by Adrian-Liviu Dorofte

Mercedes-Benz-Blog TRIVIA: History of the E-Class - PART VII


Stuttgart, Germany, Aug 01, 2008

"Stroke 8": 115 and 114 series (1968 to 1976)

* First autonomous body for the upper mid-range series

* A coupe as exclusive variant appears in 1968

* The Mercedes-Benz 240 D 3.0 is the first production car with a five-cylinder diesel engine

The new Mercedes-Benz models of the mid-size series 115 and 114 made a clean break with the "tailfin" era with its unitary body. The saloon was sporty, elegant, up to date, and above all a saloon in its own right. It was a demonstration of respectable flair and love of technical innovation. On top of that it reflected the awareness of its developers for the newly defined role of an intermediate model series. Experts and public alike greeted the new intermediate class model from Mercedes-Benz enthusiastically when it was first presented to the media in January 1968. Internally designated with the abbreviation /8 because of its year of birth, the family of vehicles was soon dubbed the "Stroke 8".

With the "Stroke 8" of 1968 Stuttgart started a design revolution that laid the foundations and set the standards for the subsequent generations of the midsize model series from Mercedes-Benz, today's E-Class. Initially the model range comprised six saloons: the four-cylinder 200, 220, 200 D and 220 D models formed the 115 series, and the two six-cylinder variants 230 and 250 were designated the 114 series. As the top-of-the-range model the Mercedes-Benz 250 was distinguished from the other models by its double front bumper. From the beginning the demand for all models was high and soon resulted in long waiting times for delivery.

Development work since 1961

Designers and engineers began planning the new model series as early as 1961 – the year in which the small tailfin had just reached the market. Project leader was Dr. Fritz Nallinger, Mercedes-Benz chief engineer, member of the Board of Management and Technical Director of Daimler-Benz AG. The technical structure of the forthcoming vehicle was determined by Karl Wilfert, Head of Body Development. Responsible for the design was Paul Bracq, assisted by Bruno Sacco. This new intermediate class had to be an independent, successful model – that was clear to Development from the start. So the shared body was no longer an option. Stuttgart therefore strove to create a complement to the new luxury class 108/109 series for the year 1968.

As early as 1960 chief engineer Nallinger defined important benchmarks for the new vehicle. In direct comparison with the luxury class model the design was to be appreciably more compact than differences between the four and six-cylinder variants of the shared body allowed. In view of the smaller exterior dimensions, it would be important to ensure good space economy in the passenger compartment. The shape had to be timeless in its simple elegance. In 1964 the designers' models already showed the outlines of the future saloon. At that point, however, different designs of the front end were still under discussion. In analogy to the former distinction between four and six-cylinder variants, the versions of the new model family with smaller engines were to get a simpler front end with horizontally arranged rectangular headlamps. Finally, in early 1965, a decision was made to refrain from such differentiation, to which the two model series numbers 115 and 114 later still would testify. This was the year in which Professor Dr. Hans Scherenberg took over project management, when Nallinger went into retirement.

Other body variants developed in addition to the saloon were a coupe, a long-wheelbase saloon and a station wagon. Whereas the sportier two-door and the long-wheelbase version of the saloon actually made it into production, the station wagon was ultimately barred from series production. On the other hand, the basic design of the rear end was later harmoniously transferred to the next model series, the 123, with only minor changes. In 1967 the production facilities for the new series were set up in Sindelfingen. Prior to the market launch proper, 1100 preproduction vehicles of the two series were produced there, limited initially to six models.

1968: Double premiere in Sindelfingen and Geneva

Mercedes-Benz presented the "Stroke 8" in 1968 in a double premiere: the series had its debut in front of trade journalists gathered at Sindelfingen in January; the general public got its first chance to assess the new saloon at the International Motor Show in Geneva that March. The six models initially available met with the broad approval of the experts and the general public. The view expressed by the motor magazine auto motor and sport that Mercedes-Benz had dared to take a "stylistic swing to the left" can surely be put down mainly to the political situation of 1968. The "Stroke 8" deserved all the more praise for its clear, classic yet modern lines and its fresh, sporty appearance.

And yet the Mercedes-Benz character that determines automotive identity was fully retained in this model. The designers and engineers handled a task well that called for innovation and sensitivity. On the one hand, a clearer distinction now was made between the luxury and upper mid-size categories in the Mercedes-Benz product line-up. On the other hand, the family resemblance between the now independent models was still visible, as were their origins in the "tailfin" generation.

Complete range: debut of the new series with six saloon models

The new Mercedes-Benz started out with six saloon models. The 200 and 220 were powered by the new four-cylinder M 115 carburettor engine, with 2-litre displacement (70 kW/95 hp) and 2.2-litre displacement (77 kW/105 hp) respectively. The 200 D and 220 D diesel variants also featured a new engine, the OM 615, in a 2-litre version with 40 kW (55 hp) and a 2.2-litre variant with 44 kW (60 hp) output. The 2.3-litre in-line six-cylinder M 180 engine of the 230 model was already familiar from the predecessor model; it developed 88 kW (120 hp), as in the "tailfin". New in the engine range was the 2.5-litre in-line six-cylinder M 114, which generated 96 kW (130 hp). For the new petrol engines of both series, Mercedes-Benz relied on proven technology: the 200 and 220 models (M 115) and the 250 (M 114) were equipped with in-line carburettor engines with two overhead valves per cylinder and an overhead camshaft. The four-cylinder power plants (petrol and diesel) proved so reliable that the 123 series that followed in 1976 was initially equipped with the M 115 and OM 615 engines.

Good handling owing to the diagonal swing axle

The outstanding constructional detail of the new model series was to be found under the boot: the "Stroke 8" models were fitted with a so-called diagonal swing axle, making this the first Mercedes-Benz production car to have a rear axle with semi-trailing arm. The diagonal swing axle, equipped among other things with auxiliary rubber springs and a torsion-bar stabiliser as standard, was an advancement of the single-joint swing axle introduced in 1954 in the 220 a, and was used in all Mercedes-Benz cars from 1955 onwards. Compared with the predecessor models, the new axle afforded distinct improvements in handling characteristics without sacrificing ride comfort. The improved handling quality was also acknowledged by international motor journalists, who were invited to the old Targa Florio course in Sicily for a preliminary road test in December 1967. Snow, ice and the narrow mountain roads of the Madonie placed great demands on the suspension, but the Stroke 8 gave an excellent account of itself.

And the "Stroke 8" was not a lightweight by any means. Wheelbase and weight of the upper mid-range series of Mercedes-Benz had grown consistently bigger from the "Ponton" (2.65 metres and 1.22 metric tons) through the "tailfin" (2.70 metres and 1.28 metric tons) to the "Stroke 8" (2.75 metres and 1.36 metric tons). However, the overall length of the new model, 4.68 metres, was less than that of the 110 series. The new proportion of overall body length to wheelbase was also visible in silhouette, with balanced proportions and clear lines. The additional weight was due mainly to measures designed to improve passive safety, which put into practice the ideas of Mercedes-Benz engineer Béla Barényi, a pioneer in this field.

Coupe emphasises sporting note

In November 1968 the model line-up of the new Mercedes-Benz was rounded off at the upper end by the 250 C and 250 CE coupes. That same winter the Stuttgart company also introduced a long-wheelbase saloon. In particular, the launch of the sporty two-door was a highly regarded premiere. After all, this was the first time the brand with the three-pointed star had offered a coupe version as an exclusive variant in the intermediate class. Of the two coupes, the 250 CE proved exclusive in a dual sense. Its 2.5-litre injection engine (110 kW/150 hp) was reserved exclusively to this body type. In the 250 CE, Bosch D-Jetronic was used for the first time in a Mercedes-Benz production car, an electronically controlled fuel injection system that made it possible to dispense with the conventional mechanically controlled multi-plunger injection pump.

Compared with the future coupes based on the E-Class, those of series 114 very closely followed the saloon in their design: neither wheelbase nor overall length differed; apart from the elimination of the B-pillar, the modified roof was evident as a result of an almost five centimetre lower roof line and the sharper rake of the windscreen and rear window. Even more exclusive, at least as far as price and unit volume were concerned, was a third body variant introduced by Mercedes-Benz in December 1968: the saloon with extended wheelbase (65 centimetres longer).

More space: long-wheelbase saloons

The concept of this vehicle was already familiar from the extended 200 D of the "tailfin" generation W 110. The long-wheelbase version of the "Stroke 8" also offered seating for the driver and seven passengers in three rows. At first, this most expensive variant of the "Stroke 8", and the one with the smallest unit volume in production (in the end output in fact added up to almost 10,000 units), was available as the 220 D and 230. In autumn 1973 the 240 D extended the offer.

The long-wheelbase saloon, like its predecessor, was mainly used as a taxi and hire car, as well as by travel firms, airlines, embassies and government authorities. Since sporty performance was less important in these cars than fuel economy, the percentage of diesels among the eight-seaters was very high across the entire series: slightly less than 78 percent of all long-wheelbase saloons were ordered with a compression-ignition engine – an appreciably higher rate than for the standard wheelbase saloons.

Chassis for bodies

In keeping with tradition, both body variants also were available as partially bodied chassis. They were fitted with special bodies by domestic and foreign bodybuilders. In particular, ambulances, fire brigade vehicles, hearses and other branch-specific special versions were produced. The ambulance bodies by Binz in Lorch and Miesen in Bonn attained a high degree of popularity. The best-known manufacturers of hearses included the coachbuilding firms of Pollmann in Bremen, Rappold in Wülfrath, Stolle in Hanover and Welsch in Mayen. Independent bodybuilders also supplied station wagons to the customer. Initially the 220 D, 220 and 230 (short wheelbase), and 220 D and 230 (long wheelbase) were made available as a basis for conversions. Then after the facelift in autumn 1973, the 240 D, 230.4 and the six-cylinder model 230.6 were also available as chassis.

New engines for the intermediate range

In April 1972 the 280 and 280 E models were added to the range. Both were available as saloon and as coupe and were powered by the newly designed 2.8-litre M 110 engine. The six-cylinder had overhead valves in a V configuration and two overhead camshafts. In the carburettor version it developed 118 kW (160 hp), and with manifold injection 136 kW (185 hp). The saloons of the new top-of-the-line "Stroke 8" models could be distinguished from the less powerful variants even without the model plate: in addition to the familiar double bumper of the 250, they had a rear bumper that wrapped right round to the wheel cut-outs, as well as two tailpipes.

On the coupe side, the 280 C superseded the 250 CE, production of which was discontinued. The 280 CE with the 136 kW (185 hp) injection engine extended the performance spectrum of the series and became the new top-of-the-range model. Since the appearance of the 280 and 280 E, the 250 was delivered to customers with the 2.8-litre power plant M 130 from the 108 and 109 series. In the "Stroke 8" the engine used was a slightly derated version, developing 96 kW (130 hp). The export version of the 250 for the USA and Canada had been coming off the assembly line equipped with this engine since July 1970.

1973: Facelift for the "Stroke 8"

Vehicle safety was the focus of an extensive facelift to which all variants of the 115 and 114 series were subjected in September 1973. Many of the new details were adopted by the engineers from the SL and SLC models of the 107 series and the current S-Class (W 116). They included, for example, flexibly mounted exterior mirrors adjustable from inside, as well as dirt-deflecting moulding on the A-pillars that kept the side windows clean even in the most inclement weather, plus a rain runnel on the rear window.

Particularly conspicuous from the rear view of the car were the ribbed tail lights for minimising dirt collection. This safety-relevant design element was to shape perceptions of Mercedes-Benz passenger cars of all classes over future vehicle generations. The four-spoke safety steering wheel from the R/C 107 and 116 series entered series production of the "Stroke 8" six months before the facelift. From March 1973 onwards, head restraints and inertia-reel front seat belts then also became part of the standard equipment of the 115/114 series.

Highlights from the luxury class and new engines

The improved models were also updated visually to match the look of the S-Class in particular. The radiator grille was now lower and wider, the side windows no longer had quarterlights, the licence plate panel was attached to the front bumper instead of underneath it, and the handle of the boot lid was given a different shape. As the front apron was also adapted to the design of the S-Class, the 250 through to the 280 E models – together with their coupe equivalents – lost their double front bumper. The only saloons of the series that continued to stand out visually from the other variants were the 280 and 280 E, since the designers left them their long rear bumper.

New four-cylinder engines were a part of the model refinements. Since autumn 1973 the OM 616 (48 kW/65 hp) in the 240 D was the top engine in the diesel model range. The 2.3-litre version of the M 115 with an output of 81 kW (110 hp) was the drive unit behind the new 230.4 model, which replaced the 220. The suffix ".4" in the model designation of the new 230 became necessary, because the six-cylinder variant with the same displacement continued to be carried in the range. To make an exact distinction, Mercedes-Benz now offered this original 230 as the 230.6 model.

Five-cylinder diesel engine as a passenger car world premiere

In July 1974 the Stuttgart company finally set standards once again in the development of diesel technology: the 240 D 3.0 of the 115 series became the world’s first production five-cylinder diesel car. Its OM 617 engine was designed as a pre-chamber unit with 3-litre displacement; the power plant generated 59 kW (80 hp) at 4000 rpm and had a torque of 17.5 mkg at 2400 rpm.

With acceleration from 0 to 100 km/h in 19.9 seconds and a top speed of 148 km/h, the 240 D 3.0 took the field with these more than respectable performance figures for a compression-ignition engine. Indeed, upon its introduction the saloon proved to be the liveliest, fastest diesel car in the world. By 1974 five-cylinder diesel engines were already seeing use in trucks and as stationary engines. But an engine like this was an innovation in the passenger car. It enabled Mercedes-Benz to take the performance limit previously encountered by the passenger car’s four-cylinder diesel engines to an appreciably higher level.

Since a pneumatic shut-off was used instead of the mechanical device in the 2.4-litre engine, the unit now could be switched off using the ignition key. The engine of the 240 D 3.0 was also started by turning the ignition key, and not by pulling a lever as in the past – an advance that at the time spelled a clear-cut edge in terms of comfort. Compared with other diesel cars, the 240 D 3.0 scored very well with its refined smoothness and economy. Fuel consumption was 10.8 litres of diesel per 100 kilometres (21.75 mpg). And so this car blazed the trail for the future success of diesel-powered cars. Mercedes-Benz installed the five-cylinder diesel in other vehicles too, beginning for example in 1978 with the S-Class 300 SD (116 series) for export to North America, and the experimental C 111-IID.

1976: A classic bids farewell

In January 1976 Mercedes-Benz launched the 123 series, the successor to the "Stroke 8". Production of the 115/114 series did not cease immediately though, continuing for a full year until December 1976. The reason for this parallel production was the long delivery time for the new W 123 and the continued strong demand for the proven "Stroke 8". In particular taxi companies ordered saloons of this series once more for cab service. The taxi trade enjoyed an especially close relationship with this model series. As a popular cab the "Stroke 8" had gone along with the colour change in the German taxi landscape from black to light ivory (code RAL 1015), prescribed for new taxis in 1970.

The "Stroke 8" remained a favourite for many years not only with German taxi drivers. The Mercedes-Benz with the highest known recorded mileage in service is a Greek taxi, a 1976 240 D. Its owner, taxi driver Gregorios Sachinidis from Thessaloniki, covered 4.6 million kilometres in this car. Since 2004 the car belongs to the collection of the Stuttgart Mercedes-Benz Museum. Vehicles like the world-record taxi further underscore the reputation of the "Stroke 8" as an indestructible and reliable long-distance runner. The respect and acknowledgement voiced by the contemporaries of the "Stroke 8" can be heard to this day in the enthusiasm of the pre-vintage and vintage car community for the 115 and 114 series.

Technical pioneer and bestseller

The after-effects of the first independent model family of the intermediate range of Mercedes-Benz are reflected not only in well-cared-for classic cars: vehicles of the ESF (Experimental Safety Vehicle) series of Daimler-Benz Research, with which technologies like the anti-lock braking system (ABS) and the airbag were tested, were based on the "Stroke 8" – for example, the ESF 05 (1971) and the ESF 13 (1972). In this way the Stuttgart intermediate range assisted in the 1970s in developing elements of active safety for the cars of today. The "Stroke 8" thus became a trailblazer of future innovations in series production.

At the end of its production life, the engines of the "Stroke 8" family ranged from the entry-level models to the top-of-the-range models 280 E (1972) and 240 D 3.0 (1974). This variety was one key to the success of the "Stroke 8", which established itself as a versatile model capable of satisfying even the most demanding of drivers. All in all, from 1968 to 1976 almost two million units of the two series were produced. This almost equals the number of vehicles manufactured by Mercedes-Benz across all passenger car series of the brand from the end of the Second World War until 1968.

115/114 series in the press

auto motor and sport, Germany, issue 8/1968, wrote of the dimensions of the 115 and 114 series: "The proportion of exterior dimensions to boot and interior is much more reasonable in the new car. This is very much an advantage for parking – one can actually manage with the average parking spaces of Central European cities. The large boot is not just theory: with 510 kg permissible payload one can make full use of it."

auto motor and sport, Germany, issue 8/1968, on the passive safety of the "Stroke 8": "Today almost every car factory claims to build a particularly sturdy central compartment and progressively deformable front and rear sections, but it is fair to say that few can match the bodies of Mercedes cars for solidity and crashworthiness, and none can surpass them."

auto motor and sport, Germany, issue 8/1968, on the four-cylinder diesel models of the 115 series: "The great and enduring sales success of the diesels is based on their unrivalled thriftiness and their long life. These are things the diesel owner expects and gets."
auto motor and sport, Germany, issue 8/1968, on the quality of the 115 and 114 series: "Nothing about this car is 'cheap', and it draws attention to this fact every day with reliable operation."

auto motor and sport, Germany, issue 2/1975, wrote of the 240 D 3.0 model: "In practical operation the 'big' diesel distinguishes itself from the smaller four-cylinder models through noticeably more refined operation. Apart from distinctly better accelerating power, mainly at medium and higher engine speeds, it very obviously profits from the shorter firing intervals which result from the larger number of cylinders. In addition, there is also the impression of substantially reduced load alteration effects between the accelerating and decelerating engine."
auto motor and sport, Germany, issue 2/1975, sums up the driving dynamics of the 240 D 3.0: "Both on the motorway and on country roads, you can keep up with the fast cars without much effort in the 3.0 – you'll be overtaken fairly seldom now."

auto motor and sport, Germany, issue 2/1975, wrote of the engine noise of the five-cylinder diesel in the 240 D 3.0: "Of course, the astonishingly low noise generation of the five-cylinder is also important in terms of pleasant driving characteristics – from medium engine speeds upwards there is practically no difference to the comparable petrol engines."

mot, Germany, issue 17/1970, wrote of the 200 D and 220 D models: "They are the technically most impressive diesel models, but also the most expensive."
auto motor and sport, Germany, issue 15/1974, presented the new 240 D 3.0: "For the first time the unusual number of five cylinders has been chosen for a car engine, so that, starting from the 2.4-litre engine, the desired increase in displacement to 3 litres was achieved not by the conventional method of modifying the bore and stroke, but by adding another cylinder."

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