For over five decades the SL models have been among the technology trendsetters in the sports-car segment. Groundbreaking inventions made it to series production for the first time in one of the Mercedes roadsters. In the 1950s, the 300 SL set the standard with direct petrol injection and all-round disc brakes, in the 1960s the 230 SL was the world's first sports car fitted with a safety body and sturdy hardtop, nicknamed the "pagoda" on account of its shape. The R 107 series offered enhanced safety in the 1970s courtesy of its advanced-design body offering 50 percent more strength, while the SL set the benchmark for other sports cars with its automatic pop-up roll-over bar, draught stop and integral seats in 1989. In its footsteps comes the current SL Roadster with new technology innovations which no other car in its class can match.

The Mercedes engineers have raised the bar even further in order to reinforce the characteristic features of the SL: safety, comfort and sportiness.

The experts in Stuttgart and Sindelfingen paid particular attention to the engines. A new six-cylinder model comes in the guise of the SL 280, which offers a compelling entry route into the world of Mercedes top-class sports cars with its 170 kW/231 hp engine. The two-seater accelerates from 0 to 100 km/h in just 7.8 seconds before going on to a top speed of 250 km/h. The V6 engine also demonstrates that effortless power delivery and good fuel economy need not be a contradiction in terms: the SL 280 consumes 9.4 litres of premium petrol per 100 kilometres (combined NEDC), meeting today’s fuel economy requirements.

The Mercedes engineers have given the SL 350 a new heart that beats very strongly: a V6 sports engine that brings the roadster's sporty characteristics to life more than ever. The extra 32 kW/44 hp, which distinguishes the new six-cylinder unit from its predecessor, is just one part of the story; another key feature of the sports engine is its responsiveness, demonstrated clearly by its high-revving flexibility. The 3.5-litre engine effortlessly laps up engine speeds normally well out of bounds for series-production engines of this displacement class. Its rated output of 232 kW/316 hp is reached at 6500 rpm and it revs up to 7200 rpm in no time at all in order to make full use
of its power reserves in certain driving situations.

The maximum torque has also been increased and is now 360 Nm at 4900 rpm: 10 Nm more than before. Even as low as 2000 rpm, the engine develops some 97 percent of its maximum torque (350 Nm), delivering high pulling power and outstanding performance. The new SL 350 accelerates from O to 100 km/h in 6.2 seconds, the top speed is electronically limited at 250 km/h.

With this SL model though, extra power does not come at the expense of fuel economy. On the contrary, the V6 sports engine boasts combined NEDC fuel consumption of 9.9 litres per 100 kilometres: 0.4 litres more economical than the previous V6 engine in the SL 350

Higher compression, advanced pistons and single-stage intake manifold

A large red "V" on the engine cover is the visual hallmark of the new high-revving sports engine. Yet the decisive modifications are hidden from view; a process of meticulous engineering was required to modify the character of the six-cylinder engine and mobilise its power reserves.

The Mercedes engineers decided to increase the power of the six-cylinder unit by increasing engine speed and going for a higher compression ratio of 11.7 : 1 (previously 10.7 : 1) to address the fundamental limitation of the naturally aspirated engine when it comes to charging. The new compression ratio, which improves fuel consumption particularly under partial load thanks to improved efficiency, has been made possible through advanced, weight-optimised pistons with a curved surface. The valve pockets needed to be milled deeper to ensure smooth valve operation. Meanwhile, reinforcements around the piston pins provide the strength to withstand the increased forces.

Since the intake manifold fitted with flaps on the previous version does not ensure a high charge at high engine speeds, it has been replaced by a single-stage intake manifold which rectifies this shortcoming. The intake manifold is made out of plastic, a material that provides a wide range of design options as well as thermal benefits. Compared with cast metal, plastic is a poor conductor so that the new intake manifold does not get as hot. Consequently the intake air is cooler -- a benefit that pays dividends in terms of even better cylinder charging.

To offset the fundamental limitations of the single-stage intake manifold at engine speeds below 4000 rpm, the camshaft position has been advanced by five degrees both on the intake and exhaust sides. The Mercedes specialists were able to dispense with "more racing-styling" camshaft tuning to increase output since the new intake manifold enables the intake valves to close earlier thanks to its modified flow characteristics. The high running quality of the six-cylinder engine has thus been retained both at idle speed and under partial load.

The higher engine speeds also necessitate modifications to the valves and valve timing: the new sports engine uses lightweight valves made out of ultra-high-strength and high-temperature-resistant steel. The sodium-cooled valve stems for the exhaust valves have a 3.4-millimetre bore.

The conical springs used to control the valves are typical features of a high-revving engine. Since conventional cylindrical springs tend to build up natural frequency vibration from certain engine speeds, they do not fully close the valves. By contrast, conical springs offer heavily dampened naturalvibration characteristics and reliably close the valves even at high engine speeds. The larger fitting length of conical springs, an enhanced intake port for optimum charging and minor modifications to the water jacket ultimately also led to the need for a new cylinder head. Other technical modifications include sturdier roller-type cam followers and a sprocket configured as a trioval, i.e. the sprocket is not round but has a barely noticeable triangular shape that effectively combats vibration in the chain drive which can occur above speeds of 6300 rpm.

The new sports engine in the SL 350 shows its qualities not only with its instant power delivery but also its decidedly throaty sound. The standard-fit 7G-TRONIC seven-speed automatic transmission adds to the sound of the SL 350, as the engine management system automatically double-declutches during downshifts. As well as producing an extremely sporty sound, this function also has entirely practical benefits: since the double-declutching equalises the rotational speeds of the crankshaft and transmission, the load-change reactions are reduced, and the gear change is smoother and more harmonious as a result. In other words, sporty sound goes hand in hand with enhanced safety in the new SL 350.

The use of the powerful sports engine also requires modifications to the brakes on the SL 350: the V6 sports car is now fitted with internally ventilated disc brakes all-round.

The newly developed eight and twelve-cylinder engines, available in the SL-Class since 2006, will remain a firm fixture in the line-up. Mercedes specialists have fine-tuned the units down to the smallest detail, managing to cut NEDC fuel consumption by 0.3 to 0.4 litres per 100 kilometres. Key engine data, performance and fuel consumption figures for the SL models at a glance:

*Electronically limited

Thanks to the new, decidedly sporty design with the pronounced V-shape of the front section, the new-generation SL is 30 millimetres longer than the previous model. The vehicle width has increased by 36 millimetres, due to the use of the much larger exterior mirrors which enhance driver safety. Wheelbase, track widths and interior dimensions remain unchanged.

The steering provides the most important link between driver and car. The set-up not only affects safety and comfort but also the car’s agility. Consequently, the Mercedes engineers have once again devoted a great deal of time to this component. The result is a technology that enables Mercedes customers to take the sporty credentials of the SL to new heights: the optional direct-steer system with variable servo assistance.

This innovation lives up to its name in every respect by providing a more direct response on bends and even more agile handling -- in a nutshell: more driving pleasure. The direct-steer system builds on the benefits of the standard-fit speed-sensitive power steering on board the SL by delivering significantly enhanced handling dynamics and, as in the past, the speed-sensitive power steering function which requires lower steering forces when driving slowly, manoeuvring or parking.

New features include a variable rack ratio, which adjusts in line with the steering angle, increasing sharply as soon as this reaches five degrees (see graphic) so that the driver only has to move the steering wheel slightly when cornering: the SL responds more spontaneously than with a constant ratio steering set-up. And so the driver literally has even better control of the vehicle.

The direct-steer system has been set up precisely so that its sporty, dynamic rack ratio makes itself positively felt particularly when handling and agility are most called for: on winding country roads, in other words at medium speed and medium steering angle.

By contrast, the benefits of the tried-and-trusted speed-sensitive power steering are retained in other handling situations and are even augmented in certain cases: for instance, the new Mercedes steering can be set up with an even more indirect ratio in the centre position than previous steering systems, providing the driver with a very assured steering feel at high speed, while improving straight-line and directional stability. When driving slowly or parking, the new technology combines with the speed-sensitive power steering to provide even more comfort than before because the direct ratio further reduces the steering effort required.

High-power bi-xenon headlamps are part of the standard specification for the new-generation SL. They combine minimum power consumption with maximum light yield, contributing significantly to road safety when driving in the dark. Mercedes-Benz also offers the Intelligent Light System based on bi-xenon technology, which further improves the driver's range of vision through appropriate headlamp activation. The five lighting functions are geared to typical driving and weather conditions, and come on automatically depending on the speed or steering angle.

Instead of the existing low-beam headlamp, the new country mode light function is used. It illuminates the left-hand edge of the road more widely and brightly so that the driver has a better view of both sides of the road. The driver’s range of vision is increased by around ten metres. The other lighting functions in the Intelligent Light System include:

A look inside leaves you with a distinct impression of sportiness and comfort - the second virtue of the SL-Class. No other sports car offers this perfect balance of sportiness and long-distance comfort. The Mercedes designers and engineers have managed to raise the quality bar even further for the new-generation SL in these areas thanks to their meticulous attention to detail and state-of-the-art technology.

One innovation serves as an example of the kind of technology available exclusively from Mercedes-Benz: AIRSCARF. This invention allows owners of a Mercedes roadster to enjoy open-air motoring for longer, even when other cabriolet fans have long since put the roof up. The optional neck-level heating system provides the option of open-top motoring even in late autumn or winter by creating an invisible "scarf" that keeps the head, neck and shoulders warm.

This system celebrated its world premiere in the SLK-Class in 2004 and has since proved a very popular option. The technology has been modified and enhanced for the new-generation SL so that the heating is now incorporated in the head restraints instead of the seat backrests as on the SLK.

The AIRSCARF principle is as simple as it is ingenious: two electric ventilators in the head restraint suck in cold air from behind and pass it through an electric heating element rated at 200 watts. A plastic duct then feeds the warm air to a specially designed ventilation outlet at the front of the head restraint. Developed by Mercedes specialists, the system delivers warmth close to the occupants, thus ensuring pleasant temperatures at driver and front passenger head height even if a wintry breeze is buffeting the roadster. Even after driving only a short distance, a pleasant temperature zone forms around the shoulders, neck and head - like a scarf of warm air.

The major benefits of this innovative Mercedes technology include low space requirements and the consistent heat output in particular. The heating element is based on advanced PTC technology (Positive Temperature Coefficient): an electric current is passed through ceramic particles which heat up in a matter of seconds and then continue to emit heat.

AIRSCARF is started by selecting one of the three different temperature settings using the switch in the door lining. With the vario-roof open the system automatically controls the blower output based on the road speed so that the neck-level heating system always optimally distributes the warm air.

And when it comes to infotainment the SL-Class is cutting-edge. Mercedes-Benz has enhanced the standard-fit COMAND system and added extra functions. The unit now not only combines car radio, CD/DVD changer and telephone functions but also features Music Register, a slot for SD memory cards and a Bluetooth interface for a mobile phone. The unit is easy to operate thanks to a large (6.5 inch), high-resolution colour display. The new functions in detail:

Mercedes-Benz also includes a Europe-wide navigation system with the optional COMAND APS with the associated data stored on a hard disc (40 gigabytes). This enables route information to be processed very quickly. The system also includes Music Register, allowing Mercedes customers to store around 1000 MP3 or WMA tracks so they can put together their own music selection for the journey. The tracks copied to the COMAND APS system from a CD, DVD or memory card are automatically recognized thanks to a stored database ("Gracenote") and indicated on the colour display. The names of the artists are also included on the display.

The LINGUATRONIC voice-operated control system is also part of the standard specification for COMAND APS. Mercedes-Benz unveiled this system in 1996 and has been enhancing functions and features ever since. The voice-operated control system in the new-generation SL is the most sophisticated ever thanks to the whole-word recognition capability. So the driver no longer has to painstakingly spell everything out but can simply say each particular word when entering a destination, selecting a radio station or calling up a name included in the phone book.

The sound output is digitised during the brief dialogue, converted into a frequency spectrum and finally analysed. Within a matter of milliseconds the computer extracts various features from the voice output and identifies the phonemes – the distinct sound units that make up speech. The software instantly verifies each sound, combines the various phonemes, compares them against the contents of a stored phoneme dictionary and also works out the acoustic probability of the word. Consequently, the system can distinguish even minute differences in pronunciation; for instance, it can differentiate between the words "street" and "straight". The system includes the phonemes for six different languages.

While the first-generation LINGUATRONIC required a computer with a mere 512 kilobytes of storage capacity back in 1996 , the voice-operated control system now needs over ten megabytes.

Music Register and the memory card slot included with COMAND APS demonstrate that entertainment was an important issue when developing the new audio units: SL owners can put together their individual music selection and take it with them on an SD card. For the first time an iPod, USB stick or other external audio devices can be easily connected up to the infotainment system in the SL, courtesy of a newly developed universal interface in the centre console; all you need is a compatible cable that is available from the Mercedes accessories range.

Dubbed the "Media Interface", this new feature is more than just an electronic "socket". The interface also includes an ECU that connects the external music storage media to the on-board electronics and the roadster's control system. This has the advantage that the iPod tracks are displayed in the instrument cluster and on the colour display in the centre console and can be conveniently selected using the buttons on the multifunction steering wheel. Moreover, the audio device's battery is also charged up as long as the portable music storage media is connected to the car via the Media Interface.

The new-generation SL literally sets the tone among sports cars with its new (optional) surround sound system. " Logic7 " is what the specialists from Harman Kardon call the technology that gives the driver and front passenger the impression they are sitting in the middle of a concert hall, a jazz club or a rock concert arena. This impressive musical feast of surround sound can be experienced even with standard stereo recordings although it reaches the height of perfection with the very latest 5.1 recordings: " Dolby Digital 5.1 " , " DTS 5.1 " and " MLP 5.1" are formats originally developed for cinema films, but which are now also used for music recordings thanks to their crystal-clear surround sound.

A 510-watt DSP amplifier distributes the music output, controlling the frequency response to generate a balanced listening experience at all times. The system responds dynamically to road speed and for the first time factors in whether the vario-roof on the SL is up or down. So passengers in the Mercedes sports car can enjoy a perfect stereo listening experience even under the open sky - your very own open-air concert on wheels.