Press Kit: Mercedes-Benz: Innovation as a tradition
Nov 20, 2007
Engine technology: Supercharger, diesel engine, direct gasoline injection, DIESOTTO
Supercharged engines by Mercedes (from 1916)
After the war, Daimler-Motoren-Gesellschaft used the experience gained in supercharging aero engines to raise the output of vehicle engines. The first supercharged Mercedes models were exhibited at the 1921 Berlin Motor Show, creating a considerable stir in the automotive world. Competition cars also were fitted with superchargers. In the Targa Florio in April 1922, Max Sailer won the production car category in a supercharged 28/95-hp Mercedes.
From 1927, one year after the merger between DMG and Benz & Cie. to become Daimler-Benz AG, powerful, supercharged sports cars were launched into the market: the S (Sport), SS (Super Sport), SSK (Super Sport Kurz = Short) and SSKL (Super Sport Kurz Leicht = Short Light). The howl of the performance-enhancing Roots blower used in the sports cars was naturally unacceptable in luxury cars such as the 770 Grand Mercedes. Thanks to effective noise suppression the engine mutated into a discreetly snoring “whisperer” from 1930. The supercharger as a mechanical pressure booster ensures that the engine’s combustion chambers are better supplied with fuel-air mixture than in a merely naturally aspirated engine. Supercharger technology lent wings to other famous Mercedes sports cars and limousines throughout the thirties.
The present-day Mercedes-Benz models with supercharging have very little in common with the first- and second-generation superchargers of the early years. There is no longer any question of disturbing noise. They discreetly provide a permanent increase in output and torque and thus contribute to weight reduction and, in conjunction with other components, also help to improve exhaust emission characteristics.
Diesel passenger cars (from 1936)
Rudolf Diesel was granted a patent for the compression-ignition engine named after him in 1892, and the first diesel engine ran successfully one year later. In this power unit the fuel was blown into the combustion chamber under high pressure by a so-called injection compressor, and this principle was at first only suitable for large stationary and marine engines.
Prosper L’Orange, an engineering genius with a passion for the diesel engine and an employee of Benz & Cie. from October 1, 1908, was the inventor of prechamber injection. It was the most important step towards the vehicle diesel engine. Between 1919 and 1921, until the first high-speed vehicle diesel engine was a reality, L’Orange made three further, important inventions: the funnel prechamber, the needle injection nozzle and the regulated injection pump.
The world’s first diesel truck was a Benz five-tonner with a four-cylinder prechamber diesel engine which generated 45 hp (33 kW) at 1000 rpm and ran successfully for the first time on September 10, 1923. It required approximately 25 percent less fuel than a comparable five-tonner with a gasoline engine. From 1926, after the merger with Daimler-Motoren-Gesellschaft, the prechamber principle developed at Benz & Cie. was the basis for production of truck diesel engines by the new Daimler-Benz corporation.
In 1936, 13 years after the introduction of the first diesel-engined truck, the Mercedes-Benz 260 D, the world’s first production diesel car, was shown at the Berlin Motor Show and caused quite a sensation. Its 2.6-liter four-cylinder power unit with the Mercedes-Benz prechamber system and a Bosch injection pump had an output of 45 hp (33 kW) at 3200 rpm and was installed in the chassis of the 200 gasoline model. Its average fuel consumption was slightly more than nine liters per 100 kilometers, considerably bettering the 13 liters of the gasoline-engined 200. In 1936 the price of diesel oil was only 17 pfennigs per liter, less than half that of gasoline. No wonder that particularly taxi drivers fell in love with this car on the spot, and since then Mercedes-Benz diesel cars have always played a leading role in this segment. The diesel’s reliability in hard day-to-day taxi operations also attracted private customers into the showrooms. Approximately 2000 units of the Mercedes-Benz 260 D were built up until 1940.
After the war, economic efficiency was in greater demand than ever before, and the four-cylinder passenger car diesel engine continued its great success in the Mercedes-Benz 170 D from 1949 and the 170 DS from 1952. These were followed by the 180 D and 190 D with the three-box body of 1953. With the fintail model, the Stroke Eight and the successor series, production figures of the diesel engine rose continuously, and it ultimately became an indispensable part of the mid-sized Mercedes series, i.e. the current E-Class. Constant improvements, larger displacements and increasing output levels, reaching a respectable 2.4 liters and 65 hp (48 kW) as early as 1973, continuously adapted it to the wishes of customers. The competitors also gradually acquired a taste for it.
In 1974 Daimler-Benz offered performance-hungry diesel drivers 80 hp (59 kW) and a new quality of refinement with the three-liter five-cylinder engine. Another eight hp (5.9 kW) were added in 1979. The first Mercedes-Benz car with an exhaust gas turbocharger was the 300 D Turbodiesel (W 123 series). With an output of 115 hp and torque of 250 Newtonmeters, this diesel engine made it into the
S-Class in 1977 – initially exclusively available in the U.S. market.
The end of 1982 saw the introduction of the compact class, the forerunner of the current C-Class, with two gasoline models which were followed by a new, 75-hp (53-kW) two-liter diesel in 1983. This engine was the first to be fully encapsulated, providing a new quality of exterior and interior comfort in a diesel car as engine noise was reduced by approximately half. With this “whispering diesel” Mercedes was once again ahead in the race, its pioneering spirit unbroken.
In April 1993, the first car diesel engine with four-valve technology and electronic engine management, known as Electronic Diesel Control or EDC, appeared on the scene. Thanks to four-valve technology the new power unit not only developed more output and a higher torque, it was also even more economical than the preceding two-valve units and set new standards for a prechamber engine in terms of pollutant emissions. EDC also played a decisive role in the 2.9-liter direct-injection diesel engine introduced in 1995. This 129-hp (95-kW) five-cylinder unit was some 18 percent more economical than a comparable prechamber engine. This also meant 18 percent lower carbon dioxide emissions as a result of reduced thermal losses during combustion. In conjunction with the adapted emission control system this also reduced emissions of hydrocarbons and particulates in the direct-injection engine by more than one fifth versus conventional prechamber diesels.
In 1997, a four-cylinder Mercedes-Benz power unit once again opened up a new chapter in the worldwide story of the car diesel engine. Its special feature was direct fuel injection using the common rail principle jointly developed by Daimler-Benz and Bosch. The magical acronym for this revolutionary advance is CDI, Common Rail Direct Injection, and is synonymous with high output, excellent torque characteristics at very low engine speeds, great fuel economy, minimal exhaust emissions and low noise.
In 2003, Mercedes-Benz became the first automobile brand in the world to offer the combination of particulate trap and compliance with the EU 4 emission norm for diesel passenger cars. In 2005 Mercedes-Benz equipped all diesel cars with maintenance-free particulate traps as standard. As a result, some 40 models from A- to S-Class will in future be equipped with a particulate trap system which requires no additives and cuts emissions of soot particles by 95 percent.
In 2005, Mercedes-Benz introduced the new diesel technology BLUETEC. Using the Selective Catalytic Reduction (SCR) process it reduces nitrogen oxides in the exhaust gases of diesel engines by around 80 percent. To achieve this, the additive AdBlue is metered into the exhaust line. AdBlue, available at gas stations, is an aqueous urea solution which uses ammonia (NH3) as an intermediate product to form the natural, harmless products water and nitrogen from the nitrogen oxides in the catalytic converter. Mercedes-Benz planned to use the great potential of this technology for diesel passenger cars as well and began testing in 2005. The first series-produced passenger car featuring BLUETEC drive was presented the following year. The Mercedes-Benz E 320 BLUETEC was launched in October 2006 in the USA. In August 2007, the company announced the start of vehicle series production of the E 300 BLUETEC for the European market.
BLUETEC is a contribution to Mercedes-Benz’s goal of making diesel vehicles just as clean in their emissions as gasoline-powered vehicles, in preparation for future emissions standards worldwide. The company pursues a three-stage plan:
1. Changes in engine design proper to make combustion as efficient and clean as possible.
2. Oxidation catalysts to cut carbon monoxide and hydrocarbon emissions, and particulate traps to reduce particulate emissions to a hardly detectable level.
3. BLUETEC technology to reduce nitrogen oxides – the remaining component of the exhaust gases and still in excess of the levels attained by gasoline engines today – by 80 percent.
But Mercedes-Benz also points to the future of the diesel drive with research on the use of fuels manufactured from biomass. They include SunDiesel®, a synthetic fuel made from biomass. In contrast to diesel fuel obtained from oil seeds, SunDiesel® can be obtained from various organic substances, including waste wood. In 2003 Mercedes-Benz set up a SunDiesel® filling station on the premises of Stuttgart corporate headquarters for the purpose of testing the new fuel.
Direct gasoline injection (from 1937)
Like supercharging technology and several other innovative design principles which became state-of-the-art in automotive engineering, gasoline injection for motor vehicle engines is a product of aero engine development. Hans Scherenberg, a Daimler-Benz engineer at the time, assumed responsibility for the gasoline injection project launched in 1934, and only three years later, in November 1937, large-scale production of the DB 601 A, a twelve-cylinder aero engine – the first with gasoline injection – began. It was clearly more powerful and economical than the carburetor version.
Scherenberg developed the gasoline injection system for earth-bound vehicles to production standards. The legendary Mercedes-Benz 300 SL, launched in 1954, was the world’s first production car with a four-stroke engine with gasoline injection. The Gullwing coupe with its unmistakable design was powered by a 215-hp (158-kW) six-cylinder engine for top speeds up to 260 km/h. In its final version built from 1955, the engine also featured gasoline injection, albeit in somewhat tamed form, and powered the magnificent Mercedes-Benz 300 S, launched in 1951 and the last protagonist of a legendary family of coupes and convertibles with frames. This six-cylinder power unit generated 175 hp (129 kW) and allowed a top speed of 180 km/h.
From 1957, engine operation was determined by a new technology: gasoline injection became indirect – intermittent manifold injection, to be precise: the atomized fuel was injection into the intake manifold rather than directly into the combustion chamber. This system was first used in the Mercedes-Benz 300 d, the last of the four versions from the 300 series built until 1962.
In late 1958, gasoline injection was introduced in large-scale production. Like the 300 d, the Mercedes-Benz 220 SE, the last evolution of the 220 series launched in 1954, had manifold injection, 15 hp (11 kW) more and a much more dynamic response than its 220 S brother with carburetor – and it was even a little more economical. Specific operating parameters such as cold-starting, warm-up, intake air temperature and altitude were communicated to the injection pump by mechanical means, as electronic systems were not yet available. Compared to the carburetor engine, the manifold-injection unit boasted improved smooth-running characteristics, performance, flexibility and accelerating power. And it was easier to service. From then on, the letter “E” in the model designation was a synonym for excellent performance in Mercedes-Benz models.
The story of direct gasoline injection at Mercedes-Benz was continued at the end of 2002 with the introduction of a new 1.8-liter, four-cylinder CGI engine. CGI stands for Stratified Charge Gasoline Injection. This is the first engine in the world to utilize the potential savings of pioneering direct injection technology combined with supercharging, charge air cooling and mass balancing. It significantly reduces both fuel consumption and pollutant emissions compared to a comparable engine with manifold injection, while providing higher output and torque ratings, the smoothness of a six-cylinder engine and lower weight by virtue of its all-aluminum construction.
The DIESOTTO engine (2007)
The Mercedes-Benz F 700 research car outlines new approaches to mobility which uses resources sparingly. The key element is a novel propulsion system which combines the advantages of the low-emission gasoline engine with the fuel economy of the diesel engine.
The decisive steps in the development of the diesel engine to its present-day standard – combining dynamic performance with low fuel consumption – were made possible by turbocharging and common rail direct injection, both pioneering inventions of Mercedes-Benz. The DIESOTTO engine even takes this development a couple of important steps further in that systematic downsizing, achieved through the reduction in displacement and the number of cylinders, improves the degree of efficiency. Over and above this, a hybrid module supports the internal combustion engine especially in stop-and-go operation. With controlled homogeneous charge compression ignition, the diesel principle of controlled compression ignition is incorporated in a gasoline engine for the first time.
During start-off and under full load, the gasoline/air mixture is ignited by a spark plug as in a conventional gasoline engine. At part-load, i.e. at low and medium engine speeds, the DIESOTTO automatically switches to controlled charge compression ignition (homogeneous combustion) within one power stroke.
This minimizes nitrogen oxide emissions thanks to homogeneous combustion at reduced reaction temperatures. Additional emission control in the DIESOTTO engine is performed by a standard three-way catalytic converter. And finally, a highly efficient engine control system was incorporated to network the individual sub-systems into a unified propulsion concept.
The F 700 is powered by a compact four-cylinder engine with a displacement of 1.8 liters, which nevertheless affords the superior performance of a luxury-class sedan. A two-stage turbocharger is responsible for the engine’s excellent responsiveness and high-torque accelerating power. In addition, the internal combustion engine is supported by the electric motor of the hybrid module for starting off. Maximum output is 175 kW (238 hp); the electric motor develops another 15 kW (20 hp), and the system’s maximum torque is as high as 400 Newton meters. Acceleration from standstill to 100 km/h in 7.5 seconds testifies to the dynamism of the F 700 whose top speed is limited to 200 km/h. Despite this outstanding performance, the F 700 has a fuel consumption in the European Driving Cycle of just 5.3 liters (44.3 mpg), which corresponds to carbon dioxide emissions of 127 grams – an extremely low level for a car of this size.
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