Mercedes-Benz C-Class with New 4MATIC

Press Release

Electronic traction system instead of differential lock

Rather than conventional differential locking systems, the 4MATIC uses the electronically controlled 4ETS traction system, an additional component of the ESP® Electronic Stability Program. This has also been further developed and now has improved traction with higher levels of comfort. 4ETS is automatically activated if one or more wheels lose their grip on the road surface. In such cases 4ETS automatically applies the brakes to these wheels individually and thus simultaneously increases drive torque to the wheels with sufficient traction. These thousandth-of-a-second braking impulses achieve three differential locks:

1. Rear axle: If one wheel is caught in wheelspin, the braking system is applied and transfers torque force equivalent to the braking force to the other rear wheel. This fulfils the function of a rear lock.

2. Front axle: The same principle as the rear axle applies to the front wheels, so that 4ETS also replaces the front lock.

3. Central lock: If both rear axle wheels are caught in wheelspin, the braking system is applied to them simultaneously, whilst the 4MATIC distributor gearbox balances out the difference in rotational speed between front and rear axle. In this way 4ETS fulfils the role of a central differential lock.

In addition, the automatic braking impulses of the 4ETS system adjust to the speed of the car:

• At low speeds braking intervention is possible in all wheels. Thus, 4ETS achieves the effect of three locks and provides maximum traction.

• At medium speeds braking pressure is restricted to the wheel not caught in wheelspin so as not to compromise driving stability. Should both rear wheels lose their grip on the road surface, the braking system is applied to them simultaneously – at this speed, stability has priority over traction.

• At high speeds 4ETS controls braking pressure on both rear wheels synchronously – even when only one of the rear wheels is caught in wheelspin. At the same time the system does without braking intervention on the rear axle, in order to achieve the best possible driving stability.

Within the context of the development of the traction system and of acceleration skid control (ASR), Mercedes-Benz engineers have fine-tuned the controls so that specific situations – such as one-sided wheelspin when pulling away – are more easily detected. The aim was to further increase acceleration with minimal wheel slip. Acceleration skid control depends on the particular driving situation and, for example, lowers the thresholds for the regulation of engine torque in bends on a smooth road surface in order to ensure the stability of the vehicle. On the other hand, the system can reduce control thresholds for the braking impulses when taking bends on a dry road surface. In this way a good balance between the best possible traction and high driving stability is achieved in any driving situation.

As with all driving safety systems from Mercedes-Benz, the 4MATIC notifies the car driver as soon as he is approaching the limits. In such cases a yellow warning light appears in the instrument cluster. This is an unmistakable signal that driving must be adapted to the road conditions.

4MATIC in combination with high-torque V6 engines

The newly developed 4MATIC drive system combines Mercedes-Benz C-Class motors with high-torque V6 engines:

• Models C 280 4MATIC, C 350 4MATIC and C 320 CDI 4MATIC are available in saloons.

• The permanent all-wheel-drive system is available with the six-cylinder diesel engine in the estate model.

The main technical data at a glance:

The newly developed, more efficient all-wheel-drive system reduces fuel consumption in the 4MATIC models in the C-Class by up to 0.5 litres per 100 kilometres. Depending on the motorization, additional all-wheel-drive fuel consumption drops by between 0.2 and 0.4 litres per 100 kilometres. The V6 engines have been modified for use in the 4MATIC models. The changes relate mainly to the oil circulation system, which needs an oil vacuum hose, an oil guard, an oil level meter tube, a fuel level plunger and a newly designed oil reservoir with integrated shaft channel. A countershaft is fed through this channel, linking the front axle gearbox with the drive shaft of the left front wheel.

The integral supports, to which the engine, front axle and steering assembly are fixed, have also been further developed for the 4MATIC models and, in spite of limited space, meet the same specifications as rear-wheel-drive vehicles. The integral support of the 4MATIC versions consists of several parts, each with a different material composition, designed to meet high demands from

Mercedes-Benz in terms of safety and service life. The force transmission points of the front axle, steering assembly and engine, and the connecting parts of the integral support are specifically reinforced.

Front axle and braking system adapted

In the course of designing the 4MATIC chassis, Mercedes-Benz engineers have succeeded in achieving the same results in terms of agility and comfort as with the rear-wheel-drive C-Class models.

The three-link front axle was borrowed for the all-wheel-drive model and, for reasons of space, modified so as to enable the torsion bar stabiliser to be placed behind the centre of wheel. It is fixed to the integral support by means of special consoles. The position of the steering gear and the steering gear shaft also differs from that of the standard model, so the front axle kinematics have been recalculated and adjusted. The C-Class multi-link rear axle remains unaltered in the 4MATIC models.

Large, internally ventilated disc brakes on the front and rear axle come as standard on all 4MATIC C-Class models.

Data and dimensions of the braking system at a glance:

*saloon and estate