Winter driving fun in the Mercedes-Benz GLK

Muamer Hodzic December 8, 2008

Soon it will be time to head for the ski slopes again, and drivers of Mercedes models with the permanent all-wheel-drive system 4MATIC can rest assured as they set off en route to their chosen winter paradise. Mercedes-Benz is demonstrating the high traction reserves coupled with directional stability and safety in the new GLK at its 4MATIC workshop. In extreme winter conditions at a height of 2500 metres on the Austrian Timmelsjoch High Alpine Road this compact SUV is demonstrating that its driving dynamics really are in a class of their own.

4MATIC control strategies for wintry road conditions
Technology in detail: The permanent all-wheel-drive system 4MATIC
Strong characters: The GLK-Class from Mercedes-Benz

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As is the case with 4MATIC’s fine-tuning on a dry or wet road, directional stability and therefore the active safety of the GLK models is always to the fore when wintry conditions prevail, too. The basic 4MATIC mechanism with a 45:55 percent torque split between the front and rear axles along with the multiple-disc limited-slip centre differential with a basic locking torque of 50 Nm adds up to an ideal solution. This basic design delivers high traction since, on the one hand, the dynamic shift in axle load toward the rear axle that occurs during acceleration is used to deliver more drive torque to the rear. Meanwhile, the multiple-disc limited-slip centre differential can also variably shift the drive torque from 30 to 70 or 70 to 30 percent between the front and rear axle, whenever the road conditions so dictate. As such, the electronic control systems ESP®, 4ETS or ASR can intervene as late as possible; the bulk of the torque is converted into traction on slippery roads.

All interventions go virtually unnoticed, but the drivers are still informed immediately if they are driving on the limit. In this case a yellow warning light flashes in the instrument panel – a clear signal to adjust their driving style to the road conditions.

The arrangement featuring a permanent design mechanism has key advantages over other systems that first need to diagnose a lack of traction before activating their 4×4 all-wheel drive. The 4MATIC on the GLK will have already made use of this valuable time to transmit drive torque via the wheels to the road.

4ETS: integrated “automatic start-off aid” for ice and snow

When pulling away in wintry conditions the engineers use the off-road algorithms on the GLK 4MATIC to develop optimum traction. Certain road conditions are automatically detected and the interventions of the 4ETS electronic traction control system adjusted so that as much acceleration as possible can be achieved with minimal wheel slip, providing optimum directional stability in the process. This strategy also allows the vehicle to pull away under adverse conditions, such as when one side of the vehicle is on an icy slope (the so-called µ-split) or both wheels on the front or rear axle have limited grip (µ-jump).

Stable conditions on wintry roads

On winding roads covered with snow and ice, vehicle stability is primarily controlled by means of engine torque regulation in the acceleration skid control system ASR. Taking into consideration the longitudinal and lateral dynamics of the vehicle continuously determined by the ESP® sensor system, the ASR control thresholds are adjusted according to the driving situation. In order to ensure stable driving conditions, on winding roads the longitudinal force must be controlled via engine torque regulation in such a way that sufficient lateral force is always available. In order to comply with this law of physics, when driving on winding roads the control thresholds for engine torque regulation on the outer wheels are reduced considerably at low frictional coefficient, ensuring that the tyres can develop sufficient lateral force.

4MATIC: top performance in all areas

The 4MATIC drive system in the GLK is among the most powerful all-wheel-drive systems there are; its control systems break new ground. Advantages over other systems with a transversely installed drive unit are achieved thanks to the basic compact, light and friction-loss-optimised design with its longitudinally positioned engine and integrated main and transfer case. Fuel consumption, for example, is at the same level as that of a comparable, conventionally driven vehicle, whilst noise and vibration levels are on a par with those in higher vehicle categories.

105 years of all-wheel-drive technology from Mercedes-Benz

The history of all-wheel drive from Mercedes-Benz begins way back in 1903, when Paul Daimler, the son of the company’s founder, creates the foundations for designing vehicles with all-wheel drive. Since then the accepted maxim has been that all-wheel drive is the number-one technology for making better and safer progress on poor roads. As the decades pass it is successfully introduced in a variety of Mercedes-Benz vehicles, in both passenger cars and commercial vehicles. Some models, such as the G-Class and the Unimog, have attained legendary status all over the world. But all-wheel drive has its benefits in everyday driving on asphalt roads too, as demonstrated by the saloons and
sports utility vehicles (SUV) from Mercedes-Benz.

4MATIC available in no less than 51 Mercedes models

The Mercedes-Benz all-wheel-drive line-up includes nine model series and offers an broad range of options: starting with the C-Class and E-Class, both available as saloon and estate versions with 4MATIC, through the S-Class, the luxury CL Coupe and the R-Class touring SUV, the Stuttgart-based manufacturer offers the compact GLK SUV as well as the GL-Class and M-Class off-roaders. The evergreen G-Class off-roader, which really comes into its own off the beaten track, will be celebrating 30 years of loyal service next year. It has a reputation as being one of the world’s best cross-country vehicles and is just one of 51 passenger car models which Mercedes-Benz offers with permanent all-wheel drive.

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