Telephone: +49 (0) 711-17-7 64 77
March 25, 2008
Winning foursomes: Four-cylinder engines from Mercedes-Benz
Innovations regularly experience market launch in four-cylinder passenger car engines
Ground-breaking DIESOTTO drive in the Mercedes-Benz F 700 premiered as a four-cylinder engine
Stuttgart. What do four-valve technology, supercharging, common rail technology and CGI direct gasoline injection have in common? Answer: They all celebrated their Mercedes-Benz premieres in four-cylinder engines. Throughout the history of the brand from Stuttgart, this seemingly unspectacular engine type has always been at the cutting edge of outstanding innovation. Even the DIESOTTO technology, which was premiered in the F 700 research car at the 2007 International Frankfurt Motor Show (IAA), was first introduced by Mercedes-Benz in a four-cylinder engine.
Along with many other factors, the number of cylinders an engine has is indicative both of driving culture and prestige. The greater the number of cylinders, the better the ride quality – it is a rule of thumb followed by almost all markets worldwide. Mercedes-Benz Cars enjoys a reputation for supplying passenger cars equipped with a diversified range of superb internal combustion engines. The smart has three cylinders, the S-Class twelve, and between the two extremes there exists an entire spectrum of other configurations. While the four-cylinder versions may seem rather unspectacular at first sight, these are the very engines to which great importance is attached time and again.
The earliest vehicles had engines with one or two cylinders but if the automobile was to prove successful it was essential to boost output by increasing the number of cylinders to four. The Phoenix car of 1898 was the first Daimler road vehicle to feature a four-cylinder engine based on the principle devised by Nikolaus Otto. It had an output of 17 kW (23 hp) – quite impressive for the day. And true to Gottlieb Daimler’s vision of mobilizing vehicles on the land, on the water and in the air, it was not long before four-cylinder engines were also being used in aviation.
Developments with Carl Benz followed a similar course. One of his major achievements, for example, was the so-called contra engine, which made its debut in 1899 as a two-cylinder unit, bringing the principle of the horizontally-opposed piston engine to production standard before it appeared with four cylinders in 1900. However, this engine was used exclusively in what was the most powerful Benz racing car at the time. That same year DMG built a four-cylinder unit for use in the first Mercedes. In many ways it was a pioneering development, featuring for example intake and exhaust valves controlled by two lateral camshafts.
Early innovations: Four-valve technology, superchargers and diesel engines
The designer engineers introduced various measures to significantly increase the output of vehicle engines, particularly in the first decade of the twentieth century. One glorious highlight was the 200 hp Benz record-breaking car – more familiarly known as the Lightning Benz – which, with its powerful 21.5-liter four-cylinder engine, became the first car to pass the magical 200 km/h barrier at Brooklands in 1909. At Benz & Cie. in 1910 four-valve technology celebrated its premiere in a four-cylinder engine. That same year DMG launched the Mercedes Knight, equipped with a four-cylinder unit that was considered both powerful and unusually quiet. 1921 saw the start of the supercharger era, when DMG introduced the world’s first production passenger car equipped with a supercharged engine – again a four-cylinder model. And in 1923 the automotive world was further enhanced by another new combustion principle, when Benz & Cie. unveiled the world’s first salable diesel truck – featuring a four-cylinder engine that attracted considerable interest as a result of its outstanding fuel economy.
When Daimler-Benz AG was established in 1926, the new company soon attached key importance to the four-cylinder engine. By this time the automobile was rapidly gaining popularity in all sectors of society; as a result the four-cylinder engine began to take on an increasingly important role. The turning point came with the Mercedes-Benz 130 (W 23), which appeared in 1934. Its relatively moderate success had less to do with its four-cylinder engine than with its unconventional design and the rear-mounted engine configuration which needed getting used to. It prepared the ground, for example, for the 170 V model (W 136) of 1936, which was built in large numbers throughout the 1930s and 1940s, and after the Second World War flourished again in modified form with such success that it played a significant part in financing the reconstruction of Daimler-Benz AG.
Four-cylinder innovations at Mercedes-Benz then alternated between diesel and gasoline engines with the advent in 1936 of the world’s first series-produced diesel passenger car, the Mercedes-Benz 260 D (W 138). A recurring leitmotif of the new engines was their increased output – although set against pure horsepower this usually went hand-in-hand with improved fuel economy. For the engineers were clear about one thing: Customers would only accept higher output if running costs remained proportionate. The 1960s saw a sharper focus on the topic of emissions, followed closely – particularly during the oil-price crises of the 1970s – by renewed calls for more fuel-efficient engines. Once again it was the various designs of four-cylinder engines that scored top marks.
Fuel-efficient and low-emission four-cylinder engines
At first sight it would seem engine development during this period followed the maxim “evolution not revolution” – and yet a second glance reveals one or two quite remarkable revolutions. Take, for example, the Mercedes-Benz 190 D, which appeared in 1983 with an encapsulated four-cylinder diesel engine to keep operating noise to a minimum – soon earning itself the sobriquet “whispering diesel”. That same year, four-valve technology also experienced a renaissance in the modern gasoline engine of the 190 model. A good ten years later another historic piece of technology was to become the focus of interest once again, when Mercedes-Benz revived the supercharger for use in its four-cylinder engines. As in the 1920s and 30s, it served to boost output – but on this occasion less with the aim of achieving top sports handling and performance than in lending the four-cylinder improved power yield and fuel efficiency. Many automotive journalists of the day lavished praise on the supercharged Mercedes-Benz four-cylinder engines which would later come close to the mark set by the brand’s six-cylinder units – praise which the designer engineers were only too pleased to hear. Because regardless of the number of cylinders, an engine in a vehicle bearing the three-pointed star should always fit the character of a Mercedes-Benz.
The four-cylinder engines then became an integral element of vehicle design in the A-Class (W 168) which made its debut in 1997. These are designed in such a way that in the event of a frontal impact they slide along the pedal floor beneath the passenger compartment. That same year, the diesel engine was hailed a hero of the revolution in engine design when Mercedes-Benz introduced CDI technology – once again in a four-cylinder unit. Then in 2002 came direct gasoline injection, first in the CLK 200 CGI (C 209) and shortly afterwards also in the C-Class. From 2005 onwards the low-emission diesel engine was given a new name – BLUETEC technology for passenger cars made its debut in a research vehicle, the Mercedes-Benz bionic car. The first production car with this technology was a six-cylinder model, the E 320 BLUETEC.
Finally, in 2007 the brand presented the F 700 research car at the International Frankfurt Motor Show (IAA), powered by the DIESOTTO engine. In this revolutionary engine the company’s researchers succeeded in combining for the first time the advantages of both gasoline and diesel principles. The vision, of which this engine is the tangible expression, extends far into the future of the internal combustion engine. And one thing is certain for the years ahead: Whether powered by four cylinders or some other cylinder configuration, the Stuttgart brand will continue to stand for economical and low-emission combustion engines as a source of power for outstanding motoring refinement.
Chronology: Four-cylinder engines from
Mercedes-Benz and predecessor brands
Nikolaus August Otto, the inventor of the four-stroke gasoline engine, had a four-cylinder prototype engine built at the mechanical engineering workshops of J. Zons in Cologne. For the first time, Otto adopted the four-stroke process of mixture intake, compression, ignition and exhaust. Looked at today, this four-cylinder four-stroke engine seems incredibly visionary, closely resembling in many of its design details much later engines. However, mechanical problems forced Otto to return for the time being to development of the earlier atmospheric engine.
Wilhelm Maybach built a four-cylinder in-line engine, initially for use only in boats. The engine had an output of 3.7 kW (5 hp) at 620/min. The cylinders measured 80 x 120 millimeters (bore x stroke). Maybach’s engine weighing 153 kilograms established the model for later engine designs – even modern drive units are based on the principles of this early four-cylinder unit. For his new engine Maybach developed a crankshaft with equally spaced throws for cylinders 1 and 4 as well as for cylinders 2 and 3. The exhaust valves were controlled by a camshaft. In August 1890 the first Daimler four-cylinder marine engine was shipped to New York. Weighing 451 kilograms, it had a six-liter displacement and an output of 8.8 kW (12.3 hp) at 390/min. Ten days later Daimler delivered a second model, this one weighing just 153 kilograms. This smaller boat engine had a 2.4-liter displacement and developed 3.7 kW (5.9 hp) at 620/min.
The Daimler Phoenix car featuring Maybach’s four-cylinder in-line engine was the world’s first road vehicle to be equipped with a four-cylinder engine. The first two vehicles of this type with 5.9 kW (8 hp) 2.1-liter engines were shipped from Daimler-Motoren-Gesellschaft (DMG) to Emil Jellinek in September 1898. In the course of 1899, DMG offered further variants of this first four-cylinder production car engine. Output ranged to a maximum of 17 kW (23 hp).
In February 1899, Daimler equipped the Graf Zeppelin airship with gasoline engines. The four-cylinder light-alloy engines (model N) each had 4.4-liter displacement and developed 11 kW (15 hp) at 700/min. The maiden flight of the LZ 1 airship, powered by two Daimler engines, took place on July 2, 1900.
A four-cylinder horizontally-opposed piston engine with 5.4-liter displacement and output of 15 kW (20 hp) was the final evolutionary stage of the contra engine invented by Carl Benz in 1897. Benz had chosen this name for his engine with horizontally positioned cylinders because the pistons, although attached to the same crankshaft, worked in contrary motion. The contra engine had several advantages over in-line engines – above all, with the cylinders set at 180 degrees to one another, dynamic masses were very well balanced. The two cylinders were slightly offset towards one another within the open-topped engine frame in order to accommodate the crankshaft’s double throw. This configuration also allowed for a more compact and flatter design of contra engine.
The four-cylinder engine developed by Maybach for the 35 hp Mercedes featured a number of innovations. For example, with six-liter displacement and generating 26 kW/35 hp at 950/min, the power unit had intake and exhaust valves controlled by two lateral camshafts. The unit also acquired the name “hammer engine” on account of its design feature of lateral valves. This was also the first time Maybach made use of the honeycomb radiator, and the engine was of lightweight design throughout.
The Mercedes Simplex was powered by a four-cylinder in-line engine. Depending on variant, this engine developed 24 kW (32 hp) at 1200/min from a 5.3-liter displacement or 48 kW (65 hp) at 1200/min from a 9.3-liter displacement. For the new Simplex models introduced in 1903 (18/22 hp, 60 hp sports car and 90 hp racing car) Wilhelm Maybach designed all-new four-cylinder engines. These featured an overhead intake valve at the center of the cylinder and a vertical exhaust valve operated via push rods. The cylinders were double-walled in the combustion zone to allow cooling water to circulate.
The chain-driven 16/20 hp Benz Parsifal was Benz’s first four-cylinder production car. That same year, Benz presented his 35 hp Parsifal, featuring a four-cylinder engine with displacement of 5.9 liters, as the top model in the series. The less powerful Parsifal models had twin engines (two-cylinder in-line units) or a single-cylinder. The Mannheim-based brand Benz & Cie. continued to develop four-cylinder technology even after Carl Benz had left the company as design engineer. The generation of Benz cars that superseded the Parsifal featured engines with dual ignition, lateral valves in a
T-configuration and spray-nozzle carburetors. The models introduced in 1905 ranged from the 18 hp Benz with 3.2-liter displacement and 13 kW (18 hp) at 1400/min to the 35/40 hp Benz with 5.9-liter displacement, which reached peak output of six to 29 kW (35 to 40 hp) at 1350/min.
Four-cylinder gasoline technology was also used to power the wheel hub motors of the Mercédès Mixte passenger cars: combustion engines with 33 or 51 kW (45 hp or 70 hp) were used to power a generator, the electrical energy from which was converted into drive power by the wheel hub motors in the front wheels. These early hybrid vehicles were built by the Austrian Daimler-Motoren-Gesellschaft. Ferdinand Porsche won the Exelberg Race as early as 1902, driving a similarly designed vehicle, a Mercedes-Lohner-Porsche.
Aero engine production at Daimler began with the production of the first four-cylinder J 4 F engine (88 kW/120 hp). That same year also saw the development of the B 4 F (22 kW/30 hp) and the D 4 F (44 kW/60 hp), also four-cylinder units.
A four-cylinder engine powered the 200 hp Benz record-breaking car, more commonly known as the Lightning Benz. The 407-kilogram engine developed 147 kW (200 hp) at 1600/min. During one record attempt on the Brooklands race circuit in 1909, works driver Fritz Erle for the first time broke the 200 km/h barrier driving the Lightning Benz. The car was to remain the world’s fastest vehicle for several years to come. The 21.5-liter four-cylinder engine had the largest displacement ever used by Mercedes-Benz and its predecessor brands in a racing or record-breaking car. The only cars to feature larger displacements were test and record-breaking cars fitted with aero engines.
For the Prince Heinrich Rally of 1910 Benz & Cie. developed special touring cars, whose four-cylinder engines were equipped with four-valve technology. Both the 5.8-liter engine (59 kW/80 hp at 2500/min) and the 7.3-liter unit (74 kW/100 hp at 2500/min) featured four overhead valves per cylinder in V-configuration. Intake and exhaust valves were driven by two lateral camshafts.
At the Paris Motor Show DMG unveiled the first Mercedes to feature a valveless Knight sleeve-valve engine, a 16/40 hp model with four-cylinder engine. Advantages of the sleeve-valve engine over other drive systems included smooth running and the potential to achieve engine speeds of up to 1600/min for four-cylinder engines. However, the sleeve-valve control gear proved to be both mechanically temperamental and costly to build. In total only around 5,500 vehicles equipped with Mercedes Knight engines were ever built.
The 37/90 hp Mercedes became the new top-of-the-range DMG model. Its four-cylinder engine had a 9.5-liter displacement and was equipped with three-valve technology (one intake valve, two exhaust valves) and dual ignition. Its design featured single cylinders with a welded coolant jacket and replaced the six-cylinder engines of 1907.
Benz & Cie. also designed gasoline engines for aircraft. One of these was the Benz FX four-cylinder aero engine designed in 1912 by Arthur Berger. In 1913 a Benz FX 9.6-liter four-cylinder engine with a nominal output of 77 kW (105 hp) won the Emperor’s Prize for the best German aero engine. Third place in the competition was also awarded to Benz & Cie.
Daimler-Motoren-Gesellschaft (DMG) successfully implemented four-valve technology in the engine of its Grand Prix car for the 1914 season. The four-cylinder in-line engine featured vertical steel cylinders. The cylinder heads, also made of steel and roof-shaped in structure, each had two intake and exhaust valves. Ignition was provided by three spark plugs per cylinder head. With its high engine speeds (77 kW/105 hp at 3100/min, maximum revs 3200/min), the engine became a model for aero engines.
The supercharger era began when DMG presented the world’s first supercharged passenger car at the Berlin Motor Show. The four-cylinder 6/20 hp Mercedes and 10/35 hp Mercedes engines were supplied with compressed air from a double-vane Roots blower for improving cylinder charge and thereby boosting output. In 1923, now with enhanced performance, the two vehicles went into production as the 6/25/40 hp and 10/40/65 hp models. Their engines incorporated V-shaped overhead valves, a vertical shaft as well as single steel cylinders, arranged in a single block and surrounded by a welded outer steel casing. These high-performance engines were designed by Paul Daimler based on the model of aero engines dating from the First World War – the aero engines that also gave rise to the technology of mechanical charging using a compressor.
Benz & Cie. introduce the world’s first diesel truck. The five-ton vehicle was powered by a four-cylinder OB 2 diesel engine developing 33 kW (45 hp) at 1000/min. In direct comparison with a spark-ignition engine of equal output, the compression ignition unit achieved fuel cost savings of 86 percent. Under testing, the OB 2 proved so promising that it was quickly decided to produce it in large numbers – and the world’s first diesel-engined production truck made its debut in February 1924 at the Commercial Vehicle Show in Amsterdam. The OB 2 prechamber diesel engine now delivered 37 kW (50 hp) at 1000/min.
Daimler-Motoren-Gesellschaft in Berlin-Marienfelde built a four-cylinder diesel engine with air injection for trucks. For this engine the Daimler engineers transferred knowledge gained in the design of diesel engines with air injection for use in submarines. The result was a four-cylinder diesel unit with an output of 29 kW (40 hp) at 1000/min. Under testing in 1923, much of which took place on the roads from Berlin to Stuttgart and back, the engine showed its suitability for everyday use.
The 5/25 hp Mercedes-Benz prototype (W 14 series), with its
1.3-liter four-cylinder M 14 engine, was one of the first cars to be developed following the merger of Daimler-Motoren-Gesellschaft and Benz & Cie. However, the vehicle never went into production.
The Mercedes-Benz 130 (W 23) was an innovative small vehicle with a rear-mounted four-cylinder 1.3-liter engine. The model was the first production car by Mercedes-Benz to feature a rear engine. The 170 H model (W 28) introduced in 1936 also had a four-cylinder spark-ignition engine mounted in the rear.
The Mercedes-Benz 260 D was the world’s first production passenger car with diesel drive. Its four-cylinder engine was fitted with a Bosch injection pump that allowed high revs and ensured a particularly fast fuel supply. The 2.6-liter engine had a compression ratio of 1:20.5 and output of 33 kW (45 hp) at 3200/min. The world’s first diesel passenger car was the result of intensive research that dated from the merger between DMG and Benz & Cie. in 1926. Among the test engines developed were a 3.8-liter six-cylinder unit with 60 kW (82 hp) and the three-cylinder OM 134 diesel with 22 kW (30 hp) used in the Mercedes-Benz 175 D (W 134) prototype. But the real step in the direction of production was the four-cylinder OM 141 engine with 26 kW (35 hp) used in the 175 DX (W 141) test cars. This ultimately gave rise to the four-cylinder 2.6-liter OM 138 diesel – based on a six-cylinder commercial vehicle diesel engine – for the Mercedes-Benz 260 D. By this time the engineers had perfected soft combustion after the pre-chamber process by using, for example, a Bosch four-plunger injection pump. The state-of-the-art four-cylinder unit already featured overhead valves, and a crankshaft running in five bearings helped ensure effective vibration damping.
The engineers began work on an entirely new generation of Mercedes-Benz diesel engines, the 300 series. The four-cylinder engine in the series was to be called OM 301. The characteristic features of the new engines were their compact dimensions as well as innovative components such as a crankshaft running in seven bearings and leaded-bronze bearings with steel-backed shells for the main and con rod bearings. The project was mothballed in 1942, however, and work on the engine series did not resume again until after the war.
The first passenger car engine built in Untertürkheim after the war was a 1.7-liter four-cylinder unit for the 170 V model. In the difficult post-war circumstances, Mercedes-Benz initially returned to tried-and-tested engines from the pre-war program when production resumed.
At the end of the Second World War, the Mercedes-Benz 170 D marked a new departure for the production of diesel passenger cars at Mercedes-Benz. Vehicles in the W 136 series with four-cylinder diesel engines were equivalent to the 170 model with gasoline engine. The 1.8-liter OM 636 I engine developed 28 kW (38 hp) at 3200/min. By 1950 Mercedes-Benz was able to introduce a modified drive system that generated 29 kW (40 hp), boosting the sedan’s top speed from 100 km/h to 105 km/h. The 170 D attracted many customers from commercial and public-authority spheres, as well as private buyers. There was also a diesel-powered variant – the 170 S – of the more comfortable, further developed 170 model. The Mercedes-Benz 170 DS (W 136 VIII D) came on the market in 1953 and was built until 1955. Its 29 kW (40 hp) four-cylinder OM 636 VIII engine was produced in very large unit numbers in order to reduce the higher production costs for the diesel unit compared with the gasoline engine. For this reason the engine was not only used in the 170 D and 170 DS models, but also in the Unimog. Daimler-Benz AG also sold the assembly as a stationary engine.
In the first four years after its introduction, the new Mercedes-Benz 180 (W 120) was equipped with the four-cylinder in-line M 136 II with 1.8-liter displacement and 38 kW (52 hp) at 4000/min. In 1957 the engine was superseded by the new 1.9-liter M 121 engine, which also powered the 190 model. Instead of lateral valves, the cylinders now featured overhead valves, the lateral camshaft was replaced with an overhead variant and output increased to 50 kW (68 hp). At the same time, fuel consumption was cut by a liter to 10.5 liters per 100 kilometers (22.4 mpg).
Aerodynamically optimized and with self-supporting bodies, the 180 D (W 120) and 190 D (W 121) models put the diesel drive system on the road in the guise of the box-body structure unveiled in 1953. The familiar four-cylinder (29 kW/40 hp) powered the 180 D at its launch in March 1954; in 1955 output was increased to 32 kW (43 hp) at 3500/min. In 1958 Mercedes-Benz then introduced the new OM 621 engine. As a 1.9-liter diesel engine it generated 37 kW (50 hp) at 4000/min in the 190 D, and from 1961 it also delivered 35 kW (48 hp) at 3800/min in the 180 D. Of the two models combined, around 235,000 units were built in total. The diesel-engined self-supporting chassis-body structure perhaps became best known thanks to the USA test drive by Bill Carroll (1954), the triple class victory of the 180 D in the Mille Miglia (1955) and the victory of Karl Kling in the Africa Rally in a 190 D (1959).
A private rally team set a new diesel world record in 1959 with a Mercedes-Benz 190 SL. The compact roadster had been specially equipped with a modified OM 621 engine. The four-cylinder unit had a two-liter displacement and developed 44 kW (60 hp). This was sufficient to set a 24-hour record at an average speed of 124.1 km/h (77 mph) in what was – the engine apart – a standard 190 SL. The private rally enthusiasts repeated their attempt in 1961. But this time the two-seater was specially prepared for the record attempt. All trim was removed and a small semi-circular glass pane was all that protected the driver from the wind. With a 48 kW (65 hp) diesel unit under the engine lid, the record car this time achieved an average of 142.3 km/h (88.2 mph) over a distance of five kilometers from a flying start.
The Mercedes-Benz 190 c (W 110) was equipped with the latest version of the M 121 gasoline engine. In the W 121 of 1956 this unit had developed 55 kW (75 hp) at 4600/min and required 11.5 liters of premium for every 100 kilometers (20.45 mpg). While fuel consumption remained the same, output now increased to 59 kW (80 hp) at 5000/min, with a top speed of 150 km/h rather than 139 km/h. The developers achieved this optimization in spite of the larger and heavier body which had been designed in line with Béla Barényi’s innovative concept to maximize passive safety.
In the tailfin Mercedes-Benz 200 D (W 110), the four-cylinder OM 621 engine featured a crankshaft running in five bearings and improved sound insulation as compared with its predecessor. This high-speed diesel unit could accelerate the vehicle to a top speed of 130 km/h (80 mph). The sprint from 0 to 100 km/h, on the other hand, took 28 seconds. In total, 159,365 sedans of the 200 D were built between 1965 and 1968; in addition there was the 200 D Universal station wagon and the 200 D with a long wheelbase (3.35 meters instead of 2.7 meters) and eight seats. The diesel drive system had by now established itself in the Mercedes-Benz mid-series, a fact demonstrated by the sales figures and differentiation of the model lineup in the late 1960s. Moreover, by now the days when diesel passenger cars had only rudimentary comfort features were long gone. As an option, compression ignition models from Mercedes-Benz were also available with automatic transmission.
The new four-cylinder OM 314 diesel injection engine had a displacement of 3.8 liters and developed 59 kW (80 hp) at 2800/min. The engine was mounted in light-duty cab-over-engine trucks, vans and special-purpose vehicles such as the Unimog.
As part of a model refinement package, the mid-series W 115/114 – better known as the Stroke Eight – was given two new four-cylinder engines. The 240 D became the top-of-the-range diesel model, while the 230.4 replaced the 220. The suffix “4” in the model designation of the new 230 was necessary to avoid potential confusion with the original 230 model, which featured a six-cylinder engine and continued to appear as the 230.6.
The new mid-series model launched in 1976 was available as a sedan (W 123) with three different four-cylinder diesel engines, which made their debuts as the 200 D, 220 D and 240 D. For the W 123, Mercedes-Benz returned to the successful diesel program used in the Stroke Eight (W 115/114). For the W 123 the engines were thoroughly revised, however, receiving among other things new cylinder head gaskets made from a material called Ferrolastik. In addition, the procedure for changing the oil was simplified, the exhaust system was improved and oil and fuel filters were modified. Statistics reveal just how popular diesel engines had become by this time. The most widely sold sedans from the 123 series were the four-cylinder 240 D (448,986 units) and the 200 D (378,138 units) diesel models.
The new four-cylinder M 102 engine made its debut in the 123 series: The two-liter M 102 carburetor engine developed 80 kW (109 hp) at 5200/min, the 2.3-liter injection M 102 unit generated 100 kW (136 hp) at 5100/min. These two M 102 variants superseded the tried-and-tested engines from the M 115 series. The all-new four-cylinder in-line M 102 was designed to be canted at a slight angle, in order to keep its mounted height to a minimum. This specification was important to enable the engine to be used in future model generations. Despite a boost in output of between 15 and 25 percent, with the M 102 the engineers succeeded in reducing fuel consumption of the W 123 by around 10 percent. They also improved its smooth running. The cylinders of the new engine were designed with hemispherical combustion chambers with a squish area in the cylinder head. The purpose of this was to guarantee maximum swirl in order that even very lean mixtures could be ignited. All these measures made this gasoline engine so unique that Mercedes-Benz was forced to abandon the partially still ongoing coordinated production system between four-cylinder gasoline and diesel passenger car engines. This system had come about in the 1950s when production numbers were much smaller.
The Mercedes-Benz energy concept led to reduced fuel consumption for individual models equipped with gasoline engines of between three and 22 percent. But the four-cylinder engines launched in 1980 were already so advanced in design that the energy measures introduced went almost unnoticed.
The four-cylinder OM 601 engine in the new compact class (W 201, introduced in 1982) was known in-house at Mercedes-Benz as the “whispering diesel”. In 1983 the compact Mercedes-Benz in the shape of the 190 D was equipped with this two-liter diesel unit (53 kW/72 hp at 4600/min). The engine was designed to be light, economical and responsive. But above all, the engine was fully encapsulated, cutting noise development by half. Alongside the 190 D, the 190 D 2.2 with a modified four-cylinder diesel engine was developed specifically for the North American market.
Four-valve technology at Mercedes-Benz underwent a renaissance in the compact class (W 201) in 1983. The 190 E 2.3-16 was a sporty variant of the compact class sedan with outstanding driving characteristics. The car’s trademark was the high elasticity of the engine. The 16-valve unit had four V-shaped overhead valves per cylinder controlled by two overhead camshafts. Air-bathed injection valves were positioned in each case just before the point at which the intake ducts divided, spraying the fuel evenly into each of the eight ducts. From a displacement of 2.3 liters, the power unit developed 136 kW (185 hp) at 6200/min. The compact class car covered the sprint from 0 to 100 km/h in 7.5 seconds, peak torque of 235 Newton meters was achieved at 4500/min, and top speed was 230 km/h.
The success story of the M 102 family of gasoline engines stood for the continuity of development at Mercedes-Benz. Tried-and-tested units have always been improved and adapted to meet new requirements. One manifestation of this long-term evolution was the significant milestone reached by the M 102 in 1985. In December that year, the one millionth four-cylinder engine in this series came off the production line. In the 124 series the four-cylinder M 102 engines were largely equivalent to those of the 123 and 201 series, although there were one or two detailed modifications. For example, the rocker arms had hydraulic valve clearance compensating elements instead of adjusting screws. New, too, was the oil filter that could be accessed from above, with the interchangeable filter cartridge bolted onto the oil filter bottom. The 2.3-liter injection engine was fitted with an electronic control unit to take care of fuel shut-off in overrun, full-load enrichment and warm-up mixture enrichment.
Mercedes-Benz offered all variants in the revised model range with an exhaust gas aftertreatment system with closed-loop three-way catalytic converter as an option. Initial exceptions to this were the 560 SEL and 560 SEC models in the ECE version. From September 1986 onwards the closed-loop three-way catalytic converter then became standard equipment on all Mercedes-Benz passenger car models equipped with gasoline engines.
At the Turin Motor Show Mercedes-Benz presented the new 190 E 1.8 model with 1.8-liter injection engine. The vehicle, with its four-cylinder engine, superseded the 190 carburetor model in the 201 series. At the same time, the 200 and 200 T carburetor models from the 124 mid-series were discontinued. It was the end of the carburetor era for passenger cars from the Stuttgart brand, 36 years after Mercedes-Benz first introduced fuel injection in a four-stroke production vehicle in the 300 SL. From the end of April 1990 the passenger car sales range now only included models with injection engines.
Mercedes-Benz presented a revised model program for the mid-series, the gasoline engine range now switched completely to four-valve technology. The four-cylinder M 111 engines with two and 2.2-liter displacement replaced the two-valve units from the M 102 model family. The new engines proved themselves with increased output and higher torque over the entire engine speed range and with reduced fuel consumption. In addition, a reduction in pollutant emissions was achieved by increasing the volume of the catalytic converter. The new M 111 series of gasoline engines with four-valve technology developed to achieve similar success to the M 102. By 1999 the two millionth M 111 had left the production line at the Untertürkheim plant. In addition, this engine also provided the technical platform for the reintroduction of supercharger technology. Mercedes-Benz cultivated the four-valve engines acoustically for their use in volume production. Almost every component was individually examined by the engineers under the aspect of noise development. The goal was “quiet energy conservation”.
The four-cylinder engines of the new 202 series all formed part of the M 111 family of gasoline engines. In designing the series, the engineers put high tractive power before top performance. As with all the latest four-valve engines in the model range, the four-cylinder in-line units were equipped with a static high-voltage ignition distributor which avoided problems of wear since it involved no moving parts. Double spark coils on the intake manifold each supplied two cylinders. The all-new 1.8-liter M 111 E 18 engine developed 90 kW (122 hp) at 5500/min and achieved peak torque of 170 Newton meters at 4200/min. The two-liter M 111 E 20 mobilized 100 kW (136 hp) at 5500/min and achieved torque of 190 Newton meters at 4000/min. The 2.2-liter engine, finally, generated 110 kW (150 hp) at 5500/min and peak torque of 210 Newton meters at 4000/min. In 1996 this unit was superseded by the C 230 with its 2.3-liter M 111 E 23 engine (110 kW/150 hp at 5400/min). The introduction of the new C-Class also brought changes to model nomenclature at Mercedes-Benz. Henceforth, a preceding letter or combination of letters was to designate the class to which a vehicle belonged, while the number referred to engine displacement as before. Many of the suffixes of letters and numbers that had previously designated engine or body variants were abandoned once and for all, since in the current range of engines and models, a distinction between, for example, two-valve engines or carburetor versions was no longer necessary.
The renaissance of supercharger technology in Mercedes-Benz cars started with the 2.3-liter four-cylinder engines in the C-Class, SLK and CLK. At the International Frankfurt Motor Show (IAA) in 1995 the company introduced the C 230 Kompressor, in which mechanical supercharging made peak torque of 280 Newton meters available from 2500 to 4800/min. However, the 142 kW (193 hp) four-valve four-cylinder engine required only 8.2 liters of premium per 100 kilometers (NEDC combined, 28.7 mpg). That made the engine about 20 percent more economical than a naturally-aspirated engine of the same output. In the C 230 Kompressor, each revolution of the mechanical blower’s rotors forced more than a liter of air into the engine. The C-Class managed the sprint from 0 to 100 km/h in 8.4 seconds, accelerated from 60 km/h to 120 km/h in 11.8 seconds, and had a top speed of 230 km/h. With this car Mercedes-Benz revived a tradition begun in the days of Daimler-Motoren-Gesellschaft. In 1918 DMG first used supercharger technology successfully in aero engines developed by Paul Daimler, and in 1922 the first supercharged Daimler car competed in the Targa Florio in Sicily.
In the E-Class E 230 from the 210 series, Mercedes-Benz introduced a new 2.3-liter engine with 110 kW (150 hp). Additional output from the engine based on the 2.2-liter four-cylinder unit was available principally in the lower to medium engine speed range. Torque of 220 Newton meters was achieved between 3700 and 4500/min. Gasoline engines for all displacement classes in the 210 series were equipped with four-valve technology. As a result they scored well for high torque and improved tractive power over a broad speed range.
An entirely new generation of four-cylinder engines featuring a light-alloy block was conceived for the Mercedes-Benz A-Class in the 168 series. The first models available were the A 140 gasoline versions with 60 kW (82 hp) and A 160 with 75 kW (102 hp). The model range was expanded in 1999 to include the A 190 with its 92 kW (125 hp) M 166 E 19 engine. Particular importance was attached to engine and transmission in the Mercedes-Benz A-Class, since the slanted alignment of the drive unit in the subfloor and in front of the pedal floor formed an integral part of the vehicle concept’s sandwich design. Positioned in front of and beneath the intermediate floor in this way, in the event of a frontal impact the drive unit slid along a slanting bulkhead beneath the passenger compartment, thereby minimizing risk of injury to passengers.
Mercedes-Benz common rail technology celebrated its premiere in the four-cylinder engine of the Mercedes-Benz C 220 CDI. The OM 611 DE 22 LA engine was equipped with innovative direct fuel injection supplied by a fuel line serving as a common pressure reservoir, an exhaust gas turbocharger with intercooler and an exhaust gas aftertreatment system with oxidation catalyst. In the C 220 CDI, the 2.2-liter engine became the forerunner of common rail direct injection (CDI). CDI engines by Mercedes-Benz attracted critical acclaim for their exceptionally smooth running, high torque and high output with low fuel consumption and low emissions.
In 1998 Mercedes-Benz introduced the Cito midi city bus. The innovative low-floor vehicle featured a diesel-electric drive system. This involved the four-cylinder OM 904 LA diesel engine to drive a generator. The electric power generated was fed to the electric traction motor. Thanks to this drive technology, the Cito was notable for jolt-free, continuous acceleration; in addition, with the aid of batteries to store energy it made completely emissions-free operation possible over short distances. The Cito was voted “International Bus of the Year 2001” at the Feria Internacional de Autobuses y Autocares (F.I.A.A. International Bus Show) which took place in Madrid from November 22 to 25, 2000.
In December 1999 the two-millionth four-cylinder gasoline engine in the M 111 series left the Untertürkheim plant. Produced from 1992 onwards, the engine with four-valve technology was used in models in the C-Class, E-Class, M-Class and CLK-Class as well as in the V-Class and the Sprinter. This engine family also included the revised four-cylinder engines which Mercedes-Benz introduced in June 2000 for the C-Class station wagons, the E-Class sedans and station wagons and for the CLK coupe and convertible models.
Together with Hyundai Motor Company and Mitsubishi Motors Corporation, DaimlerChrysler set up the Global Engine Alliance L.L.C. This joint venture for the development and production of four-cylinder in-line gasoline engines has its headquarters in the United States of America. In 2004 DaimlerChrysler and Hyundai Motor Company changed their strategic alliance. Nevertheless, work continues on the joint development and production of a family of four-cylinder gasoline engines, the so-called World Engine.
In the Mercedes-Benz CLK 200 CGI a revolutionary generation of gasoline engines had its premiere, featuring direct gasoline injection based on the principle of Stratified Charged Gasoline Injection (CGI). These direct gasoline injection engines used 16 percent less fuel than comparable engines with conventional manifold injection. The microprocessor-controlled direct gasoline injection was combined with a hot-film air flow sensor (HFM) and mechanical turbocharging with the aid of a compressor. In addition to the new injection technology, a new generation of four-cylinder engines also celebrated their debut, which thanks mainly to the unique TWINPULSE system set new standards in this displacement class in terms of power delivery, torque characteristics, noise levels and fuel consumption. Two four-cylinder models were available: The CLK 200 KOMPRESSOR (120 kW/163 hp) with conventional fuel injection and the CLK 200 CGI (125 kW / 170 hp) with direct gasoline injection. To complement the TWINPULSE system, Mercedes-Benz equipped the new CGI gasoline engine with leading-edge direct injection technology, which reduced fuel consumption of the two-liter four-cylinder unit to a meager 7.9 liters per 100 kilometers (NEDC combined, 29.7 mpg). In the CGI engine, air and fuel were not mixed until they reached the combustion chambers. Fuel was injected into each cylinder by a high-pressure pump at an angle of 42 degrees and a pressure between 50 and 120 bar, dependent upon operating requirements. Here, fuel droplets formed a mixture cloud with the air particles, which was guided toward the spark plug by specially shaped piston recesses. For purposes of comparison, in the four-cylinder engine with conventional technology, fuel injection pressure measured approximately 3.8 bar. In order to create optimum swirl motion that ensured combustion of the mixture cloud was as fast and complete as possible, the CGI engine featured two separate intake ports, the flow characteristics of which were developed as a result of a carefully tailored set of processes. One of the intake ports in each case was equipped with an adjustable swirl flap. The high-pressure fuel pump was driven off the intake camshaft; the pressure in the fuel line (rail), with a direct link to the injectors, was monitored by a fuel pressure regulator controlled by the ECU which in turn received signals from a special pressure sensor.
The two-liter variant of the new Mercedes-Benz A-Class (W 169) was equipped with a turbocharger. With this A-Class engine the A 200 TURBO opened up new dimensions. Output generated was 142 kW (193 hp), equivalent to 71 kW (96 hp) per liter of displacement – making the four-cylinder unit one of the most powerful engines in its displacement class. Peak torque of 280 Newton meters was available over a wide engine speed range up to 4850/min. The engines in the A 150, A 170 and A 200 also had a larger displacement compared with the predecessor model, as well as a variable intake manifold to improve tractive power at lower engine speeds. The A-Class turbo-engine was also used in the B-Class.
The Mercedes-Benz bionic car concept vehicle, with which the brand launched its BLUETEC initiative for passenger cars, was powered by a four-cylinder turbodiesel with common rail direct injection and two-liter displacement. The diesel engine delivered 103 kW (140 hp) and required 4.3 liters of fuel per 100 kilometers for the standard EU driving cycle (54.7 mpg). The concept car achieved an impressive reduction of nitrogen oxides equivalent to around 80 percent compared with production vehicles. This was made possible by the world’s first use in a passenger car of SCR (Selective Catalytic Reduction) technology. For the bionic car the developers opted to inject AdBlue, an aqueous urea solution, the supply reservoir being accommodated conveniently in the concept car’s spare wheel well. One filling was sufficient to last the equivalent of a maintenance interval for a modern Mercedes-Benz diesel engine.
Mercedes-Benz introduced BLUETEC as standard for commercial vehicles. In the commercial vehicle segment this technology designed to minimize emissions was based on an SCR catalytic converter and injection of AdBlue into the exhaust flow. Engines in the 900 series with BLUETEC thereby cover the complete bandwidth of variants previously offered with the EURO III standard. The basic OM 904 LA model, a water-cooled four-cylinder in-line engine with three-valve technology, develops 95 kW (129 hp) at 2200/min. The engine features a turbocharger, intercooler, fully-electronic engine management and nine-hole injection nozzles capable of up to 2000 bar injection pressure. Peak torque of 500 Newton meters is available from 1200 to 1600/min.
Mercedes-Benz unveiled its highly environmentally-compatible BLUETEC emission control technology in combination with a consumption-optimized four-cylinder engine for the first time at the Geneva Motor Show in February 2007. In terms of ensuring compliance with the even stricter EURO VI emission standard, applicable to all new vehicles Europe-wide from 2015, the Vision C 220 BLUETEC showed the way ahead. Boasting an output of 125 kW (170 hp) and peak torque of 400 Newton meters, the Vision C 220 BLUETEC requires only 5.5 liters of diesel per 100 kilometers (42.7 mpg). The first production vehicle to benefit from this configuration will be the C 250 BLUETEC, scheduled for market launch in 2009. This model will be the first passenger car to feature the new generation of four-cylinder diesel engines from Mercedes-Benz.
At the International Frankfurt Motor Show (IAA), Mercedes-Benz unveiled the DIESOTTO engine in the F 700 research vehicle. This forward-looking four-cylinder unit, with a displacement of only 1.8 liters, combines the strong points of the low-emission gasoline engine with the consumption benefits of the diesel drive. Its carbon dioxide emissions of a mere 127 grams per kilometer correspond to consumption of only 5.3 liters of gasoline per 100 kilometers (44.3 mpg), extremely low for a vehicle of this class. DIESOTTO technology is an innovative, advanced development of the combustion engine by Mercedes-Benz, incorporating pioneering controlled auto ignition (CAI), direct fuel injection and turbocharging. The engine in the F 700, a four-cylinder unit featuring two-stage charging, attains the performance level of a current S-Class car with a 3.5-liter naturally aspirated V6 gasoline engine or the three-liter V6 turbodiesel.
Further information from Daimler is available on the internet at: www.media.daimler.com
Daimler AG, Stuttgart, with its businesses Mercedes-Benz Cars, Daimler Trucks, Daimler Financial Services, Mercedes-Benz Vans and Daimler Buses, is a globally leading producer of premium passenger cars and the largest manufacturer of commercial vehicles in the world. The Daimler Financial Services division has a broad offering of financial services, including vehicle financing, leasing, insurance and fleet management.
Daimler sells its products in nearly all the countries of the world and has production facilities on five continents. The company’s founders, Gottlieb Daimler and Carl Benz, continued to make automotive history following their invention of the automobile in 1886. As an automotive pioneer, Daimler and its employees willingly accept an obligation to act responsibly towards society and the environment and to shape the future of safe and sustainable mobility with groundbreaking technologies and high-quality products. The current brand portfolio includes the world’s most valuable automobile brand,
Mercedes-Benz, as well as smart, AMG, Maybach, Freightliner, Sterling, Western Star, Mitsubishi Fuso, Setra, Orion and Thomas Built Buses. The company is listed on the stock exchanges in Frankfurt, New York and Stuttgart (stock exchange abbreviation DAI). In 2007, the Group sold 2.1 million vehicles and employed a workforce of over 270,000 people; revenue totaled €99.4 billion and EBIT amounted to €8.7 billion. Daimler is an automotive Group with a commitment to excellence, and aims to achieve sustainable growth and industry-leading profitability.
Daimler Communications, 70546 Stuttgart/Germany