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Winter driving fun in the Mercedes-Benz GLK

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Winter driving fun in the Mercedes-Benz GLK

    Press Information Winter driving fun in the Mercedes-Benz GLK

    December 7, 2008 Contents Page

Safer, more pleasurable driving on snow and ice

     2 The GLK 4MATIC gets to grips with winter

4MATIC control strategies for wintry road conditions

     6 Best traction, stable and safe handling

Technology in detail

     14 The permanent all-wheel-drive system 4MATIC

Strong characters

     17 The GLK-Class from Mercedes-Benz

At a glance

     18 All-wheel-drive passenger car models from Mercedes-Benz

The descriptions and information in this press kit apply to the international Mercedes-Benz

    model range and may vary from country to country.Daimler Communications, 70546 Stuttgart, Germany Mercedes-Benz A Daimler Brand

    Page 2 Safer, more pleasurable driving on snow and ice

    The GLK 4MATIC gets to grips with winter

    Stuttgart/Hochgurgl 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. Because the performance of the drive configuration on roads affected by snow or ice is truly impressive. Mercedes-Benz is demonstrating the high traction reserves coupled with excellent 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.

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

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 3 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 4x4 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

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 4 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.

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 5 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 Coupé 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.

Contacts:

    Wolfgang Zanker, tel. +49 711 17-75847, email: wolfgang.zanker@daimler.com

    Inka Halba, tel. +49 711 17-75849, email: inka.halba@daimler.com

More information from Mercedes-Benz is available online at:

    www.media.daimler.com

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 6 4MATIC control strategies for wintry road conditions

Best possible traction, stable and safe handling

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 4x4 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.

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 7 Kamm circle: the laws of physics sets limits

    Just like any all-wheel-drive system, 4MATIC in the GLK has to abide by the laws of physics, a fact clearly illustrated in what is known as the “Kamm circle”. The fundamental rule is that a tyre is only able to transfer a certain level of overall force to the road surface. If a large amount of force is required in a longitudinal direction, for example when accelerating or braking, the lateral forces available are reduced. When cornering the reverse applies. In this case a particularly high degree of lateral force is needed for directional stability, whilst the longitudinal force potential is restricted. When designing the drive mechanism and fine-tuning the control systems, engineers‟ skills are called upon to use this correlation in such a way that the very best possible handling is ensured in any conditions. The frictional coefficient µ describes the physical grip between the tyres and the road surface. On a dry road this figure is high (µ=0,9), and on a snow-covered road it is low (µ=0,3).

    Despite the engineers‟ best efforts, it is ultimately the drivers themselves who determine how safe they are on the road. They should always adapt their driving style in accordance with wintry conditions and ensure that their vehicle is suitably equipped; winter tyres are absolutely essential.

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 8 Balance of forces in the “Kamm„s Circle”

Like every other all-wheel-drive system, the 4MATIC on the GLK-Class obeys the laws of driving physics. These interrelationships are described in the “Kamm„s Circle”. A basic law of physics states that a tyre can only transfer a certain total force onto the road. If a large amount of longitudinal force is required during acceleration or braking, the available lateral force is reduced (left-hand graphic).A large amount of lateral force is required during cornering to maintain directional stability; the longitudinal force potential is thus limited (right-hand graphic). The engineers„art in designing the drive mechanism and fine-tuning the control systems is to exploit these interrelationships to ensure optimum handling characteristics whatever the conditions.

    The employees at the Mercedes-Benz Technology Centre have a wealth of experience at their fingertips in this respect. The first all-wheel-drive system was created over 100 years ago, and the engineers also occupy a leading position where the fine-tuning of all-wheel-drive control systems is concerned. 4ETS celebrated its world premiere in 1997 in the first generation of the M-Class, development work having begun as far back as 1993. Mercedes-Benz thus enjoys the most extensive experience of all car manufacturers with these systems.

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

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 9 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).

    So when starting off on µ-split one side of the GLK is on snow or ice and the other on asphalt. There are major differences in the coefficient of friction between the left and right-hand side of the vehicle. On all vehicles with open axle differentials the wheel with the lowest coefficient of friction limits the maximum transferable driving power. If the driving power rises above the maximally transferable power, the wheels on snow or ice start to spin, and the GLK would not be able to start off. This situation is immediately registered by 4ETS and the spinning wheels are baked by precisely the right amount of pressure build-up in the wheel brakes. As the wheel with the higher coefficient of friction is now supported via the brake force of the wheel with the lower coefficient of friction, the GLK starts to move. Following the start-off process, the wheel characteristics are observed very closely and the brake pressure controlled in such a way that, as far as possible, there is no difference in speed between the individual wheels. The braking force applied by 4ETS simulates, as it were, a higher coefficient of friction on the side with ice or snow, which, in an ideal case, corresponds to the coefficient of friction on the asphalt side. This produces an optimal transverse locking effect on the axle differentials, resulting in the maximum possible acceleration on µ-split.

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

    Page 10 Pulling away easily on different road surfaces (µ-split)

The adhesion between the tyres and road is considerably higher on the asphalt side than on the side of the road covered with ice. 4ETS detects this situation and prevents the wheels from spinning on the icy road by applying the brakes on specific wheels.The torque is thus balanced at the axle differentials because the same adhesion is simulated on the ice-covered side as on the asphalt side. The GLK manages to pull away.

Starting off on “µ-jump”, where one of the GLK‟s axles is entirely on ice or snow

    and the other axle is on asphalt, is made more difficult by the large differences in coefficient of friction between the front and rear axle. On vehicles with an open longitudinal differential the axle with the lower coefficient of friction determines the transferable driving power. Whilst the multiple-disc limited-slip centre differential with its basic locking torque of 50 Newton metres does have a balancing effect, it is unable to even out these extreme differences in coefficient of friction. In these conditions, too, both wheels on the axle with the lower coefficient of friction start to spin if the driving power exceeds the maximum transferable driving power at this coefficient of friction. 4ETS helps here by immediately recognising and braking the spinning wheels. This enables the axle with the higher coefficient of friction to be supported by the braked axle with the lower coefficient of friction

    and the GLK starts to move.

Daimler Communications, 70546 Stuttgart, Germany

    Mercedes-Benz A Daimler Brand

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