Since the premiere of the first four-wheel drive BMW model – BMW 325i – in 1985, BMW has expanded its experience in this field with new models and the continuous development of this technology.
Undoubtedly, one of the landmarks is the intelligent BMW xDrive all-wheel drive which was first used in 2004 on the BMW X3 and BMW X5, and is now available for almost the entire range of models. Since that time, engineers focused not only on improving traction and vehicle stability.
In addition to a high degree of functionality and enhanced cornering dynamic, minimizing the loss of such a system as well as reducing weight, were the main priorities required to maintain fuel consumption and emissions low. For this, the intelligent BMW xDrive all-wheel drive is always adapted at concept car level (sedan / coupe, SAV, SAC), the objective being the implementation of the optimal solution.
Now, the fundamental difference from previous versions is that for the first time the BMW xDrive is based on a front-wheel drive concept with a transversely arranged engine. The Active Tourer has already proven that front traction technology meets the requirements of the brand in terms of dynamics.
This is mainly due to the new range of modular engines with three and four cylinders, which, due to modern TwinPower Turbo technology excels in equally with a high performance and remarkable efficiency. With the BMW 225i xDrive Active Tourer (average combined fuel consumption: 6.5 to 6.4 l / 100 km and CO2 emissions: 152-148 g / km), and BMW 220d xDrive Active Tourer (average consumption: 4,8- 4.6 l / 100 km, CO2 emissions: 127-122 g / km), the intelligent all-wheel drive is available now for peak engine range, so as to improve traction, cornering stability and other car dynamics, with the objective of increasing safety and driving pleasure. Both models come with BMW xDrive in their standard form combined with an eight-speed Steptronic transmission.
The transfer of power from the front engine to the rear is achieved through an Angle (Power Take-Off) transfer case from the front differential. The most important component of the all-wheel drive system is a multi-plate clutch electrohydraulically (Hang-On controlled) integrated in the rear axle transmission. This facilitates continuous variable torque distribution between front and rear wheels.
Appropriate controls are provided by an electronic control unit; also an electrohydraulic pump is located on the rear axle.
To ensure optimum power distribution to the front and rear wheels, the drive system is managed from the control unit Dynamic Stability Control (DSC).Now, only if the torque distribution between the front and back is not sufficient to maintain the Active Tourer in the desired parameters, DSC intervenes by reducing engine power and / or by decelerating individual wheels. Furthermore, DSC takes over as a transverse locking differential: if one wheel is spinning without transferring power, it is automatically slowed, and the axle differential directs more power to the opposite wheel.