With snow, sleet, freezing fog, black ice, temperatures hovering around zero and severe frosts, the winter months hold some unpleasant road conditions in store for drivers. Despite these impediments, however, drivers of Mercedes models equipped with the 4MATIC permanent all-wheel-drive system can set off for the daily commute to work or savour the drive to the next winter wonderland with complete peace of mind. This is because the 4MATIC drive concept boasts formidable performance on snow-covered or icy roads. The E-Class 4MATIC in particular stands out for its blend of high traction reserves, excellent directional stability, peerless safety and exceptional comfort levels. Mercedes-Benz is demonstrating the capa-bilities of the Saloon and Estate models by staging a 4MATIC Workshop in extreme winter conditions on the Timmelsjoch high alpine road in Austria.
As with the 4MATIC system's set-up on a dry or wet road, directional stability and, therefore, active safety are paramount at all times when wintry conditions prevail, too. The mechanical principle of the 4MATIC system, featuring a 45:55 torque split between the front and rear axles and a multi-disc limited-slip centre differential with a basic locking torque of 50 Nm, offers all the right ingredients. This basic design enables high levels of traction, as the dynamic shift in axle load toward the rear axle that occurs during acceleration is harnessed to deliver more drive torque to the rear wheels. However, the multi-disc differential lock is also able to shift the drive torque between the front and rear axles, varying the split between 30:70 and 70:30 as the road conditions dictate. Consequently, intervention by the ESP®, 4ETS or ASR electronic control systems can be delayed for as long as possible and the bulk of the drive torque converted into tractive power, even on slippery roads. All control system interventions go virtually unnoticed, yet drivers still know straight away if they are driving on the limit: in such instances, a yellow warning symbol flashes in the instrument cluster as a highly visible prompt to adapt their driving style to the road conditions.
The drive mechanism's permanently engaged design offers key advantages over other systems that first need to diagnose a lack of grip before activating the 4x4 drive. The 4MATIC on the E-Class will have already made use of this valuable time to start transmitting drive torque via the wheels to the road.
When pulling away in wintry conditions, the E-Class 4MATIC models are designed to develop maximum traction. To this end, certain road conditions are automatically detected and the interventions of the 4ETS electronic traction control system adjusted so as to achieve the greatest possible acceleration while minimising wheel slip, ensuring optimum directional stability in the process. This strategy also allows the vehicle to pull away under the most adverse conditions, such as when one side of the vehicle is on an icy slope (µ-split) or both wheels on the front or rear axle have limited grip (µ-jump).
On twisting roads covered with snow and ice, vehicle stability is primarily controlled by the ASR acceleration skid control system's regulation of engine torque. The ASR control thresholds are adjusted according to the driving situation based on the vehicle's longitudinal and lateral dynamic readings as continuously measured by the ESP sensor system. If vehicle stability is to be maintained, the longitudinal force when cornering must be controlled by means of engine torque regulation in such a way that there are sufficient reserves of lateral force at all times. In order to comply with this physical correlation, when cornering on road surfaces with a low friction coefficient the control thresholds for engine torque regulation at the wheels on the outside of the bend are reduced considerably so that the tyres can develop sufficient lateral force.
The 4MATIC powertrain in the E-Class is one of the best-performing permanent all-wheel-drive systems on the market. The basic design concept, with the engine installed longitudinally and the integral transmission and transfer case unit, produces a compact, lightweight arrangement that minimises frictional losses, heralding a number of benefits compared to other passenger car systems with a transverse power unit and selectable 4x4. Fuel consumption, for instance, is a mere between 0.2 and 0.6 litres more per hundred kilometres than on a com-parable model with conventional drive, while vibration and acoustic comfort meet the high standards expected of the E-Class.
Mercedes-Benz achieves the standard of ride comfort which all versions of the E‑Class are renowned for courtesy of the highly sophisticated DIRECT CONTROL suspension with adaptive shock absorbers, an intelligent body design with excellent rigidity, plus enhanced seats which are also available with massage and climate control functions. The weight-optimised DIRECT CONTROL system, featuring a three-link front suspension and multi-link independent rear suspension, automatically adapts to the changing driving situation by varying the damping forces, resulting in a substantial improvement in ride comfort. The air suspension system – optional for all 4MATIC models and standard on the E 500 4MATIC – is combined with a continuously variable, electronically controlled damping system that processes a series of sensor signals and controls each wheel individually. So, not only do Mercedes customers experience the best in ride comfort, they reap the benefits of excellent handling safety and sporty agility too.
Carefully balanced control of the interior climate is especially important in the winter. This is why Mercedes-Benz offers THERMOTRONIC luxury automatic climate control for the E-Class. Apart from regulating the climate separately for the driver, front passenger and passengers in the rear, this system allows individual pre-settings to be programmed too. It furthermore includes a pollutant sensor which automatically switches to air recirculation mode if it detects any sudden increase in the carbon monoxide or nitrogen oxide levels in the outside air – when driving through a tunnel, for instance. Another highlight of the THERMOTRONIC system is the residual heat function: pressing the "Rest" button heats or ventilates the passenger compartment for around 30 minutes when the engine is switched off. The E-Class is equipped as standard with THERMATIC, a two-zone automatic climate control system. Here, the interior air is kept clean by a large, hermetically sealed fine-particle combination filter which is 96 to 98 percent effective. Thanks to the activated-charcoal coating, gaseous substances can also be filtered out by the fine-particle combination filter.
THERMATIC and THERMOTRONIC heat up the passenger compartment of the E‑Class extremely efficiently, even after a cold start on winter mornings. This is thanks to a heating output of eleven kilowatts, equivalent to the capacity of the central heating system in a modern family home. On the diesel models, a heat exchanger with six integral PTC heating elements (PTC = Positive Temperature Coefficient) is also activated when the outside temperature falls below a certain level in order to boost the effect of the main heat exchanger with an electrical output of around 1200 watts. The assistance from the PTC heater is necessary due to the high thermal efficiency of today's CDI engines, which is precisely what makes them so economical and means that they dissipate considerably less heat to the coolant under partial load conditions than conventional engines.
The Mercedes-Benz all-wheel-drive line-up encompasses 52 passenger car models across nine model series and offers an impressively wide choice: besides the E-Class and the C-Class, which likewise comes in both a saloon and an estate variant, the 4MATIC portfolio is enriched by models from the S-Class, CL luxury coupé and R‑Class touring SUV ranges too. There is also the compact GLK as well as the GL‑Class and M-Class off-roaders. Still going strong after 30 years in production, the G-Class truly comes into its own off the beaten track and continues to rank as one of the best cross-country vehicles in the world.
There is a reason why Mercedes engineers are so skilled in the development of groundbreaking all-wheel-drive concepts. The history of all-wheel drive at Mercedes-Benz dates all the way back to 1903. Since then, the accepted maxim has been that all-wheel drive is the best technology for making quicker and safer progress under the most adverse conditions. Over the course of the years it has been successfully employed in a variety of Mercedes-Benz models. 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 operation on asphalt roads too, as demonstrated by the 4MATIC saloons from Mercedes-Benz. The innovative drive concept received its saloon premiere in the W 124 E-Class model series back in 1987. The 4ETS system made its debut aboard the M-Class in 1997. Mercedes-Benz has therefore amassed a wealth of experience with these electronic control systems – more in fact than any other car manufacturer.