At the Geneva Motor Show 2006, Mercedes-Benz is unveiling two vehicles that pave the way for an all-new generation of diesel vehicles: the Vision CLS 320 BLUETEC and the Vision GL 320 BLUETEC. The state-of-the-art BLUETEC technology makes CDI models from Mercedes-Benz the cleanest diesels in the world in any vehicle category. Added to this is the exceptional torque, economical performance and high operating range they are so renowned for. This is precisely why Mercedes-Benz is getting ready to launch the BLUETEC technology in a passenger car model in Europe too by no later than 2008.

By introducing the innovative modular BLUETEC technology package, Mercedes-Benz has transformed the diesel engine into a high-tech propulsion unit with the potential to comply with even the most stringent emission standards anywhere in the world. Equipped with BLUETEC, the Mercedes-Benz CDI models become the cleanest diesels in the world in any category and also consume between 20 and 40 per cent less fuel than comparable petrol-powered models. This makes both the Vision CLS 320 BLUETEC with an expected fuel consumption of 7.9 l/100 km (NEDC) and the Vision GL 320 BLUETEC with an expected 9.9 l/100 km (NEDC) the most economical and cleanest-running models in their category.

Registrations of new diesel passenger cars in Western Europe totalled 7.2 million last year, meaning that every second customer opted for a diesel: at Mercedes-Benz, the diesel percentage is even higher at 54 per cent. With fuel prices expected to keep rising, the economical and clean diesel-powered vehicles from Mercedes-Benz hold one answer with a guaranteed future.

BLUETEC is a modular concept, which combines various perfectly harmonised technical measures aimed at both minimising untreated emissions inside the engine and at effective aftertreatment of the exhaust gases. The result is a gradual and systematic minimisation of all relevant emission constituents. Passenger cars equipped with this technology incorporate an oxidising catalytic converter and a particulate filter as well as systems for effectively reducing nitrogen oxides. This is where the BLUETEC technology comes in. BLUETEC is not just the cleanest diesel technology in the world; its low consumption in real terms helps customers to make tangible fuel savings.

The first series-produced model to feature BLUETEC technology will be the E 320 BLUETEC which will become available to customers in the USA from Model Year 2007. The company plans to launch a BLUETEC diesel passenger car in Europe too by no later than 2008. The development work for the European market is geared towards reducing nitrogen oxides to a minimum, adapting the technology to European driving habits and implementing BLUETEC technology with, as far as is possible, zero impact on fuel consumption (CO2). The wide-scale introduction of BLUETEC throughout Europe is dependent on the availability of sulphur-free diesel fuel (<10 ppm) in all European countries.

Diesel powered passenger cars - yet another Mercedes-Benz success story

Mercedes-Benz was the first to implement Rudolf Diesel's combustion principle in a truck engine over 80 years ago. And the Mercedes-Benz 260 D unveiled exactly 70 years ago in March 1936 was the world's first ever production passenger car with a diesel engine. This technology is significantly more efficient than the petrol engine and has been optimised over a period of many years. One innovation in particular – the common-rail direct injection system in conjunction with four valves per cylinder introduced in 1997 – has had a major impact on the development of the modern diesel engine. Since then, the abbreviation CDI has come to stand for unsurpassed fuel economy and a major boost in torque – which means the car has better pulling power and is more fun to drive. As a result, diesel vehicles often have the edge over similarly powered petrol models.

The few disadvantages that diesel models previously had compared to their petrol counterparts related to specific diesel emissions, especially particulate matter and nitrogen oxides. However, since the introduction of the maintenance-free particulate filter for its diesel passenger cars to coincide with EU4 emission standard compliance in autumn 2003, Mercedes-Benz has also brought about an exemplary reduction in particulate matter. And although it has succeeded in cutting nitrogen oxide emissions by some 75 per cent through engine modifications alone in the past 15 years, Mercedes-Benz wants to go even further still. The objective is clear: the ingenious BLUETEC technology gives Mercedes Benz diesel engines the potential to comply with the world's most stringent emission standards. In other words, Mercedes Benz is set to offer the cleanest diesel in the world in every vehicle category.

Today's Mercedes-Benz diesel engines also stand for agility, sportiness and reliability, as demonstrated last spring when three standard-specification E 320 CDI models broke a clutch of impressive records in Laredo (Texas). For one, a new average speed record of 224.823 km/h (139.699 mph) was set in a 30-day endurance test covering over 100,000 miles (160,934 km). These vehicles were fitted with a sophisticated emission-control system, including a standard-specification maintenance-free particulate filter. Independent testing conducted subsequently by the TÜV (German technical inspection authority) confirmed that, despite the gruelling record-breaking drives, the vehicles still met the current stringent EU4 emission limits and the particulate filter was in perfect operating order, meaning particulate emission levels were comfortably within the EU4 limits too.

BLUETEC – the emission-control technology from Mercedes-Benz

The Mercedes-Benz development engineers have been advancing emission-control solutions for a number of years, one of the main aims being to ensure compliance with future emission standards in Europe, Asia and the USA. One focus of these activities is devising effective and economical methods for reducing nitrogen oxides ("denoxing"). This technology for the cleanest diesel in the world is called BLUETEC.

In order to bring together all these technologies within a single, appropriate package, Mercedes-Benz is following a graduated plan that includes the following phases:

• Optimisation of the engines and their combustion processes to minimise untreated emissions. This includes electronic engine management; four valves per cylinder, third-generation common-rail direct injection with piezoelectric injectors, a turbocharger with a variable nozzle turbine and exhaust gas recirculation.
• Oxidising catalytic converters to minimise emissions of carbon monoxide (CO) and unburned hydrocarbons (HC).
• The particulate filter, fitted as standard in all Mercedes-Benz diesel passenger cars in many countries since summer 2005, reduces particulate emissions by as much as 98 per cent, thus easily undercutting the current EU4 particulate limits (0.025 g/km). This technology also ensures compliance with the US limits currently in force.
• Nitrogen oxides – whose concentration in the untreated emissions from diesel engines is higher than in petrol engines due to the specific combustion process in diesel engines – are reduced to such an extent that even the world's most stringent exhaust gas limits can be fulfilled. This is where the BLUETEC technology comes in. The reduction is achieved either with an advanced DeNOx storage catalytic converter and SCR catalytic converter, as featured in the Vision CLS 320 BLUETEC, or with the more complex but even more effective AdBlue injection. The Selective Catalytic Reduction (SCR) process creates the most effective method of exhaust gas aftertreatment currently available and enables nitrogen oxide levels to be reduced by up to 80 per cent. The Mercedes Benz engineers are showcasing the combination with AdBlue injection in the Vision GL 320 BLUETEC and are developing the process for use as a standard system in passenger cars.

The SCR process is based on the injection of the reducing agent AdBlue into the exhaust gas stream. AdBlue is an aqueous urea solution that is carried in a separate tank. Since an average of around 0.1 litres per 100 km (1 to 3 per cent of diesel consumption) is all that is required, the tank can be designed so that it only needs to be refilled when service staff is carrying out regular, scheduled maintenance. When AdBlue is injected into the pre-cleaned exhaust gas, ammonia (NH3) is released, causing the nitrogen oxides to be converted into harmless nitrogen and water in the downstream SCR catalytic converter. The decisive factor in ensuring that the catalytic converter works extremely efficiently is precision metering of the AdBlue to match the engine's current operating state. Choosing which technological solution to use depends both on the vehicle concept concerned and on the required "denoxing" rate.

BLUETEC already a success in commercial vehicles

However, BLUETEC technology is not altogether new. In Europe, it has already been employed extremely effectively in Mercedes-Benz commercial vehicles with a GVW over six tonnes. This technology has proved a resounding success in more than 10,000 Actros, Axor and Atego trucks. In this case, BLUETEC reduces the nitrogen oxide levels considerably, meaning that these vehicles already comply with the emission standards due to come into force for trucks from 2009. In Europe, the AdBlue supply network already comprises some 1,500 filling points.

CLS 350 CGI - world debut for innovative direct petrol injection system

Following intensive development work, Mercedes-Benz is now presenting the world's first petrol engine with spray-guided direct injection. The 215 kW/292 hp six-cylinder engine will go on the market in the second half of 2006 in the CLS-Class. In the European driving cycle, this innovative injection technology from Mercedes-Benz achieves fuel consumption improvements of ten per cent over the highly efficient V6 petrol engine with port injection and fully variable valve timing: the figures for the CLS 350 CGI are 9.1 - 9.3 litres per 100 km. Thus Mercedes-Benz has succeeded in combining a substantial increase in output with a significant increase in fuel economy.

This pioneering injection system is another trend-setting technology from Mercedes-Benz. It achieves much better fuel efficiency, and thus also higher thermodynamic dynamic efficiency, than conventional wall-guided direct injection systems. The new system will form the basis for future engine development work in this output class.

The new Mercedes-Benz six-cylinder engine achieves near-total combustion, which results in reduced emissions. A further important advantage of the CGI engine is stratified charge operation, an operating mode during which the engine is run with high excess air and thus excellent fuel efficiency. Now, thanks to multiple injection, it is for the first time possible to extend this lean-burn operating mode to higher rpm and load ranges too. During each compression stroke, a series of injections takes place, spaced just fractions of a second apart. This has the effect of significantly improving mixture formation, combustion and fuel consumption. Where previously stratified charge operation was only possible in the low part-load range, the new Mercedes direct-injection engine can still operate in this lean-burn stratified mode at speeds in excess of 120 km/h. When driving on main roads and motorways at largely constant speed and with proper anticipation, the CGI engine outperforms the fuel economy of the six-cylinder engine with conventional injection technology by up to 1.5 litres per 100 km, a saving of up to 15 per cent.

Effortless performance twinned with excellent fuel economy

Low fuel consumption and excellent power delivery are never at odds on the new Mercedes-Benz direct petrol injection model. On the contrary, the engine delivers 15 kW/20 hp more power than the conventional-injection V6 and four percent more torque.

Thus the V6 combines its excellent fuel economy with a level of performance never previously offered in the six-cylinder segment. The CLS 350 CGI accelerates from 0 - 100 km/h in just 6.7 seconds and has an electronically governed top speed of 250 km/h. The key figures for the new CGI engine are:

• Displacement 3498 cc
• Compression ratio 12.2:1
• Maximum power 215 kW/292 hp at 6400 rpm
• Maximum torque 365 Newton metres at 3000 - 5100 rpm

With fuel consumption of 9.1 - 9.3 litres per 100 kilometres (NEDC combined cycle), the four-door Coupé has a range of approximately 870 kilometres on one tank filling.

Pioneering invention: outward-opening piezoelectric injectors

The most important components of the innovative spray-guided direct petrol injection system are the fast-acting, high-precision piezoelectric injectors, which are responsible for virtually all the advances associated with this pioneering combustion technology. The piezoelectric valves have injectors which open outwards to create an annular gap just a few microns wide. This gap shapes the fuel jet and produces a uniform, hollow cone-shaped spray pattern. The microsecond response times of the piezoelectric injectors provide the basis for delivering multiple injections per compression stroke, and thus for lean-burn operation. By allowing flexible and efficient control of the combustion process they play a key part in ensuring the engine's outstanding fuel efficiency.

With the aid of fluid dynamics simulations, the pistons have been designed with special piston bowl geometry which concentrates the lean mixture in the area around the spark plug and prevents it from spreading out towards the cylinder wall. The piston shape plays its part in ensuring near-total combustion, low fuel consumption and low emissions.

A high-pressure pump and downstream fuel rail and pressure control valve are responsible for delivering the fuel and regulating the quantity supplied. The peak fuel pressure in this system is 200 bar - around 50 times the fuel pressure in a conventional petrol injection system. The injection system also features a water-cooled heat exchanger to cool the fuel.

Dual effect: low engine-out emissions and high exhaust temperatures

The Mercedes-developed combustion process featuring multiple closely spaced injections on each compression stroke also results in smoother operation and improved emissions performance. Measurements show that engine-out hydrocarbon emissions in the warm-up phase are almost halved. Furthermore, since the injection and combustion processes can be actively controlled, it is also possible to raise temperatures in the exhaust manifold and thus speed catalytic converter warm-up. Just eleven seconds after starting from cold, the direct petrol injection engine reaches an exhaust temperature of over 700 degrees Celsius. Emissions are controlled by two close-coupled three-way catalytic converters with linear oxygen sensor control, which goes into operation immediately after the engine starts from cold.

To reduce nitrogen oxide emissions, Mercedes-Benz has adopted a two-part strategy. This comprises, firstly, dual electrically controlled and cooled exhaust gas recirculation which, depending on engine operating conditions, redirects up to 40 per cent of the exhaust gases back into the cylinders. Secondly, it also comprises two underfloor NOx adsorber catalytic converter. Under lean operating conditions, these converters adsorb the nitrogen oxides. Periodically, during brief regeneration pulses, the nitrogen oxides are then desorbed, reacting with other exhaust gas constituents to form harmless nitrogen. Sensors upstream and downstream of the catalytic converters monitor their operation.

In addition, the new CGI engine also incorporates the same unique package of high-tech features as its conventional-injection counterpart. This includes four-valve cylinder heads, variable intake and exhaust camshaft timing, two-stage intake manifolds, balancer shafts and intelligent thermal management with an electronically controlled thermostat. The crankcase and cylinder heads are of aluminium and the cylinders and cylinder liners are of low-friction, thermally resistant, lightweight aluminium-silicon alloy.

All fuel-carrying components of the CGI engine are of high-grade steel or brass; the rails in the area of the two cylinder banks and the housing of the high-pressure pump are of forged high-grade steel.

The new CLS 350 CGI is designed to operate on sulphur-free unleaded premium fuel and its state-of-the-art technology gives it the potential to adapt to emissions standards of the future. In Western Europe, the CLS direct petrol injection model will replace the current CLS 350.