4MATIC: high-performance all-wheel-drive system with sophisticated control systems

The 4MATIC powertrain at the heart of the Mercedes-Benz GLK-Class is one of the most capable all-wheel-drive systems on the market. The driving dynamics systems ESP, ASR and 4ETS are superbly harmonised with each other; when they go into action their quality of control is so good that top-notch longitudinal and lateral dynamism coupled with superb handling stability are ensured under all conditions, both on and off-road. Thanks to the compact, lightweight and frictionoptimised concept, with a longitudinally installed engine and block-design main transmission and transfer case, the system offers various advantages over its counterparts equipped with a transversely installed drive unit. Fuel consumption, for example, is about on a par with that of a comparable conventionally powered vehicle, while the minimal vibration and noise levels rival those of today's luxuryclass models.

The 45:55 percent basic distribution of the drive torque between the front and rear axle - along with the ESP, ASR and 4ETS dynamic handling control systems - ensures effortless and predictable performance in all conditions. Optimum traction, maximum driving stability and superlative handling are assured at all times. When tuning the control systems, the engineers at the Mercedes-Benz Technology Center (MTC) made neutral self-steering behaviour a top priority. Only when the physical limits of driving are neared is there a slight oversteer tendency. All GLK models display these characteristics, even if road conditions vary widely. Whether it be dry or wet. On snow, ice or unsurfaced roads. If drivers never know whether to expect understeer or oversteer, they become unsure. This problem - a frequent occurrence in the SUV category - is solved once and for all by the Mercedes-Benz GLK-Class. The newly developed multi-disc clutch in the centre differential supports the system if the friction between the tyres and the road surface is particularly low, for example on snow or ice. A basic partial locking torque of 50 newton metres between the front and rear axle produces a significant increase in traction whilst the high level of directional stability is maintained.

The "G" button on the centre console makes the GLK with off-road engineering package even more assertive on rough terrain. Pressing the button activates a special driving program which varies the shift points of the 7G-TRONIC transmission, "softens" the accelerator pedal characteristics and activates the ESP off-road function. In this mode the system is designed to operate with a higher degree of wheel slip while retaining directional stability. This control strategy improves traction off-road, particularly on low-friction surfaces such as sand, gravel or stone chippings. There is also a manual transmission mode, in which the shift paddles on the steering wheel can be used to change between the gears. A further switch activates the Downhill Speed Regulation (DSR) system, which automatically maintains a pre-programmed speed on steep downhill inclines. The off-road-specific body dimensions are equally impressive. The large ground clearance of 201 millimetres (GLK 280 4MATIC) and the short body overhangs (front 816 mm, rear 957 mm) make for favourable angles of approach and departure - 23 degrees and a maximum of 25 degrees, respectively. Meanwhile the relatively short wheelbase length of 2755 millimetres and the vehicle weight of 1830 kilograms, which is remarkably low for an SUV, allow the GLK to make good headway on even the most topographically demanding of terrain.

As well as a tyre pressure loss warning system, the tried-and-tested Electronic Stability Program (ESP) for the GLK incorporates a vehicle/trailer stabilisation function, which defuses critical driving situations involving a trailer before they become dangerous by applying the individual wheel brakes as and when required. The towing capacity is 2000 kilograms.

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