Mercedes-Benz-Blog TRIVIA: The History of the S-Class - PART X


Stuttgart, Germany, May 19, 2005

Mercedes-Benz S-Class, 140 series (1991 to 1998)

In March 1991 the new S-Class generation (W 140 series) made its debut at the Geneva Motor Show. The body design incorporated the typical traditional Mercedes-Benz stylistic elements and thus fitted un-obtrusively into the homogenous design of the passenger car model series. As had already been the case with the SL models in the R 129 series, with the new S-Class the distinctive trademark radiator grille was given a new stylistic interpretation while retaining the traditional basic shape. This variation on a classic theme was designated the “in-tegrated radiator” and with its much narrower chrome frame the radia-tor shell was organically integrated into the engine lid. For the first time, the Mercedes star was positioned not on top of the radiator grille, but slightly to the rear on the engine hood. The overall aim of the design concept of the new S-Class generation was to achieve a high degree of aerodynamic quality while at the same time respecting a maximum of everyday practicality.

As with the predecessor models of the W 126 series and generations of Mercedes-Benz premium-class series before them, the normal version was also accompanied by a long-wheelbase variant, in which the additional 100 millimeters served exclusively to increase legroom in the rear. As far as the engine was concerned, initially four units were available on the domestic market, of which only the 5.0-liter V8 four-valve M 119 was an old and familiar friend. As with the 500 E model from the W 124 series, the engine featured the fully electronic Bosch “LH Jetronic” injection system, controlled via a hot-wire air mass sensor. The other three engines were newly developed: Like the 5.0-liter unit, the 4.2-liter four-valve V8 was based on the 4.2-liter two-valve engine, and the six-cylinder in-line engine with 3.2-liter displacement was based on the 3.0-liter four-valve unit introduced two years earlier. An interesting detail to note here is that the model designation of the 3.2-liter and 4.2-liter models did not reflect exactly the displacement as had always been the case in the past. Instead, for the sake of ho-mogeneity the designations 300 SE/SEL and 400 SE/SEL were cho-sen.

The twelve-cylinder

The 6.0-liter V12 M 120 engine was an entirely new design, not just the first series-produced twelve-cylinder Mercedes-Benz passenger car, but also the most powerful Mercedes-Benz car engine of its day with a rated power output of 300 kW (408 hp). With rated torque of 580 Newton meters, it reached the 500-newtonmeter mark at 1600/min. As with the six-cylinder and the two V8 engines, the twelve-cylinder was also equipped with four-valve technology, variable intake camshaft and an electronic injection system with hot-wire air mass sensor. With all engines a high priority was placed on minimizing exhaust emissions and reducing fuel consumption. The new fully elec-tronic ignition system calculated the optimum ignition point from 300 ignition maps, tuned for each cylinder individually and to the knock limit in each case. The M 120 was the only twelve-cylinder engine worldwide to feature this cylinder-selective anti-knock control. This alone made possible the high compression ratio of 10:1, necessary for optimum use of fuel.

Engine and drive management was also completely new. Here, all con-trol modules communicated with one another via a common data channel, which meant that the control units were jointly active. This served for rapidly warming up the catalytic converters on cold-starting the engine, for example, as well as for acceleration skid control (ASR) and for the new engine friction torque control, which maintained han-dling stability during power-off situations on slippery road surfaces.

The V12 offered the world’s largest catalytic converter unit for pas-senger cars. With a seven-liter volume in order to avoid any excess fuel consumption on account of the catalytic converter, it ensured a high degree of long-term stability. Thanks to an innovative concept involv-ing a double-walled and triple-insulated exhaust manifold, as well as double-walled pipes, the ceramic catalytic converters – embedded in insulating expandable matting – reached the optimum operating tem-perature in a very short time.

Environmental compatibility

In addition to optimizing and reducing exhaust emissions, the W 140 series also featured a number of other details that made it a pioneer for environmentally compatible automotive production. It heralded the age of the CFC-free (chlorofluorocarbons) car and set new standards in terms of recycling. The plastic components used were not only re-cyclable and clearly identifiable, they were also to a large extent manu-factured using regranulated plastics. In 1992 the W 140 series won an environmental award from the US Environmental Protection Agency, the “Stratospheric Ozone Protection Award.”

Apart from reducing fuel consumption and optimizing environmental compatibility, development of the W 140 series placed a special em-phasis on raising comfort and safety to new levels of perfection. In this respect, the meticulous design and coordination of the running gear played a particular role. A newly developed double wishbone front axle, with the main point of load application mounted on a subframe, provided front suspension – a system designed to isolate the body from audible and perceptible vibrations. Rear suspension was derived from the multi-link independent suspension of the other passenger car series, although radically revised in terms of wheel location and modi-fied in line with the special requirements of the S-Class. To take ac-count of the significantly greater longitudinal and transverse forces, the link geometry was also redesigned. Of particular interest was the crossed design of the upper links, which allowed axle space to be kept to a minimum in spite of the long control arms.

In terms of active safety the S-Class sedans in the W 140 series were known for their exceptionally good straight-line stability even on un-even road surfaces, their low crosswind sensitivity, precise and re-sponsive steering and handling which remained relatively unaffected by the size of payload. The brake system for the eight and twelve-cylinder models was a fundamental innovation. By distributing more braking power to the rear wheels, it was possible to improve the fade resistance of the brake system and reduce wear to the front wheel brakes.

High degree of ride comfort

Ride comfort in the W 140 series was improved significantly once again. Any tire noise and vibrations transmitted to the passenger cell were largely reduced, the pitching motion on moving off and braking was minimized, rolling motion on cornering or uneven road surfaces was reduced and the steering was made virtually insensitive to jolts transmitted from the road. A so-called “parameter steering” with speed-sensitive steering moment was fitted as standard to the eight and twelve-cylinder variants, reducing the steering effort required by the driver at low speeds, for example when parking.

Safety had already been taken to high standards in the predecessor model series, but here numerous measures achieved further improvements. The new body structure, for example, provided even more safety in all types of accidents. And a series of small design appointments designed to reduce hazards from potential impact points also gave added protection to other road users.

The first soundproofed glass windows to be fitted to a passenger car series also made a significant contribution to improving comfort and incorporated a range of safety and comfort features. They avoided the tendency to fog or ice up and reduced condensation, gave better heat insulation as well as soundproofing from external noise, improved ex-ternal air flow and eliminated wind noise caused by window seals.
Two further design details – folding exterior mirrors and extendable guide rods to help with reversing – gave drivers additional assistance when maneuvering in small spaces with poor visibility. The electrically-operated exterior mirrors could be folded back to gain extra space when maneuvering in tight situations by means of a centrally-positioned switch on the center console, the same switch serving also to angle the mirrors correctly. In order to assist with judging distances to obstacles when performing reversing maneuvers, two extendable guide rods were integrated into the rear fenders to left and right. Two seconds after selecting reverse gear, the pneumatically operated 65-millimeter-long chrome rods automatically extended vertically, return-ing again eight seconds after a new gear had been selected.

Diesel for Europe

At the Paris Motor Show in October 1992, the 300 SE 2.8 and 300 SD Turbodiesel models were introduced, adding two cheaper and particu-larly economical variants to the S-Class range. The 300 SD attracted particular attention – a vehicle that had been exported to the USA since October 1991, but which was now the first diesel model in the S-Class to become available in Europe. The 300 SD was powered by a 3.5-liter six-cylinder engine with exhaust-gas turbocharger, a unit which was in principle the same as the one used in the predecessor model from the W 126 series, but now in a revised version delivering 110 kW (150 hp). Like the 300 SE, the second new arrival, the 300 SE 2.8, offered a six-cylinder in-line unit with four-valve technol-ogy – also a member of the M 104 family of engines. The newly devel-oped 2.8 liter variant was used from the same point in time in the W 124 series also and was equipped with a microprocessor-controlled di-rect injection system in which the hot-wire air mass sensor had been replaced by a hot-film air flow sensor. In addition to the two new mod-els, the eight and twelve-cylinder versions appeared in Paris with re-vised engines. All three units did away with mixture enrichment under full load, resulting in a minor loss of output but bringing benefits in terms of emissions.
In June 1993 the model designations were changed to come in line with other series in the passenger car range; the “S” was now placed before the three-figure number, and suffixes such as “E”, “D” and “L” were omitted. The 500 SE, for example, became the S 500, and ac-cording to the new system of nomenclature the 600 SEL was renamed the S 600 long. Ever since, the trunk lid has documented only the class and engine displacement and not the body variant (normal or long-wheelbase version) – this was entirely apparent to anyone taking a closer look. The most significant changes came in redesigning the 4.2-liter and six-cylinder models. Instead of the figures used hitherto, which had been rounded off to full hundreds in order to enhance the uniformity of the overall image, the figures used corresponded to the actual displacement values. Thus the 300 SE for example became the S 320 and the 300 SD was now known as the S 350 Turbodiesel. In addition to these purely formal changes, the two 3.2-liter models also benefited from a number of technical improvements. The previously used engine was replaced with a revised version that had already been in service since October 1992 in the W 124 series and now also fea-tured a variable-resonance intake manifold and a direct injection sys-tem with hot-film air flow sensor. These improvements permitted an increase in torque and meant both maximum output and maximum torque could be achieved at lower engine speeds. Thanks also to an additional reduction in friction losses, fuel consumption was reduced by a total of 7.5 percent and overall performance marginally improved.

Discreet revisions

At the Geneva Motor Show of March 1994 the S-Class sedans were presented with discreet stylistic modifications. A series of modified de-tails gave the optical illusion of a lighter, better proportioned and more dynamic appearance – even though external dimensions remained un-changed. This was achieved by a distinctive “tucking-in” of the lower parts of the bumpers and side skirts and by the horizontal subdivision of these surfaces by means of a beading running all the way round. The effect was reinforced by modifying the design of the headlamps and radiator protection grille. In the modified headlamps with opti-mized variable-focus reflectors, which increased light output by 60 percent, the dipped-beam compartment was no longer separated by a central bar from the high-beam compartment, thus lending the illusion of greater breadth. This impression was underlined by the addition of colorless glass covers for the front turn indicator lamps. The six-cylinder and eight-cylinder models were also given a newly designed, more slender radiator grille with a vertical articulation at the center. For the V12 models there was also a special version with chrome-plated transverse fins and appreciably broader chrome frame. Formal modifications to the rear end were also a significant factor in the har-monious overall image of the S-Class. For example, the lower radii of the trunk lid joints were rounded off in the same style as the coupe models. The taillight band was made broader beneath the rear lamps and shaped to fit the new bi-chromatic design of the rear lights. This served to flatten off the height of the trunk and to make the rear end as a whole appear broader and lower set.

From May 1995 the ultrasonic reversing aid “Parktronic” was available as an option. Ultrasonic signals emitted by the system were reflected by any obstacle encountered and the distance between vehicle and obstacle was then calculated by an electronic control unit. Transmit-ters and receivers of the ultrasonic signals were combined in sensors integrated into front and rear bumpers, without diminishing in any way the protective function of the bumpers. Parktronic was fitted as stan-dard equipment to the V12 models from 1995 onwards. At the same time, the now superfluous guide rods in the rear fenders were discon-tinued in all S-Class limousines.

Improved engines

Since the model refinement measures introduced in 1994 essentially affected design, the eight-cylinder and twelve-cylinder models saw a number of technical improvements in September 1995. A completely new five-speed automatic transmission with torque converter lock-up clutch – a unit that had been fitted to the S 600 coupe since May 1995 – now replaced the four-speed transmission with hydraulic con-trol in the sedans. At the heart of this technological miracle was an electronic transmission control unit which adapted gear-shifting rap-idly and automatically to any given driving situation and which con-tinuously exchanged data with the electronic engine management sys-tem. In addition to these pioneering innovations, the new automatic transmission was also much more compact and lighter than were comparable five-speed transmissions. To further improve fuel con-sumption and reduce harmful emissions the engines underwent more revisions. The two V8 engines were given a modified crankshaft, an optimized valve control system, lighter pistons, dedicated ignition coils for each cylinder and an improved electronic engine management sys-tem of the Motronic ME 1.0 type which integrated a hot-film air flow sensor in the place of the hot-wire air mass sensor. Modifications to the V12 engine were less extensive and affected only the arrangement of the ignition coils and the electronic engine management system. Thanks to the various modifications to the engine and the introduction of the new automatic transmission, fuel consumption for the V8 and V12 models could be cut by seven percent on average without any loss in output, and exhaust emissions by over 40 percent. September 1995 also saw the introduction of the Electronic Stability Program (ESP) as an option for all S-Class models with eight-cylinder engines, a system that helped the driver to correct driving errors by automatically counteracting momentary instability by sensor-controlled brake inter-vention, thus contributing to active safety. ESP was introduced as standard equipment in both twelve-cylinder models.

In addition to the model refinement package outlined above and pre-sented at the IAA in Frankfurt, in September 1995 a new S-Class vari-ant was premiered: The S 600 long-wheelbase Pullman. Developed as a new official representational sedan and equipped with special pro-tection technology, this vehicle continued a long Mercedes-Benz tradi-tion. The special-production car measured 6,213 millimeters in length and was therefore exactly one meter longer than the long-wheelbase S 600. The extra length served to benefit the rear passengers, com-fortably accommodated on seats arranged in vis-√†-vis format and separated if required from the driver’s compartment by a glass parti-tion. The Pullman sedan in the W 140 series was also available as both S 500 and S 600 without armoring. The first units of both variants were produced in August 1996.

In line with tradition, the normal five-seater sedans in the S-Class were also available as armored versions – with a choice of 5.0-liter V8 or 6.0-liter V12 engine. Production of both these armored models began in February 1992, one year after main production start-up for the W 140 series.

Further improvements

In June 1996 the S-Class underwent further improvements. Now the five-speed automatic transmission with torque converter lock-up clutch and electronic engine management was also available for the six-cylinder models – as an option on the S 280, and as standard on all other models. At the same time the ASR acceleration skid control sys-tem also became part of the basic equipment on the six-cylinder mod-els. Other innovations to note included sidebags as standard for driver and front passenger on all models, seat occupancy sensors to operate the front passenger airbags, an “intelligent” rain sensor that controlled the wiper interval in accordance with the volume of spray on the front windshield, and luggage nets in the trunk and front passenger footwell. Xenon headlamps with headlamp wash/wipe system and dynamic headlamp range adjustment were available as optional equipment. Ex-ternally, too, the S-Class sedans had undergone slight modifications when they were presented in June 1996; immediately apparent were the satin-finish detachable body components, now painted in the color of the car rather than as previously in the contrast color.

Apart from these detail improvements described above, in June 1996 a model change in the S-Class came into effect: The S 350 Turbodiesel was replaced by the S 300 Turbodiesel. In contrast to its predecessor, the new diesel model offered a turbo engine with four-valve technology and intercooling. Engine output was 20 kW (27 hp) higher, at 130 kW (177 hp); torque was increased by 20 Newton meters and available over a broad range of engine speeds; exhaust emissions and fuel con-sumption were much lower as a result of optimized combustion. The S 300 Turbodiesel came as standard with the electronically controlled five-speed automatic transmission.
From December 1996 the S 280 and S 320 models with automatic transmission were also equipped with the ESP dynamic handling con-trol system. At the same time a new innovation had its world premiere as an additional active safety feature – Brake Assist, which was fitted as standard in all R 129 and W 140 models from December 1996. Brake Assist (BAS) was able to recognize emergency braking situations and if required to boost brake power to a maximum more quickly than was previously the case, thus shortening stopping distances consid-erably.

A landaulet for the Pope

In March 1997 a further variant in the W 140 series was produced: The long-wheelbase S 500 landaulet, a one-off vehicle for Pope John Paul II. The landaulet soft-top was operated electrohydraulically to afford a clear view of the Holy Father seated on his centrally positioned thronal seat. It was also equipped with folding seats for two attendants.

At the Paris Motor Show in September 1998, the public was intro-duced to six S-Class sedans from the W 220 series, which now suc-ceeded the W 140 series after a period of seven and a half years. Se-ries production of the 140 models at the Sindelfingen plant was stopped at this point, and only the armored versions and the Pullman sedans continued to be built. By September 1998, a total of 406,532 W 140 series sedans were produced, of which 28,101 units had diesel engines.

At the start of its career and particularly in Germany, the largest ever S-Class did not have an easy time – despite the car’s undeniable quali-ties. A valedictory appeared in the Frankfurter Allgemeine Zeitung of August 25, 1998 under the headline: “The end of the good patriarch. Sentimental farewell: The S-Class was always better than its reputa-tion.” This obituary written by Wolfgang Peters included the lines: “...No other car offered such ride comfort and suspension, and no other car in this size category could be driven in such safety and with such agility at the same time. The S-Class was a giant that had been taught to dance on the points of its toes. [...] The new S-Class promises to be lithe and lissome: Some of us are missing the fatter version already.”

The 140 series in the press

Auto, Motor und Sport, Germany, volume 7/1991, on the Mercedes-Benz 600 SEL: “With dimensions such as these, there is little to be said about the inte-rior: The sense of space is almost wasteful, even more so in the rear than in the front, since the opulent height in the rear is particularly apt for giving the impression of riding in a mobile living room. … It would not be wrong here to describe this as the world’s finest car – any less would be to do Mercedes an injustice.”

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