MUNICH, Germany — BMW is preparing to upgrade all of its four-wheel-drive models with an advanced new torque-vectoring system aimed at improving on-road agility. Called Dynamic Performance Control, the new system was developed with German engineering specialist ZF. It's based around BMW's four-wheel-drive xDrive arrangement but adds a series of additional electromagnetic clutches in a modified rear-mounted differential housing to further enhance its operation.
Dynamic Performance Controls works in conjunction with sensors in the ABS system that measure steering angle, yaw rates, road speed and torque developed by the engine. They are capable of apportioning drive between the front and rear axles as in today's models, as well as from side to side at the rear for what BMW describes as a more neutral cornering stance.
The idea is to direct drive to where it can be used most effectively, in an operation not dissimilar to that of a traditional locking differential on a rear-wheel-drive car. If the car understeers, for example, xDrive will redirect more drive to the rear wheels and, if required, the Dynamic Performance Control system will then load up the outside rear wheel with greater torque for improved balance.
During oversteer, it reverses the action, sending the majority of drive through the front wheels and, if necessary, increasing torque to the inside rear wheel to stabilize the car during cornering (see diagram).
Unlike similar systems developed by rival carmakers, BMW's Dynamic Performance Control operates both under load and on the overrun, meaning the car continues to be stabilized even when the driver steps off the throttle at midcorner.
BMW is remaining tight-lipped on when Dynamic Performance Control will be introduced. However, signs are it will appear first on the upcoming X6 before heading into other models, including the X3, X5 and four-wheel-drive versions of the 3, 5, and next-generation 7 Series. Also earmarked to accept the new system is BMW's as yet unnamed seven-seat MPV and a secret new junior four-wheel drive that's tipped to slot into the German carmaker's lineup beneath the X3.
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