The new generation of Automatic transmission
The fully automatic transmissions are available in two versions:
The latter is currently reserved for the C 32 AMG and the SLK 32 AMG. Both are automatic planetary gear transmissions, which are linked to the engine via a torque converter with slip-controlled torque-converter lockup. The automatic gear change is electronically controlled, resulting in virtually no discernible interruption of tractive power.
Uninterrupted power flow: automatic transmission management
When "D" (Drive) mode is selected, the gears are changed automatically, without interruption of tractive power. Intelligent computer units control the transmission and adapt individually to the driving style of the driver in question. These transmissions also have reactive potential, detecting, for example, and uphill gradient or a towed load and adapt individually to the driving style of the driver in question. These transmissions also have reactive potential, detecting, for example, and uphill gradient or a towed load and adapting the shift processes accordingly. As well as the Standard mode, "S", a Winter mode, "W", can be selected. In this mode, upshifts at a lower engine speeds and a suppression of dynamic handling programs, e.g. the dynamic full throttle downshift, reduce the number of difficulties, associated with driving on slippery surfaces. The Touchshift function (Tipfunction) also allows the gears to be selected manually. The selected gear is displayed in the instrument cluster.
AMG Speedshift automatic transmission
Unlike the 5-speed automatic transmission with Touchshift (Tipfunction), AMG Speedshift combines for the first time the convenience of a fully automatic transmission and the dynamism of a manual transmission. The shift program of the automatic transmission with AMG Speedshift function was configured to match the sporty character of Mercedes-AMG vehicles: the shift points and shift logic are geared to the performance map to the relevant high-performance engine, achieving highly responsive gear changes, up to 35% faster than with the standard automatic. The torque-converter lockup is also active from 1st gear, making the car respond even faster to the accelerator in any given driving situation.
The right gear on every bend
The AMG Speedshift transmission also has an active braking downshift function, which is activated by defined deceleration values. This means, for example that the transmission automatically shifts down before bends a sensible function for a sporty driving style. As with the standard automatic transmission, the gear is held on bends taken at speed with a certain lateral acceleration - preventing load-change effects and unnecessary gearshifts. This produces an active and safe driving sensation. In addition, selection of the appropriate gear on exiting the curve allows instant acceleration.
Overtaking made easy
Easy, safe overtaking maneuvers are aided by the "Optimum gear function". Moving the selector lever towards the "-" position and holding it there immediately engages the gear which, irrespective of the speed and engine map, offers the best acceleration values for overtaking. In addition, when driving downhill, this function engages the gear in which the engine braking is most effective.
New transmission functions for other model series The "Optimum gear function" and the braking downshift function have also been integrated in the C-Class automatic transmissions since June 2001 and will be introduced successively to the automatic transmissions of other model series.
The right transmission for every driver
Which transmission suits the customer best is a question that can only be decided in face-to-face discussions followed by a test drive. It is important that the customer is not given the impression that the automated functions of the Sequentronic represent and inexpensive fully automatic transmission. The essential differences between the Sequentronic ant the other transmissions are therefore outlines again here.
6-speed manual transmission vs. Sequentronic
In comparison with the traditional 6-speed manual transmission, the Sequentronic offers a series of functions, which noticeably support the driver. Even the process of moving off is optimized by the automatic, electro hydraulic clutch and gearshift preventing unintended stalling o the engine. In Manual shift mode the gear change is sequential, i.e. reduced to one shift plane (=/-), so shifting errors are no longer possible. All shift commands are passed by and electrical impulse from the selector lever to the transmission; shifting itself is reduced therefore t a minimal movement. Engaging the clutch and declutching is automatic - there is no need for a clutch pedal. When shifting up or down, all gears must be shifted through by briefly nudging the selector lever. The electronic transmission management ignores invalid shift commands, which lie outside the engine speed band. This results in increased road safety and prevents technical damage from the outset.
Which shifts fastest?
The discussion in the specialist press as to whether the fastest gear processes and hence the best acceleration values are achieved with a manual transmission or the Sequentronic is irrelevant to the ordinary car driver. Because while test drivers and racing professionals achieve top values on accelerating with a 6-speed manual transmission, even very skilled ordinary drivers will seldom approach the values of the Sequentronic with a standard manual transmission. With both transmissions the shift process requires time: declutching and engaging the clutch, manual shifting, engaging the gear in the transmission and the associated interruption of tractive power. In terms of normal road traffic, the advantages are on the side of Sequentronic, on the one hand as a result of the short shift time - nudging the selector lever is all that is required - and on the other hand because of the clear gain in comfort, resulting form the omission of the clutch pedal and the simplified shift gate.
Intelligent Sequentronic management supports the driver
The intelligent control electronics also automatically change the gear if the engine speed exceeds or falls below defined levels. This is convenient for the driver because the shift processes are reduced on coasting to a stop and a full-throttle acceleration. The selectable Autoshift mode (A) is also a step towards greater ease of use. Using this, the driver leaves all of the shift work to the control electronics, which significantly eases stress when driving in the city and in stop/start traffic. The control unit recognizes the vehicle's status via the ASR speed sensor and engages the ideal gear according to the position of the accelerator and the load. Here the shift map is designed to support a fuel-efficient driving style. While the manual 5/6-speed transmission can be viewed as the gearshift for price-conscious and for purists, Sequentronic is the right transmission for dynamic, active drivers with an eye on comfort, which likes to shift manually but don't want to forgo a certain level of added convenience.
Sequentronic versus 5-speed automatic transmission with Touchshift
The essential difference between Sequentronic and the 5-speed automatic transmission with Touchshift (Tipfunction ) lays in the shift pauses that Sequentronic requires for every gear change (even in Autoshift mode), and in the noticeable interruption of tractive power associated with these. With a fully automatic transmission, this is compensated for by the use of the torque converter - the gear changes are almost imperceptible to the driver and passengers. In addition, the hill holder function, the choice between the Standard, "S", and Winter, "W", modes and the intelligent control electronics are further components which are designed to relieve the burden on the driver. Drivers who appreciate ease of use will therefore prefer the fully automatic transmission while active drivers will wee the Sequentronic as the ideal choice.