4MATIC: Automatic braking impulses provide electronic traction control

  • 4ETS Electronic Traction System instead of differential locks
  • Exemplary traction and driving stability under difficult road conditions
  • 4MATIC works flawlessly together with ESP®
4MATIC from Mercedes-Benz is among the most effective all-wheel drive systems for passenger cars. It works in tandem with the Electronic Stability Program (ESP®), which is standard equipment in all Mercedes passenger cars. Thanks to this intelligent combination, models equipped with 4MATIC are considered trendsetters in terms of driving safety (= ESP®) and traction (= 4MATIC).
With its exemplary driving stability and perfect traction, 4MATIC shows off its strengths especially in bad weather conditions such as wet or icy roads and snow. The system also provides further reserve traction and helps drivers to control their vehicles’ behaviour when starting out from a standstill, accelerating, driving at higher speeds around bends or mastering tough terrain. This is how 4MATIC enhances the already exemplary handling properties of Mercedes models. At the same time, it provides the safety and superior performance associated with the Mercedes-Benz brand, even under unusually challenging driving conditions.
Drivers of Mercedes-Benz models equipped with 4MATIC enjoy the advantages of these exemplary handling properties as well as the level of driving comfort typical of the Mercedes brand. This performance is guaranteed by the modified designs for the front and rear axles, and by the all-wheel drive models’ precisely adjusted springs and shock absorbers, which in saloons and estate cars correspond to the tuning for rear-wheel drive models. Still another 4MATIC feature that ensures greater comfort is the fact that it dispenses with the conventional differential locks used in other all-wheel drive passenger cars. These differential locks diminish driving comfort and require more maintenance.
Use of traction system instead of mechanical differential locks
Instead of mechanical differential locks, 4MATIC-equipped Mercedes-models feature the electronically controlled 4ETS traction system. If one or more wheels lose their grip on the road, the system is automatically activated and brakes each wheel individually. As a result, the drive torque on the wheels simultaneously increases with sufficient traction. The extremely fast braking impulses make it possible to achieve an effect equal to that of three differential locks:
  • 1. Rear axle: If one wheel begins to spin, it is braked; and a drive torque corresponding to the braking torque is transferred to the other rear wheel. This is equivalent to the function of a rear lock.
  • 2. Front axle: The same principle used with the rear axle applies to the front wheels, allowing the ESP® component 4ETS to also replace the front lock.
  • 3. Central differential lock: If both wheels on the rear axle begin to spin, they are simultaneously braked; and a drive torque corresponding to the braking torque is transferred to the front axle. This torque does not exceed 40 per cent of the total drive torque. This is how ESP®/4ETS equals the effect of a central differential lock.
The drive torque is distributed in a 40 : 60 ration to the front and rear axles, respectively. The Mercedes engineers chose this torque distribution because it offers the best precondition for safe handling properties and optimal traction.
Stability programme combined with traction control system
As an integral element of the Electronic Stability Program (ESP®), the 4ETS Electronic Traction System relies on sensors that provide a wealth of information on the speed at which the wheels are turning, the steering angle, and the vehicle’s rotational motion and transverse acceleration. A micro-computer uses this data as a basis for correctly adjusting the automatic braking impulses, depending on the driving situation. This improves traction when starting out from a standstill on a slippery surface and provides greater stability during challenging driving manoeuvres.
At low speeds, 4ETS brakes up to three wheels, which provides the same effect as three differential locks and ensures maximum traction. At higher speeds, the system reduces the automatic braking impulses to ensure driving stability. This combination of ESP® and 4ETS with permanent all-wheel drive does not only make the 4MATIC models extremely safe automobiles; it also opens up a new dimension of dynamic driving for motorists.
As with ESP® in model variants with rear-wheel drive, a 4MATIC-equipped vehicle also immediately warns drivers when they approach a critical limit. In this case, a yellow warning light in the instrument cluster begins to flash. This is a clear signal warning drivers to adjust their driving behaviour to the road conditions.
Drive unit comprises the engine, automatic transmission and transfer case
The heart of the 4MATIC is a single-step transfer case with an open central differential, which equalises the speed of the axles. It is directly connected to the automatic transmission, combining with the engine, torque converter and front-axle drive to form a complete drive unit. The engineers designed the front-axle drive system as a so-called hang-on unit: It “hangs” in space-saving fashion on the engine’s oil pan. The power transfer is provided by a universal joint between the transfer case and the front-axle drive.
The downforce on the front axle is achieved using quiet-operating spur gears, which simultaneously function as oil pumps and ensure the supply of lubricant to the transfer case. In rear-wheel drive models, the differential works on the rear axle and is connected with the drive unit via a shortened drive shaft.
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