• W 116 series
• W 126 series

Mercedes-Benz S-Class, W 116 series (1972 to 1980)
A brand-new premium-class vehicle generation was presented to the public in September 1972. The first officially designated “Mercedes-Benz S-Class” – internal designation W 116 – replaced the W 108/109 series and was initially comprised of three models: the 280 S, 280 SE and 350 SE.

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The 280 S and 280 SE models featured the six-cylinder engine M 110 with dual overhead camshafts that had made its debut in the W 114. Six months later the S-Class saloon was also offered with the larger 4.5-liter V8 engine in parallel to the 450 SL and 450 SLC. At the same time the 450 SEL was introduced, its wheelbase lengthened by an extra 100 millimetres; as with its predecessor models, the additional space served to increase legroom in the rear. The long version was also available from November 1973 as a 350 SEL and from April 1974 as a 280 SEL.

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One noteworthy engineering innovation first featured as standard in the W 116 series saloons was the double-wishbone front suspension with zero-offset steering and anti-dive control, as tested originally in the C 111 experimental vehicle. This permitted further dynamic handling improvements. Rear suspension was essentially the same as the design that had by this stage been tried and tested over many years in the Stroke Eight models and which was also in use in the 350 SL. The 4.5-litre models were fitted with a coupled-link axle.

High level of security
In terms of passive safety, too, the S-Class was at the forefront of engineering. The variety of safety design features integrated for the first time into the 350 SL were of course included without exception in the S-Class saloons. The fuel tank, for example, was no longer positioned in the rear end but above the rear axle for protection in case of accident; in the interior, maximum protection was offered by the heavily padded instrument panel, yielding or recessed switches and levers, and a four-spoke safety steering wheel with impact absorber and broad padded boss. The most significant improvement over the predecessor series was the even stronger safety passenger cell with stiffened roof-frame design, high-strength rigid roof and door pillars and reinforced doors. By controlling the deformability of front and rear end it was also possible to improve considerably energy absorption in the front and rear crumple zones.

Special wind deflectors on the A-pillars guaranteed good visibility. In wet conditions these served as channels for dirty water, keeping the side windows clean in bad weather. Other safety features included wrap-around turn indicator lamps that provided good visibility even from the sides, and large rear lights, which offered good resistance against soiling thanks to their ribbed surface profile.

The Mercedes-Benz 450 SEL 6.9
In May 1975 the company presented the 450 SEL 6.9 – the new top model in the series and true successor to the Mercedes-Benz 300 SEL 6.3. The powerful 6.9-liter V8 engine, developed from the highly successful 6.3-liter unit, achieved an output of 286 hp (210 kW) and maximum torque of 56 mkg (549 Newton metres). The hydropneumatic suspension with self-levelling – featured for the first time in a Mercedes-Benz passenger car – guaranteed the utmost in ride comfort. Other special equipment included in the standard specification for the top-of-the-range model were the central locking system, air-conditioning and a headlamp wash/wipe system. As was the case with its direct predecessor, the 450 SEL 6.9 proved an immediate success; although it was more than twice as expensive as the 350 SE, a total of 7,380 units were built during its four-and-a-half year production period.

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Between November 1975 and February 1976 the direct fuel injection system in the 2.8-liter, 3.5-liter and 4.5-liter injection engines was converted to fall in line with more stringent emissions standards now in force in most European countries. The electronically controlled Bosch “D-Jetronic” was abandoned in favour of the newly developed mechanically controlled Bosch “K-Jetronic”. In all three cases conversion was achieved with only minor loss in output; at the same time, compression was slightly reduced in the 2.8-liter and 3.5-liter engines. For ease of maintenance these modifications also included breaker-less transistorized ignition and hydraulic valve clearance compensation for both V8 engines.

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As with the 2.8-liter injection engine, compression was reduced also in the carburettor engine, similarly causing a slight decrease in output. Two years later, from April 1978, the original output was once again offered in all three models with injection engines. In contrast to the carburettor version, compression in the 2.8-liter injection unit was raised to its old value, and the previous output in the two V8 models was achieved largely by modifications to the exhaust system.

A diesel in the S-Class
In May 1978 the model range in the W 116 series was expanded even further. As the latest addition to the family, the 300 SD attracted just as much attention among connoisseurs as had done the 450 SEL 6.9 three years earlier – although it was positioned at the opposite end of the performance scale. For the first time in the history of this vehicle category, the new S-Class model was powered by a diesel engine. The 3.0-liter five-cylinder unit, that had proved so successful in the mid-range 240 D 3.0 and 300 D models, was given a turbocharger for its new role, enabling output to be increased to 85 kW (115 hp). Development of this unusual S-Class variant, which was offered exclusively in the USA and Canada, was begun with the aim of meeting the fuel consumption standards recently introduced by the US government. The most decisive factor here was the so-called Corporate Average Fuel Economy, an invention of the Carter administration, which denoted the average fuel consumption of all passenger car models in a manufacturer’s range. By extending the range to include conventionally economical diesel models it was possible to bring the fleet’s average fuel consumption under the legal limit.

A technical innovation of ground-breaking significance was offered as a world exclusive in the S-Class saloons of the W 116 series from fall 1978: The anti-lock brake system (ABS), developed in collaboration with Bosch, which guaranteed a vehicle’s unrestricted steering response even under emergency braking and thus made a vital contribution to active safety. Today almost a commonplace and available even in small cars, at the time the market launch of ABS was seen as nothing short of sensational.

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Safety of a rather different nature was offered by the armoured version of the W 116 series. Protection design underwent further improvements based on the sum of experience gained during development of the armoured 280 SEL 3.5. Taking the eight-cylinder models as a whole – the 350 SE, 350 SEL, 450 SE and 450 SEL – a total of 292 units were built as armoured vehicles for delivery to special customers, including many state institutions in Europe and overseas.

The successors to the first S-Class series – the W 126 models – were presented in September 1979 at the Frankfurt IAA. But that did not put an immediate end to the W 116 series; production was gradually phased out for each model between April and September 1980. Of the 473,035 units built in this model series, the last vehicle to leave the Sindelfingen plant was a 300 SD.

The W 116 series in the press
Auto, Motor und Sport, Germany, volume 2/1973, on the Mercedes-Benz 350 SE:
“The pleasure of driving a Mercedes 350 SE is sadly an expensive one and affordable only by a minority. This is regrettable, because for the considerable financial outlay one gets not only representation and a status symbol, but also more importantly a wealth of benefits that one would wish for in any car: A high degree of active safety and crashworthiness, perfected body design, outstanding comfort, large reserves of energy, effortless driving and exemplary craftsmanship. And all these highly desirable features come together to form an overall image in which one thing stands out above all – that this is one of the world’s most perfect cars.”

Car, England, June 1975, on the Mercedes-Benz 450 SEL 6.9: “A car of such speed and weight must have demonstrably good roadholding and handling, and this one is no disappointment in anything from a hairpin to a three-figure-bend: the suspension soaks up the bumps, the transmission is wonderfully smooth and admirably easy to control (either by a sensitive accelerator foot or a hasty hand at the lever), and the steering is servo-assisted in a way that highlights the nearly neutral responses of the vehicle.”

Automobil Revue, Switzerland, May 15, 1975, on the Mercedes-Benz 450 SEL 6.9: “It is a real joy, given the present climate, to witness the launch of a car that offers the connoisseur the utmost in driving pleasure – and at any speed. The 6.9 is testimony not only to the optimistic outlook of those responsible for its design, but also to their having the courage of their convictions.”
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Mercedes-Benz S-Class, W 126 series (1979 to 1991)
In September 1979, Daimler-Benz presented a new S-Class generation at the IAA in Frankfurt. The range of models available in the W 126 series was comprised initially of seven vehicles: Choice was from four engines (from the 2.8-liter six-cylinder carburettor unit with 115 kW/156 hp to the 5.0-liter V8 light-alloy engine with direct fuel injection and 176 kW/240 hp) and two body variants – in addition to the normal version, a lengthened variant, as had traditionally been the case with premium-segment saloons for generations. In this case, lengthening of the wheelbase by 140 millimetres was more apparent than otherwise and as usual the extra space served exclusively to increase legroom in the rear and the entry width for the rear doors.

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In addition to improving ride comfort and safety, development of the new model series focused on decreasing energy consumption. The use of weight-reducing materials and an aerodynamic body optimized in the wind tunnel (cd= 0.37, compared with cd= 0.41 in the W 116 series) helped the new S-Class achieve a ten-percent reduction in fuel over its predecessor models. The two eight-cylinder engines of the predecessor series were replaced with two redesigned units with larger displacement and light-alloy crankcase. The 5.0-liter engine, which replaced the 4.5-liter cast iron unit, was already familiar as the power unit from the 450 SLC 5.0, while the 3.8-liter light-alloy engine was developed based on the long-serving 3.5-liter V8 with cast iron block. With both higher output and reduced weight, the new V8 engines could now achieve improved performance while at the same time using less fuel. The carburettor and injection versions of the 2.8-liter six-cylinder remained in the range unchanged.

Diesel for export
The W 126 series also saw development of a diesel version for export to the USA. Like its predecessors, the 300 SD Turbodiesel offered a turbocharged 3.0-liter five-cylinder engine, though with output now increased by ten hp (7.4 kW) to 125 hp (92 kW).

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Chassis design was essentially the same as for predecessor models. The new S-Class saloons also featured a diagonal swing-axle at the rear and double-wishbone front suspension with zero-offset steering. The 5.0-litre models were again fitted with the coupled-link axle.

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The body design incorporated state-of-the-art findings in safety research. Thanks to its new design principles the passenger compartment was now able to withstand the so-called “offset crash” unscathed at a speed of 55 km/h. The W 126-series saloons were the first production cars worldwide to meet the criteria of the frontal offset crash.

Many of the characteristic design elements of the S-Class are to be found beneath the waistline. For the first time, a Mercedes-Benz passenger car had no bumper bars in the classical sense, having instead generously proportioned plastic-coated bumpers that were seamlessly integrated into the car’s front and rear aprons. Broad lateral protective strips made of plastic created a visual link between front and rear aprons, positioned at bumper height between the wheel arches.

A coupe joins the range
At the IAA in Frankfurt of fall 1981, two years after the debut of the W 126 series, an elegant coupe was added to the family, available only with eight-cylinder engines. Both V8 units underwent comprehensive revision as part of the recently initiated “Mercedes-Benz Energy Concept”, a program geared to reducing fuel consumption and harmful emissions. In addition to an increase in compression, the list of improvements included camshafts with modified valve timing, air-bathed injection valves and electronic idle speed control. Camshafts with modified valve timing enabled maximum torque to be achieved at a lower engine speed and in the case of the 3.8-liter engine torque was even increased. This unit was subjected to particularly thorough revision: In order to achieve a more favourable volume-to-surface ratio, the bore was reduced and the stroke increased. The modified 3.8-liter V8 thus benefited from a slightly larger displacement. But by way of compensation for their significantly better fuel economy, the two eight-cylinder units were obliged to accept a minor drop in output. In both cases, rear axle ratios were tuned to meet the modified characteristics of the engines and were significantly longer. And the two six-cylinder units also saw a whole series of minor modifications that likewise led to fuel economies, even if these were less dramatic. These measures did not affect power output.

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Four years after the launch of the Energy Concept the company carried out a comprehensive model refinement package, so that in September 1985, once again at the IAA in Frankfurt, it was able to introduce a completely revised S-Class line-up. Visual aspects were subjected to moderate revision; first and foremost this affected the bumpers and protective side moulding, but also the wheels, which were changed from 14 to 15 inches. This also brought with it a safety element, since it allowed larger brake discs to be fitted. Top priority, however, was give to the restructuring of the engine range.

Two newly-designed six-cylinder units, which had been premiered nine months earlier in the mid-range W 124 series, now replaced the trusty 2.8-liter M 110 engine. In the place of the carburettor version came a 2.6-liter direct injection unit, while the parallel-developed 3.0-liter unit became successor to the injection variant of the M 110. A new addition to the range was the 4.2-liter V8 engine, developed by increasing the bore of the 3.8-liter unit and now fitted to the S-Class saloon, the SEC coupe and the SL. The 5.0-liter engine was also modified. Now equipped with an electronic ignition system and the electro-mechanically controlled Bosch “KE Jetronic” injection system, it generated an output of 180 kW (245 hp).

5.6-liter displacement
The most spectacular innovation in the engine range was a 5.6-liter eight-cylinder unit, which was developed by lengthening the stroke of the 5.0-liter V8 and which unleashed an output of 200 kW (272 hp). If required, an even more highly compressed version was also available that delivered a mighty 221 kW (300 hp), although it was not possible to combine this unit with a closed-loop emission control system. But even without catalytic converter this so-called ECE version met emissions standards set down by the Economic Commission for Europe. The models fitted with this engine variant – the 560 SEL and 560 SEC – were in their day the most powerful Mercedes-Benz production cars ever built.

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All variants in the revised model range – with the exception of the 560 SEL and 560 SEC in the ECE version – were available on request with a closed-loop emission control system with three-way catalytic converter. In each case the series version was the so-called “catalytic converter retrofit version”, for which the vehicle was delivered without catalytic converter and oxygen sensor, but with the multi-functional mixture preparation and ignition system. These “retrofit versions” could be fitted with the closed-loop catalytic converter without difficulty at a later date. This gave customers maximum flexibility in choosing the moment to convert their vehicle – a not insignificant advantage, given that unleaded gasoline was not universally available at the time. From September 1986 the closed-loop catalytic converter was standard equipment on all Mercedes-Benz passenger car models with gasoline engines; the retrofit versions were available until August 1989 – with a corresponding price discount.

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With the introduction of the new model range, the diesel model – which was still reserved exclusively for US export – was replaced by a modified variant. The new 300 SDL was presented with the additional space of the long version and featured an entirely new design of engine. This was based on the familiar 3.0-liter six-cylinder unit from the mid-range W 124 series, although this too was equipped with a turbocharger. The six-cylinder turbodiesel now delivered 110 kW (150 hp) – 44 kW (60 hp) more than the basic version without supercharger and almost 22 kW (30 hp) more than the five-cylinder engine of the predecessor model.
As was expected, the running gear of the facelifted models displayed no fundamental modifications. Nevertheless, the rear axle design was modified in a few details in order to improve ride comfort and reduce engine noise. In addition, all models in the W 126 series were now fitted with 15-inch wheels and larger brakes to match. The design of the optional light-alloy wheels – these were only standard equipment on the 560 SEL and 560 SEC – was updated to match those of the compact-class and mid-range model series.

Minor modifications
The other stylistic modifications carried out on the improved models of the W 126 series not only served to update the design, but were also integrated for specific technical reasons. By lowering the aprons it was possible to further reduce front axle lift forces and improve airflow at the rear. This also had the effect of further enhancing directional stability and road adhesion when moving at speed, an aspect of considerable importance with respect to the performance of the new top-of-the-range 560 SEL.

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The lateral protective strips were now smooth in design rather than grooved, and like the bumper system they reached down lower and included additional trim on the frame side members. As the 5.6-liter models came with wider 215/65 VR 15 tires as standard, unlike their lower-powered sister models, front apron and fender beading were modified in shape in order to create the necessary lateral clearance for the front wheels.

In September 1987, when the S-Class encountered an unusually chilly easterly wind in the form of the BMW 750 i, higher-performance variants of all V8 engines were introduced. Compression ratios in all cases were increased to 10:1, and additional measures were taken to improve performance by between six and ten percent depending on the model. The effect was even clearer in the case of the variants with catalytic converters: By optimizing the emission control equipment the designers succeeded in significantly reducing power loss due to the catalytic converter. The ECE version of the 5.6-liter V8 was discontinued without a replacement, since as a result of the treatment to increase output the catalytic converter retrofit version was now also capable of developing 221 kW (300 hp).

At the Paris Motor Show in September 1988, the model range was expanded to include the 560 SE from the W 126 series, thus making the 5.6-liter engine available in a saloon with conventional wheelbase.

A new diesel variant
From June 1989 a new variant with diesel engine was produced, although this too was only available in the USA. Production of the previous 300 SDL had already come to an end in September 1987. The 350 SDL model had a new 3.5-liter six-cylinder engine that had been developed by increasing the bore and stroke of the tried-and-tested 3.0-liter unit. The new turbodiesel was designed more for torque than output and, with exhaust gas recirculation and oxidation catalyst, generated 10 kW (14 hp) less than its predecessor in spite of the larger displacement. But the 350 SDL’s 100 kW (136 hp) was more than adequate, especially given the speed limits that applied throughout the USA. Maximum torque was increased by almost 15 percent and was reached at just 2000/min. In June 1990 the 350 SD with a conventional wheelbase was introduced to go alongside the 350 SDL.

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As was the case with the predecessor series W 116, the eight-cylinder W 126 models were also available as armoured variants. Protection design had been further perfected after intensive development work and a total of 1,465 units were produced. Two 500 SEL models are of particularly interest here, both with a wheelbase extended by 200 millimetres and roof raised by 30 millimetres. The first of these was built in January 1983 and served as an additional representational vehicle in the company’s own car pool. The second was built on commission from the Vatican for the Holy Father and handed over to Pope John Paul II in August 1985.

As successors to the W 126 series, eight W 140 series saloons were introduced at the Geneva Motor Show in March 1991. Although the new models went into production only a month later, the plant continued to turn out saloons of the 126 series for export for a while. Production of most variants came to an end between August and October 1991, although the last few armoured models did not come off the production line until April 1992. During the entire 12-year production period a total of 818,036 saloons left the production lines in Sindelfingen, 97,546 of them with diesel engines. That made the W 126 the most successful premium-class series in the history of the company.

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The W 126 series in the press
Auto, Motor und Sport, Germany, issue 22/1979, on the S-Class from the W 126 series: “On driving you quickly realise that at Daimler-Benz quietness is part of civil responsibility. Any mechanical noise – even with the six-cylinders – remains discreetly in the background. Moreover, it is nothing short of striking to note just how thoroughly the Mercedes developers have managed to eliminate wind noise.”

Road & Track, USA, February 1980, on the S-Class of the W 126 series:
“Hurrying back through the woods over a rather bumpy stretch of road, I was reminded of how well a Mercedes rides and handles. A live-axle car could be made to do the latter, but not without scrambling your brains. The W 126 does a marvelous job at both tasks and stops quickly too.”

Frankfurter Allgemeine Zeitung, Germany, May 24, 1986, on the Mercedes-Benz 300 SE:
“The 300 SE holds its line like a ship on a fixed course. Any unevenness in the road surface is swallowed with ease by the springs and dampers. No other car achieves such a degree of comfort out of steel and rubber. The large steering wheel allows you to corner with caution as well as with joyful abandon. It does everything you want. The running gear reveals unusually high reserves of safety.”

Source: Daimler AG