Mercedes-Benz SL EvolutionMercedes-Benz SL Evolution

Published: Apr 19, 2012
Words by Ya'acov Zalel

The term SL-Class refers to the marketing variations of the vehicle, including the numerous engine configurations spanning five design generations.
In 1950, as the German automotive industry began to recover from the horrors of World War II, Daimler-Benz made the decision to go back into motor racing. Rudolf Uhlenhaut a gifted engineer and driver, was the head of the passenger car research at the automaker and was also involved in their racing program during the '30s. He received the responsibility for the project and in a few months, he built a chassis, codenamed W194, which became the basis for the 300 SL.

«The Racing Car That Inspired the Mercedes-Benz SL»
The 300 stood for Daimler's most prominent model at the time, from which the heavy axels, the engine (in a modified version), and the drivetrain were adopted. In order to save weight, Daimler engineers developed a tubular spaceframe chassis made of thin tubes joined together to form triangles. The frame weighted 50 kg, hence the acronym SL, Super Light in English, or Superleicht in German. It was a tremendous relief to the 3.0-liter 170hp engine, which was installed at the front in a 50 degree inclination to the left in order to improve the hood's profile and lower the car's center of gravity.

The engine was fed by carburetors and power was transmitted to the rear wheels. The thin aluminum body panels were hand-crafted by Daimler coachbuilders. The Gullwing doors, which became the car's trademark, were a consequence of the wide body needed to achieve the chassis' high rigidity. All in all it was a proper exercise in mechanical engineering that created an impressive race car that won four out of five races it took part in during the 1952 season. These included the 24 Hours of Le Mans, the Jubilee Grand Prix for sports cars at the Nurburgring, the Bern Prize for Sports Car, and the 3,100 km road race across Mexico, the Carrera Panamericana. It only failed to win the Mille Miglia, in which two 300 SLs placed 2nd and 4th. In the years to come, this racing car became the inspiration for the famous SL-Class.

The Mercedes 300 SL Coupe - the World's First Supercar

Two individuals, whose names are neither Benz nor Daimler, influenced the fate of Daimler immensely and both of them were able salesmen. The first one was Emil Jellinek, whose story belongs in another era. The second was Maxi Hoffman, Daimler's US distributor, who promised Daimler's top executives that he will be able to sell 1,000 units of the 300 SL in the US. In doing so, he forced them to consider re-engineering that successful race car into a road car.

The result of Hoffman's request were three models based on two platforms: the 300 SL Gullwing (aka the Coupe), the 190 SL open-top, and the 300 SL Roadster. The first two debuted at the International Motor Sport Show in New York in 1954. The Gullwing Coupe was an advanced development of the W194 racing chassis; its 3.0-liter 215hp engine was much stronger the W194's engine due to the installation of a mechanical fuel injection system, the first of its kind in a passenger car. It was a real supercar with a top speed of 155 mph. Its aerodynamic shape was an imitation of the original SL combined with its combat and racing capabilities as well.

It was heavier, due to the need for passengers' convenience items and a more extensive interior finish. On the road, it had a tendency to oversteer under acceleration. Since no electronic speed limiter was available, sometimes a note with a recommended 120 mph top speed could be found stuck to the dashboard. In just three years, 1,400 300 SL Coupes were sold before it was replaced by the roadster (W198 II) on the same spaceframe chassis, but adapted to standard doors and without the fixed head cover. It was propelled by the same 3.0-liter 215hp engine.

The headlamps received a rectangular shape in a portrait position. The hood was decorated as before with two, longitudinal bulges; a retractable roof was installed, though from 1958, a removable hard-top version was also available.

For Relaxation, the Mercedes 190 SL Was the Best

With all the symbolic importance of the Mercedes 300 SL, the second iteration of the 1st generation, the 190 SL, was even more popular. It was based on a derivative W121 chassis and was propelled by a 1.9-liter 105hp engine; good enough for relaxed open-top driving. The 190 SL did not even pretend to possess a racing pedigree. It was an elongated and elegant car with an exceptionally long engine bay against a short trunk, and with a retractable soft roof made of fiber.

That car was "intended for a class of customers who want to travel large distances themselves at high cruising speeds in this externally very sporty looking car," as wrote the design engineer Josef Muller. Its body lines were similar to those of the Gullwing version and the 1.9-liter engine with overhead camshaft was good enough for 106 mph. On the hood was one longitudinal and centrally located bulge and the dashboard was different from that of the coupe. It goes without saying that Hoffman didn't encounter any difficulties in moving those 1,000 cars he promised to sell.

By the end of the model's life in 1963, 25,881 units of the 190 SL were sold along with an additional 1,858 units of the 300 SL Roadster. All in all, over 29,000 first generation SL class units were sold. It was a strong and promising start for the new line.

French Design Shaped the Most Elegant SL Ever

Two extremely talented designers took part in creating the Pagoda: Frenchman Paul Bracq, who was only 30 years old when the car was launched. He designed it with subtle artistic flair that is evident all throughout the car. He is also responsible for the individual pagoda-shaped roof. The second designer was Bela Barenyi, probably the most prolific inventor in the history of the motor industry, who contributed a few advanced safety features.

The exterior of the 230 SL is characterized by distinct, straight lines and the unmistakable SL front-end. The proportion from the hood to the trunk was more evenly distributed than before, therefore the car looks more gentle and less powerful. The headlamps are posing in portrait position (as in the W198 II), the air intakes beyond the front wheels disappeared and the two longitudinal bulges on the hood were erased. The dashboard design was almost the same as that of the 300 SL Coupe. It had two prominent round gauges, one for the speedometer the other for a tachometer, and between them was a longitudinally positioned set of gauges.

«The Most Elegant SL Ever»
Like its predecessor, it was a two-seater with an optional extra rear transverse seat, just like in the 190 SL. Since the basis for the W113's floor unit was the W111's floor, the world's first saloon with a safety body innovation was copied to the W113 chassis as well. It was designed to reduce injury hazards in accidents and seatbelts were optional. The body adopted from the 220 SE was characterized by more subtle lines, particularly at the front-end. It was first introduced as 230 SL with a 6-cylinder 2.3-liter 148hp engine. The car was a bit heavier than competing models though a few panels were made of aluminum in order to lighten it. Later editions were the 250 SL and the 280 SL, both with inline 6-cylinder engines. The 230 SL was available as a roadster with a user-friendly folding soft top or a thoroughbred hardtop coupe. Those roof versions were later adapted later to the 250 SL and the 280 SL. The 230 SL Pagoda in its coupe version also displayed its abilities in long distance rallying, a motorsport format that no longer exists. In 1963, it won the Spa-Sofia-Liege long-distance rally, one of the most grueling and respected events on the calendar.

The Longest Life Span of a Mercedes-Benz Model

For 18 long years, Daimler produced the R 107 SL (R stands for Roadster), the longest run of an SL Class model. It had a slick and elegant body that was beefier than its predecessor. The coupe version maintained a few cues from the Pagoda roof, though it lacked the charisma of the previous two generations. The front-end was characterized by the rectangular grill, and the headlamps were positioned in a landscape position as opposed to the previous portrait position.

The main novelty of this generation was the integration of V8 engines, the first SL-Class with an engine larger than the six-cylinder. Bizarrely, the first version used a 4.5-liter engine but was named 350 SL and only when exports to the US began, in 1972, the 450 SL, with the same engine, was born. However, the 350's engine sputtered 200hp and the 450's engine was more powerful with 224hp. As with the previous generation, this one was available as either an open top (either in soft top or hard top version) or a coupe, which was called the SLC. It was based on the R 107 but had a few different design cues.

This was produced for 'only' 10 years before it was replaced by the new SLC in 1981. During the 18 year SL life span, there were versions like the 280 SL and 280 SLC (with an inline six-cylinder 185hp engine, a response to the oil crisis of 1973), 300 SL (inline six-cylinder 188hp engine, towards the end of model production), 420 SL (V8 218hp engine), 380 SL and 380 SLC (V8 218 engine) 500 SL and 500 SLC (V8 240hp engine). The engines evolved throughout and during the last few years of the generation they were equipped with the first catalytic converter systems. Once again a lot of efforts were made to ensure the innovation of safety features.

These were thanks to a carefully defined crumple body behavior and body shell, a high-strength A-pillar, and interior appointments uncompromisingly designed according to safety criteria. When production ended, more than a quarter million third generation SLs were produced and a record was set for the longest production period of one model by Daimler-Benz in the company's history.

The Revolutionary Mercedes SL

Bruno Sacco, one of Daimler's most influential post-war designers, was responsible for the transition from the 18 year old R 107 model to the R 129. From the front the change is clear: no more three-pointed star with two metal stripes stretching out from both sides. Instead, the star is surrounded by seven stripes. To complete the front-end's revival, two new almost square headlamps were adopted. However, they weren't relatively big and dominant as were the headlamps from previous models.

Sacco gave the R 129 a modern and dynamic look with a windscreen slanted sharply backwards, and the front grille is also tilted backwards. The stance is more aggressive, but the overall visual impression is of a more rounded car with less sportive ambitions. The hood is sleek without any bulges. The antiquated interior design, with the large round gauges from the '50s and old materials from the '60s was replaced with one unit of three smaller gauges with modern fonts. The round air vents gave way to almost invisible rectangular units, and the center console became a command center for various ancillaries that were popular at the time.

The car remained a two-seater though two small rear seats, suiting for babies, were installed. As far as engines were concerned, the R 129 had quite a few inline-sixes, V8s, and even the first V12 engine in an SL. Another first for the series was the automatic roll-over bar which was used for the first time in a road car. So as not to impair open-top driving pleasure with a permanently installed, rigid roll bar, a flexible solution was realized which activates the roll-over protection only if needed. When not in use the safety bar is deposited in front of the soft-top compartment.

When a roll-over threatens, the sensor-controlled roll-over bar is electromagnetically triggered, raised into position by the force of pre-compressed springs within 0.3 seconds and secured by pawls. The high-strength center pillars, connected over a large area with the rear longitudinal members, serve as a basis for mounting and as support. In addition to automatic triggering in an emergency, by means of a switch the driver can choose to raise and lower the bar slowly, with a hydraulic element carrying out the action. An ABS system was also a new innovative concept that later became a common feature in almost every car.

Mercedes SL Class Loaded with Electronic Wizardry

The fifth generation SL was unveiled in July 2001, presenting its unique variant of the automaker's then double-rounded-headlamp configuration theme. The transverse stripes were increased in size and reduced to three. However, the most notable exterior design change was the new bulbous roof, as opposed to the angular build of the previous generation. It accentuated the elongated hood along with the short and compact trunk and decorated the car with an energetic look.

The interior design was also changed as the cluster of three gauges was replaced with two separate round gauges. The SL 500, with an output of 306hp, was the first model to arrive on the market. It was later joined by the SL 55 AMG with a supercharged V8 engine and 476hp. In 2002, the SL 350 featuring a 3.7-liter V6 with 245hp engine followed. And in January 2003 Mercedes-Benz finally introduced the 600 SL with the powerful 500hp 5.5-litre V12 biturbo engine as their new flagship model. The standard equipment included leather-upholstered seats plus a memory function for the electric seat and steering wheel adjustment.

Other standard features included a multifunction steering wheel, automatic climate control, and stereo car radio. As optional extras, innovative assistance systems like the DISTRONIC proximity control, the automatic emergency call system TELEAID, the control and display system COMAND or the electronic tire pressure monitoring system were available. A facelift was done for 2008. From the side view the air intakes in the wings are prominent (though there were also similar air intakes in the previous model), as they were a typical feature of the first 300 SL. The headlamps became less prominent and better integrated into the body work.

The hood was also beautifully shaped with two elongated bulges. The steeply raked windscreen emphasises the sports car character and accentuates the low, wedge-shaped silhouette. Unlike its predecessors, the R 230-Series SL always carried its hardtop build around a vario-roof system. At the push of a button the roof opens or closes in a 16-second process. An extremely complex swivelling mechanism ensures that the three roof components disappear into the upper part of the trunk.