The new AMG SPEEDSHIFT MCT 7-speed sports transmission guarantees an exceptional emotional experience and sheer driving pleasure. Equipped with seven gears, three driving modes and a double-declutch function, the power transmission of the new CL 63 AMG represents sheer emotive appeal. At the same time it makes a considerable contribution to fuel economy – and specifically in combination with the Controlled Efficiency drive mode with stop/start function and generator management included as standard features. Accordingly the AMG MCT transmission impresses with a combination of unique functions which no other manufacturer offers.
The AMG SPEEDSHIFT MCT 7-speed sports transmission is an innovative
power transfer system that made its debut in the high-performance SL 63 AMG Roadster in 2008. It combines the sporty, direct and agile feedback of a manual transmission with the maximum convenience of an automatic transmission. Featuring seven gears, three driving modes and a double-declutch function, the 7-speed sports transmission offers superb versatility. 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.
Consumption-optimised Controlled Efficiency (“C”) drive mode
During its development and adaptation 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 coupled with a reduced number of gearshifts in all driving situations. When moving off in “C”, the MCT 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.
Controlled Efficiency stop/start function as a new feature
The Controlled Efficiency stop/start function is also being used in an AMG model for the first time. This system is standard equipment in the CL 63 AMG, and permanently active in the fuel economy driving mode “C”. Once the driver comes to a halt e.g. at a red traffic light, the V8 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 in the AMG main menu shows the driver that the Controlled Efficiency 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 “Stop/start inactive” and a yellow “ECO” symbol. In the two more performance-oriented driving modes “S” (Sport) and “M” (Manual), the start/stop function is always deactivated. If required, the driver can also switch it off while in “C” mode as well.
The eight-cylinder biturbo engine also features a new 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” and “M” for even more driving pleasure and dynamism
The engine and transmission come across as much more agile in the “S” (Sport) mode. 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 are around 25 percent fasterthan in “C”. In the manual shift mode “M”, gearshifts at full throttle take just 100 milliseconds, a reduction of 50 percent compared to “C”. In “S” and “M” modes, the engine management system partially suppresses the cylinders: interrupting ignition and injection under full load 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” and “M” driving modes the automatic double-declutching function is active. Every manual or automatic downshift is accompanied by precisely metered double-declutching – incrementally from “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 AMG MCT
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 gears can be shifted using the steering wheel shift paddles – whatever the driving mode. The electronic key for selection of the three driving models is located to the left of the COMAND controller. The powerful electronic transmission control unit with its integrated 80 MHz processor guarantees immediate downshifts – for example when approaching traffic lights or if the driver requires fast acceleration when overtaking.
The Direct-Steer system, Torque Vectoring Brake and crosswind stabilisation are the three new systems available as standard on the CL 63 AMG with immediate effect. In combination with the AMG sports suspension and AMG high-performance braking system, these unique high-tech systems provide the highest level of driving dynamics, ride comfort and active safety.
Less steering effort, more agile handling with the same outstanding straight-line stability – the Direct-Steer system in a nutshell, which is now fitted as standard to the CL 63 AMG. A key feature of the Direct-Steer system – which is well-known in the S-Class – is the variable-ratio steering rack that operates using purely mechanical means. While the power steering around the central position utilises an indirect ratio to promote excellent straight-line stability, this alters from a steering angle of around five degrees: really small steering angles are all it takes to perform precise cornering, noticeably improving handling on winding country roads. The steering angle requirements have also been modified, enabling the driver to steer the AMG Coupé far more easily, particularly on urban roads. Compared with a steering system with a constant ratio, the number of revolutions from lock to lock is reduced by around 25 percent with the Direct-Steer system.
Another advantage of the purely mechanical Direct-Steer system is the absence of any elaborate actuators and complex sensors – with associated benefits in terms of weight, installation space and susceptibility to faults. The constant steering response is also advantageous compared with other variable steering systems that sometimes require the driver to adapt quickly to what are fast changing situations on the road.
The Direct-Steer system is based on the familiar speed-sensitive power steering system which reduces the power assistance as the road speed increases. Easy manoeuvrability on urban roads where large steering angles and thus a great deal of power assistance is required, is coupled with reduced support at high speeds, say on the motorway – all of which improves straight-line stability and handling safety.
Torque Vectoring Brake optimises driving dynamics and handling safety
A further improvement in driving dynamics as well as active handling safety comes courtesy of the Torque Vectoring Brake. If the Electronic Stability Program ESP® detects the onset of understeer, short one-sided braking intervention on the vehicle’s inside rear wheel generates a specific yawing moment around the vehicle’s vertical axis within a fraction of a second. Consequently, the AMG CL-Class handles precisely and remains under control at all times as well as also bolstering active handling safety by reducing the tendency to understeer.
Automatic crosswind stabilisation as standard
The AMG sports suspension based on Active Body Control (ABC) also comes as standard with automatic crosswind stabilisation. The ABC control electronics vary the wheel load distribution so that the effect of crosswinds is virtually compensated for or reduced to a minimum. If the CL 63 AMG is affected by a crosswind, the ABC control unit utilises the yaw-rate, lateral acceleration, steering angle and speed sensors of the Electronic Stability Program ESP® to trigger diagonal wheel load distribution instantly – for instance on the left front and right rear wheel. The associated steering effect reduces the effect of the crosswind. Crosswind stabilisation is activated at speeds above 80 km/h while travelling in a straight line or on slight bends. The function is deactivated if the driver himself makes heavy, brusque steering corrections.
The AMG sports suspension all but entirely eliminates the body movements that occur when moving off, cornering and braking. Bends are negotiated with far less roll; the body roll caused by fast evasive manoeuvring is effectively suppressed. Other notable features of Active Body Control are the variable roll moment distribution between the front and rear axles, which the system carries out automatically according to the speed. The computer uses various acceleration sensors to obtain information on the current driving situation and compares this data with those from the pressure sensors in the spring struts and the level sensors on the control arms. The system then computes the control signals that the servo-hydraulic valves at the front and rear axle transform into precisely metered flows of oil.
Briefly pressing the Sport button next to the AMG instrument cluster changes the characteristics of the AMG sports suspension: the roll angle through fast corners is reduced further, the shock absorbers and springs also respond firmer to promote agility. At speeds of between 65 and 100 km/h, ABC automatically lowers the body by as much as 15 millimetres to reduce wind resistance. If more ground clearance is needed when driving on poor road surfaces, the level of the vehicle can be raised by 40 millimetres at a speed up to 30 km/h by simply pressing a button.
Thanks to so-called loading adjustment, the active suspension control also takes the current vehicle weight into account as part of its calculations. As such the CL 63 AMG is able to achieve identical levels of driving dynamics when in a laden condition too.
AMG high-performance compound braking system based on ADAPTIVE BRAKE
Based on the ADAPTIVE BRAKE system, the AMG high-performance braking system continues to set the benchmark for stopping power, sensitivity and fade resistance. The front axle features a double floating brake calliper; this technology combines the advantages of a sliding-calliper disc brake – reduced heat transfer to the brake fluid and clear advantages in terms of comfort thanks to the brake lining guide mechanism – with the efficiency of an extra large fixed calliper brake. At the rear, braking is handled by a large sliding frame-type calliper. Internally ventilated, perforated composite brake discs at the front and rear with a diameter of 390 and 365 millimetres respectively ensure the shortest stopping distances, remarkable resistance to fading and outstanding sensitivity.
The hydraulic dual-circuit braking system is controlled electronically, permitting the inclusion of numerous driver assistance functions that improve safety and comfort – such as “priming” the braking system in critical situations: if the driver suddenly switches from the accelerator to the brake pedal before emergency braking, ADAPTIVE BRAKE increases the pressure in the brake lines and applies the pads to the brake discs, so that they can grip instantly with full force when the brake pedal is pressed. In wet weather, the system injects regular, short brake impulses to ensure that the film of water on the brake discs is wiped off and the brakes can work as effectively as possible. This automatic brake-drying function is always activated when the windscreen wipers have been in operation for a certain time; the driver does not notice the finely metered braking impulses.
After the CL 63 AMG has been braked to a standstill, briefly pressing the brake pedal a little further is all that is required to activate the HOLD function. The coupé is then held by the brakes, even if the driver’s foot comes off the brake pedal. In this way ADAPTIVE BRAKE prevents the car from rolling forward inadvertently when stopped at traffic lights or stuck in stop-and-go traffic, and from rolling back when facing a slope. The HOLD function is deactivated automatically when the car moves off.
Attractive light-alloy wheels featuring a new AMG triple-spoke design
AMG light-alloy wheels featuring a new triple-spoke design and painted in titanium grey with a high-sheen finish provide the contact with the road. 255/40 ZR 19 tyres are fitted on 8.5 x 19 wheels at the front, while 275/40 R 19 tyres are combined with 9.5 x 19 wheels at the rear.
Exclusive optional extras from the AMG Performance Studio include AMG double-spoke forged wheels, painted in black and polished. The dimensions are: 255/35 R 20 tyres on 8.5 x 20 wheels (front) and 275/30 R 20 tyres on 9.5 x 20 wheels (rear).
