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MERCEDES-BENZ SLR MCLAREN ROADSTER - THE ULTIMATE CONVERTIBLE

Cutting-edge technology
In the mid-1950s, the Mercedes-Benz SLR acquired a hallowed status in the world of motor racing. Quite apart from its long list of legendary race victories, its avant-garde technology and thrilling design instantly transformed it into a blueprint for all high-calibre Gran Turismo touring cars. The new Mercedes-Benz SLR McLaren Roadster, which will be receiving its world premiere in autumn 2007, is likewise rife with charisma and technology that is ahead of its time. Just like today's Formula 1 racing cars, the Mercedes-Benz SLR McLaren Roadster boasts a carbon-fibre construction that gives it very high levels of safety and exceptional torsional stiffness on a par with the Coupé version. This combines with a chassis with motorsport origins to produce outstanding handling characteristics. The 460-kW/626-hp AMG supercharged V8 engine under the bonnet of the new high-performance sports car propels it to a top speed of 332 km/h, matching the outstanding mark set by the Coupé. Despite the fact that the Roadster comes with a fully retractable soft top to fuse pure open-air driving bliss with the ultimate in performance, by no means do its occupants have to compromise on comfort or everyday practicality. The new Roadster thereby succeeds in taking driving culture and motoring pleasure into a whole new dimension for open-top super sports cars.

The SLR McLaren Roadster is bound to carve out a very special name for itself amongst the ranks of high-performance open-top sports cars. This is thanks to its motor-racing genes and the use throughout of high-tech materials that - despite all their inherent benefits - are generally only ever found in a few individual components of even premium series-production cars, if at all, due to the high costs and elaborate manufacturing processes involved.

This is particularly true of the high-strength yet lightweight carbon-fibre composite materials (CFRP) that are used. Mercedes-Benz and its Formula 1 partner, McLaren, have gathered many years of experience with this material that is conventionally used in the aviation and space industries. In an impact, carbon fibres have a level of energy absorption that is four to five times higher than that of steel or aluminium, while the weight advantage of this high-tech material over steel is around 50 per cent.

The new high-performance Roadster capitalises on all of these benefits. The complex carbon-fibre technology has furthermore undergone intelligent redevelopment for the Roadster's monocoque. The result is low weight as well as exemplary energy absorption courtesy of unique carbon-fibre crash structures, which translates into excellent occupant safety, plus a level of torsional stiffness that is unprecedented for an open-top car. This gives rise to the sort of scintillating performance that is normally the preserve of super sports cars with a fixed roof.

Puristic soft top designed for high speeds
The SLR McLaren Roadster's exceptional credentials are given a further boost by the fully retractable soft top that blends seamlessly into the vehicle's flowing lines. The newly developed material it is made from not only promises everyday practicality in all weathers, it also enables the high-performance sports car to attain speeds which are highly unusual for a roadster. For example, the top speed of 332 km/h with the roof up matches the extraordinary figure set by the Coupé. When driving with the top down, the vehicle's favourable aeroacoustics still allow the occupants to converse with one another at speeds far in excess of 200 km/h.

The roof opens and closes semi-automatically in around ten seconds, thereby harmonising the desire for supreme convenience with the Roadster's purist character. To open the roof, the driver simply has to release the catches in the roof frame and lift it up slightly before the electrohydraulic mechanism folds it together. The aluminium bow integrated into the front section of the roof forms a stylish cover for the soft top when it is folded down. A high standard of safety comes in the form of steel-reinforced A-pillars and two fixed rollover bars.

Streamlined aerodynamics and racing suspension
The Roadster's handling, aero acoustics and aerodynamics were carefully honed for high-speed driving in the wind tunnel. It borrows the same aerodynamic concept already familiar from the Coupé, comprising an airbrake incorporated into the boot lid, an encapsulated under body, as well as a diffusor in the rear bumper for generating maximum downforce.

In order to obtain optimum weight distribution for flawless handling dynamics and high braking stability, the Mercedes-Benz SLR McLaren Roadster is designed as a front-mid-engined sports car with the drive unit placed behind the front axle. Its AMG supercharged V8 engine, featuring air-to-water intercooler, three-valve technology, dry-sump lubrication and four metal catalytic converters, is installed in a low-set position for a correspondingly low, and therefore favourable, centre of gravity. Coupled to an AMG Speedshift R five-speed automatic transmission, the power unit's 460 kW/626 hp and peak torque of 780 Nm launch the Roadster from 0 to 100 km/h in a fleeting 3.8 seconds.

The open-top two-seater is equipped with a suspension that was bred on the race track, an electro hydraulic brake system, as well as high-endurance carbon-fibre/ceramic brake discs which offer optimum braking performance, thermal resistance and durability.

High-tech materials for excellent torsional stiffness and exemplary occupant protection

Carbon-fibre-reinforced body, ceramic brake discs
Rigidity and crash safety of the highest order
Comprehensive safety system with adaptive front airbags

Many things seem impossible - until someone proves otherwise. The new Mercedes-Benz SLR McLaren Roadster rebuts a long-standing prejudice, by demonstrating that an open-top high-performance sports car can be every bit as torsionally stiff as a closed coupé. The proof of this is outstanding handling characteristics and undiluted open-air driving pleasure to way beyond the 300 km/h mark, paired with excellent comfort on long journeys and unrestricted practicality for day-to-day driving, which together makes the new Roadster an open-top super sports car with a difference.

Underpinning all of this is the systematic and intelligent use of high-tech materials for the body and safety technology. As in the Coupé, the body shell of the high-performance Roadster, including the front-end and rear-end structure, the passenger cell, the swing-wing doors and the bonnet, is made entirely from carbon-fibre-reinforced plastic. This lightweight yet extremely rigid material originated in the aviation and space industries and has also proven its benefits in today's Formula 1 racing cars. Compared to steel, the high-tech material represents a weight saving of around 50 per cent.

Scientists at DaimlerChrysler Research played an instrumental role in the development and transfer to series production of carbon-fibre materials in the aviation industry, where they are used predominantly for fins, rudders and landing flaps. Quite apart from this, the experts at Mercedes-Benz and McLaren have gained extensive experience with this exotic material, as well as acquiring tremendous expertise in its processing, from their work on racing cars. This invaluable know-how has also been put to good use in the new Mercedes-Benz SLR McLaren Roadster, whose entire body harnesses the benefits of carbon-fibre-reinforced plastics (technical abbreviation: CFRP). Only the two engine mounts are made from aluminium. Even in super sports car circles, such extensive use of this expensive, high-tech material is still somewhat of an exception.

Carbon-fibre materials for low weight and high torsional stiffness
Mercedes-Benz and McLaren opted for widespread use of CFRP because of the evident beneficial effects carbon fibres have on rigidity and energy absorption. What's more, components made from this material weigh up to 50 per cent less than comparable steel components offering the same strength and as much as 30 per cent less than aluminium components. This makes CFRP the material of choice for manufacturing high-performance cars, because lower weight not only means lower fuel consumption but also outstanding transfer of power to the road. The lower the mass that has to be accelerated and braked, the better the agility. Owing to the consistent use of carbon-fibre-reinforced plastics, the primary structure of the Mercedes-Benz SLR McLaren Roadster is indeed considerably lighter than the conventional steel construction of a comparable front-mid-engined vehicle.

Intelligent advance in carbon technology
Compared to the Mercedes-Benz SLR McLaren, which marked the first ever use of carbon-fibre technology to such a large extent in series car production, the way in which the material is applied has undergone further advancement for the Roadster. By optimising the arrangement of the different layers of carbon-fibre matting, the engineers were able to minimise the unavoidable weight increase produced by the Roadster's roof without any loss of strength. This allowed the high-performance Roadster to retain an exceptionally high, coupé-like level of torsional stiffness that is unprecedented for a cabriolet but without any significant increase in weight, despite the mechanism for the soft top.

The roof's design meant there were other components in the Coupé that the design engineers were unable to transfer directly either: the A-pillars with their integral steel reinforcements, as well as the windscreen frame, the rear wings, the boot lid and the swing-wing doors have all been redesigned, although they continue to be made from carbon-fibre-reinforced material of course. In contrast to the Coupé, the unmistakable swing-wing doors inspired by the legendary SLR racing car from 1955 - or the Uhlenhaut Coupé as it is affectionately known - have a frameless design on the new Roadster so as not to lose any of that open-air driving sensation. As on the Coupé, the doors are attached to the front roof pillars and swing forwards and upwards through an angle of 107 degrees when they open. This door concept makes for a sensational appearance.

CFRP achieves high energy absorption capacity
Apart from their extreme stiffness, the state-of-the-art carbon-fibre-reinforced materials are also renowned for their excellent energy absorption. The absorption capacity is around four to five times higher than that of metallic materials. Formula 1 constructors have been exploiting this quality for several years, manufacturing the crash structure of their racing cars from CFRP. It is primarily as a result of this that the risk of injury in high-speed accidents in this Blue Riband motorsport event has dropped significantly.

The monocoque - or, to put it another way, the passenger cell - of the new Mercedes-Benz SLR McLaren Roadster is also made entirely from this high-tech material. In the event of a head-on, side-on or rear-end collision, it offers the passengers a highly rigid and hence secure survival space.

The new A-pillar, with its additional internal reinforcement in the form of a high-strength steel tube, also has a role to play here. The arrival of the Mercedes-Benz SLR McLaren Roadster thereby marks the series-production debut of a highly complex steel/carbon-fibre compound that combines high strength with the elasticity required for safety reasons. Fixed rollover bars behind the seats complement the safety concept. They ensure the passengers are afforded an outstanding level of protection even if the vehicle should turn over.

Carbon-fibre crash elements in the front structure
At the rear, two internal side members made from laminated carbon fibre and a robust cross member assume the task of energy absorption in the event of a crash. In an impact from the side, the occupants are protected by the broad, low-set sills containing multi-shell deformable elements made from specially reinforced carbon-fibre materials as well as two aluminium sections incorporated into each door. The sturdy shell of the SLR seats also has a protective function in a rear-end or side-on collision and is likewise built from highly resilient carbon-fibre material.

It is in the front structure of the SLR body shell that the impressive safety properties of the innovative fibre composite are particularly evident. Here, two conical carbon-fibre-reinforced plastic elements - each approximately 620 millimetres in length, weighing just 3.4 kilograms and consisting of an encased inner web - are enough to absorb the full impact energy in a defined frontal collision without exceeding the tolerable deceleration threshold for the passengers. The carbon-fibre composite members are bolted onto the aluminium structure of the engine mounts behind them. This means that the Roadster, just like the Coupé, has a front crash structure manufactured entirely from carbon fibre.

In a collision, the fibres of the CFRP elements shred from front to rear, absorbing the energy of the impact with a constant rate of deceleration. Thanks to this steady deformation behaviour and the high-strength monocoque, the energy absorption of the CFRP side members can be precisely calibrated. The engineers achieve this, for example, by creating a constantly changing cross-sectional area for the components. This fine tuning means that the deceleration values result not only in predictable energy absorption behaviour but also in a weight advantage, because this design uses only as much material as is actually needed.

CFRP components in automated series production
Carbon-fibre composite components for racing cars and for the aviation and space industries are generally manufactured by hand - a time-consuming process. By contrast, many of the carbon-fibre components for the SLR Roadster are manufactured in an automated series-production process. To do this, the Mercedes engineers divided the manufacturing process into separate stages, with manufacture of the preform being followed by impregnation with resin and hardening.

In order to allow extensive automation of the manufacturing process for the carbon-fibre preform, the materials experts at Mercedes-Benz studied the work of their colleagues in the textile industry and adapted the highly automated manufacturing methods used in this sector, such as sewing, knitting, weaving and braiding, for the processing of high-performance CFRP fibres.

To take an example, the web in the middle of the SLR's side members is formed from several layers of carbon fibre placed on top of one another and sewed together by machine. Once the piece has been cut to shape and the ends folded up to form a double-T section, the web blank is inserted into a polystyrene braiding core. Next, a specially developed braiding machine forms the braided side member casing around this core using 25,000 extremely fine, individual carbon filaments which unwind simultaneously from 48 reels. This technology allows the fibre material to be braided around the core at a precisely calculated angle to create the required contour. Several layers are even laid on top of one another in certain areas, depending on the required thickness.

In a further manufacturing process, a computer-controlled tufting machine joins the inner web to the braid of the side member. The braiding core is then removed and the preform for the side member cut to the correct size. Finally, the preform is injected with resin.

Several patented solutions had to be developed and tested in order to ensure short cycle times and high repeat precision for this manufacturing process – both of which are crucial for series production. The manufacture of the complex fibre structure of the side members using a braiding machine requires a cycle time of just twelve minutes, which illustrates the potential output that this innovative manufacturing technology offers.

The British company McLaren Composites also manufactures over 50 components made from carbon-fibre and glass-fibre-reinforced plastics for the high-performance Roadster. Here too, familiar processes from the aviation industry were adapted and redeveloped. The degree of integration achieved in the manufacture of the body shell is particularly remarkable. The entire floor assembly, for example, including all support members and securing elements, is made in a single piece. High-strength bonding and riveting techniques ensure a lasting connection between the individual carbon-fibre components of the chassis and the body. The aluminium engine mounts are not only bolted to the carbon-fibre composite firewall, they are bonded into place too. The carbon-fibre structure includes integral metal link points for the aluminium and steel rear axle.

Purist Roadster soft top with coupé-like qualities
The carbon-fibre body is crowned by the snug-fitting soft top roof. The lean, sporty soft top nestles close to the passenger compartment, emphasising the Roadster's flowing form. The silhouette appears even more elongated than on the Coupé version and gives the vehicle's lines an even more pulsating look – especially with the roof down, of course. The design team paid painstaking attention to the tiniest of details in order to achieve harmonious integration of the roof. This included carefully smoothing out the transition between boot lid, roof and rear wall to make it perfectly flush so that even this area of the Roadster seems to have been cast from a single piece, both with the roof open and closed.

The soft top retracts fully in order not to disrupt the flowing forms when driving with the roof down. To open the roof, the driver simply has to release the catches in the roof frame and lift it up slightly; the side windows then open and, once a concealed switch in the centre console has been pressed, the roof folds together in a "Z" and stows itself away behind the seats on a level with the boot lid. The roof can only be operated with the vehicle stationary for safety reasons. Drivers are able to make the very most of every break in the weather as the semi-automated mechanism opens and closes the roof in just over ten seconds flat, thereby harmonising the desire for convenience with the purist nature of this top-class Roadster.

However puristic the roof's design may appear it is in actual fact highly elaborate, with three carefully harmonised layers that ensure excellent insulation and therefore pleasant levels of comfort, even in poor weather. A newly developed roof material featuring different coloured threads for warp and weft creates a striking, yet very elegant-looking finish, whose curious formation ties in fittingly with the car's carbon-fibre structure.

The front section of the roof incorporates a fixed header bow made from aluminium. Not only does this give added stability, it also dispenses with the need for an additional cover when the roof is down, as it lies perfectly flush with the tail's contours. This is once again a reflection of the puristic character of the SLR Roadster.

Furthermore, the hard roof shell, the short spacing between the bows and the optimum attachment of the roof fabric give the soft top on the SLR Roadster very different properties from the majority of cabriolet roofs. There is none of the usual prominent arching outwards at high speeds; even at top speed, its contour alters by just a couple of millimetres at the rear. Drivers of the new high-performance two-seater from Mercedes and McLaren can therefore push it all the way to its top speed far beyond the 300 km/h mark with complete peace of mind, even with the roof up.

Honed for high speeds in the wind tunnel
The Roadster's handling, aero acoustics and aerodynamics were optimised for high-speed driving in the wind tunnel. It borrows the same aerodynamic concept already familiar from the Coupé, comprising a front splitter, flat under body and diffusor, as well as a speed-controlled airbrake incorporated into the boot lid. This unique concept keeps the axle load perfectly balanced whilst maintaining high, uniform downforce at the front and rear axles. There has only been a slight increase in the Cd figure for the Roadster compared to the Coupé, measuring 0.376 with the roof closed and 0.4078 with it open (airbrake in 10° setting for both measurements).

The aerodynamics engineers have also taken great care to make the Roadster a shining example in terms of its aero acoustics too. Painstakingly meticulous work on the soft top bay, on the roof itself and on the transition point from the soft top to the body have cut wind noise substantially. As an example, the distance between the roof when closed and the boot lid was fine-tuned with such precision that no additional sealing lips are required here. The airstream felt in the passenger compartment when the roof is down is furthermore reduced to great effect by a Plexiglass draught-stop bearing the SLR lettering, that measures little wider than a hand and is inserted between the two rollover bars. Thanks to the sophisticated aerodynamics and the highly effective draught-stop there is very little turbulence even at speeds in excess of 200 km/h, allowing the occupants to converse with ease.

Restraint system with adaptive airbags, sidebags and kneebags
A state-of-the-art restraint system comprising six airbags, belt tensioners and belt force limiters completes the SLR Roadster's elaborate safety concept, ensuring that it meets all Mercedes standards in this regard too.

In the event of a head-on collision, the electronic control unit first triggers the high-performance belt tensioners, which can pull up to 15 centimetres of loose belt strap taut in fractions of a second, reducing the forward displacement of the occupants caused by the impact. The Mercedes-Benz SLR McLaren Roadster is also fitted with kneebags, which - together with the two-stage airbags - provide a large protective cushion for the driver and passenger in a frontal collision, complementing the effect of the seat belts and belt tensioners.

Upfront sensors for rapid airbag deployment
The belt tensioners are also activated if a roll-over situation is detected, triggered by a roll-over sensor which reliably recognises this type of accident and relays its data at lightning speed to the central control unit for the restraint systems. The sensor is located in the centre tunnel.

A sophisticated system of sensors also allows adaptive control of the front airbags, which deploy according to the severity of the accident. If the sensors register a light head-on collision, they each trigger just one chamber of the two-stage gas generators so that the 64-litre driver airbag and 125-litre passenger airbag are deployed with a lower internal pressure. If the sensors register an accident of a higher severity, the electronics also trigger the second chamber of the gas generators and the airbags inflate with a higher pressure.

Two upfront sensors on the radiator cross member fulfil an ancillary function for this adaptive deployment of the restraint systems. Thanks to their forward positioning in the front structure, they detect the severity of the impact even earlier and more precisely. The deployment algorithm uses both this signal and the signal from the central crash sensor on the centre tunnel.

While the occupants sink safely into the airbags, the belt force limiters reduce the force exerted by the belt strap on the upper body, further decreasing the risk of minor chest and shoulder injuries.

Sidebags with additional protection for the head
Protection in the event of an impact from the side is optimised by the integral sidebags in the doors. These cushion both the head and the upper torso which is why they are referred to in specialist circles as "head/thorax bags". In a side-on collision, this specially developed sidebag rips open a seam above the armrest and inflates within milliseconds to form an asymmetrically shaped airbag, the upper edge of which extends higher than that of conventional sidebags. The airbag's design reduces the risk of the head hitting against the side window or any object which may penetrate the interior.

The automatic child seat recognition system, developed by Mercedes-Benz, is also part of the SLR's standard equipment. It deactivates the passenger airbag if one of the special child seats from the Mercedes-Benz accessories range is installed on the passenger seat. These child seats have a transponder system which receives and responds to signals from two antennae in the seat upholstery. As a result of the exchange of data, the airbag electronics recognise that a child seat is fitted and deactivate the airbag on the passenger side since its deployment is not desirable in these circumstances. The belt tensioner and sidebag remain activated, offering the young passenger additional protection in the event of an accident.

V8 power plant with motor racing in its genes

High-tech power plant with 780 metres of torque
Metal catalytic converters for low exhaust emissions
Side pipes reminiscent of the SLR models from the 1950s
5-speed automatic transmission with 3-level manual shift program

An abundance of power and high-tech features from the world of motor sport - these are the defining characteristics of the V8 engine in the Mercedes-Benz SLR McLaren Roadster, with its 5.5-litre displacement, a cylinder angle of 90 degrees, screw-type supercharger and a crankshaft supported by five bearings. Which all means that the V8 power unit developed by Mercedes-AMG fits perfectly into the high-performance concept of the new open-top Gran Turismo.

The key data at a glance:

Cylinder arrangement	V8
Cylinder angle	90o
Valves per cylinder	3
Displacement	5439 cc
Bore/stroke	97.0/92.0 mm
Cylinder spacing	106 mm
Compression ratio	9.0 : 1
Output	460 kW/626 hp at 6500 rpm
Max. torque	780 Nm at 3250-5000 rpm
Engine weight	232 kg
Power/weight ratio	1.9 kW/kg

From a mere 1500 rpm, the SLR power plant delivers in excess of 600 Newton metres of torque, rising to 700 Newton metres at 2000 rpm. The maximum of 780 Newton metres is available from 3250 rpm and remains constant over a broad rev range up to 5000 rpm. The sublime torque delivery is coupled to the agile responsiveness of a sporty engine whose high-performance character is never in any doubt: a peak output of 460 kW/626 hp says it all. The SLR is thereby endowed with what is currently one of the most powerful engines to be found in a series-produced sports car, and achieves class-beating performance figures as a result.

0 - 100 km/h	3.8 s*
0 - 200 km/h	10.9 s*
0 - 300 km/h	30.8 s*
Top speed	332 km/h*

Fuel consumption is 14.5 litres per 100 kilometres (NEDC combined consumption).

Power from screw-type supercharger
To ensure good cylinder charging, the engine has a belt-driven supercharger between the two banks of cylinders featuring two screw-shaped aluminium rotors that are Teflon-coated to keep friction losses to a minimum. Its innovative technology allows a significantly higher charge pressure than conventional belt-driven chargers because the two rotors can attain a top speed of around 23,000 revs per minute, forcing air into the intake system of the 5.5-litre power plant at a maximum overpressure of 0.9 bar. This means that they compress around 1850 kilograms of air into the eight combustion chambers every hour - which is as much as 30 per cent more than the figure achieved by rival charging systems.

In order to maintain the greatest possible efficiency at all times, the AMG engineers created an intelligent engine management system which regulates the operation of the screw-type supercharger according to engine speed and load. Consequently, the charger is only called into action when it is really needed. Nevertheless, the system ensures that maximum power is available the instant it is summoned by a squeeze of the accelerator. This prompts the electronics of the engine management system to trigger an electromagnetic coupling, which immediately activates the supercharger that is driven by a separate poly-V-belt. Because the charger delivers its output in fractions of a second, even the most perceptive driver will not notice the non-supercharged phases. The charger system's air recirculation flap is opened under partial throttle conditions to help reduce fuel consumption.

Two intercoolers with separate water circuit
In addition to the supercharger, the electronics also monitor all other variables relevant to the engine - including both the power train management for the pedal-sensitive drive characteristics and the implementation of spontaneous interventions by the transmission or ESP®. The electronics also ensure optimum control of the water circuit for the intercooling system, as efficient intercooling is essential for maximising output. This is because cold air is denser than warm air and therefore contains significantly more oxygen for combustion. In the Mercedes-Benz SLR McLaren Roadster's V8 engine, two separate intercoolers are responsible for this key task - one for each bank of cylinders. This ensures that loss of pressure is very low.

The engine-mounted intercoolers operate on the highly efficient principle of an air-to-water heat exchanger: after being compressed and hence heated by the supercharger, the air is cooled down via the system's own, separate water circuit - making the process independent of the ambient temperature. This enables the V8 to deliver its maximum output and torque spontaneously at any time.

However, the tremendous output of the 8-cylinder engine in the new SLR Roadster not only demands effective cooling of the combustion air, it also results in an overall increase in engine cooling requirements. The engineers made allowance for this by incorporating generously proportioned cooling air inlets and outlets as well as a powerful 850-Watt suction fan.

Crankcase with dry-sump lubrication
The Mercedes-AMG GmbH engineers also applied their extensive experience in the world of motor sport and in the design of high-performance engines to other details of the SLR power plant. The entire engine housing, for example, and the enclosed bottom section of the crankcase are cast in aluminium. Each crankshaft is finely balanced and is supported by five bearings made from a high-endurance material for lasting transfer of the immense forces generated by the supercharged engine.

The pistons are forged and are therefore only manufactured in very small numbers. Like the forged lightweight connecting rods, they are precision gauged and weighed then allocated to the individual engines in such a way as to produce minimal mass balancing tolerances. The pistons slide in extremely durable, wear-resistant and friction-optimised barrels made from a special compound which is otherwise only used in motor racing. Dual oil injection ensures efficient piston cooling.

The design of the power plant’s oil cooling system also draws on the experience gathered at the race track: a sophisticated dry-sump lubrication system with an oil capacity of around eleven litres combines with a five-speed oil suction pump and a two-speed oil pressure pump to maintain reliable lubrication under the full spectrum of driving conditions. An important secondary effect of the dry-sump lubrication technology, which is usually only found in racing cars, is that it reduces the engine's overall height, allowing it to be installed lower down and producing a low centre of gravity that favours dynamic handling.

In line with the customary practice at Mercedes-AMG, each SLR engine is manufactured by hand. In order to attain the very highest quality, the principle of 'One man, one engine' is applied. This means that each power plant is the responsibility of one AMG engineer, who carries out the entire engine assembly process – from installing the crankshaft in the engine block and assembling the camshafts and the supercharger, right through to the cabling.

Powerful high-pressure pumps in the tanks
The SLR's high-performance engine draws its fuel from two interconnected aluminium tanks. In order to keep the centre of gravity as low as possible in the interests of exceptional handling dynamics, the tanks are installed low down on the left and right in front of the rear axle. The tanks, which have a total capacity of 97 litres (of which twelve litres form the reserve), are equipped with two integral high-pressure fuel pumps. These are controlled by the engine management system and ensure that the fuel supply matches the engine speed and load. Here once again, a highly effective solution was developed that is specific to the SLR: one pump operates constantly while the second only cuts in as required.

Four metal catalytic converters for efficient emissions control
Secondary air injection and dual ignition give the engine the prerequisites required for low exhaust emissions. A sophisticated exhaust system complements these measures: the cascade-design two-pipe system consists on both sides of a close-coupled firewall catalytic converter plus, in the same housing, a main catalytic converter with a special precious-metal coating. The state-of-the-art metal design allows extremely thin walls, resulting in a very low exhaust backpressure. Thanks to its cutting-edge engine management and emission control technology, the V8 engine in the new SLR meets the stringent EU4 emissions limits as well as the current limits.

On each side of the vehicle, the catalytic converter housing opens into a rear silencer which flows into two stainless-steel tailpipes with a diameter of 60 millimetres just behind the front wheels. These side pipes – a further reminder of the 1950s SLR racers – pave the way for a smooth-surfaced under body, which is instrumental in giving the new Mercedes-Benz SLR McLaren Roadster its first-rate aerodynamic properties. The silencers are folded several times into precisely calculated acoustic sections which produce the Roadster's distinctive thrilling engine sound. The volume of each silencer is 19.6 litres.

Manual transmission program for shift times worthy of a racing car
Likewise designed for high performance, the five-speed automatic transmission was developed by Mercedes-Benz and has been used successfully in several exceptionally powerful models. It has been specially optimised for very high torque and also offers the driver the option of choosing between different shift characteristics. The transmission transmits the engine's power via a finely balanced aluminium and steel power train to the differential and the rear axle.

It includes the Speedshift system that was developed by Mercedes-AMG for particularly sporty motoring and also offers a wide range of functions in the new SLR Roadster. Drivers can decide, for example, whether to leave the gearshift work to the automatic transmission or to shift gears manually. They are also able to select the shift speed, which determines how sporty the gearshifts are. A rotary switch in the centre console offers a choice of three program settings: "Manual", "Comfort" and "Sport". The activated programme is indicated in the instrument cluster display by the letters "M", "C" or "S".

"Comfort" and "Sport" are automatic shift programs which, as the names indicate, place the emphasis either on comfort or on a more sporty drive. In "Manual" mode, on the other hand, the driver can select the five gears either using the shift paddles on the steering wheel or the selector lever's Touch shift function. When "Manual" is selected, there is also the option of choosing between three shift-speed levels for fine-tuning a sporty driving style:

Level I = "Sport"
Level II = "Supersport"
Level III = "Race"

The higher the level, the shorter the shift and response times inside the automatic transmission, and hence the shorter the gearshifts themselves.

Top performance for the race track and the road

Aluminium double wishbone suspension with 18-inch wheels
High-endurance brake discs made from carbon-fibre-reinforced ceramic
Electro hydraulic brake system optimises effect of ESP®
Airbrake in boot lid extends automatically

Highly advanced motor racing technology, high-performance control systems and state-of-the-art materials – a unique combination which helps the Mercedes-Benz SLR McLaren Roadster to score top figures in three key handling criteria: agility, active safety and comfort. In the process, the SLR suspension lives up to all of the expectations a discerning car driver might have of a Gran Turismo bearing the Mercedes star.

The axle design is evidently the handiwork of experienced racing car developers, with double wishbones assuming the task of wheel location at the front and rear. The lower links are arranged so that the wheels have a negative camber when the springs compress and when cornering at speed. This ensures the best possible contact with the road in any situation. At the same time, the axle technology prevents the front of the car from diving when braking heavily and the rear from squatting when accelerating.

As on the Coupé, aluminium was the material of choice for the new Mercedes-Benz SLR McLaren Roadster's suspension. The wishbones are made from forged aluminium, while the wheel carriers are cast in aluminium. In addition to a whole host of other advantages over conventional steel designs, the lightweight nature of the material allows the suspension to react significantly faster and more sensitively.

The relatively long wheelbase of 2700 millimetres also contributes to the SLR Roadster's exemplary handling and is most evident in the car's exceptional directional stability. Meanwhile, the large track width combined with the low centre of gravity enables high cornering speeds.

Combined spring/damper units at the front and rear axle and an anti-roll bar at the front round off the suspension concept. The anti-roll bar is positioned above the front axle and is controlled via rocker arms, like on a Formula 1 car. This means that it does not take up any installation space which could disrupt the smooth line of the under body - a vital factor when it comes to the sports car's outstanding aerodynamic properties.

The speed-sensitive rack-and-pinion power steering also fits in with the intelligent lightweight concept. In comparison with other steering systems, this design is characterised by a significantly lower weight. Thanks to its low installation position in front of the engine and its ratio of 12.6, the steering system responds directly to the driver's commands and executes them with supreme precision. The three-spoke steering wheel has a diameter of 380 millimetres and is fitted with an electric motor which allows it to be positioned to suit the individual driver. It can be adjusted by 60 millimetres for reach, and its height can be varied by 2.7 degrees.

Ceramic brake discs for high-endurance performance
The exceptional properties of the electro hydraulic brake system in the Mercedes-Benz SLR McLaren Roadster are complemented to perfection by the brake discs made from fibre-reinforced ceramic that can be found at both the front and rear wheels. Their development is based on the one hand on the results of DaimlerChrysler materials research and, on the other, on the experience with high-tech brakes that Mercedes-AMG has amassed in touring car and GT racing. Here, Mercedes-Benz yet again underlines its leading role in the development of groundbreaking technologies for automotive production.

In manufacturing the brake discs, the carbon fibres, powdered carbon and resin are pressed into shape at high pressure and baked with a silicon infiltration at temperatures of around 1500 degrees Celsius to form the ceramic. The benefits of this composite material are considerable: in addition to their extremely sensitive response, the Mercedes-Benz SLR McLaren Roadster's brake discs are able to withstand temperatures of up to 1000 degrees Celsius which results in tremendous fade resistance when braking from high speed, all while producing as much as 2000 hp of braking power.

Further advantages of the revolutionary new brake material include:

the long life of the brake discs – up to 300,000 kilometres
the low maintenance requirements of the corrosion-free brake discs
up to 60 percent less weight than conventional brake discs - a further bonus in terms of dynamic handling and ride comfort
even more comfortable braking - the low thermal expansion of the ceramic discs means reduced thermal judder under high loads. Similarly, the cold judder familiar from cast-iron brake discs also lessens significantly with ceramic brakes.

Brake pad area of 440 cm2 at the front axle
The design of the callipers was specially adapted to the fibre-reinforced ceramic brake discs. To this end, Mercedes-Benz developed eight-piston fixed brake callipers which give the front axle excellent stopping power. Special channels, which actively feed cooling air to the outside of the brake callipers, ensure optimum cooling of the brakes.

In the Mercedes-Benz SLR McLaren Roadster there is a total brake pad area of 440 square centimetres at the front axle alone - an exemplary figure which, in combination with the extremely robust high-tech material the brake discs are made from, allows a maximum rate of deceleration of up to 1.3 g.

The braking data at a glance:

	Front axle	Rear axle
Calliper Piston diameter	8-piston fixed calliper 28/32 mm	4-piston fixed calliper 28/30 mm
Brake disc Disc diameter Disc thickness Brake pad area	Internally ventilated 370 mm 36 mm 2 x 118 cm²	Solid 360 mm 26 mm 2 x 48 cm²

Pop-up rear spoiler - the airbrake
The outstanding performance of the SLR is also aided by the extending spoiler in the boot lid that is referred to as the "airbrake". If the driver steps heavily on the brake pedal, the rear spoiler rises to an angle of 65 degrees to increase the contact pressure and, as a consequence, the braking forces that can be exerted at the wheels. When braking from high speeds, it lends the SLR outstanding stability, while the noticeable increase in aerodynamic drag boosts the braking effect even further.

In most situations the electronics automatically control the airbrake as required. However, the driver may also adjust the setting manually by pressing the switch in the centre console to raise the rear spoiler to an angle of 30 degrees.

Sporty handling dynamics combined with reassuring active safety
The electro hydraulic brake system in the SLR Roadster processes a raft of sensor data describing the current driving status, and uses this to instantaneously calculate and meter the optimum brake pressure for each wheel. A high-pressure reservoir holds the brake fluid, which flows into the system at a pressure of 140 to 160 bar. This also enhances the operation of the Electronic Stability Program (ESP®), which keeps the SLR safely on track by applying targeted brake pulses to the individual wheels and/or reducing the engine torque. Thanks to even faster and even more precisely metered brake pulses from the high-pressure reservoir, ESP® can stabilise a swerving vehicle smoothly and at an early stage. It was therefore possible to permit a very sporty driving style with controlled side-slip angles in keeping with the character of the high-performance car, but without compromising active safety in any way.

On top of this, the electro hydraulic brake system gives a significant boost to active safety in critical situations too:

Emergency braking: the system interprets the driver's sudden switch from the accelerator to the brake as an indication of an emergency situation and is able to react automatically. With the aid of the high-pressure reservoir, the system increases the pressure in the brake lines and brings the brake pads into contact with the brake discs, so that they can grip with full force the moment the driver steps on the brake.
In the wet: brief, regular applications of the brakes wipe away the film of water that forms on the brake discs so that the brakes can always operate to full effect. This automatic drying function is activated whenever the windscreen wipers have been operating for a certain length of time. The finely metered brake pulses are imperceptible to the driver.
Braking on bends: thanks to variable brake force distribution, the brake system is able to exert an active influence over the sports car's self-steering characteristics. Rather than always applying the brake pressure to the wheels on the inside and the outside of the bend in the same ratio, as with conventional brake systems, distribution of the braking forces is adapted to the situation. The system automatically increases the brake pressure at the wheels on the outside of the bend because, due to the higher wheel contact forces, these wheels are able to transmit greater braking forces. At the same time, the braking forces at the wheels on the inside of the bend are reduced, benefiting the cornering forces which are so important to directional stability. The result is more stable braking behaviour and excellent deceleration figures.

The electro hydraulic brake system also offers special additional functions for even greater safety and comfort:

The Soft-Stop function allows drivers to draw to a particularly gentle stop, which will be appreciated above all in city traffic involving frequent stops at traffic lights. It is made possible by finely metered pressure control. The Soft-Stop function is permanently activated; a rapid build-up of stopping power is only ever given priority by the system in response to emergency or full brake applications, or when travelling at manoeuvring speeds.
Start-Off Assist prevents the car from unintentionally creeping forwards or rolling backwards on hills and steep gradients. A brief but firm press of the brake pedal is all it takes to activate this function.
Tailback Assist can be activated using the cruise control lever when the vehicle is at a standstill or when coasting at speeds of up to 15 km/h. The advantage of this function is that in stop-start traffic the driver only needs to use the accelerator; when the accelerator is released, the system brakes the SLR to a halt at a constant rate of deceleration. Tailback Assist can remain active up to a speed of 60 km/h. It is automatically deactivated at higher speeds.

18-inch wheels as standard
Attractive 18-inch light-alloy wheels make up part of the standard specification for the Mercedes-Benz SLR McLaren Roadster. The sporty, 10-spoke wheels are shod with tyres of different widths at the front and rear. 19-inch turbine-design wheels, which emphasise the dynamic character of the Gran Turismo to particularly stunning effect, are available as an optional extra.

Tyres	Wheels	Wheel design
Front: 245/40 ZR 18 Rear: 295/35 ZR 18	9.0 J x 18 ET 45 11.5 J x 18 ET 44	10-spoke design (standard)
Front: 245/35 ZR 19 Rear: 295/30 ZR 19	9.0 J x 19 ET 45 11.5 J x 19 ET 44	Turbine design (optional extra)

An electronic control system monitors the air pressure in the Roadster's tyres. Its sensors are situated in the tyre valves and measure both the air pressure and air temperature inside the tyre. Since it is not possible to install cable connections to the wheels, the information is transmitted by radio. Each sensor sends its data readings about once a minute to special antennae in the wheel arches which relay the information to a control unit. Individual signal identifiers allow this unit to distinguish between the signals from the four wheels and thereby provide the driver with exact information on the air pressure in each tyre in the cockpit's central display.