Mercedes Benz

OFFICIAL PRESS RELEASE

San Diego, USA, Jan 14, 2011

Power transmission: Maximum driving pleasure, reduced consumption

RACE START, double-declutching function, seven gears, four transmission modes and stop/start function: the power transmission of the new CLS 63 AMG combines extreme emotional appeal, maximum driving pleasure and optimum economy. The AMG SPEEDSHIFT MCT 7-speed sports transmission excites with a combination of unique options which no other automotive manufacturer is able to offer in this format.


The AMG SPEEDSHIFT MCT 7-speed sports transmission is exclusive to Mercedes-AMG and combines the sporty, direct and agile responsiveness of a manual transmission with the maximum comfort of an automatic transmission. MCT stands for Multi-Clutch Technology and indicates that only clutch elements are employed to perform gearshifts. A compact wet start-up clutch, which runs in an oil bath, replaces the conventional torque converter. Thanks to its low rotational inertia, the transmission responds instantaneously and dynamically without the losses typical of a torque converter transmission – thereby helping to save fuel. The AMG sports transmission also impresses with its low weight of just 80 kilograms, which has been made possible through the use of lightweight magnesium for the transmission housing. Vibrations are effectively eliminated by a new, two-stage torsion damper, with resulting benefits in perceived passenger comfort.

Stop/start function fitted as standard

As already featured in the S 63 AMG and CL 63 AMG, the Controlled Efficiency stop/start function is also fitted to the CLS 63 AMG as standard. This system is permanently active in the consumption-optimised "Controlled Efficiency" (C) driving mode. Once the driver comes to a halt e.g. at a red traffic light or in a traffic jam, the engine is automatically switched off. Once the brake pedal is released or the accelerator is depressed, the engine is immediately restarted and the car is able to move off quickly. Intelligent technology guarantees a comfortable and immediate starting procedure: a crankshaft sensor which recognises the direction of rotation registers the resting position of all eight pistons. For an automatic engine start, the cylinder with the most favourable piston position receives an injection of fuel into its combustion chamber. The precise piezo-electric injectors greatly assist this process, as they make particularly fast starts possible.

The engine management ensures that the engine is only switched off if certain preconditions are met. The starter battery must have sufficient charge, for example, and the engine must be at the necessary operating temperature for efficient emissions control. The same applies to the interior temperature selected by the driver: if this has not yet been reached, the engine is not switched off when the car comes to a stop. The onboard network management system makes sure that active audio, telephone or video functions are not interrupted by the stop/start function.

A green "ECO" symbol shows the driver when the stop/start function is active. Should one of the above criteria be preventing activation of the system, this is shown in the central display by the message "Start/stop inactive" and a yellow "ECO" symbol. In the more performance-oriented driving modes "S" (Sport), "S+" (Sport plus) and "M" (Manual), the start/stop function is always deactivated.

Consumption-optimised Controlled Efficiency ("C") drive mode

When adapting the MCT sports transmission to the AMG 5.5-litre V8 biturbo engine, the AMG engineers paid special attention to the new driving mode Controlled Efficiency ("C"). The emphasis was on delivering minimum engine speed in the highest possible gears in all driving situations. When moving off in "C", the transmission always selects second gear and shifts decidedly early to the next higher gears if the driving style permits. At 60 km/h for instance, sixth gear will already be engaged – not only improving fuel consumption but also noise levels. Thanks to its powerful, readily available torque even at low engine speeds, the AMG V8 biturbo unit is absolutely ideal for this style of driving. Controlled Efficiency also means convenient gearshifts and a "soft" accelerator response set-up for outstandingly smooth power transfer. The use of a new low-friction oil as well as the implementation of further detailed measures in the AMG SPEEDSHIFT MCT 7-speed sports transmission enhance the efficiency and ensure an additional reduction in consumption.

The eight-cylinder biturbo engine also features a generator management system: whenever the engine is on the overrun or when braking, kinetic energy is used to charge the battery rather than being wasted as heat in the usual way. In all other operating modes a combination of onboard network and generator management enables the generator to be kept at a low voltage. This reduces the load on the engine and makes for fuel savings of around 0.15 litres per 100 kilometres according to the NEDC standard, and up to 0.2 litre per 100 km in city traffic with its frequent overrun and braking phases.

Drive modes "S", "S+" and "M" for even more driving pleasure and dynamism

In addition to Controlled Efficiency ("C"), three transmission modes are available to meet the demands of drivers looking for a more dynamic ride: in "S" (Sport) mode, the engine and transmission take on a much more agile character. Accelerator pedal movements trigger a more direct traction response, making the downshifts more spontaneous. The engine speed is allowed to reach a higher level in each gear, while the gearshifts in "S" are around 25 percent faster than in "C". Turning the rotary switch in the AMG DRIVE UNIT a notch further to the right activates "S+" mode. Sport plus shifts the gears another 25 percent faster than in "S". The same applies to the manual shift mode "M". In "S+" and "M" modes, gearshifts at full throttle take just 100 milliseconds.

The engine management system partially suppresses cylinders in "S", "S+" and "M" modes: precisely interrupting ignition and injection under full load for brief periods leads to even faster gearshifts than before. The highly emotional vocals are an appealing side effect of this lightning-fast process.

Ultra-fast, spontaneous multiple downshifts are another forte of the AMG SPEEDSHIFT MCT 7-speed sports transmission. For instance, kickdown allows gearshifts straight from seventh down to fourth gear, or from fifth to second. In the "S", "S+" and "M" driving modes the automatic double-declutching function is active. Every manual or automatic downshift is accompanied by precisely metered double-declutching – with increasing intensity from "S" through "S+" to "M". And this not only adds to the driver's emotional experience: the load-free downshift minimises load-change reactions, which pays particular dividends when braking into bends – and also enhances safety in the wet or on ice.

No automatic downshifts in manual "M" mode

In manual “M” mode the driver also benefits from the high torque of the V8 biturbo engine, as there is no automatic downshift under full load and kickdown; the transmission remains steadfastly in the selected gear. Moreover, the 7-speed sports transmission does not perform an automatic upshift in manual mode when the rev limit is reached. In “M” mode the AMG instrument cluster displays the current gear and alerts the driver to the need for an upshift just before the needle reaches the red zone. This means that a particularly sporty driver can use the superior performance potential to its fullest extent. When approaching the lower rev limit, e.g. when braking the vehicle, there is an automatic downshift to the next lower gear.

The powerful electronic transmission control unit with integrated 80 MHz processor controls spontaneous downshifts – for example if the driver suddenly needs power for dynamic acceleration.

AMG DRIVE UNIT with RACE START function

The AMG DRIVE UNIT is the central control unit for the AMG SPEEDSHIFT MCT 7-speed sports transmission and all driving dynamics functions. On the left next to the selector lever is the electronic rotary switch to select the four drive modes including activation of the RACE START function. Underneath are three buttons for additional functions: the first controls the 3-stage ESP®, the second the AMG RIDE CONTROL sports suspension.

The third, bearing AMG lettering, is used to store the personal set-up. Briefly pressing the AMG button brings up the configuration options, whilst holding down the button allows you to program the required set-ups - this is confirmed by an audible signal. The current settings may be viewed in the AMG instrument cluster by pressing the AMG button at any time.

The RACE START function delivers maximum dynamism: while the vehicle is at a standstill, the driver can activate the ESP® sports function and press the brake pedal with their left foot. Having preselected the RACE START program using the rotary switch, a confirmation message comes up on the AMG central display. The driver then simply needs to confirm the RACE START function by pulling the “Up” shift paddle once, fully depressing the accelerator and taking his foot off the brake. The optimum start-up engine speed is set fully automatically and the CLS 63 AMG accelerates away with flawless traction – all the way up to top speed, if so required. The driver does not need to shift gear manually; the AMG transmission changes gear with lightning-fast shift times.

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