| In September 1979 a new generation of the S-class was presented at the motor show IAA in Frankfurt. The range of models of series 126 first comprised seven types. There was a choice of four engines_- from the 2,8_ltr.-6_cyl.-carburettor engine with 156_PS to the 5,0_ltr.-V8-all aluminium engine with petrol injection and 240_PS. Furthermore, one could decide between two body variants. Beside the normal version there was a prolonged variant as had been offered for generations in the upper-class limousines. This time the enlargement of the wheel base with 140 mm was more remarkable than usual. As always it all was of benefit to the driver's leg room and the entrance width of the rear door.
Important in the development of this new series were next to a higher driving comfort and safety the reduction of energy consumption. Using weight reduced materials and a less air resistant body, optimised in the wind tunnel, helped the new S-class to reduce its fuel consumption by 10_% in comparison to its preceding models. The two eight-cylinder engines of the previous series were replaced by two redesigned aggregates with enlarged displacement and all-aluminium crankcase. The 5,0_ltr.-engine which took the place of the 4,5_ltr.-grey cast iron aggregate was already known from the 450_SLC_5.0. The 3,8_ltr.- all-aluminium engine had been developed after the example of the fife litre engine from the time tested 3,5_ltr.=V8 with grey cast iron block. Due to their higher power with reduced weight the new V8-engines made a better driving performance combined with a more economic fuel consumption possible. The carburettor and injection version of the 2,8_ltr.-6_cyl.-aggregate remained unchanged in the program.
From series 126, too, a diesel version was produced for export to the USA. As its previous model, type 300_SD was also provided with a supercharged 3,0_ltr.-5_cyl.-engine. Ist power, however, was increased by 10_PS to 125_PS.
The layout of the vehicle basically corresponded to the previous models. The new S-class-limousines, too, were equipped with a semi-trailing arm rear axle as well as a twin control-arm front wheel suspension with zero steering offset.
The body had been constructed according to the newest insights into safety research. Thanks to new construction principles the passenger cell now also remained unharmed at an offset impact_- the so-called ,offset crash"- at a collision speed of 55_km/h. World wide the limousines of series 126 were the first series vehicles fulfilling the criterion of an asymmetric offset crash.
The characteristic design elements of the new S-call present themselves more in the lower zones. For the first time a Mercedes-Benz car hat no classical bumpers any more. In stead, there were generously dimensioned plastic-coated bumpers seamlessly integrated into the front and rear apron. Broad side protection strips formed an optical link between front and rear apron, placed at the height of the bumpers between the wheel cut-outs.
In autumn 1981, two years after its debut, series 126 was completed by an elegantly designed coupe version shown at the motor show IAA in Frankfurt. The car was only available with an eight cylinder engine. Within the ,Mercedes-Benz energy concept" for reducing consumption and pollutants, presented at the same time, the two V8=aggregates had been thoroughly redesigned. Next to an increase of compression, a camshaft with changed timing, air-circulated injection valves and an electronic idle-speed control device stood on the list of improvements. Due to the changed cam shift adaptation the torque maximum could be shifted towards lower numbers of revolution. In case of the 3,8_ltr.-engine it was even increased. This aggregate was thoroughly changed. In order to obtain a more favourable volume-surface ratio the bore was reduced and the stroke increased.
Thus the modified 3,8_ltr.=V8 showed a slightly increased displacement. In both eight cylinders slight power reductions had to be taken into account compensated, however, by a considerably improved economic efficiency. In both cases the rear axle transmission ratio was adapted to the changed characteristics of the engine. The two six-cylinder engines were also changed in a number of details, thus also achieving some economising effect. The power potential, however, was not affected by these measures.
Four years after the presentation of this energy concept a comprehensive model improvement was launched. Once again at the motor show IAA in Frankfurt, in September 1985, a completely new type program of the S-class was introduced. Besides a discreet face lifting, primarily concerning the bumpers, the side-impact protection and the wheels, a restructuring of the range of engines was in the forefront.
Two newly constructed six-cylinder-aggregates which had made their debut in the medium-size series W_124 nine months before now replaced the time-tested 2,8_ltr.-dohc-engine M_110. In stead of the carburettor version a 2,6_ltr. =injection engine was now used. The 3,0_ltr.=aggregate, developed at the same time, replaced the injection variant of the M_11O. A further newcomer in the program was a 4,2_ltr.-V8-engine which had come into existence by boring out the 3,8_ltr.-aggregate, replacing the latter now in the S-class limousine, in theSEC-coupe an the SL. The 5,0_ltr.=engine had also been modified. It was now equipped with an electronic ignition system and an electronically-mechanically controlled injection system Bosch KE-Jetronic. Its power amounted to 245_PS.
The most spectacular novelty within the range of engines was the 5,6_ltr.=eight cylinder, developed from the 5,0_ltr.=V8 by prolonging its stroke. It mobilised a power of 272_PS. On demand an even higher compressed version was available. It proudly developed 300_PS, but could not be combined with a regulated emission control system. But even without a catalyst, the so-called ,ECE-version" corresponded to the exhaust-gas limits fixed by the European Economic Commission ECE. When first coming on the market, types 560_SEL and 560_SEC, equipped with this engine variant, were the most powerful standard cars built by Mercedes-Benz up to that time.
For all variants of the redesigned range of models - except for types 560_SEL and 560_SEC in ECE-version - a regulated emission control system with a three-way catalyst was available on demand. The standard version was the respective so-called ,RF-version", a car without catalyst and lambda probe, but with the multifunctional mixture preparation and ignition system. Retrofitting a ,back fitting vehicle" with a regulated catalyst was always possible and without problems. This handling allowed the client the highest possible flexibility as to the time of refitting. Since, at that time, unleaded petrol was not available everywhere, this was a considerable advantage. Since 1989 the regulated catalyst has been part of the standard equipment of all Mercedes-Benz passenger car models with Otto engine. Back fitting models_ continued to be available on demand till August 1989 with a respective reduction in price_.
With the introduction of the new type range the diesel model, which has always been exclusively reserved for export to the USA, was also replaced by a modified variant. The new type 300_SDL presented itself with more space as in all prolonged version and a totally reconstructed engine. It was based on the 3,0_ltr.-6_cyl.-aggregate known from the medium size series 124, but once more equipped with a turbocharger. The six-cylinder turbo diesel now mobilised 150_PS_- 60_PS more than the basic version without supercharging and almost 30_PS more than the fife cylinder engine of the previous model.
The chassis of the improved types was - as expected - not changed very much. A few details at the rear axle construction had been modified in order to improve driving comfort and running smoothness. Furthermore all models of series 126 were now equipped with 15_inch-wheels and respectively larger brakes. The design of the available all-aluminium wheels, which were only standard in the 560_SEL and 560_SEC, had been actualised and adapted to the compact class and middle class series.
All further stylistic changes which had been of benefit to the improved models of series 126 had not only served to actualise the design, but had also been developed for very down to earth technical reasons. By pulling down the aprons the front lift could be decreased further and the down stream at the tail improved. Thus driving stability in speeding could be increased once more. This aspect was of special importance to the driving performance of the new top model 560_SEL.
The protective strips at the side were now smooth and had no grooves any more. Like the bumper system, they now came further down and comprised additional panelling of the frame side rails. Since the standard 5,6_ltr.=types - in contrast to their less powerful sister models - had been equipped with broader tires of dimension 215/65_VR_15, the shape of the front apron and the wing bead had been changed in order to achieve the necessary free travel at the side.
In September 1987, when the S-class was exposed to a sharp competition from the BMW 750_i, unknown so far, power-increased variants of all V8=engines were introduced. In all cases, the compression was heightened to ten and with the help of other measures the power could be further increased by 6 to 10_% according to the model. Even more drastic was the effect on the catalyst variants. By optimising the emission control system, the power decrease, caused by the catalyst, could be considerably reduced. The ECE-version of the 5,6_ltr.-V8 could be dropped without replacement because after the ,power cure" the RF-version was able to mobilise 300_PS as well.
In September 1988 type 560_SE, presented at the Paris car salon, completed the range of models of series 126. Now the 5,6_ltr.-engine was also available for a limousine with normal wheel base.
From June 1989 onwards a new variant with diesel engine was produced. It continued to be reserved for export to the USA only. The production of the previous 300_SDL had already run out in September 1987. Type 350_SDL had a newly developed 3,5_ltr.-6_cyl.-engine which had been developed from the time-tested 3,0_ltr.-aggregate by reboring and prolonging the stroke.
In the development of the new turbo diesel the torque was more important than the power. With its exhaust gas recirculation and oxidation catalyst it mobilised 14_PS less than its predecessor - in spite of its larger displacement. With 136_PS, however, the 350_SDL was well motorised, especially when taking into account the generally valid speed limit. The maximum torque could be increased by almost 15_% and was available from 2000_/min. From June 1990 onwards, in addition to the 350_SDL, the 350_SD with normal wheel base was also on the market
As already practised with the previous series 116, a version of the eight cylinder model of series 126 with special protection was also available. The protection technology was further perfectionised by intensive development work. All in all the proud number of 1.465 cars were produced. A speciality were the two vehicles from type 500_SEL. They were built with wheel base prolonged by 200_mm and a roof extension of 30_mm. The first vehicle, produced in January 1983, completed the company-owned fleet by a further representative car. The second vehicle was built for the Holy Father on demand of the Vatican and handed over to Pope John Paul II in August 1985.
As successors to the series 126 eight limousines of series 140 were presented at the Geneva car salon in March 1991. Even though the series production of the new models started only one month later, the production of the limousines of series 126 was continued for some time. Between August and October 1991 most variants were built for the last time. Within a period of 12 years, 818.036 limousines had left the production halls of Sindelfingen. Among them were 97.546 with diesel engines. Thus type range 126 has been the most successful upper-class series within the history of the company.
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