The four-wheel drive system in an SUV has evolved over the years, from the mechanical era to today's more complex electronic systems. Newer technologies have only made it easier to drive through challenging terrain and situations but to fully understand how these systems work one has to drive the vehicle in an off-road environment. We were recently at the BMW Xperience event in Gurgaon to drive the BMW xDrive range of vehicles - the X5, X6 and the new X3 on a test course specially designed by international experts, for customers and the media.
The track included ten simulated obstacles that each brought out BMWs' 4WD capabilities. xDrive is BMW's four-wheel drive system that monitors the driving situation constantly and distributes the power between axles. The system splits drive between the front and rear axles depending on the situation and surface. Normally, the torque split is 40/60 between the front and rear to give the vehicle a rear-wheel drive character and prevent understeer. Power distribution can be altered and can vary between 50:50 and 0:100 percent to the front and rear axles respectively. So when there is a sudden change in requirement depending on the resistance from the road surface, the system varies the torque split within a fraction of a second. This key feature helped me drive the course with ease.
The first obstacle was the wheel slip area where one of the four wheels was placed on rollers to simulate loss of traction, the system intervened in a few seconds and sent the power to the remaining wheels with more traction and I was out in a jiffy. The second obstacle was a series of moguls placed alternatively to simulate a situation where one wheel would have no contact with the ground. As I drove on, the BMW comfortably passed the first mogul but since one of the wheels was in the air, there was zero traction with the wheel just rotating. My instructor who guided me through the entire drive asked me to accelerate slightly, the xDrive system then intervened by locking the wheel and sent more torque to the rest of the wheels to get out smoothly. The third obstacle was a dry river bed that was effortlessly passed by the BMW.
The next obstacle simulated a steep uphill and downhill section to test the angle of approach and departure and also use the hill hold and hill descent feature. The hill descent feature enables the driver to limit the vehicle to single digit speeds, this helped me drive down the hill without the need to accelerate or brake.
Next was a drive through a water bed and then on to a side slope. Driving on a slope was to highlight the lower centre of gravity on BMW SUVs, a vehicle with higher centre of gravity has a higher probability of toppling over in such situations. The next obstacle was a set of rumblers, where the ground clearance of the vehicle was highlighted, the BMW X range vehicles have varying ground clearance levels but all of them went past the rumblers without a scrape. The next set of obstacles included a small hill and a sand bed. Apart from us, existing BMW owners also got a chance to drive the course under the expert guidance of international BMW trainers and appreciate the potential of their BMWs. Driving an SUV is fun on the road but to drive it on a course designed to check the capability of the vehicle is something every off-road enthusiast must do.
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