BMW

Bring it on! 2009 BMW 335i xDrive, Part Two

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March 4, 2009

2009 BMW 335i xDrive. Click image to enlarge

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2009 BMW 335i

Ottawa, Ontario – Without a lot of heavy weather in the Ottawa region, we took advantage of any small opportunity to head to a parking lot to play with the BMW 335i xDrive.
One needs to dig back through the literature, not to mention the owner’s manual, to appreciate the level of fine tuning that BMW offers drivers with its xDrive all-wheel drive system. By itself, xDrive doesn’t sound that much different than other systems we’ve driven this winter: an electronically controlled, multiple plate clutch located behind the transmission divides power between the front and rear axles. In normal driving conditions, the split is 40 per cent front and 60 per cent rear. Depending on conditions – placing the rear wheels on ice and the front on pavement, for example – the system will adjust the power delivery as much as 100 per cent to the front or rear.

The xDrive is integrated with the car’s other electronic active safety systems, particularly the Dynamic Stability Control.

2009 BMW 335i xDrive. Click image to enlarge

DSC applies braking force to distribute power from side to side, allowing the car to move forward even if only one wheel has traction, or to prevent skidding out of control. In severe situations, DSC will also reduce engine power. In rear-wheel drive cars, DSC is the main tool used to keep the car on the road. But in all-wheel drive cars, DSC is an assistant to xDrive. The latter limits under- and oversteer by continuously modulating power between the front and rear axles based on input from steering angle and yaw rate sensors, while the former applies brake pressure or reduces engine power as needed. To prevent the vehicle from pushing out of a bend, the brakes are applied slightly on the inner wheel. At the same time, the control system feeds exactly the right level of power to the wheels in order to set off the brake forces acting on the car.

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