At the International Motor Show in Geneva, Mercedes-Benz, the inventor of the diesel engine for passenger cars, is showing the future of the modern diesel engine and its wide range of possible uses. In mid-2005, Mercedes-Benz will become the first automobile brand in the world to equip all of its diesel passenger cars with particulate filters as standard. This initiative will not only apply to Germany; it will also be in effect in Austria, Switzerland and the Netherlands.

In Geneva, seven gleaming silver show cars, including even purebred sports cars such as the SL- and SLK-Classes, represent the most advanced diesel technology. At the same time, these vehicles are the latest highpoint in the extraordinary development of the diesel.

The story began seven decades ago, in 1935, when Mercedes-Benz introduced the world’s first diesel passenger car in a small production series — the 260 D. To date, the Mercedes brand has produced more than seven million diesel passenger cars, and it is a leader in the development of diesel technology. Especially in recent years, the engines have been greatly improved as a result of tremendous advances in all areas.

For decades, the diesel engine was recognized only for its long service life: reliable and robust, for sure, but it also suffered from a reputation for being a bit boring. Over time, this perception of the diesel has been replaced by an entirely new image: Today, modern diesel engines are associated with attributes such as sportiness, agility, driving comfort and driving pleasure and, not least, environmental compatibility. And Mercedes engineers have played a vital role in this transformation.

This amazing development is most clearly confirmed by taking a look at the figures: The world’s first diesel car, for example, the Mercedes-Benz 260 D from 1935, generated a paltry 45 hp (33 kW), which corresponds to 17.7 hp per litre of engine displacement (13 kW/l). In the new C 320 CDI, the recently introduced V6 diesel engine generates 224 hp (165 kW) from three litres of displacement - which is equivalent to 75 hp/l (55.2 kW/l); in other words, more than four times the power of its “ancestor” of 70 years ago.

Equally dramatic was the increase in torque, the decisive factor in generating power from low engine speeds. From 98 Nm in the 170 D of 1949, the torque has risen to 510 Nm in the current C 320 CDI. Or, to put it another way, the roughly 55 Nm per litre of displacement available in 1949 has been replaced by today’s 170 Nm, a more than three-fold increase.

Even more impressive, of course, is the fuel economy of modern diesels. Whereas the world’s first diesel passenger car consumed 0.3 litres of fuel per 100 kilometres to generate one kW, today’s C 320 CDI uses only 0.04 litre per kW for the same distance — an extraordinary 90 per cent reduction in fuel consumption. Or, in other words, the engine uses one tenth of the fuel required by the first diesel. In addition to conserving resources, of course, this development is also more environmentally compatible.

A diesel particulate filter that’s well-suited for everyday use

At the same time that fuel efficiency was increased, emissions were radically cut. Introduced in the C- and E-Classes in October 2003, the world’s first additive-free particulate filters already reduced emissions below the levels proscribed by the stringent EU emissions limits that have also been in force for diesel vehicles since January of this year. These limits stipulate that emissions be reduced by more than 81 per cent (carbon monoxide) compared to 1995. In addition, particulate emissions have to be reduced by more than 80 per cent over the same time period.

Mercedes-Benz achieved these reductions by combining EU-4 compliance technology with a diesel particulate filter that works reliably without needing fuel additives. What’s more, this filter achieves an excellent operating performance and low fuel consumption without requiring any additional servicing measures, making it eminently suitable for everyday use. Although the filter must be eventually regenerated, this is achieved by adjusting, in accordance with requirements, various engine-control functions, such as fuel injection, intake-air throttle, exhaust-gas recirculation and boost-pressure control. Test results show that, after high mileage, the residual ash in the filter is up to 75 per cent less than that produced by additive-dependent filter systems. Sulphur-free fuels and specially developed engine oils will mean these diesel particulate filters can have an even longer service life.

Mercedes-Benz continues to focus its entire innovative capacity on reducing particulate and nitrogen oxide emissions to the very limits of what is still measurable — utilising CDI technology and future homogeneous diesel combustion processes. In doing so, the brand that originally adapted diesel engines for use in passenger cars has given a clear signal in support of the diesel engine, which still has a great future ahead of it, according to the experts.

State-of-the-art diesel power for all vehicle body types

With its fleet of silver diesel cars in Geneva, Mercedes-Benz is showing the direction that developments will be headed in the future. This claim to spearheading developments is highlighted by the uniform paint job for the show cars, which also points the way to the future. The paint covers the body panels like a metallic skin, emphasizes the design lines more strongly than any previous paint job and makes them more lively by means of targeted light reflections. The paint’s remarkable sparkle and brilliance is the result of a newly developed process that was used for the first time by Mercedes-Benz. While the pigments in a conventional metallic paint measure between 100 and 300 nanometres in size, those in the new ALU-BEAM paint are even much smaller (30 to 50 nanometres). In addition, the pigments are specially worked so that they are more uniformly spread within the paint’s surface. As a result, light is reflected with even greater brilliance and the paint’s sheen is substantially enhanced.

The seven diesel show cars also demonstrate the current engines’ extremely wide range of possible applications. In line with their high technical demands, the Mercedes engineers have made the engines so exceedingly clean and powerful, and at the same time smooth-running, that they can be easily used with all vehicle body types.

The direction in which the engineers at Mercedes-Benz are taking compression ignition engines is being shown in Geneva by the two diesel-powered roadsters that boast record performance figures. A new V8 engine generates 231 kW/315 hp in the Vision SL 400 CDI and provides the eight-cylinder’s crankshaft with an outstanding torque of 730 Nm. The SLK 320 CDI tri-turbo, meanwhile, can generate an impressive 210 kW/286 hp and 630 Nm of torque from three litres of displacement (70.3 kW and 211 Nm per litre of displacement).

Three turbochargers in the SLK-Class

The SLK 320 CDI tri-turbo is based on the new V6 diesel engine, which achieves new levels of performance thanks to a two-stage supercharging system. It consists of three turbochargers, of which two are located on the outside next to the cylinder banks while the larger third turbocharger is situated between the V of the cylinders. At low engine speeds and loads, air flows through all three turbochargers (i.e., large and small), with the small turbochargers doing most of the work. When engine speed increases and the flow is continuous, the large turbocharger takes over supplying the greatest share of the charge pressure and the smaller turbochargers are turned off by means of a bypass system. At high engine speeds and loads, only the large turbocharger is running. Performance is further heightened as a result of an enlarged intercooler and larger pipe diameters for the charge air and the exhaust.

Sporting a modified tachometer with a red zone extending from 4,500 to 5,000 rpm and the self-confident appearance of the SLK 55 AMG, the vehicle is a proud member of the Mercedes-Benz diesel family. The new engine gives the roadster an impressive boost and allows it to perform prodigious feats: It takes the car but 5.3 seconds to accelerate from 0 to 100 km/h, and it can travel a distance of 1,000 metres in just 24.4 seconds from a standing start. The top speed is meanwhile electronically limited to 250 km/h. With this kind of performance, the SLK 320 CDI tri-turbo has a unique standing even among thoroughbred sports cars. And fuel economy is just as impressive, since, despite the incredible driving performance, the diesel roadster consumes only 7.5 litres of fuel per 100 kilometres (NEDC overall consumption).

New V8 diesel for the SL-Class

The new drive in the Vision SL 400 CDI also belongs to Mercedes-Benz’ third generation of CDI engines. To create this system, the engineers took the familiar four-litre V8 diesel and enhanced many of its components while also adding state-of-the-art piezo injectors, new turbochargers and an optimised water/charge-air cooling system. Taken together, all of these measures allow the engine to bring forth its power and torque in an even more harmonious fashion. The SL 400 CDI accelerates from zero to 100 km/h in 5.8 seconds. As such, this diesel sports car justifiably bears the legendary letters “SL”.

Diesel driving pleasure with new V6 engine

Maximum driving pleasure is also offered by the Mercedes-Benz vehicles powered by the new standard equipment V6 CDI engine. The Mercedes engineers have further developed the engine’s common rail direct injection and are using third generation technology to realise even more advances in terms of power, fuel consumption, exhaust emissions and combustion noise. Newly developed piezo injectors work much faster and more precisely than the previous solenoid valves and ensure the fuel supply to the cylinders is very accurately measured. This means the fuel injection is even more precisely adjusted to engine speeds and loads — five fuel injections per power stroke with a peak pressure of up to 1,600 bars are possible.

Thanks to precise valve timing, the V6’s emissions of nitrogen oxides and particulates more than satisfy the stringent Euro 4 limits. Two oxidation-type catalytic converters handle the conversion of the carbon monoxide and hydrocarbons. For the further reduction of particulate emissions, Mercedes-Benz is relying on its maintenance-free particulate filter system.

The V6 diesel also features the most advanced technology in terms of the materials used, design, fuel injection and valve timing. In a world first for a diesel engine of this displacement and power class, Mercedes-Benz developed an aluminium crankcase with grey cast iron cylinder liners, which especially helps to reduce weight.

Sports Tourer concept car with exciting diesel technology

In Geneva, Mercedes-Benz is presenting two new sports tourer concept vehicles with the most advanced diesel engines and a new space concept. With their spacious interiors and exemplary comfort, the new Compact Sports Tourer of the Mercedes-Benz B-Class, which is simultaneously marking its world premiere in Geneva, and the Grand Sports Tourer Vision R offer the best conditions for a relaxed and enjoyable ride.

The show car version of the Grand Sports Tourer Vision R is powered by the new V6 diesel engine; the most powerful diesel available in the new B-Class is the B 200 CDI, which delivers 103 kW/140 hp and 300 Nm of torque. Also newly developed, this turbocharged diesel with common rail direct injection gives the Compact Sports Tourer the power it needs to sprint from zero to 100 km/h in 9.6 seconds. The B 200 CDI’s maximum speed is 200 km/h. And despite this superior performance, the engine’s fuel consumption is below the six litre mark: 5.6 litres per 100 kilometres (combined consumption).

The CLK 320 CDI convertible offers top-down pleasure with diesel power

The Mercedes-Benz CLK 320 CDI convertible provides pure driving pleasure, almost unlimited open-air enjoyment and unsurpassed comfort for four occupants. The advanced V6 engine powers the elegant convertible from zero to 100 km/h in 8.5 seconds and delivers a maximum speed of 245 km/h. And at 7.1 litres per 100 kilometres (NEDC overall consumption), the fuel consumption is impressively low.

M-Class — new off-roader with diesel

The new Mercedes-Benz ML 320 CDI, which made its world premiere this year, continues to reign as the trendsetter among today’s off-road vehicles. With its third generation V6 diesel engine, 7G-TRONIC seven speed automatic transmission as standard, improved 4ETS four-wheel drive system, AIRMATIC air suspension and the PRE-SAFE® preventive occupant protection system, the M-Class again demonstrates its leading position in this rapidly growing market segment, which Mercedes-Benz created in 1997 with the predecessor model.

The advanced diesel engine delivers the power to accelerate the ML 320 CDI from zero to 100 km/h in 9.4 seconds and achieves a remarkable top speed of 210 km/h — and with a fuel consumption of only 9.4 litres of diesel per 100 kilometres (NEDC overall consumption).

E 320 CDI estate features impressive combination of diesel and four wheel drive

And the Mercedes-Benz E 320 CDI 4MATIC demonstrates that diesel engines are also very compatible with today’s comfortable, four wheel drive saloons. With the V6 diesel, the E-Class delivers sports car acceleration — from zero to 100 km/h in 7.0 seconds — and a maximum speed of 244 km/h. This makes the Mercedes-Benz E 320 CDI one of the fastest cars on the road, though its fuel consumption of 8.1 litres per 100 kilometres (NEDC overall consumption) makes it a really frugal performer.

The diesel engine has a great future

In spite of all the advances of recent years, the potential of Mercedes-Benz’ modern diesel engines is still far from fully exploited. Today, the systems operate with an injection pressure of up to 1,600 bars. By making further adjustments and optimising the injectors, the injection pressure of today’s CDI diesel engines for passenger cars will be increased to 1,800 bars and higher. This will result in further increases in performance while simultaneously reducing fuel consumption and emissions.

In the Mercedes-Benz labs, the engineers are testing new materials for the combustion chamber and continuously working to optimise the chamber’s shape in order to increase combustion pressure in the future. Flow researchers are meanwhile enhancing the swirl of the fuel. The more uniformly the drops of fuel are distributed within the combustion chamber, the greater will be the output and less emissions will be produced. By employing new homogenous combustion methods, the researchers at Mercedes-Benz plan to prevent the creation of NOx and particulates even during the combustion phase. Injection plays a key role in this process, which is why the aim is to achieve an optimum dosing of the fuel at high injection pressures and with improved nozzle openings. As a result, diesel technology will be attracting even more attention in the future.

This is also indicated by customers’ increasing interest in this technology. More than seven million Mercedes-Benz passenger cars have been ordered with diesel engines since 1949, and the pace of sales is set to increase even further.

Source: Daimler-Chrysler AG - ©Pictures: Daimler-Chrysler AG

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