| BMW's successful off-roader, the X5, has reached
that stage in its life when it is time for a revamp. The Bavarian manufacturer,
though, has resisted the temptation to give it a mild facelift and gone
much further in invigorating this vehicle.
The revised X5 features a minor facelift but features the introduction of the xDrive four-wheel drive system |
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The principal change is to the four-wheel drive system the new X5 was
the first model to feature xDrive, although it can now be found on the
new X3 as well. A centrally mounted, electronically driven, muilti-plate
clutch and BMW's familiar DSC (Dynamic Stability Control) system to regulate
torque to the wheels are the two key ingredients. Being electronically
driven, rather than hydraulically which takes time for the pressure to
build up, the clutch provides instant power transfer in all situations
and is far quicker and less reactive than other systems. It is also fully
variable, constantly monitoring and channelling optimum drive forces from
axle to axle. It can distribute power from an extreme of 100% torque going
to the rear axle and none to the front with the clutch fully open, to
a complete reversal with 100% torque directed to the front wheels and
none to the rear with the clutch completely closed, and all stages in
between. It takes just 100 ms to react. Whenever the car threatens to
oversteer, the multi-plate clutch is closed with power fed to the front
wheels to pull the car around the corner. Where it detects understeer,
torque is fed to the rear wheels.
Slightly restyled headlights and grille denote this is the new X5 |
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DSC sensors constantly monitor individual wheel speed, steering angle,
lateral acceleration and yaw rate angles giving xDrive the predictive
information it needs. Power is also cut and brakes applied when the system
detects a loss of traction at one or more of the wheels. It is this combination
that gives BMW's all-wheel drive system an advantage, it claims, over
four-wheel drive systems using viscous coupling or a Torsen differential
that respond mechanically to a difference in speed and torque. BMW also
claims that it is also superior to systems using a Haldex coupling like
that in the Audi TT which uses engine control data alongside wheel speed
signals. Conventional all-electronic systems, such as the Mercedes 4matic,
also need at least one wheel to be spinning for power reduction.
The suspension set-up would be familiar to owners of the current 7 Series
since it is derived from that model, but the X5 comes with pneumatic springs
rather than conventional steel springs. Double axle self-levelling is
available as an option on both axles this not only has the benefit of
keeping a constant ride height but also improving handling on normal roads.
In addition to the six-cylinder 3.0i petrol engine that has been carried
over , the revised X5 has the benefit of three new engines the six-cylinder,
second generation 3.0 diesel, the new eight-cylinder V8 4.4i and the high-performance
4.8is that is due this spring. The 3.0 diesel differs from that on the
outgoing model in that it sees an 18% increase in power to 221 ps (162
kW) while maximum torque has been improved by 22% to 500 Nm (369 lb ft)
between 2,000 and 2,750 rpm. These improvements are due to the second-generation
common-rail fuel injection system with a higher delivery pressure of 1,600
bar compared to 1,350 bar on the previous engine. It is managed by a new
Digital Diesel Electronics (DDE5) engine management system that also controls
the combustion process and managing the rapid glow plug heating system.
The Valvetronic 4.4i engine is a slightly modified version of that first
seen in the 745i SE and recently introduced in the 545i SE. Power output
is up from 290 ps (213 kW) to 324 ps ((238 kW) leading to a 0-100 km/h
acceleration (0-62 mph) time of 7.0 seconds, 0.5 seconds quicker than
its predecessor. Maximum torque remains the same at 440 Nm (324 lb ft)
at 3,700 rpm.
6-speed manual gearboxes are standard on both the 3.0i and the 3.0d although
both are available with automatic transmissions a 5-speed box for the
former and a 6-speed box for the diesel that is also mated to the 4.4i.
A manual gearbox is not available on this model.
Cosmetic changes include changes to the headlamps so that they now take
on a sweeping, curved profile with twin corona rings as sidelights in
a design that has become a BMW trademark. The eight-cylinder models feature
bi-xenon headlamps as standard and as option on the six-cylinder models
adaptive headlamps will be available as an option from this spring. The
kidney grille has become taller and wider and incorporates the distinctive
wave-profile vertical slats while there are subtle changes to the bonnet
contours so that there are more pronounced styling curves. The rear lamp
clusters have been revised with horizontal-lined surround glass and the
boot features a soft-close mechanism. The only interior change is to the
steering wheel.
Since the first model came off the production line at Spartanburg in North
Carolina in September 1999, the X5 has been a runaway success. The new
model with its sophisticated xDrive system and new engine and transmission
line up looks set to continue its appeal in the marketplace.
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