Quote:
Originally Posted by DJKhan85
I normally hate browsing these AWD threads since most people have no idea how any of the AWD systems actually work. Instead they just believe the marketing hype that gets played by the individual companies. I am glad that your post proves people still go out there and do hard research on AWD systems. 
Most of the AWD systems rely heavily on computer intervention (except for the aforementioned STI, which is different than the other subaru AWD systems). The computer will either cut power, open/close a clutch that controls power to the rear wheels (as does xdrive, at least the versions I read about in the 2008 models) or brake wheel(s) to get the power where the computer determines it should be sent.
From what I recall the xdrive system has the front axle connected to the output of the transmission via a chain system that cannot be decoupled. There is then a clutch pack that power must go through from the transmission to get to the rear wheels. The only way I can see the claim "100% of power to either axle" being true is if you take into account the brakes on one axle being applied, momentarily, to stop the wheels on that axle. Then the power has no where to go but to the other axle.
I wonder if the xdrive system is different across all BMW models or if it's just computer programming. |
It's not a permanent torque split anymore. I believe its a wet clutch variable system so you can literally get 100% to either axle.
Performance wise, it all relies on how they tune the system and its sensors.