During The Development And Testing Phase

High-performance drive and power transmission systems call for high-tech suspension and braking systems. In this area too the SL 63 AMG is able to fulfil all of the expectations which are made of it. As with the body, the experts from Affalterbach also turned to aluminium for the AMG sports suspension too. The steering knuckles and spring links on the 4-link front axles are therefore also made of aluminium, as are virtually all of the suspension parts on the multi-link independent rear suspension. The integral support frame for the front-axle halves, steering gear and engine is also produced in aluminium. Driving dynamics also feature as part of AMG's new design. The sports suspension based on Active Body Control (ABC) has come under the spotlight. During the development and testing phase, active suspension control was specially optimised in terms of cornering performance. Basically the ABC suspension all but entirely eliminates the body movements that occur when moving off, cornering on uneven road surfaces and braking. Bends are negotiated with far less roll; the body roll caused by fast evasive manoeuvring is effectively suppressed.

The control elements of this system are the damper struts, in which a hydraulic servo cylinder is arranged in series with the steel spring. By retracting and extending, this cylinder actively adjusts the length of the spring and therefore the spring force of the damper strut. As a result, conventional torsion-bar stabilisers can be dispensed with on the front and rear axles. High-performance control electronics in permanent dialogue with the engine and transmission control unit ensure that the forces of the four damper struts are adapted practically instantly. A new feature is the visual ABC display in the COMAND system menu: driver and front passenger can monitor the individual actions of the active suspension control on each of the wheels in real time. As an option, the AMG performance suspension is also available for the SL 63 AMG from the AMG Performance Studio. Damper characteristics can be made stiffer by up to 30 percent in both modes. This provides for even less body movement and is recommended when striving for high-speed laps on a closed-off racing circuit, for example.

Another notable feature of Active Body Control is the variable roll moment distribution between the front and rear axles, which the system carries out automatically according to the driving situation and 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. In addition, the SL 63 AMG is fitted with hydraulic all-round self-levelling which helps to ensure a constant vehicle level irrespective of the load being carried. One new development is the electromechanical AMG speed-sensitive sports steering: with its constant and direct ratio of 14:1, it enables a sporty response from the central position and supports the vehicle's largely linear understeer/ oversteer characteristics. The result is light-footed, agile cornering behaviour and clear feedback at critical limits.

And that is not all: for the first time, the top-of-the-range AMG model features power assistance which adapts according to the suspension mode. In "Comfort" mode, the AMG speed-sensitive sports steering responds comfortably, with a higher degree of steering assistance. In "Sport" mode on the other hand, the driver feels less steering assistance - which translates into an improved sense of road feel. This benefits both response and steering precision, particularly at high speeds and when adopting a sporty driving style. In addition to more precise steering and a more comfortable feel at the wheel, the new electric power steering offers a range of additional advantages. It makes an important contribution to efficiency, since the steering assist function only requires power when the driver actually steers. Compared with the previous model with regular hydraulic power steering, this enables savings of up to 0.3 litre/7 g CO2 per 100 km (NEDC combined) to be achieved.

In the new steering system the steering gear and the supporting servo-motor form a single compact unit and are mounted on the integral support frame made of aluminium and positioned in front of the wheel's centre line. As previously, the SL 63 AMG offers 3-stage ESP as standard: the Electronic Stability Program supports three individual control strategies at the push of a button. The ESP button in the AMG DRIVE UNIT allows the driver to choose between "ESP ON", "SPORT Handling" mode, and "ESP OFF" - with the currently active mode shown in the display of the AMG instrument cluster. In "ESP ON", the onset of handling instability leads to braking intervention at one or more of the wheels, accompanied by a reduction in engine torque. Briefly pressing the ESP button activates "SPORT Handling" mode. In this mode the braking intervention to counter oversteer or understeer, as well as the accompanying reduction in engine torque, allows a higher dynamic threshold and, for instance, corresponding drift angles - the driver benefits from significantly enhanced driving enjoyment. As soon as the driver operates the brake pedal, all of the normal ESP functions are restored.