The automatic transmission shift timing is controlled electronically and hydraulically (so-called EN·management). This means that the automatic transmission hydraulic system is controlled by an electronic control unit that selects the correct gear shift point depending on vehicle speed and engine load.
In order to better match the driver's individual driving style and driving modes, the automatic transmission is equipped with a sophisticated adaptive control system (AGS). When selecting gears, in addition to various conditions such as uphill or downhill, slippery roads or stop-and-go situations, this system takes into account the driver's driving style. AGS analyzes the position and movement of the accelerator pedal, vehicle speed, centrifugal acceleration (on turns) and deceleration when braking.
Based on the information received, the system evaluates the driver type and switches to one of the four main programs. In this case, switching can be done from the XE program of increased efficiency through the E and S programs to the pronounced sports program XS. A driver with pronounced sports ambitions can, if necessary, set the operating mode only to the sports program by setting the operating mode selection lever to position 4. On a slippery road, an additional winter program is automatically activated (Wintarprogramm), allowing to increase traction and stability during movement.
Steptronic system - automatic with AGS and manual switching of driving modes
The Steptronic system installed on some models, along with automatic gear shifting, allows manual (step-by-step) gear shifting using a second, short linkage. Step-by-step gear shifting is typical for sports cars and motorcycles.
In automatic mode, for which the mode selector lever must be in position D when driving forward, automatic switching to one of the five gears is carried out using the adaptive control system. Using the left-hand shifter, the driver, on the other hand, can change gears as desired. When the mode selector lever is moved to the left from position D to position M, the currently engaged gear is retained. Subsequent pressing of the lever in the direction of "+" or is accompanied by switching to a driving mode in a higher or lower gear, respectively.
Compared to conventional manual gear shifting, the Steptronic system is more progressive and comfortable and is equipped with protection against incorrect driver input. Inadmissible engagements, such as downshifts at too high engine speeds, are ignored by the system. During acceleration, the system automatically shifts up to a higher gear without driver intervention until the engine speed limiter is triggered. During acceleration using the Kick-Down mode, the system automatically shifts to the lowest possible gear at the current engine speed.
When coasting, the Steptronic system automatically shifts into third gear to ensure sufficient traction during subsequent acceleration.
To assess the performance of the automatic transmission and to correctly troubleshoot, experience working with such transmissions and expensive special devices are required.
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