Car Design News: New BMW X5 in Depth

Page 1: Short Version (I)
Page 2: Short Version (II)
Page 3: The Concept
Page 4: Driving Dynamics
Page 5: All Wheel Drive
Page 6: Power Units
Page 7: Automatic Transmission
Page 8: Exterior
Page 9: Interior
Page 10: Body & Safety
Page 11: The iDrive Control System
Page 12: Features and Equipment (I)
Page 13: Features and Equipment (II)
Page 14: Production
Page 15: Specifications

All-Wheel Drive

Even more precise: intelligent BMW xDrive all-wheel-drive technology.
Permanent all-wheel drive with variable power distribution.
Optimised control quality for Integrated Chassis Management.

Superior driving qualities in every situation and on all kinds of roads are among the outstanding fortes of the new BMW X5. This superiority is ensured above all by intelligent, permanent BMW xDrive all-wheel-drive technology.

Allowing variable distribution of drive power between the front and rear axles, this electronically controlled all wheel-drive system not only ensures optimum traction at all times, but also enhances driving dynamics to an unprecedented standard. BMW xDrive thus benefits the vehicle�s agility, driving stability and motoring comfort through its fast and precise reactions to any change in driving and surface conditions, combining the dynamic benefits of rear-wheel drive with the traction advantages of all-wheel-drive.

Indeed, thanks to the many advantages and features of BMW xDrive, BMW has now become the world�s most successful manufacturer of all-wheel-drive vehicles in the premium segment.

To distribute drive power quickly and with optimum precision, xDrive, DSC Dynamic Stability Control, and engine management are all networked with one another through BMW�s ICM Integrated Chassis Management.
This ensures a perfect balance at all times of drive power, individual intervention by the brakes on each wheel, and engine management, with the optionally available Active Steering also being integrated in this network. When oversteering in bends and in brake manoeuvres on varying surfaces with a split frictional coefficient, Integrated Chassis Management is able to countersteer smoothly and precisely to prevent the vehicle from swerving out of control and regain stability on the road. The result of this intelligent network in practice is a supreme standard of both driving dynamics and active safety.

New ICM control concept for even greater precision.

The network linking BMW xDrive and DSC Dynamic Stability Control serves, inter alia, to provide infinite and variable distribution of engine power between the front and rear axles, at the same time allowing forced power distribution among the two wheels on each axle and therefore acting as a transverse lock.

Should, therefore, one of the wheels start to spin without transmitting power to the surface, it is automatically slowed down by DSC intervening on the appropriate brake, the differential in the final drive feeding more power to the opposite wheel.

The new control structure in Integrated Chassis Management ensures even faster and more precise interaction of xDrive and DSC. While so far engine and brake management were largely independent of longitudinal force management in influencing the steering behaviour of the vehicle, the three control circuits on the new BMW X5 now act parallel to one another:
With longitudinal force management controlling the distribution of drive power between the front and rear axle, brake management is able to intervene individually in the brakes in the interest of enhanced traction and driving dynamics. As a further function, engine management is able, where necessary, to reduce or increase drive forces.

This precise network established with DSC allows the xDrive all-wheel-drive system in the new BMW X5 to respond quickly and precisely to changes in driving conditions and enhance driving dynamics in the process.

Permanent all-wheel drive with variable distribution of drive power.

Driving straight ahead under normal conditions, the new BMW X5 distributes drive power between the front and rear axle in a 40 : 60 ratio, thus retaining the dynamic benefits and the typical features of standard drive so characteristic of BMW.

Whenever necessary, however, this distribution of drive power may be varied significantly: Depending on individual requirements, the flow of torque between the front and rear axles may be changed infinitely and variably all the way from 0 : 100 to 50 : 50. So in an extreme case with the rear axle no longer being able to convey any power to the road, the BMW X5 will run briefly with fully locked all-wheel drive, establishing a rigid connection to just one axle in the same way as a 100 per cent longitudinal lock with a conventional all-wheel drive system.

Instantaneous, variable and precise transmission of drive power is ensured by the control units in the power divider and by DSC control. DSC starts out by calculating the clutch distribution forces required as a result of various criteria such as the steering angle, the position of the gas pedal, engine speed and road speed. Then, via the power divider control unit, the system determines the desired clutch force just right in each situation, thus establishing the optimum distribution of power between the front and rear axles.

The power divider fitted directly downstream of the transmission first feeds drive forces through its main shaft to the rear axle on a rigid drivetrain.
The electronically controlled multiple-plate clutch on this main shaft then diverts the appropriate amount of torque by way of a layshaft to the front axle, completing this entire operation within 100 milliseconds at the very most.

Optimum power distribution under all conditions.

The driver of the new BMW X5 benefits permanently and consistently from the unique qualities and features of BMW xDrive. When setting off under normal conditions, the multiple-plate clutch remains closed up to a speed of 20 km/h or 12 mph, with power being distributed in a 50 : 50 split.
Then, depending on driving conditions and road surfaces, the system distributes engine power variably as a function of requirements.
And whenever the driver accelerates particularly fast or when the wheels on one axle start to lose their grip, power distribution is varied immediately in the interest of optimum traction and pulling force.

The system acts quite differently whenever the new BMW X5 sets off on winter roads or rough tracks. If, for example, when setting off from a snowbound car park on to a road already cleared of snow, only the front wheels are resting on a hard surface with suitable grip, almost 100 per cent of the drive power transmitted is diverted to the front axle within just 0.1 seconds, without the intervention on the rear-wheel brakes and its inherent loss of power typical of a conventional system. As a result, the BMW X5 sets off smoothly, quickly and safely even in such a case.

Agile and stable in bends and when accelerating.

In bends xDrive in the new BMW X5 reduces both under- and oversteer by distributing engine power quickly and sensitively between the front and rear axle: Should the rear end of the vehicle start to move out (oversteer), for example, the multiple-plate clutch will close even harder, feeding more drive power to the front wheels. This allows the rear wheels to build up more side forces and the vehicle will be stabilised.

Being combined with DSC, BMW xDrive recognises any such oversteer at a very early point in time and intervenes before the driver even notices the change in conditions.

When understeering, the vehicle �pushes� over its front axle out of the bend � and again, any such tendency is recognised at an early point by DSC evaluating the data received. The system responds by immediately reducing drive power on the front axle, switching all the way in an extreme case to 100 per cent rear-wheel drive.

DSC will only intervene in the brakes to stabilise the vehicle when variable distribution of power alone is no longer sufficient to compensate any over- or understeer.

The new BMW X5 is particularly agile in quickly climbing a mountain pass, where the inner rear wheel in a bend will often tend to spin whenever the driver accelerates dynamically out of a hairpin. In such a case BMW xDrive immediately draws power from the rear wheels and feeds this extra �muscle� to the front axle, ensuring once again that all the power provided by the engine is actually used to drive the vehicle.

Homogeneous driving behaviour.

BMW xDrive all-wheel drive is even able to handle an abrupt change in engine power without the slightest effort, the driver of a BMW X5 not even noticing a change in power distribution. For while the time-lag between pressing down the gas pedal and building up engine power is at least 200 milliseconds, the multiple-plate clutch will close or open completely within just 100 milliseconds, thus ensuring absolutely smooth and homogeneous driving behaviour in every situation.

On uphill gradients with a slippery surface such as ice or snow, locking action between the front and rear axles will prevent individual wheels from spinning. Accordingly, DSC is only required to cut in much later, reducing engine power or applying the brakes only under far more difficult road conditions.
Then, when continuing on the road or track, the locking action built up in this way prevents the risk of losing longitudinal or lateral traction on individual wheels, again offering the driver safe and agile driving behaviour.

Manoeuvring and parking: easy and precise thanks to BMW xDrive.

Last but certainly not least, BMW xDrive eliminates a well-known side-effect of rigid all-wheel-drive systems: By completely disconnecting the two axles, BMW xDrive changes when parking or manoeuvring into a 100 per cent rear-wheel drive system, again without the driver having to intervene in any way.
All the driver will notice, as a pleasant side-effect, is that there is no torsion on the drivetrain or unwanted forces acting on the steering.

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