[moldcad]

Recently I tried to dyno my car on one of the most popular and widely used Dyno systems in EU - the Maha 3700 (it's particularly popular in Germany). Of course, the guy running it was assuring me he knows how to go around the xDrive. We put my car on the rollers, fixed it by the towing hooks, and he started testing. I was outside observing my car's wheels, and noticed that after he increased rpm above some 3k, the front wheels just slowed down to a complete stop, while only the rear ones were spinning like crazy! Worried about my xDrive coupling, I told him to stop the crap and we of course never completed the measurements. I'm still worried about some long-term damage that might occur to my car's xDrive system, though.

Any thoughts? Are the front wheels supposed to spin down, and under which circumstances? If so, how do you dyno xDrive cars on a Maha (I know for the fact Germans do that a lot)? Also, when o a dyno - shoulld DSC be on, off, or DTC only?

[lovec1990]

Hi moldcad im not expert, but isnt xdrive suposed too send 100% power too rear wheels when you go faster than ~80mph?

[moldcad]

Heard that too, but we never accelerated up to 80 mph; on the first press on accelerator all 4 wheels started spinning, but at some 4k RPM, still on the 1st gear, the front then slowed down to a complete stop....

[lovec1990]

if you ask me car would show error if xdrive would sustain damage and if you had DSC on
i belive computer decided that car does need all power on rear tires

[moldcad]

We did try with both DSC on and off - same results...

An error message would remain permanent if something broke down totally; if the clutch disks were damaged but are still functional no error would be displayed... this is what worries me most.

[lovec1990]

if i were so worried i would already called my dealer and ask if i can talk with their mechanic about this

[moldcad]

I went straight to my dealer and asked him to check the error codes in my car - God, what a mess! Literally a flood of DSC, Drive Train, and even brake (including electronic handbrake) fault codes!!! They say they managed to clear them all, but I'm panicking whether my car wasn't seriously harmed by this idiot with Maha dyno, who claimed he had successfully measured "thousands" of various cars (including xDrvie) before me!

[lovec1990]

only way too find if xdrive is damaged you need too put it apart and check for damage.Is your car at the moment working normaly?

[moldcad]

I am in touch with a nice guy from the Maha Facebook page (https://www.facebook.com/MAHADynamometers), who promised to check and return to me with some explanation. In the meantime, I suspect the LPS3000 model I used doesn't have roller synchronization, and what happened is my xDrive BMW developed a fault condition. I did a research and know for sure that when xDrive "feels" error conditions, it de-couples the front axis to avoid damage... This is the only explanation of this behaviour (front wheels spinning down to a full stop) that comes to my mind. What do you think?

Or maybe the LPS3000 does have the roller synchronization, but it needs to be explicitly enabled by the operator? Whatever it is, I pray to God no damage was done...

[lovec1990]

if it is safety thing then there should be no damage, did you do any modifications too car?

[moldcad]

...not to the drivetrain, no.

[lovec1990]

what about any modification too engine or any upgrades with aftermarket plug in computers?

[moldcad]

Nothing of that kind, but what's a connection?

[lovec1990]

xdrive is controled by computer and everything is connected so bad modification could couse troubles thats my theory, but for you i think your expert is not so good with xdrive

[ezmaass]

If the rollers weren't synced perhaps this was the problem as the system would think there was a slip and couldn't correct it? I know that when they dyno certain RWD cars you need a front roller synced to the rear to avoid the car thinking there isn't a condition where the wheels are just spinning. Unless there was a problem prior, I'd be surprised if this did any damage. Sounds like you never got passed 1st gear and 4k RPM.

[Grover432]

There is not point in freaking out. If you damaged the drivetrain, it will fail at some point and you'll pay to fix it. Why worry about it now unless you are planning to recover damages from the guy who said he was an "expert" at dyno testing?

[BMWrules7]

Originally Posted by moldcad

Recently I tried to dyno my car on one of the most popular and widely used Dyno systems in EU - the Maha 3700 (it's particularly popular in Germany). Of course, the guy running it was assuring me he knows how to go around the xDrive. We put my car on the rollers, fixed it by the towing hooks, and he started testing. I was outside observing my car's wheels, and noticed that after he increased rpm above some 3k, the front wheels just slowed down to a complete stop, while only the rear ones were spinning like crazy! Worried about my xDrive coupling, I told him to stop the crap and we of course never completed the measurements. I'm still worried about some long-term damage that might occur to my car's xDrive system, though.

Any thoughts? Are the front wheels supposed to spin down, and under which circumstances? If so, how do you dyno xDrive cars on a Maha (I know for the fact Germans do that a lot)? Also, when o a dyno - shoulld DSC be on, off, or DTC only?

Well, first of all don't worry about the error messages. Xdrive powered the rear and fronts thinking all was well. Next, xdrive determined that the fronts and the rears we not running at similar speeds. The xdrive computer is going to see this as either impossible or you're driving on a really messed up surface (which in reality you were).

At some point, the xdrive logic (given the extended time in this condition) is going to write this off as a sensor fault with wheel speed. It has to.

At that point, Xdrive is not going to allow your front wheels to provide power when the sensors are failing. Thus, power will only be applied to the rear.

Of course, there will be countless errors in your log. They are a cascade, however, and won't reveal anything useful.

Next, some countries require a dyno for emissions. BMW knows this. BMW is not going to let blow your Xdrive because it's sitting on a low quality dyno built for most cars.

You have nothing to worry about. You don't have a POS car. What you did was not unthinkable. Even if you had the right dyno, these things can fail or be misconfigured. Bmw isn't going to let your Xdrive burn up for this kind of thing.

To the contrary, have you ever studied your drive train? It is a beast. It is not some cheesy piece of crap. Relax. You're fine.

[moldcad]

Thanks for the consolation!