4x4 vs. AWD - Page 2

Dr. T · #11 03-20-2006, 06:10 PM

Yeah, the DSC off button only turns off the traction control. The vehicle is always in 4wd/awd which is infinitely variable from 50-100% between the front and rear wheels.

Wonder what would happen if one shut off the dsc and then popped the clutch at 6k rpm? A 4 wheel burnout...???

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peoe2 · #12 03-20-2006, 06:12 PM

Quote:

Originally Posted by MysticBlueX3

What was BMW thinking putting that 4x4 in the light?

Based on my understanding:
- XDrive: distributes power between front and rear axles
- DSC: uses the brakes to distribute power from left to right

If for example your rear passenger wheel is on ice, rear driver wheel on concrete. You start the vehicle:
- With DSC on, the brakes will be applied to your rear passenger wheel because of loss of traction due to the ice.
- With DSC off, both back wheels will get the same amount of power and the vehicle will slip. Since both back wheels and both front wheels get the same amount of power with DSC off, it explains the 4x4 icon.

This is just a thought, only BMW knows...

xx3 · #13 03-20-2006, 06:18 PM

Correct me if I am wrong but isn't 4 wheel drive the same as all wheel drive?

Unless of course if you've fitted extra wheels onto your X...

(Then a 6 wheel drive X wouldn't be the same as a 4 wheel drive X).

Quote:

Originally Posted by xx3
wowowowow...

Since when does the X3 have an AWD switch ?!? Its permanent 4 wheel drive !

uhhhhh... ... Are you saying X3 does not have X-Drive? Reading page 50-51 of your manual. Normally the X3 is in AWD unless if you push the DSC button lighting up the 4X4 light which enables 4 wheel drive.

Edit: The X3 does not have a 4X4 switch. It is permanently AWD. It is capable of 4x4 but that is determined by x-drive, not by the push of a button.

No it did not say or mean that the X3 does not have Xdrive.

Maybe by 4x4 you mean that the front and rear wheels are getting exactly 50% of the output..? In that case Xdrive can mediate and do that when it 'feels' like it...

White05X3 · #14 03-20-2006, 07:52 PM

DSC is not related to awd or x-drive. DSC uses wheel speed sensors, steering angle sensors, speed sensors and probably a host of other sensors (driver's seat moisture sensors probably) to determine whether or not tires are slipping and whether or not the car is on the planned trajectory. If a tire is slipping DSC retards the throttle and can even apply individual brakes. In over or understeer conditions DSC can indvidually apply brakes to return the vehicle to the intended path.

X-drive is always on. To the inquiry as to what would happen if you turn DSC off and do a 6,000 clutch drop, I can tell you this... while I did not use 6,000 I did use many rpms (DSC off) when I launched my x3 during the auto-x. I got a bit of wheel spin from the back but nowhere near as much as if I was in a pure rwd. Unlike traditional rwd, during at-the-limit cornering a strong application of throttle did not induce power oversteer. Nor for that matter did early throttle application induce terminal understeer (much to my surprise). It was pretty cool!

AzNMpower32 · #15 03-20-2006, 08:36 PM

turning off DSC has nothing to do with affecting the AWD system xDrive. Normally DSC works with xDrive (they're two seperate things) to keep driving safe. Like someone mentioned, xDrive is never shut off and the X3 remains a variable-AWD unless there's a failure in the system, in which case the X3 defaults to rear drive.

Pressing the DSC button shuts DSC off but retains DTC (Dynamic Traction Control), which has a higher threshold of intervention so you can move in deep snow, dirt, gravel...etc. Holding the DSC button for 3 secs shuts off DSC and DTC, but xDrive itself is unaffected.

xx3 · #16 03-20-2006, 09:45 PM

Quote:

Originally Posted by White05X3

To the inquiry as to what would happen if you turn DSC off and do a 6,000 clutch drop, I can tell you this... while I did not use 6,000 I did use many rpms (DSC off) when I launched my x3 during the auto-x. I got a bit of wheel spin from the back but nowhere near as much as if I was in a pure rwd. Unlike traditional rwd, during at-the-limit cornering a strong application of throttle did not induce power oversteer. Nor for that matter did early throttle application induce terminal understeer (much to my surprise). It was pretty cool!

I'm hoping you don't have an automatic...

I've seen too many transmissions get ruined at my highschool with idiots revving their cars and dropping the transmission into 'D'... Oh the horror !

MysticBlueX3 · #17 03-20-2006, 11:44 PM

Quote:

Originally Posted by xx3

Correct me if I am wrong but isn't 4 wheel drive the same as all wheel drive?

I think 4 wheel drive = 4 wheels same power, same speed at all times. AWD = computer and sensors determine how much power each wheel gets.

rickp · #18 03-21-2006, 12:21 AM

This may be a good read.

http://auto.consumerguide.com/Articl...le/FA_4WD.html

JCL · #19 03-21-2006, 12:55 AM

I would agree with the link that rickp posted.

In essence, 4wd is what you get when you add a transfer case to a 2wd truck.

AWD is a marketing term that describes all wheels driving, and is usually applied to cars or cross-overs that start as fwd or rwd vehicles.

In a technical sense, a 4wd is an AWD, for a vehicle with four wheels. There are no real technical differentiators, just terms invented by marketing departments.

And I agree with a previous poster, that putting a 4x4 label under the DSC symbol in 2004 or so, is one of the stupider things that we have seen BMW do.