BMW X5 for 2004 - In Depth

Press Release

BMW X5 for 2004 ??????????????????????????????????????? In Depth

New xDrive all-wheel drive system, Valvetronic V-8 engine and freshened design highlight extensive enhancements for BMW??????????????????????????????????????s Sports Activity Vehicle

Four years after its introduction, the BMW X5 has long since firmly established itself as a unique and coveted offering in the luxury sport-utility field. If the very combination of ???????????????????????????????????BMW???????????????????????????????? and ???????????????????????????????????SUV???????????????????????????????? seemed unlikely back then, well, it was; for this reason, BMW decided to give the X5 a more apt name ???????????????????????????????????????Sports Activity Vehicle ??????????????????????????????????????? to distinguish it from the ordinary run of SUVs. In the meantime, the SAV concept has become so established and respected that the X5 Series is BMW??????????????????????????????????????s third-biggest seller in the U.S. In fact, so successful is the X5 that it is soon to be joined by a second SAV line, the X3. For 2004, the X5 Series gets an extensive round of product enhancements that freshen its steady, strong appeal to customers who value the attributes of an SUV ??????????????????????????????????????? robust construction, all-weather/all-road and trailer-towing capabilities, commanding driving position, ease of loading cargo ??????????????????????????????????????? but also seek the attributes of a BMW: precision handling, brilliant performance, elegant design, tasteful luxury and premium quality. The changes include:

• A new all-wheel drive system, xDrive, that adjusts front/rear torque proportioning according to road and operating conditions ??????????????????????????????????????? with lightning-fast, ultra-sensitive response that optimizes both traction and handling.
• Adoption of the acclaimed Valvetronic V-8 engine in the X5 4.4i model, resulting in greater power (+25 hp) and significantly improved fuel economy.
• New 6-speed transmissions ??????????????????????????????????????? manual in the 6-cylinder X5 3.0i model, automatic in the X5 4.4i.
• Freshened exterior design, with an entirely (yet subtly) new front end, new taillights and several fresh colors.
• Standard rain-sensing windshield wipers and automatic headlight control.
• New wheel designs for four of the five available wheel/tire configurations.
• Enhanced interior equipment, including 8-way power seats in both models, and new optional wood treatment. Here too, the color selection is expanded.
• Availability of the BMW Assist services and telematics system.

There are two X5 models for 2004: the X5 3.0i at $40,995 base price including destination charge; and the X5 4.4i, at $52,195. A successor to the ultra-high-performance X5 4.6is will be announced later in the ??????????????????????????????????????04 model year.

Four years of critical acclaim for a unique vehicle concept

At the beginning, there was a certain skepticism that it was possible to make a vehicle combining those SUV traits and BMW??????????????????????????????????????s traditional strengths. Yet in its first encounter with the X5, Car and Driver (February ??????????????????????????????????????00) seemed convinced. After enumerating factors that (in ordinary SUVs) conspire against BMW-like attributes, the magazine concluded that ???????????????????????????????????BMW has created a vehicle that is, in many ways, the most desirable and fun to drive of the lot. Hey, if you??????????????????????????????????????re gonna be a heretic, you might as well go for the gold.???????????????????????????????? During its first four years of production, the X5 has garnered lavish praise. Automobile Magazine, naming it one of its All-Stars in the February ??????????????????????????????????????01 issue, concluded that ???????????????????????????????????BMW??????????????????????????????????????s X5 is not only a great SUV but a great vehicle regardless of category.???????????????????????????????? In April ??????????????????????????????????????03, Motor Trend concluded a 1-year/20,000-mile test of an X5 4.4i with this summary: ???????????????????????????????????If we had our druthers, ours would still be parked in the MT garage.???????????????????????????????? And the April ?????????????????????????????????02 Car and Driver concluded after a 40,000-mile Long-Term Test of the X5 4.4i that, ???????????????????????????????????This is still by far the best-looking SUV on the market and the most fun to drive.???????????????????????????????? Other observations from this report included:

• ???????????????????????????????????The X5 became a favorite winter highway cruiser because of its strong engine, reassuring grip, and comfortable leather-clad seats.????????????????????????????????
• ???????????????????????????????????The rear seats were judged to be comfortable by adults. Parents liked it that belted-in kids at either end of the bench couldn??????????????????????????????????????t quite reach each other.????????????????????????????????
• ???????????????????????????????????The suspension is great on dirt roads.????????????????????????????????
• ???????????????????????????????????Plenty of room for us and the supplies for our tailgate party before the concert.????????????????????????????????

Customers also continued to vote for the X5. In September ??????????????????????????????????????03, fully 3,276 units were delivered in the U.S., a 31% increase over September ??????????????????????????????????????02. Thus the freshening for ??????????????????????????????????????04 was not planned in order to increase already robust sales; instead, it is a manifestation of BMW??????????????????????????????????????s constant drive toward ever better motor vehicles.

The new xDrive system:
variable torque split, quick reflexes, in adapting to changing driving conditions

The original X5 all-wheel drive system utilized a planetary center differential that apportioned driving torque to the front and rear pairs of wheels in a ratio of 38% front/62% rear. Intervention by the traction-control function of the Dynamic Stability Control (DSC) system influenced this basic torque split as required by traction conditions. The new xDrive system, like its predecessor housed in a transfer case behind the transmission, takes an entirely different path to assigning driving torque to the front and rear wheels. In its essence, xDrive operates as follows:

• Driving torque is always transmitted to the rear wheels.
• The portion of torque transmitted to the front wheels is controlled by a multi-disc clutch that can be fully open, fully engaged or at any level of partial engagement in between.
• Engagement pressure on the multi-disc clutch is applied by a servomotor, which in turn is directed by an electronic control system that receives inputs from the DSC system via sensors for:
  Rotational speed of each wheel
  Steering angle
  Brakelight switch
  Vehicle yaw and lateral acceleration.
  
• The servo motor exerts engagement pressure on the multi-disc clutch via a linkage consisting of levers, a ball ramp and a disc cam.

Considering the front and rear wheels as two pairs, the rears always drive; the proportion of the total driving torque transferred to the front pair at any given time depends upon the degree to which the multi-disc clutch is engaged (i.e. the engagement pressure exerted by the servo motor). As more torque is transferred to the front wheels, a smaller proportion goes to the rear. With full traction at all wheels, the maximum proportion to the front is 50%; in a situation where both rear wheels are on slick ice and the fronts are getting traction, the proportion going to the rears can approach zero. All-wheel drive is essentially permanent; under normal traction conditions, the circumstances which cause xDrive to operate in rear-wheel drive only are:

• During very tight cornering with little engine torque, to permit large wheel-speed variations between the front and rear wheels (such as when parking).
• In tight curves with low to medium torque.
• When the vehicle tends to understeer markedly.
• Anytime the antilock braking function is active.

In normal driving, the clutch is operated with minimum slip, resulting in a torque split around 40% front / 60% rear; this is similar to the 38% / 62% permanent split provided by the previous planetary center differential. Under conditions of uneven traction, the control system interprets wheel-speed data to determine the front / rear driving-torque proportions; additionally, the DSC traction-control function can intervene to reduce engine torque and apply individual wheel brakes, thus assisting in achieving the maximum possible usable force to move the vehicle. Via the DSC switch on the console, the driver can also elect to de-activate engine intervention, leaving only the brakes; this function is referred to as ADB-X (Automatic Differential Brake for all-wheel drive). But xDrive does not optimize traction alone; it can also optimize handling characteristics, enhancing both agility and stability on non-slippery as well as slippery road surfaces. Via the same type of logic DSC employs to recognize and correct for excessive over- or understeer, xDrive adjusts the front / rear torque split to avoid these tendencies. If undesirable oversteer is sensed, the multi-disc clutch is further closed, sending the additional torque to the front wheels. If excess understeer is detected, xDrive opens the multi-disc clutch completely, leaving no driving torque at the front wheels. All this occurs without any overt indications to the driver; the driver merely enjoys optimum vehicle dynamics under a wide range of driving and road conditions. xDrive even varies the front / rear torque split according to acceleration on dry pavement, increasing the proportion to the rear wheels under heavier acceleration and decreasing it under lighter acceleration, a feat the system??????????????????????????????????????s algorithms are programmed to accomplish. In connection with all these adjustments to the front / rear torque split, it??????????????????????????????????????s essential to note that xDrive makes them ultra-quick; reaction times (from sensing to control actions) have been reduced so much that it could almost be said that the system operates pro-actively. At the ???????????????????????????????????bottom line,???????????????????????????????? xDrive deals optimally with a wide spectrum of traction conditions. More remarkably, the system also optimizes vehicle dynamics or, more popularly expressed, handling; it adds to the X5??????????????????????????????????????s inherently great agility for this type of vehicle. xDrive will also be found in the new BMW X3; the X5 transfer case is heavier-duty than that of the X3, with larger dimensions and one more disc in its multi-disc clutch.