The Technology Behind The New Mercedes-Benz SLS AMG

The Mercedes-Benz SLS AMG has been developed from the ground up. The 'Gullwing' has no predecessor and shares little in common with any other Mercedes model series. The specification essentially set out to combine superlative driving dynamics with hallmark Mercedes safety. The 241‑kilogram lightweight aluminium spaceframe plays a crucial role in achieving this goal. For the first time, the outer skin as well as the complete bodyshell structure have been made entirely out of aluminium – a new milestone for Mercedes-Benz and AMG.

Aluminium has been used more systematically than ever on the new 'Gullwing'. Maximum longitudinal and lateral dynamism and superb steering precision have been achieved not just with an ultra-light yet extremely rigid structure – the best possible conditions for the material aluminium. Optimum static and dynamic flexural and torsional rigidity also plays an important role, along with channelling and transferring extreme longitudinal and lateral forces from the drive train and chassis. The aluminium spaceframe comprises cast aluminium components and aluminium sections. Cast components are used at the force nodes or in areas with high levels of function integration – in other words, wherever high forces need to be transferred or where large components, such as the gullwing doors or the dashboard, are attached.

The cast components offer the advantage of specific dissipation of forces and the opportunity of tailoring the wall thickness locally and individually to load requirements. As a result, higher stiffness required at certain points, such as at the suspension connection points, can be realised. Furthermore, each point of a component only needs to be as thick as necessary, saving weight in areas subject to minimal loads.

Topology optimisation has enabled the cast components to be fine-tuned specifically in terms of weight: ribbed structures run exactly in the load directions; in areas subjected to lower loads, the wall thickness is minimised. Take for example the roof side member: this highly stressed yet weight-optimised cast aluminium component forms the structural load path between the front and rear roof frame, while being used at the same time to anchor the hinges for the gullwing doors.

Torsionally stiff structure weighing just 241 kilograms

Lightweight aluminium sections connect the force nodes to a sturdy structure. The large, low-set cross-sections of these aluminium sections ensure high resistance torque, thus providing the required direct transfer of drive, braking and suspension forces. The structure prevents unwanted flexibility; the vehicle responds rigidly, almost without twisting and directly.

45 percent of the intelligent, weight-optimised aluminium spaceframe is made out of aluminium sections, 31 percent out of aluminium sheet, 20 percent out of aluminium cast and 4 percent out of steel. Maximum occupant safety requires the use of ultra-high-strength, heat-formed steel in the A-pillars. The bodyshell weighs 241 kilograms – an absolute benchmark in the super sports car segment when compared with the peak output of 420 kW/563 hp.

Low centre of gravity and transverse reinforcing struts for superb dynamism

The entire vehicle concept has been designed to achieve a centre of gravity that is as low as possible. This applies both to the low connection of the drive train and axles as well as to the arrangement of the stiffness-relevant bodyshell structure, which has been kept as low as possible. Examples include the rigid flexural and torque connections between the front and rear section and the safety passenger cell, which have been realised consistently using force paths that are as low as possible. This results not only in a low centre of gravity but also a harmonious and, thus, efficient force path in the vehicle structure.

Another prominent feature of the uncompromising lightweight construction design is the transverse reinforcing struts at the front and rear axle that are integrated into the bodyshell structure. The sections connect the side members precisely where the highest forces act upon the bodyshell under dynamic cornering. The advantages of this sophisticated solution include unrivalled transverse rigidity and the absence of heavy secondary stiffening or supports.

Maximum safety with hallmark Mercedes quality

The new 'Gullwing' also meets the very high standards of passive safety traditionally found on Mercedes-Benz vehicles. Consequently, the aim of lightweight design plus outstanding crash performance was geared from the outset to the vehicle's low centre of gravity and the optimum routing of force and load paths. The crash load paths are specifically routed around the passengers – this applies both to front, rear-end and side collisions as well as to roof impacts.

The types of accidents that occur under real conditions formed the basis for the entire bodyshell design: for instance, the continuous side member runs from the front cross-member to the side skirt and routes the impact energy into the extremely rigid sill structure in a frontal collision. Upshot: the passenger cell does not deform during the standard frontal impact tests. A typical feature of the 'Gullwing' is the engine arrangement as a front-mid engine. Its position behind the front axle creates a large deformation zone in front of the engine. This in turn enables a reduced weight bulkhead to be fitted, since it needs to absorb far less energy in the event of a frontal crash than on a vehicle with a conventional engine position. The torque tube, which connects the engine to the dual-clutch transmission located at the rear axle, also improves crash safety: both in the case of a frontal and rear-end collision, the torque tube takes the stress off the bodyshell structure because it can specifically absorb and transmit impact energy.

Sophisticated computer simulations helped optimise all the structure components. To make doubly sure, over 1000 computer-simulated complete vehicle crash tests were conducted. The aim was to achieve outstanding crash performance with low weight. The relevant structural cross-sections were dimensioned for all the load paths in line with load considerations. Variables included the geometric design of the load paths and the selection of the most suitable aluminium alloys for each component in terms of energy absorption, stiffness and strength. At the same time, the selection of optimum bonding technology and the consistent stipulation of wall thickness for each component, taking into account loads when driving and during a crash, were also crucially important.

State-of-the-art restraint systems with eight airbags

The state-of-the-art restraint systems provide the perfect complement to the high-tech body structure. Occupants in the SLS AMG enjoy standard-fit three-point seat belts with belt tensioners and belt force limiters. This equipment is rounded off with eight airbags: two adaptive airbags for the driver and front passenger, a kneebag for the driver and front passenger, two sidebags integrated in the seats and two separate windowbags deployed from the door waist rail.

During development, the super sports car underwent over 35 crash tests; additional component tests were carried out as a double check. The new Mercedes sports car naturally meets all specific national impact configurations required for certification. Added to which are all the existing ratings and consumer tests as well as the particularly demanding in-house crash tests, some of which push the car far beyond any applicable legal requirements. Each vehicle must pass all these tests before receiving the highest accolade of vehicle safety: the Mercedes star.

Exclusive hand-built production

The aluminium spaceframe and body are hand-built in compliance with the most stringent quality standards. Highly qualified specialists put together the aluminium components using cutting-edge techniques. Depending on requirements, a suitable joining technology is used – rivets, bonding, soldering and bolts. And just as you would expect from a new Mercedes-Benz car: the highest precision during production guarantees optimum production and product quality.

Design and development

Virtual and real – digital and genuine prototypes promote the highest standards

For the first time in its 40-year-plus history, Mercedes-AMG GmbH has assumed full responsibility for the design and development of a completely new vehicle. The experience gained in over four decades of motor racing, plus the huge know-how in building top-class performance cars as well as joint development with selected Mercedes-Benz development departments at the Mercedes Technology Center (MTC) in Sindelfingen provide absolutely solid foundations for this undertaking.

Exhilarating driving dynamics and hallmark Mercedes everyday practicality – these attributes are a core part of the specification for the Mercedes-Benz SLS AMG. The Mercedes-AMG specialists at the Affalterbach location turn to cutting-edge simulation programmes and extensive test drives across all continents to realise these ambitious objectives. The design and development of the new super sports car was approved at the end of 2006.

Before the first 'genuine' prototype is produced, the virtual prototypes must first get up to speed. The new 'Gullwing' was initially brought to life on the computer – as a digital prototype (DPT). Painstaking analysis helps determine how the objectives for the new super sports car can be met. Whether it is weight distribution, engine position, centre of gravity, suspension design, driving dynamics, aerodynamics, ergonomics, crash performance or production process – state-of-the-art simulation programmes enable the vehicle and all its characteristics to be modelled realistically. The digital prototype is thus a complete virtual car.

Digital prototype provides the basis for initial development prototypes

The digital prototype also helps to plan and develop the first ready-to-drive development prototypes, in other words cars that are fitted with the first engineering components such as engine, brakes or suspension, the so-called mulettos. Thanks to the virtual preliminary work, the test vehicles used since spring 2007 were already highly mature from the off. State-of-the-art measurement systems in the vehicles provide useful data, such as the temperature of the engine oil, coolant and brake discs – the focus, however, may also be on lap times, such as on the North Loop of the Nürburgring, as well as measureable, precisely defined driving dynamics manoeuvres to compare various axle kinematics variants, or spring and damper variants.

Since summer 2008, the first 'genuine' camouflaged prototypes of the SLS AMG have been undergoing testing around the world. Whether it is the air conditioning system, tyres, suspension, engine cooling system, dynamic handling control systems or brakes: the meticulous standardised AMG development and testing programme on test circuits and racetracks, Alpine passes and specifically defined public roads promotes consistent further development and troubleshooting – and thus reliably delivers the highest possible quality. Over 40 vehicles are permanently in use at the same time.

Key testing stages at a glance:

Development of engine, transmission, drive train, air conditioning system

• Altitude testing in Denver, Colorado (USA), Lesotho (South Africa), Mont Ventoux (France) and Granada (Spain)
• High-temperature testing in Death Valley, California (USA), in Upington (South Africa), Idiada test facility (Spain) and Phoenix, Arizona (USA)
• Test drives in Los Angeles, California (USA)
• Low-temperature testing in Arctic Falls and Arjeplog (Sweden)
• Testing in the climate tunnel in Stuttgart

Development of cooling and fuel system

• Various test drives on the high-speed circuits in Nardo (Italy), Laredo (Texas) and Papenburg (Germany)
• Testing in Upington (South Africa) and in Death Valley, California (USA)
• Testing in the wind tunnel in Stuttgart

Development of brakes and control systems

• Testing of the brake system on the high-speed circuit in Nardo (Italy) and on the Großglockner Pass (Austria)
• Testing of dynamic handling control systems at the Idiada test facility (Spain),

Arjeplog (Sweden) and Boxberg proving ground

At the same time, individual components such as the engine, drive train, transmission, suspension and brakes, as well as the entire body structure are also being tested to the limits on test rigs.

Accelerated endurance testing under gruelling conditions

Endurance testing complements the extensive vehicle development; it simulates and compresses the entire (and particularly punishing) vehicle lifetime into a short period. The aim is to ensure a high degree of maturity before vehicle production starts in the Mercedes-Benz plant in Sindelfingen. 

Endurance testing at a glance:

Endurance testing on a mixture of public roads:

• Testing of interaction of all components and systems in everyday use. This test phase calls for the vehicles to be loaded to the permissible gross vehicle weight and to follow a precisely defined test programme comprising country roads, motorways and urban roads

'Heide' endurance testing (named after the poor post-war roads across the 'Lüneburger Heide'):

• Developers focus on the durability of the suspension components, the entire body and the integral subframe to which the front axle, steering and engine are attached. The test vehicles are loaded up to the permissible gross vehicle weight

Accelerated endurance test:

• Whole vehicle testing focussing on drive train and suspension. Particular feature of the AMG programme: 10,000 kilometres on the North Loop of the Nürburgring and 10,000 kilometres on urban roads

Full-throttle endurance test:

• Extreme acceleration and deceleration sequences with extensive full-throttle operation; places high level of stress on cooling, fuel supply and braking systems

Global endurance test:

• Whole vehicle testing focussing on drive train, suspension

and body

Corrosion endurance test:

• Corrosion testing on the entire vehicle simulates the toughest dynamic and climatic conditions

Final board approval:

• Overall review of development and production maturity

Around 30 Mercedes-Benz SLS AMG test vehicles will clock up some 1.25 million test kilometres before development finishes in January 2010. The ultimate goal is 'final vehicle approval' – production of the first customer vehicles, the long awaited 'job No. 1' can begin.