When the automobile was invented in 1886, the reciprocating piston engine became the generally established form of vehicle drive. However, there were also other principles for combustion engines that could use the power of a fuel explosion to propel the vehicle.
Felix Wankel was the inventor of the rotary piston engine, an initial model of which he patented in 1933. The basic principle of the engine is that the pistons rotate, instead of moving up and down, which means that the engine can be made relatively smaller and run more quietly. Since the basic idea and its advantages are immediately obvious, Mercedes-Benz focused intensively on the Wankel engine from 1962, in the belief that it might even replace the reciprocating piston engine. At the Frankfurt International Motor Show (IAA) in 1969, the brand unveiled the C 111 - and the futuristic experimental car caused a sensation.
The first version had a three-rotor engine, developing a total of 206 kW (280 hp) from 600 cubic centimeters of chamber volume per rotary piston, giving the car a top speed of 260 km/h, and needing just five seconds to accelerate from standstill to 100 km/h. Then, from 1970, the large four-rotor engine was used in the C 111-II. This engine developed 257 kW (350 hp), giving a top speed of 300 km/h. This second version of the C 111 was able to accelerate from a standstill to 100 km/h in a very impressive 4.8 seconds. Some engines in the C 111-I featured a complex dual ignition system, which was difficult to adjust, and the four-rotor engine was subsequently built with single ignition exclusively. Both engines were equipped with direct injection.
Despite all the benefits it offered, the Wankel engine basically had drawbacks in three different areas, in light of the contemporary state of the art. Firstly, it was difficult to ensure its durability. Secondly, its emissions behavior was inferior to the reciprocating piston engine at the time; in the early 1970s, against the background of greater environmental awareness and the oil crises, these problems, in conjunction with the third drawback, its higher fuel consumption, spelled the end of the road for the Wankel engine, and its development was discontinued.
Looking back, Dr. Kurt Obländer, head of Engine Testing within the C 111 project, assessed the Wankel engine as follows: “Our four-rotor engine with gasoline injection was the best that could be achieved with this particular engine design. The multi-rotor version called for peripheral ports for the intake air and exhaust gas ducts. We were able to find engineering solutions to the complex problems of engine cooling and engine mechanics. But the main problem - poor thermodynamic efficiency - remained. The elongated and not exactly compact combustion chambers resulted in reduced fuel efficiency, which meant higher consumption and excessive pollutant content in the exhaust gas. These drawbacks were inherent in the basic design.”
But setbacks of this kind could not cloud the generally positive outlook. Mercedes-Benz researchers considered further alternatives, for example, the stratified-charge (CVCC) engine. A 1974 press release stated that “the principal aim of this development is to combine the advantages of the diesel engine in the part-load range with the good performance of the gasoline engine at full load. The two-stage internal combustion stratified-charge engines now being developed at Daimler-Benz may offer a more economically efficient solution than the gasoline engine with catalytic converter in its current state of development. The design of a CVCC engine is largely similar to that of a conventional gasoline engine, but its combustion chamber is divided into a main combustion chamber and a small ante-chamber. […] The advantages of two-stage combustion are that much leaner mixes […] can be burnt. Thanks to the increased supply of oxygen, there are more complete combustion and fewer pollutants in the exhaust gas. Another result of the excess air during combustion is a sharp drop in peak temperatures, which, in turn, reduces the formation of nitrogen oxides. […] It is impossible to say whether and when this engine […] will go into production.”
The engineers’ hope: The gas turbine
One of the benefits of the “Auto 2000” research car unveiled in 1981 was that it helped to test three different drive systems. A V8 gasoline engine was a conventional engine in a modified form, featuring a cylinder shut-off system to reduce consumption in the part-load range, and a V6 diesel engine with two turbochargers to achieve better torque characteristics and a quicker accelerator response at lower engine speeds. A gas turbine was used as a third variant, initially developing 94 kW (128 hp), and later 110 kW (150 hp). The two-spool turbine ran on diesel fuel and was developed using ceramic materials. It successfully completed its initial trial run in May 1981. In all three drive variants, an automatic transmission converted the energy.
Researchers at the time placed great hopes in the gas turbine. Its particular working principle gave it a range of useful properties: good torque characteristics, no water cooling, vibration-free and low-wear operation, a straightforward ignition system, good cold starting, and low emissions. The fact that it was able to run on different types and qualities of fuel was another advantage for use in motor vehicles. However, although the results were promising, development proved a dead end because of the narrow range within which the gas turbine could operate efficiently at the contemporary state of the art.
Unfortunately, many such research commissions result in a dead end. At the same time, there is almost an equal number where the opposite is the case, where research is successful and the result is a great invention that changes everyday technology and the people’s lives. Because of the uncertainty of the outcome, research always requires a degree of daring to get underway. In the case of a business enterprise, for example, this is reflected in the budgets provided for the research departments, and also in the degree of independence given to all the staff who work there. The innovation history at Daimler AG in the field of alternative drive systems clearly shows that the right approach brings great dividends. After all, this is the only way that the automobile can be constantly improved.
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Group photo: In the 1970s and 1980s, Mercedes-Benz tested different propulsion concepts – with a correspondingly large fleet of test vehicles. The photo was taken on the test track in Stuttgart-Untertürkheim in 1981. |
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Group photo: In the 1970s and 1980s, Mercedes-Benz tested different propulsion concepts – with a correspondingly large fleet of test vehicles. The photo was taken on the test track in Stuttgart-Untertürkheim in 1981. |
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Mercedes Electrique: “The most reliable, quietest and most modern electric city car.” Advertisement of 1907. |
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Rapid start: In 1908, the Berlin fire brigade opted for the Mercedes Electrique with electric drive and purchased a fleet consisting of four vehicles. The wheel hub motors in the front wheels are clearly visible. |
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Mercedes Mixte on the front cover of the magazine “La France Automobile”, edition of November 9, 1901. |
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Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested. |
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Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested. |
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Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested. |
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Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested. |
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Ready for boarding: Mercedes-Benz city bus with hybrid electric drive of 1979. The internal combustion engine powered a generator which produced electricity for the traction motor. |
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Ready for boarding: Mercedes-Benz city bus with hybrid electric drive of 1979. The internal combustion engine powered a generator which produced electricity for the traction motor. |
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Ready for boarding: Mercedes-Benz city bus with hybrid electric drive of 1979. The internal combustion engine powered a generator which produced electricity for the traction motor. |
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Diesel-electric operation in cities: In the Mercedes-Benz Cito (1998), a four-cylinder engine powered a generator which produced electricity for the traction motor. Purely electric operation was possible over short distances. |
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Diesel-electric operation in cities: In the Mercedes-Benz Cito (1998), a four-cylinder engine powered a generator which produced electricity for the traction motor. Purely electric operation was possible over short distances. |
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Energy providers: The Mercedes-Benz OE 302 electric test bus (1969) needed five battery modules which were installed underneath the floor. |
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Diesel-electric: The Mercedes-Benz OE 302 test city bus was powered by electricity, its batteries being charged by a diesel engine. This vehicle marked a new start in hybrid drive development in 1969. |
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No clutch pedal: The driver of the Mercedes-Benz OE 302 electric test bus (1969) only had to actuate the accelerator and brake with his feet. |
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Diesel-electric: The Mercedes-Benz OE 302 test city bus was powered by electricity, its batteries being charged by a diesel engine. This vehicle marked a new start in hybrid drive development in 1969. |
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Early example of an electric car: The chassis of the 30/35-hp Mercedes with wheel hub motors (built from 1905 until 1909). |
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Refueling at the mains: Two Mercedes-Benz test vehicles with electric drive, photographed in 1995. |
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Testing in the early 1990s: Mercedes-Benz MB 100 D van with electric drive; a city bus version of this model was also set up. |
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Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans. |
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Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans. |
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Emissionsfrei unterwegs: Der in Serie gefertigte Duo-Bus, hier ein Exemplar aus dem Jahr 1993, hat einen reinen Elektroantrieb mit doppelter Energiezufuhr. Die Antriebsenergie kommt entweder aus einer Unterflur-Batterie oder gelangt per Oberleitung ins Fahrzeug („O-Bus“). Das bringt Flexibilität abseits des Leitungsnetzes. |
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Transparency: The X-ray picture of a Mercedes-Benz C-Class with electric drive of 1993 shows the layout of components. |
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Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans. |
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Test car with ZEBRA battery: Mercedes-Benz 190 with electric drive, 1993. |
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Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans. |
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Novel electric drive: The Mercedes-Benz 190 used as a test car in 1991. |
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Novel electric drive: The Mercedes-Benz 190 used as a test car in 1991. |
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Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans. |
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Zero-emission motoring in the city: In July 2006, the smart brand launched a pilot project in London. The fortwo ed (electric drive) generates an output of 30 kW (41 hp) for adequate performance and has a range of some 100 kilometers (62 miles). |
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Zero-emission motoring in the city: In July 2006, the smart brand launched a pilot project in London. The fortwo ed (electric drive) generates an output of 30 kW (41 hp) for adequate performance and has a range of some 100 kilometers (62 miles). |
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High level of ride comfort: In early 1982, Mercedes-Benz began testing electric drive systems in passenger cars. The station wagon from the 123 series largely corresponded to the production version but its load compartment was reduced in size by the fact that it accommodated the battery. |
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High level of ride comfort: In early 1982, Mercedes-Benz began testing electric drive systems in passenger cars. The station wagon from the 123 series largely corresponded to the production version but its load compartment was reduced in size by the fact that it accommodated the battery. |
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High level of ride comfort: In early 1982, Mercedes-Benz began testing electric drive systems in passenger cars. The station wagon from the 123 series largely corresponded to the production version but its load compartment was reduced in size by the fact that it accommodated the battery. |
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Testing in city traffic: Mercedes-Benz 307 E van with electric drive (1980). |
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On the test track in Stuttgart-Untertürkheim: Mercedes-Benz 307 E van with electric drive (1980). |
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Propulsion energy at times of hardship, available ex factory: Mercedes-Benz 170 VG (1935) with wood gas burner. |
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Mercedes-Benz L 307 van of 1975: Test vehicle with hydrogen propulsion and hydride storage unit. |
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Test bus of 1971: The six-cylinder spark-ignition engine of the Mercedes-Benz OG 305 operated on natural gas – with very low pollutant emissions. |
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Prototype with electric drive: The Mercedes-Benz A-Class (W 168 series) of 1998 derived its energy from a ZEBRA high-performance battery on a sodium/nickel chloride basis. |
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In 1992, Mercedes-Benz presented a “Flexible Fuel” test car based on the 300 SE S-Class model (140 series). It engine management was designed for variable mixed methanol/ gasoline operation with a methanol proportion of up to 85 percent. |
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Adjustable engine management: In 1990, Mercedes-Benz presented the 300 E-24 for variable mixed methanol/gasoline operation. |
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Special setup: The Mercedes-Benz 450 SL test car (R 107 series) of 1974 had a spark-ignition engine optimized for operation on methanol. The engineers used the console and additional switches for controlling and monitoring the fuel system. |
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Three test vehicles from Mercedes-Benz (from left to right): LE 306 electric van (1972), OE 302 electric test bus (1969), OG 305 natural-gas test bus (1971). |
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Energy carrier for the future: In 1988, hydrogen was tested as a fuel in Mercedes-Benz vans and passenger cars. |
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Mercedes-Benz 200, 1981: Test car for the combined supply of the internal combustion engine with gasoline and liquefied gas. |
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Methanol operation and energy recuperation: The Mercedes-Benz O 305 test city bus on the test track in Stuttgart-Untertürkheim (1981). The vehicle was also tested in regular service. |
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Environment-friendly vehicles: Mercedes-Benz city bus with electric drive, van with electric drive and passenger car (123 series) for mixed methanol/gasoline operation. The photo was taken around 1980. |
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Methanol as a fuel: In 1979, the Federal German Ministry of Transport launched a research project named “Alternative Energies for Road Traffic”. Mercedes-Benz participated in a field test in Berlin with different vehicles, among them the 230 model (123 series). |
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Methanol as a fuel: In 1979, the Federal German Ministry of Transport launched a research project named “Alternative Energies for Road Traffic”. Mercedes-Benz participated in a field test in Berlin with different vehicles, among them the 230 model (123 series). |
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Gratifyingly low emissions, more efficient power output: The Mercedes-Benz 450 SL test car (R 107 series) with a spark-ignition engine optimized for operation on methanol was presented to the public in 1974. |
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B-Class F-Cell |
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NECAR 1, 2 and 3: From van to A-Class. |
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Mercedes-Benz Concept Vehicles, NECAR 1: An MB 100 van served as basis. |
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Mercedes-Benz Concept Vehicles, NECAR 1: The cargo space is packed with equipment. The stacks are arranged beneath the yellow hydrogen flask. |
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The Technology of the Fuel Cell and its Operating Systems, The operating principle of the fuel cell. |
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Matured: After the completion of the test stage, several units of the NGT Sprinter (Natural Gas Technology) were put into service, for instance by RHENAG in April 1996. |
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Matured: After the completion of the test stage, several units of the NGT Sprinter (Natural Gas Technology) were put into service, for instance by RHENAG in April 1996. |
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In 1992, Mercedes-Benz presented a “Flexible Fuel” test car based on the 300 SE S-Class model (140 series). It engine management was designed for variable mixed methanol/ gasoline operation with a methanol proportion of up to 85 percent. |
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Hydrogen testing: Mercedes-Benz also investigated the suitability of hydrogen as an energy supplier for internal combustion engines in vans. |
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On the way into the future: Different vehicles – the photo shows a Mercedes-Benz 230 E – were used in 1993 for testing hydrogen as a fuel for the internal combustion engine. |
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On the way into the future: Different vehicles – the photo shows a Mercedes-Benz 230 E – were used in 1993 for testing hydrogen as a fuel for the internal combustion engine. |
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Production car: In March 2006, smart presented the forfour lpg (liquefied petroleum gas) with a liquefied-gas tank in addition to the gasoline tank. In combined operation, the car has a range of 1,300 kilometers (over 800 miles). |
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Production car: In March 2006, smart presented the forfour lpg (liquefied petroleum gas) with a liquefied-gas tank in addition to the gasoline tank. In combined operation, the car has a range of 1,300 kilometers (over 800 miles). |
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Production car: In March 2006, smart presented the forfour lpg (liquefied petroleum gas) with a liquefied-gas tank in addition to the gasoline tank. In combined operation, the car has a range of 1,300 kilometers (over 800 miles). |
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Spectacular test car: The Wankel or rotary-piston engine was tested in the Mercedes-Benz C 111-I (1969, shown in the photo) and C 111-II (1970). |
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Spectacular test car: The Wankel or rotary-piston engine was tested in the Mercedes-Benz C 111-I (1969, shown in the photo) and C 111-II (1970). |
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On the way into the future: Different vehicles – the photo shows a Mercedes-Benz 230 E – were used in 1993 for testing hydrogen as a fuel for the internal combustion engine. |
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V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems. |
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V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems. |
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V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems. |
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V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems. |
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V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems. |
