The history of the Mercedes-Benz SL-Class
Jan 10, 2012
Open the way for the vario-roof: Mercedes-Benz SL, R 230 series (2001-2012)
  • Open-top car and coupé in one – the roof folds in 16 seconds
  • Equipped with the most advanced dynamic handling systems
  • Lightweight body with a high proportion of aluminium
The R 230-series SL was presented to the press in July 2001 at Deichtorhallen in Hamburg. Owing to a combination of advanced electronic chassis systems which was unique in the world at the time, the R 230 offered an outstanding driving experience coupled with highest levels of operating safety and so set trends for sports cars and car building in general.
At market launch, the first model available was the Mercedes-Benz SL 500 with an output of 225 kW (305 bhp). In autumn 2001, it was joined by the SL 55 AMG with a supercharged V8 engine and 350 kW (476 bhp). In 2002, the SL 350, featuring a 180 kW (245 bhp) 3.7-litre V6 engine, followed, and finally in January 2003 Mercedes-Benz introduced the SL 600 with the powerful 368 kW (500 bhp) 5.5-litre V12 biturbo engine as its new flagship model.
The extensive standard equipment of the SL included, for example, leather-upholstered integral seats plus memory function for the electric seat and steering wheel adjustment (additionally stored in the electronic ignition key); multifunction steering wheel, automatic climate control and stereo car radio. As optional extras, innovative assistance systems like the DISTRONIC proximity control system, the TELEAID automatic emergency call system, the COMAND control and display system or an electronic tyre pressure monitoring system were available.
Leather, fine wood and aluminium are the materials used to create the typical exclusivity and perceived value of the SL. There was a choice of two types of leather, four high-quality trim variants and five appointment colours. Matt-finished chrome framed the four individual, classic chronometer-style instruments on the dashboard and was also to be found in other details of the interior.
The design combines tradition and future
The design of the R 230 series blends tradition and future through distinctive details. For instance, the air intakes in the front wings take up a typical feature of the 300 SL from the 1950s. The thin, wing-like segments on these side air intakes – called fins by experts – also are a reminiscence. The designers use this stylistic element additionally to give a sporty touch to the grilles of the openings on the bonnet.
The horizontally elongated radiator grille has always been an unmistakable feature of the SL. The R 230 series took up this tradition, but showed it in an up-to-date interpretation, thrusting a louvred radiator grille with a flatter slope than previously into the wind. This, in combination with the more pronounced wedge shape of the body, made the front end appear very dynamic and powerful. The four louvres surrounded the Mercedes star, which in its accustomed size and position clearly indicated the brand to which the two-seater belonged.
These typical traditional SL features harmonised with the new elements, the headlamps, for example: on each side two of the familiar four “eyes” merged into one without giving up their basic oval shape. The up-to-date clear-lens look effectively enhanced the standard bi-xenon headlamps and gave an additional touch of brilliance to the front-end design.
The long bonnet took up the curves of the headlamps and carried them towards the rear in a terse arch. The design of the muscular wings also evolved from this ensemble. The soft lines of the bonnet and wings merged smoothly into the taut lines that gave structure to the sides of the body at the shoulderline. Another line developed in the lower part of the wings from the verve generated by the side air intakes. It gave a formal hold to the large, quiescent surfaces of the doors, creating a visual bond with the rear end. The steeply raked windscreen emphasised the sports car character, accentuating its low, wedge-shaped silhouette.
16 seconds of roof acrobatics
Unlike its predecessors the R 230-series SL always carries its hardtop with it. The integration of the SL’s steel vario-roof into the car's flowing lines is proof of the car's high design quality.
At the push of a button, or via remote control, the roof can be opened or closed within 16 seconds. An extremely complex swivelling mechanism ensures that the three roof components disappear into the upper part of the boot in a space-saving way. Underneath it, 235 litres of luggage space are available. With the top up, the vehicle offers 317 litres of space, including the luggage box in the spare wheel recess: that amounts to 52 litres more than the previous model. Since mid-2002, a glass sunroof variant is also available.
Further features underscored the impression of dynamism and elegance created by the R 230 series, for example the body with the powerfully shaped front apron, the muscular curves and the pronounced wedge shape, but also stylistic elements like the distinctive outline of the side skirts, the wide wheels (diameter: 43.18 centimetres) or the oval tailpipes of the exhaust system. All body parts – from door handle to bumper – were painted the colour of the car body so that from a formal viewpoint and in terms of its colour the sports car appeared cast in one piece. This also applied to the rear end, characterised by large, triangular-shaped tail lights. Here again instead of a play of colours, there was elegant consistency: the tail light lenses were a uniform red – special filters in front of the reflectors ensured that the turn indicators still appeared yellow and the reversing light white.
SBC™ Sensotronic Brake Control
The technical innovations of the R 230 series included the Sensotronic Brake Control SBC™ electrohydraulic braking system, which had its première in this series. It operated in conjunction with the ESP® Electronic Stability Program and the Active Body Control ABC active suspension system, which minimises body movements and any tendency to skid when cornering and braking.
Sensotronic Brake Control SBC™ was also a gateway to the world of future “by wire” systems that no longer transmit the driver’s commands mechanically or hydraulically, but electronically – by cable. The most important performance characteristics of SBC™ include extremely dynamic brake pressure build-up and a reliable “feel” for driver and vehicle behaviour thanks to sophisticated sensor technology. For example, the system interprets a rapid shifting of the driver’s foot from the accelerator to the brake pedal as an emergency situation, automatically increases the pressure in the brake lines and simultaneously positions the brake pads on the brake discs so that they can grab the disc without delay and with full force when the driver depresses the brake pedal. Thanks to this, the stopping distance is three per cent shorter in an emergency stop. In addition, thanks to variable brake force distribution, SBC™ affords more safety when braking on bends or on difficult surfaces, depending on wheel contact force and slip. Owing to greater dynamics and precision SBC™ also enhances the performance of the BAS Brake Assist and the ESP® Electronic Stability Program.
This package of highly efficient electronic control systems initiated a revolutionary trend in automobile manufacture in the area of chassis, handling safety and driving dynamics.
Suspension with ABC Active Body Control
These systems are supported by wheel suspensions which react sensitively in conjunction with the ABC Active Body Control. At the front a state-of-the-art four-link system ensures optimal road roar and tyre vibration characteristics, precise wheel location and steering. The lower elements of the front axle, the steering gear of the rack-and-pinion steering, and the engine mounts are connected with an aluminium frame-type integral support which also celebrated its première in the new SL.
In the SL of the R 230 series, the multi-link independent rear suspension, still unsurpassed for wheel location, is made entirely of aluminium for the first time, including wheel carriers and sub-frame. To improve the oversteer/understeer characteristics even more, the axle geometry was modified in detail.
Safety redefined
Ever since the “Pagoda” at the latest, the abbreviation SL has been synonymous with pioneering achievements in the areas of active and passive safety in open-top sports cars. With an entirely new, comprehensive concept the R 230-series SL clearly outstrips the previous safety standards to make it a model in the area of vehicle safety in particular for sports cars. The concept makes allowance for all aspects of active and passive vehicle safety – from accident avoidance with the aid of electronic handling dynamics systems like SBC™, Active Body Control ABC, Brake Assist BAS, acceleration skid control ASR, or ESP®, to the structural integrity of the body with a high level of passenger cell rigidity in every conceivable type of accident.
Some of the things contributing to occupant protection together with the high-strength body structure: two-stage airbags for driver and front passenger, new head/thorax bags in the doors, newly developed integral seats, high-performance belt tensioners, belt force limiters, or the sensor-controlled roll-over bar, which goes into action, whether the vario-roof is open or closed.
In the event of an accident, the TELEAID automatic emergency call system (optional extra) developed by Mercedes-Benz ensures that emergency services and police are automatically alarmed and guided to the accident scene by satellite navigation.
Safety development between rating tests and reality
The R 230-series SL has passed the most rigorous crash tests such as an offset frontal impact at 64 km/h or the 90-degree side collision at 50 km/h, both of which are included in the European NCAP (New Car Assessment Program) procedure and which make the highest demands on the vehicle structure, especially in the case of open-top cars. The engineers devoted just as much attention to the aspect of ease of repair, which they investigated in frontal and rear impacts at a collision speed of 15 km/h in each case. The body structure of the SL affords the greatest possible safety to occupants and meets the objective of reasonably priced repair.
In a frontal or rear collision at speeds above 15 km/h, the bodyshell structure of the SL provides an exemplary high level of occupant protection thanks to many innovative details. Around 33 per cent of the bodyshell is made of high-strength sheet metal affording maximum resistance coupled with minimum material thickness. All components crucial to crash safety and body stiffness are made from high-strength steel sheet. The fuel tank is made of sheet steel and is located in a protected position above the rear axle.
Fuel economy a high priority
Fuel economy in the R 230-series SL is a topic which runs like a thread through many chapters of the design specifications. The lightweight body plays a decisive role in achieving a favourable fuel economy in all the vehicle variants: bonnet, front wings, doors, boot lid, tank partition and other components are made from aluminium; in particular the 1.40 metre long bonnet is a remarkable lightweight component.
The sophisticated aerodynamics of the smooth body including underbody, designed to reduce drag, helps to save fuel as well as minimise noise. The drag coefficient value of 0.29 for the closed car is a very remarkable figure; in the previous R 129 (with hardtop) it was still 0.32. The open-top SL of the R 230 series has a cd of only 0.34 (R 129: cd = 0.40 with the side windows closed).
Debut with the SL 500
In summer 2001 the SL 500, featuring a 5-litre V8 engine (M 113) delivering 225 kW (306 bhp) and torque of 460 newton metres debuted first. It was one of the most powerful engines of its segment, did clearly better than the stringent EU 4 emission standards required, and accelerated the SL 500 from 0 to 100 km/ in 6.3 seconds. The top speed was 250 km/h (electronically limited). The proven five-speed automatic transmission with electronic control, two shift programs and torque converter lockup clutch were standard equipment in the SL 500. A newly developed touch shift permitted very fast manual gear-changes.
In September 2001, the SL 55 AMG followed with its première at the IAA International Motor Show in Frankfurt on the Main. Equipped with a new V8 supercharged engine, it was the most powerful Mercedes-Benz passenger car at the time. The 5.5-litre power plant (M 113) developed 350 kW and delivered a maximum, constant torque of 700 newton metres from 2650 rpm to 4500 rpm. The car spurted from 0 to 100 km/h in 4.7 seconds; its electronically-limited top speed was 250 km/h. The engine was combined with a five-speed automatic transmission including steering wheel gearshift buttons.
The AMG version was distinguishable on the outside from the SL 500 among other things by bumpers with an even more powerful styling, distinctively shaped side skirts, dark-tinted tail lights, exclusive multi-spoke wheels (diameter: 45.72 centimetres) and four chrome-plated exhaust pipes.
In the interior, the more firmly upholstered integral seats with a special perforation and coloured topstitching, high-quality aluminium trim elements with a sand-cast look, and dashboard instruments with light dials, silver-coloured symbol discs and red needles emphasised the character of this sports car.
In 2002, the SL 350 followed, with a 180 kW (245 bhp) 3.7-litre V6 engine (M 112). It accelerated the car in 7.2 seconds from 0 to 100 km/h and achieved an electronically limited top speed of 250 km/h. It featured SEQUENTRONIC automated six-speed manual transmission as standard, operated via two shift paddles on the steering wheel. The electronically-controlled five-speed automatic transmission with touch shift was available as an optional extra.
A V12 engine in the flagship model
In January 2003, Mercedes-Benz presented the SL 600 with a 368 kW (500 bhp) 5.5-litre V12 biturbo engine (M 275) as new flagship of the series. It produced a tremendous torque of 800 newton metres, available already at 1800 rpm and constant up to 3600 rpm. The newly-developed Mercedes-Benz twelve-cylinder engine with two turbochargers and air-to-water intercooler, three-valve-per-cylinder technology, alternating-current twin-spark ignition and other high-tech innovations is one of the most advanced passenger car engines in the world. It affords effortless superiority in any driving situation. The SL 600 needed only 4.7 seconds to go from 0 to 100 km/h. Its top speed was electronically limited to 250 km/h. From the outside the SL 600 can be recognised by a radiator grille with discreet chrome inlays, silver-painted brake callipers, V12 emblems on the side air intakes, bi-xenon headlamps and exclusive light-alloy wheels. The front wheels have tyres of size 255/40 R 18, the rear wheels tyres of size 285/35 R 18.
Only 12 units: SL 350 “Mille Miglia Edition 2003”
Based on the SL 350, in June 2003 Mercedes-Benz presented the “Mille Miglia Edition 2003” special model to commemorate the legendary road race. Only 12 of these were built. They were painted in a special “Silver Arrow” metallic finish and had matt-finished aluminium shoulderline trim strips, beautifully designed light-alloy wheels (diameter: 45.72 centimetres), wide-base tyres of size 255/40 ZR 18 (front) and 285/35 ZR 18 (rear) and “Mille Miglia” badges in the air outlet grilles of the front wings and on the boot lid.
The vario-roof of the special model was made of glass and gave the passengers a panoramic view. The special features in the interior included two-tone nappa leather appointments: the seats were in “classic red”, an accent colour already used in the legendary SL sports cars of the 1950s. The roof was lined with soft Alcantara, and the trim elements on the centre console and the doors were aluminium with a matt-finished surface. With the aid of a new laser technique the designers worked the “Mille Miglia” logo and even the course of the thousand-mile race into the leather covers of the head restraints.
Other standard equipment items on the special model included the control and display system COMAND, the parking assist PARKTRONIC, multicontour backrests, CD changer and sound system. The V6 engine of the special model was combined with a five-speed automatic transmission as standard.
A special model on the 50th birthday
In 2004, Mercedes-Benz celebrated the appearance of the 300 SL in 1954 with the special model “Edition 50”, available as SL 350 and SL 500 in a series limited to a total of 550 units. The visual highlights included a matt silver-painted radiator grille with chrome trim strips, light-alloy wheels (diameter: 45.72 centimetres) in turbine design, shoulderline trim strips in a high-sheen finish, a draught-stop frame with high-sheen finish and darkened tail lights.
In the interior, the instrument cluster was trimmed with a leather/Alcantara combination. The seats, luxury climatised seats with multicontour function as standard, had nappa leather covers; the head restraints showed a lasered “Edition 50” logo. The trim elements in the interior were made of a decorative new aluminium material or, alternatively, black ash wood. Depending on personal taste, if desired the leather appointments also could be had in two-tone condor silver/black or single-tone designo black with topstitching in quartz. A comprehensive range of standard equipment was included: for example, the COMAND APS radio and navigation system with CD changer and surround sound system, but also bi-xenon headlamps with headlamp cleaning system and PARKTRONIC.
In 2004, the new top-of-the-range model, the SL AMG was launched. Powered by an AMG 6.0-litre V12 biturbo engine producing 450 kW (612 bhp) and a torque of 1000 newton metres, it was the mightiest production roadster in the world. Impressive proof of the exceptional power of the AMG twelve-cylinder engine was the fact that it could accelerate from a standstill to 100 km/h in just 4.2 seconds. In 2004, the V12 biturbo engine won the “International Engine of the Year” award in the category “Best Performance Engine”.
2006: facelift for the R 230 series
Five years after its launch, Mercedes-Benz upgraded the SL. The 2006 Geneva Motor Show was chosen as debut event. Engines, drive system and suspension in particular were given a sportier tuning.
The V8 engine (M 273) of the SL 500 was a new design; it now had a displacement of 5.5 litres and developed an output of 285 kW (387 bhp). It accelerated from 0 to 100 km/h in just 5.4 seconds. In the USA the vehicle was sold as the SL 550.
The six-cylinder engine of the SL 350 was a new development, too. The 200 kW (272 bhp) V6 power plant (M 272) delivered around 11 per cent more output while enabling fuel savings of more than 1 litre per 100 kilometres. The combined NEDC consumption was 10.3 litres per 100 kilometres. The SL 350 accelerated from 0 to 100 km/h in 6.6 seconds, making it over half a second faster than the previous model.
At the top of the model range was the V12 biturbo engine of the SL 600. Its output rose to 380 kW; the maximum torque, to 830 newton metres. With the twelve-cylinder engine this SL sped from 0 to 100 km/h in just 4.5 seconds.
The V6 and V8 models of the facelifted SL-Class are equipped as standard by Mercedes-Benz with the 7G-TRONIC seven-speed automatic transmission. The actively regulated suspension system Active Body Control ABC (standard equipment for the SL 500 and SL 600, optionally available for the SL 350) was further improved. It now reduces body movements in dynamic handling situations by as much as 60 per cent versus the previous model.
The body design was discreetly updated to include new bumpers with three large openings for cooling air, a more pronounced wedge shape, and fog lamps with chromed trim rings. The radiator grille now had three louvres with chrome elements painted matt silver. New light-alloy wheels made for an impressive side view. The horizontally-divided tail lights with red-and-white covers in clear-lens look made the muscular rear end of the SL appear even broader.
The interior was also redone showing, for example, leather upholstery with a softer grain, new interior colours, aluminium trim elements with a prism pattern, and metal door sills embossed with Mercedes-Benz lettering.
From spring 2007, for models SL 350 and SL 500 a Sports package has been available for 2,975 euros extra. It sets the tone in the interior with contrasting topstitching in silver, perforated leather and aluminium trim elements. The look is determined among other things by large five-spoke light-alloy wheels (diameter: 48.26 centimetres) behind which silver-painted brake callipers are visible. Perforated brake discs at the rear conduce to excellent deceleration. The 7G-TRONIC Sport automatic transmission with shift paddles on the steering wheel is also included in the configuration. Furthermore, the distinctive visual features include darkened tail lights.
In 2008, a comprehensive package of refinements was then applied to the R 230 series. The proven vehicle range was retained but supplemented by the SL 280 (170 kW/231 bhp) with a 3.0-litre V6 engine (M 272), so that there are now two six-cylinder models; both engines are based on the same basic unit and have the same engine number. Also available is the SL 63 AMG, whose naturally aspirated V8 engine (M 156) develops 386 kW (525 bhp); as transmission it has the AMG Speedshift MCT, featuring a so-called wet start-up clutch instead of a torque converter.
The most conspicuous element of the model refinement package is the new front design: it adapts the SL to the brand’s current car design and focuses attention on a broad and thus very dominant radiator grille. It enhances the powerful look of the SL face, which appears surprisingly new but at the same time very familiar. Powerdomes on the bonnet enhance the vehicle’s strong visual impression. At the rear a newly designed diffusor-look bumper creates associations with racing.
The list of further refinements for the facelifted SL-Class is long. The technical innovations now include the optional Direct-Steer system, the Intelligent Light System with five light functions adapted to typical driving situations, and the AIRSCARF® neck-level heating invented by Mercedes-Benz, which can extend the open-top driving season into the cooler time of the year.
Exclusive high-performance coupé for the highly discerning
In November 2008, Mercedes-Benz presented the SL 65 AMG Black Series as an exclusive top-of-the-line model of the R 230 series. This high-performance coupé was developed in the AMG PERFORMANCE STUDIO and offered thoroughbred motorsport engineering. The AMG 6.0-litre V12 biturbo engine delivered 493 kW (670 bhp) and 1000 newton metres of torque. As comparison: the SL 65 AMG, on which this top model was based, was powered by an AMG 6.0-litre V12 biturbo engine with an output of 450 kW (612 bhp). The SL 65 AMG Black Series could accelerate from a standstill to 100 km/h in 3.8 seconds, reaching a speed of 200 km/h in just 11.0 seconds on its way to its top speed of 320 km/h (electronically limited).
Meanwhile, the SL 63 AMG was a sensation on the world’s most famed racetracks: in the 2008 and 2009 Formula 1 seasons the car acted as official F1™ Safety Car. A newly-developed AMG sports exhaust system with a larger diameter and special rear silencers enabled the AMG high-rev naturally-aspirated engine to breathe with even greater freedom – and sound even sportier. The AMG SPEEDSHIFT MCT 7-speed sports transmission provided sheer driving dynamism with steering wheel gearshift paddles enabling gear changes in 100 milliseconds.
A specially-developed coil suspension enabled optimum racetrack performance, allowing an individual suspension set-up for each specific track. Perfect traction, no matter what the weather conditions, was guaranteed by the combination of three-stage ESP® and a rear-axle differential with a 30-per cent blocking effect. Larger-dimensioned and additional coolers for engine and transmission oil, coolant water and power steering ensured absolute reliability despite even tropical outside temperatures.
The R 230 series carried on the extraordinarily successful history of the Mercedes-Benz SL in the 21st century. A total of 170,000 customers have chosen one of the sports cars assembled at the Bremen facilities. In the spring of 2012, the new SL, of the R 231 series will see its market launch, representing the next generation of these SL production sports cars.
The R 230 series in the press
Regarding the Mercedes-Benz SL of the R 230 series, “ auto motor und sport” , Germany, No. 12/2004, noted in a test report on the SL 500: “Lots of comfort, lots of safety, solid design, a pinch of sportiness, horsepower à la carte, plenty of fresh air and, as of most recently, a hardtop in the boot – this rare blend secures the two-seater a special position that makes it virtually unrivalled.”
“Autorevue”, Austria, No. 7/2008, described the stages of open-top driving in a Mercedes-Benz SL 350 in these words: “Progressive climate stages on a cool evening: first you raise the front and rear side windows, then you ask the passenger to put up the draught-stop. Then you might switch off the seat ventilation and switch on the seat heater. The air conditioner radiates basic warmth. The Airscarf – that seductive neck-level heating system that we miss on the sofa in our living room – follows, in three heat levels. Last stage is the big roof number, amazingly graceful. And everything’s just fine.”
Shortly after the debut of the Mercedes-Benz SL 65 AMG Black Series “ Road & Track” , USA, No. 1/2009, wrote: “Will anyone buy an SL 65 AMG Black Series for street use? Probably not. But for those few who might, the car is quite civilized on the road. The ride is firm, but not overly so. To truly appreciate the incredible prowess of the SL Black Series, take the car to the track. Its sheer power and speed, together with confidence-inspiring handling, make it one of the most satisfying supercars in the world.”
Technical highlights of the Mercedes-Benz SL, R 230 series
  • Vario-roof with sophisticated folding mechanism and a folding time of 16 seconds
  • Roll-over bar retains its full functionality even with the vario-roof closed
  • Electrohydraulically controlled SBC™ Sensotronic Brake Controlbrake system
  • Suspension with ABC Active Body Control
  • Innovative head-thorax airbags in the doors
  • Drag coefficient cd = 0.29 (with closed roof)
  • Use of lightweight components for optimum fuel economy
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