Quote:
Originally Posted by IMS-340MP
Of course they move with the car like the front wheels in a RWD car, but not using the engine power.
So assuming the same weights above in RWD the engine has to rotate 50 Kgs of drive shafts weight while in xDrive the engine has to rotate 100 Kgs of drive shafts weight.
Quote:
Originally Posted by NISFAN
So you're saying the front driveshafts don't move when in xdelete?
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Ok, so if you accept that the front driveshafts rotate with the front wheels, and front and rear wheels will rotate at same rotational speeds, where does the energy come to drive them in xdelete mode? It's not free.
Answer is they are driven by the road, therefore increasing the drive drag on the chassis. I have to add the additional force to drive the extra drivetrain drag to the rear wheels to over come it. That is no more efficient than if I just powered the front driveshafts directly from the engine. In both cases both sets of prop-shafts and diffs will be rotating at exactly the same speeds.
The only way you get around this drag is if you fit freewheeling front hubs like some off roaders have.
In summary, an xDrive's 100-200 time is sure to be identical whether you run in xdelete mode or not.