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The most innovative components of the new 4MATIC include the power take-off to the rear axle which is integrated in the 7G-DCT automated dual clutch transmission and the rear-axle gear unit with integrated, electrohydraulically controlled multi-disc clutch. This set-up enables fully variable distribution of the drive torque between front and rear axle. Additional benefits of this design are a lower system weight than is available from the competition and high efficiency. Similarly to the front-wheel drive versions, all 4MATIC models also boast good energy efficiency.
The 4MATIC all-wheel drive is a completely new development tailored to the requirements of the new models with front-wheel drive. The future all-wheel drive line-up from Mercedes-Benz will be heralded in the coming year by the CLA-Class and the particularly agile and powerful CLA 45 AMG. While the technical basis is identical on all versions, the AMG models feature a modified power output to the rear axle.
Integrated power take-off unit (PTU) channels power to the rear axle
The new 4MATIC is being combined with the 7G-DCT seven-speed automated dual clutch transmission which was premiered in the B-Class. The power flux to the rear powertrain is provided by a compact power take-off unit (PTU) which is fully integrated in the main transmission and is supplied with lubricant from the latter's oil circuit. This configuration gives rise to substantial weight advantages in comparison to rival systems which branch off power by means of an add-on component with its own oil circuit. Together with the friction-minimised tapered roller bearings, the PTU achieves an excellent level of efficiency.
The low system weight of the new 4MATIC is not attributable solely to the PTU. Other weight-stripping measures include a compact rear-axle gear unit, inductively hardened rear-axle side shafts in hollow design and weight-optimised propeller shafts. The system weight of the new 4MATIC is up to 25 percent lighter than the all-wheel drive versions offered by the competition.
The two-part cardan shaft is vibrationally decoupled, with an axially moving joint at the front compensating the movements of the engine-transmission unit and preventing transfer to the rear powertrain. To minimise crash-induced stress, the cardan shaft is fitted with a crash joint.
Completely new development with torque-on-demand rear axle
The electrohydraulically actuated multi-disc clutch integrated in the rear axle gear unit is responsible for fully variable torque distribution. Operating principle: when the multi-disc clutch is open, the CLA is driven almost exclusively by the front axle. When the clutch is closed, the rear axle comes into play. This means that the drive torque can be shifted in fully variable mode between front and rear axle according to the given situation (torque on demand).
The system pressure to activate the rear axle is supplied in milliseconds by the rotor-type pump which is integrated in the rear-axle gear unit. The pump is activated automatically as soon as only minimal speed differences apply between front and rear axle. Pressure control is performed by a proportioning valve under the steering of the ESP®.
Intelligent control systems for more enjoyable driving
The 4MATIC is activated according to the basic principle of "as often as necessary, as rarely as possible". This means that when the underlying conditions allow, the all-wheel drive CLA models run almost exclusively in particularly economical front-wheel drive mode. As soon as the driving situation requires, drive torque is channelled to the rear axle as appropriate. The reverse process takes place just as quickly: as soon as additional drive torque is no longer necessary at the rear axle – e.g. in case of heavy braking manoeuvres with ABS intervention – the rear powertrain is deactivated and torque is reduced to zero.
In case of understeering or oversteering under load, the drive torque is first of all distributed such as to stabilise the vehicle. Only if these measures fail to have a stabilising effect do the control systems adapted to 4MATIC conditions, such as ESP® or 4ETS, intervene to keep the CLA stable. With this strategy, the developers have managed to combine two key requirements defined in the performance specifications: optimum energy efficiency coupled with maximum driving dynamics and driving safety.
Individual: driving modes to suit personal driving styles
The torque distribution ratio is also dependent on the activated shift programme of the 7G-DCT dual clutch transmission. The ECO programme results in torque distribution of a conservative nature. Less torque is channelled to the rear axle, resulting in gentler handling and supporting an economical driving style at lower revs. In SPORT or MANUAL mode the activation times are shortened and more torque is distributed to the rear axle in the interests of a dynamic, sporty driving style. On the AMG versions, adaptation of the 4MATIC controller takes place in accordance with the 3-stage ESP®.
New 4MATIC featuring in the Mercedes-Benz CLA
The future all-wheel-drive line-up from Mercedes-Benz will be heralded in the coming year by the CLA-Class and the particularly agile and powerful CLA 45 AMG. The new Mercedes-Benz CLA adopts the avant-garde design of the Concept Style Coupé into series production almost 1:1. In keeping with its sporty positioning, the CLA is available with high-torque turbo engines rated at up to 155 kW (211 hp), sports suspension and the newly developed 4MATIC. The technical highlights include numerous driving assistance systems, such as advanced COLLISION PREVENTION ASSIST.
CLA 45 AMG: the most dynamic way to experience the new 4MATIC
As the high-powered top model of the new compact class, the CLA 45 AMG broadens the portfolio of Mercedes-Benz's high-performance brand to offer a fascinating high-performance vehicle in this class, too. The newly developed AMG 2.0-litre four-cylinder turbo petrol engine will set new standards in its engine capacity segment: with maximum torque of well over 400 Newton metres and low fuel consumption, AMG is aiming to lead the competition. In conjunction with the specially adapted 4MATIC version for this engine-power class, the CLA 45 AMG will be one of the most dynamic, powerful and efficient four-cylinder series-production compact cars.
Elegant in all weathers: the CLS Shooting Brake 4MATIC
The CLS Shooting Brake sees Mercedes-Benz making its mark once again with a creative design concept that underscores its leading role in the design field. Surprising yet unequivocally coupé, the CLS Shooting Brake's proportions create a crouched posture, as if the vehicle were poised to make a leap: long bonnet, narrow window profile with frameless side windows, roof sloping dynamically towards the rear and continuing to the tail end of the vehicle. Only at second glance does it become clear that the Shooting Brake actually has five doors and offers more in terms of functionality. In essence it represents an unprecedented version of a sports car with five seats and a large tailgate.
Like all 4MATIC models from Mercedes-Benz, the high-powered and high-torque CLS 350 CDI 4MATIC (195 kW/265 hp, 620 Nm) and CLS 500 4MATIC (300 kW/408 hp, 600 Nm) feature a permanent all-wheel drive system which guarantees optimum traction and the best possible agility and safety – particularly in wintry road conditions.
New GL- and GLK-Class all set for their first winter
The new GL-Class which is available from November 2012 is the pinnacle of perfection in the ATV and SUV world. It offers a luxurious interior with seven full-size seats and superlative ride comfort accompanied by highly dynamic performance on dry, wet or wintry roads. The premium SUV also boasts outstanding off-road capabilities, thanks to new suspension developments and innovative dynamic handling control systems which enhance both driving pleasure and safety on the road. In a nutshell, the GL-Class is a seven-seater, all-terrain S-Class.
The optional ON&OFFROAD package for the GL-Class uses six different driving modes to optimise driving dynamics and handling safety by providing the optimum drive control needed to cope with the wide spectrum of operating conditions encountered both on and off road. Drivers have the choice of an automatic mode, two specially programmed off-road modes as well as three on-road modes – "Winter", "Sport" and "Towing". The winter driving mode of the ON&OFFROAD package improves handling on glazed frost, snow and ice or when using snow chains and offers additional safety.
When the ON&OFFROAD package is combined with another optional feature, the ACTIVE CURVE SYSTEM, a specially programmed winter set-up offers dynamic driving pleasure while giving the driver excellent control over the vehicle for a high degree of handling safety. At the same time, the system is capable of giving the GL-Class greater traction, especially in wintry road conditions with low grip levels. What’s more, this set-up boasts even greater directional stability in tighter corners thanks to a special control algorithm that is programmed into the system.
April witnessed the premiere of the second new SUV to be launched in 2012: the revamped GLK-Class from Mercedes-Benz. This SUV is now able to demonstrate its outstanding capabilities in wintry conditions, too. Its claim to leadership of the compact SUV segment is underscored by trailblazing assistance systems, engines matching efficiency with agility, a new design and an extended range of equipment and appointments.
The 4MATIC on the GLK is based on the version featuring on the C-, E-, CLS- and S-Class, whereby its outstanding off-road capability sets it apart from the saloons and coupés, however. For keen off-road enthusiasts, an Offroad Engineering package is additionally available to further broaden the scope for off-road adventures. At the touch of a button a special drive programme is started which varies the shift points of the 7G-TRONIC, "softens" the accelerator characteristics and activates the ESP® off-road functions with off-road ABS and a special off-road 4ETS system. An additional switch activates Downhill Speed Regulation (DSR).
Even the best all-wheel drive is no substitute for winter tyres
Like any other all-wheel drive system, the 4MATIC versions have to abide by the laws of driving physics. The fundamental rule is that a tyre is only able to transfer a certain level of overall force to the road surface. If a particularly high degree of longitudinal force is required during acceleration or braking, for example, the available lateral force is reduced. When cornering, the reverse applies: now a large amount of lateral force is required to keep the vehicle on course, while the longitudinal force potential is restricted. The engineers' skill in designing the drive mechanism and fine-tuning the control systems lies in their ability to exploit these correlations in such a way as to ensure the best possible handling characteristics under all conditions. The frictional coefficient µ describes the physical grip between the tyres and the ground. This figure is high on a dry road (µ = 0.9) and low on a snow-covered road (µ = 0.3).
Despite all the engineers' efforts, it is ultimately the drivers themselves who determine how safe they are out on the road. They should always adapt their driving style in accordance with the prevailing wintry conditions and ensure that their vehicle is suitably equipped; winter tyres are absolutely essential here.
The full works: the 4MATIC range from Mercedes-Benz
In addition to the described models, the 4MATIC range also extends to the saloon and estate versions of the E- and C-Class, the luxurious S-Class, the CL luxury coupé, the four-door CLS Coupé and the R-Class. The M-Class and the legendary G-Class round off the range in the SUV and ATV segment. The all-wheel drive line-up from Mercedes-Benz also includes an exotic model in the guise of the SLS AMG Electric Drive. Four electric motors on this vehicle guarantee tremendous thrust, with fully variable and selective drive torque distribution to the individual wheels. In all, the 4MATIC range currently comprises 51 models. And when the compact models featuring the new 4MATIC generation round off the range next year, it will really be a case of all-wheel drive all-round! The 4x4 family from Mercedes-Benz will then cover almost 60 models.
Credits: Daimler AG
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