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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?
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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.