias..
OK this in not exactly right. Clutch pack in the transfer case will vary between a min of 50% rear to a max of 100% rear in most conditions people will see. You are right about 40/60 on dry roads going straight with no wheelspin. When car is OFF clutches to front axle are disengaged as you say. RWD is always engaged as the driveshaft coming out of the tranny is a solid link (no clutches between it and the tranny or rear diff) so the minimum TQ to the rear is always 50%.

Quote:
Also when you reach highway speeds, no power is going to the front so I would assume the xDrive system disengages the front axle so less parts are moving and the front wheels are just rotating because the rear wheels are pushing the car.
I think up to 100 MPH on dry road driving straight not turning it is still 40/60. I have also read at very low speeds (parking lots) FWD is disabled when rear has traction (no wheel spin). Above 100 MPH it disengages front. I have read elsewhere that speed is a bit lower but cannot confirm.

Also there is a very confusing case described where on glaze ice, when the rears both have zero traction and the fronts have some, BMW says xDrive sends almost all TQ to the front, which is impossible unless you write science fiction for a living. Or write politcal speeches.
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      11-18-2010, 04:31 PM   #110
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I think up to 100 MPH on dry road driving straight not turning it is still 40/60. I have also read at very low speeds (parking lots) FWD is disabled when rear has traction (no wheel spin). Above 100 MPH it disengages front. I have read elsewhere that speed is a bit lower but cannot confirm.

Also there is a very confusing case described where on glaze ice, when the rears both have zero traction and the fronts have some, BMW says xDrive sends almost all TQ to the front, which is impossible unless you write science fiction for a living. Or write politcal speeches.
Haven't heard about the low speed thing...not doubting you though.

I've heard the front disengages around 70mph.....again can't confirm either.

I don't know about your last statement lol....I do agree though. How can 100% of the power go to the front if the rear is always engaged?
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