By optimising the diesel engine, Mercedes-Benz has time and again been setting new milestones for the future of the internal combustion engine. With BlueTec and CDI BlueEFFICIENCY models, in particular, Mercedes-Benz engineers have succeeded in recent years in making the powerful and economical diesel engine as clean as the petrol engine. In 2010 all CDI BlueEFFICIENCY E-Class models with six-cylinder diesel power plant, for example, already meet the EU5 emission standard, and the BlueTEC model E 350 BlueTEC with urea injection even meets the future EU6 standard. Diesel-hybrid vehicles like the E 300 BlueTEC HYBRID and the Atego BlueTec Hybrid truck now represent a further step towards the future of the diesel engine.

BlueTec for commercial vehicles and BlueTEC for passenger cars

The introduction of BlueTEC in the passenger car in 2006 marks the beginning of a new era in Mercedes-Benz diesel-powered cars. The engineers of the Stuttgart-based brand initially developed this visionary emission control system for commercial vehicles, introducing it to the market in 2005. BlueTec (it is spelled differently if referring to cars or commercial vehicles) immediately set standards for the reduction of the pollutants in diesel exhaust gas, which promptly was reflected in success on the market: in February 2006 the 10,000th BlueTec truck with Euro 5 engine was delivered to a customer. And in 2008 more than 160,000 vehicles with BlueTec were in operation – with a great many more to come. This is a good foundation for developing BlueTEC for diesel passenger cars.

Considering the history of innovation of the diesel passenger car at Mercedes-Benz, the step to incorporate BlueTEC into present-day cars is only logical: the Stuttgart brand built the first diesel passenger car in 1936. 1971 saw the one-millionth car with compression-ignition engine since the Second World War roll off the assembly line. And in 1976 the C 111-II with diesel engine set standards on its record-breaking run in Nardo. The history of diesel technology is punctuated again and again by such major innovations – especially owing to the initiatives of Mercedes-Benz. Since about 1990 the pace of technological development has picked up very strongly. And this is why in 2006 BlueTEC became the latest standard of this diesel evolution.

Where the development of the compression-ignition engine into a clean and powerful drive for future automobiles can take us is shown by studies like the S-Class S 320 BlueTEC Hybrid, presented at the Frankfurt International Motor Show in 2005, which combines the low-emission diesel with an electric motor. With an electric motor integrated in the powertrain, the concept car was a “mild hybrid”, with significantly reduced fuel consumption especially in inner-city stop-and-go traffic. The diesel engine switches itself off whenever it is not required. All the modifications and features combined reduce the fuel consumption of the BlueTEC HYBRID by some 20 percent versus the comparable predecessor model. The combined output of this S-Class car is 179 kW (243 hp); the combined torque is as high as 575 Newton metres. The car accelerates from standstill to 100 km/h in 7.2 seconds, and its top sped is electronically limited to 250 km/h. Fuel consumption (New European Driving Cycle) is as low as 7.7 litres per 100 kilometres. The study made this very clear: at
Mercedes-Benz the diesel has great potential as a high-tech drive of the future. And this future already was within close reach, for a few years later BlueTEC HYBRID cars were being built in series.

But for the first, in 2006 the clean Mercedes-Benz BlueTec commercial vehicles were the trendsetters for the car sector, as the highly innovative system for reducing nitrogen oxides (NOX) and other emissions also lends itself to application in passenger cars: BlueTEC reduces nitrogen oxides to such an extent that the toughest emission limits worldwide can be met.

In early 2006 Mercedes-Benz then presented BlueTEC for passenger cars as a ready-for-production package consisting of several components. The extensive optimisation of the engines and the combustion processes taking place inside them constitutes the basis of this package. With solutions like multi-hole injection nozzles, the use of the latest generation of CDI technology and other measures, the raw emissions are cut to an extremely low level. This is where the emission control system with an oxidising catalytic converter (for hydrocarbons and carbon monoxide) and a particulate filter comes in. The final stage is nitrogen oxide reduction by the BlueTEC component proper.

It’s the world’s cleanest diesel: in late 2006 the E 320 BlueTEC hit the US market as the first production BlueTEC car. The E 320 BlueTEC is an innovative model which is based on the sophisticated E 320 CDI V6 and relies on the BlueTEC technology developed by Mercedes-Benz. BlueTEC is the designation for a highly efficient method of minimizing nitrogen oxide emissions already used in commercial vehicles. In contrast to commercial vehicles, the E 320 CDI BlueTEC does not make use of AdBlue® injection but reduces nitrogen oxides with a system based on an improved storage-type catalytic converter.

Three E 320 BlueTEC vehicles also took part in the 13,600 kilometre “E-Class Experience Paris – Beijing” from October to November 2006. This long-distance trip involving a total of 36 Mercedes-Benz E-Class Saloons recalled an adventurous long-distance journey organised in 1907, but which went in the opposite direction, from Beijing to Paris. Despite this major event in the important automotive market China, the E 320 BlueTEC was first put on the market in the United States.

The question may occur why the E 320 BlueTEC made its debut in the USA. One reason, of course, is the growing demand for economical and at the same time clean cars in that country, caused by rising fuel prices. But there’s yet another reason for this specific timing: “The introduction of clean diesel fuel in the USA is something we have been fighting for alongside others for a long time, and an opportunity we wish to use from Day One,” said Dr Thomas Weber, member of the Board of Management of Daimler AG responsible for Research, when the car was introduced in Las Vegas, Nevada. Modern diesel-engined cars which, in West Europe, account for more than half of new registrations annually, were unable to develop their full potential in the USA due to the excessively high sulphur content in the fuel until then. This changed at the end of 2006 thanks to the nation-wide introduction of clean diesel fuel with a sulphur content of just 15 ppm (15 cubic centimetres of pollutant per cubic metre of fuel). The so-called Ultra Low Sulfur Diesel (ULSD) would be available at up to 76,000 filling stations in the USA in a first step and thereby permit the use of BlueTEC. With this innovative diesel technology, Mercedes-Benz is also able to remain below the strictest globally applicable limits where nitrogen oxide emissions are concerned. Hence, all the preconditions for the breakthrough of modern diesel technology in the USA are fulfilled.

Encouraged by the success of the E 320 BlueTEC developed for the North American market, Mercedes-Benz decided to present the E 300 BlueTEC of the 211 series as first passenger car with BlueTEC for the European market at the end of the year 2007. It easily is the cleanest diesel in its class and fully meets the requirements of the Euro 5 exhaust emission standards.

Mercedes-Benz demonstrated the direction in which developments in the passenger car sector are going with concept vehicles in 2006, first and foremost the Vision GL 320 BlueTEC and the Vision CLS 320 BlueTEC. The GL has an SCR catalytic converter with AdBlue injection; the CLS, like the E-Class, features an improved nitrogen-oxide storage-type catalytic converter.

The Vision GL 420 BlueTEC presented in 2007 then demonstrated that great fuel economy and extremely low emissions can be achieved with BlueTEC – also, and in particular, in large and powerful cars. The high-performance V8 diesel engine develops 216 kW (290 hp), has a torque of 700 Newton metres and is expected to have a fuel consumption of just 9.8 litres per 100 kilometres. The car’s independent styling expresses the special status of the GL 420 BlueTEC and at the same time meets the wishes of Mercedes-Benz customers in the USA for even greater exclusiveness and individualisation. The redesigned, distinctively swept-back front end with its dominant radiator grille expresses the extraordinary performance of the V8 diesel engine in the car’s appearance and gives the car a dynamic forward thrust even when it’s stationary. These self-assured looks are enhanced by flared wheel arches, representative 21-inch wheels and lateral floorboards.

At the North American International Auto Show (NAIAS) in Detroit in January 2007, Mercedes-Benz displayed three new BlueTEC models with SCR exhaust gas aftertreatment which it built in series beginning in 2008. On this occasion, Dr. Thomas Weber had this to say: “With SCR, our clean and efficient diesel engines comply with the stringent American Bin 5 norm. This also applies to the three new V6 BlueTEC models R 320 BlueTEC, ML 320 BlueTEC and GL 320 BlueTEC which we will launch into the US market in 2008.”

In the brand’s systematic expansion of its BlueTEC model line-up, Mercedes-Benz was backed up by a J. D. Power study in 2007: “Global Outlook for Diesel” predicts a share of diesel-engined cars in new registrations of well over 15 percent in North America by 2015. The precursor is the E 320 BlueTEC which is already available in the market. With 35 miles per gallon or 6.7 litres per 100 kilometres, it is by far the most economical car in its class in the United States.

The response to BlueTEC in the USA is extremely positive, as illustrated by the distinctions awarded by renowned American science and engineering journals for the BlueTEC technology developed by Mercedes-Benz at the end of 2006. Scientific American named BlueTEC as one of the 50 groundbreaking innovations in science and technology of the year 2006. Popular Science, the oldest and best-known scientific journal, included BlueTEC in “Best of What’s New”, its list of the year’s best product innovations. Ward’s Automotive Group, a leading publisher of numerous media and trade journals for the motor industry, nominated the engine of the E 320 BlueTEC for its listing of the ten best drive systems of the year 2007.

In 2007, motor editors from 22 countries elected the E 320 BlueTEC as the “World Green Car 2007” at the International Auto Show. This award recognises the role of Mercedes-Benz as pacemaker of a novel diesel technology which makes the compression-ignition engine as clean as a petrol engine.

The diesel principle has come a long way from Rudolf Diesel’s invention to the modular BlueTEC system. Time and again the company contributed decisive innovations to develop the diesel drive to its present level. Thus, the compression-ignition engine presents itself today as a high-performing and economical high-tech drive with the potential for meeting even the toughest international emission limits in the future. Not only the powerful six-cylinder power plants were to profit from this, but the state-of-the-art four-cylinder diesel engines from Mercedes-Benz as well.

So at the Geneva Motor Show in February 2007, Mercedes-Benz for the first time presented the environmentally compatible BlueTEC emission control technology in combination with a four-cylinder engine with optimised fuel economy. The Vision C 220 BlueTEC outlines the approach to compliance with the further tightened Euro 6 emission norm which will come into force for all new vehicles throughout Europe in 2015. At an output of 125 kW (170 hp) and a maximum torque of 400 Newton metres, the Vision C 220 BlueTEC consumes 5.5 litres of diesel per 100 kilometres. This is the result of ongoing development of diesel engine technology and intelligent energy management.

Dr. Dieter Zetsche, Chairman of the Board of Management of Daimler AG and Head of Mercedes-Benz Cars, commented on this new development as follows: “The modern four-cylinder diesel engine with BlueTEC emission control is a prime example of cutting-edge technology with a safe future. With our diesel strategy, we provide the answer to the question of how fuel consumption – and thus carbon dioxide emissions – can be lowered, how all exhaust gas constituents including nitrogen oxides can be further reduced, and superior motoring pleasure can be ensured at the same time. We are convinced that the modern diesel currently represents the best and most efficient solution in this respect.”

With the Vision C 220 BlueTEC, Mercedes-Benz outlines the next steps in the BlueTEC initiative in very concrete terms – an initiative the company launched in the USA in autumn 2006. The Vision C 220 BlueTEC undercuts forthcoming emission limits – even the significantly tightened Euro 6 limits which will apply to all new vehicles from 1 September 2015. To give an idea of the reductions required, here are a few figures: compared with the currently applicable limit values, particulate emissions have to be reduced by a factor of five for compliance with the Euro 5 limits which will come into force on 1 January 2011. And according to Euro 6, the nitrogen oxide limit will be just 30 percent of the limits applicable in 2007. All Mercedes-Benz diesel cars with standard particulate filters already complied in 2007 with the particulate limits to be introduced in 2011.

At the 2007 International Motor Show in Frankfurt am Main, Mercedes-Benz displayed an entire fleet of especially economical and clean automobiles with intelligently combined drive technologies – studies as well as production vehicles. They included eight BlueTEC models and seven hybrid vehicles. The motto of the whole presentation was “ TrueBlueSolutions”, showing environment-friendly drive solutions for the future of the automobile.

For instance, the S 300 BlueTEC HYBRID as study of a production model for the near future featured a unique combination of BlueTEC and hybrid technology, offering a combined output of 165 kW (224 hp) and maximum combined torque of 560 Newton metres, comparable with the figures for a big-displacement petrol V8.

Also on display at the Mercedes-Benz stand: the new E 300 BlueTEC for the European market and the 320 BlueTEC models of the R, ML and GL-Class. In addition, a preview of the near-series studies C 250 BlueTEC, with the new generation of the Mercedes-Benz four-cylinder diesel engine, and E 300 BlueTEC HYBRID could be seen.

Sustainable mobility has been a corporate mission pursued by Daimler AG for years. The company is working on low-emission and ever more economical vehicle models with great commitment. The focus is on reducing not only carbon dioxide but also all other pollutants which have to be taken into account on the road to sustainable mobility. The results of these ongoing efforts are remarkable: from 1995 through 2007, the carbon dioxide emissions of Mercedes-Benz vehicles have declined by some 20 percent, and this rate is clearly higher than the 14 percent reduction achieved by the European motor manufacturers on average. It should also be noted that no other motor manufacturer can beat this rate.

A host of technical innovations was required to achieve this reduction within the Mercedes-Benz vehicle fleet. An impressive example of this is BlueTEC technology for diesel engines. Shortly after its introduction in the passenger car it was already helping to make the Mercedes-Benz models the most efficient and cleanest diesel-engined vehicles in their respective categories.

Since 2008 these innovations also include BlueEFFICIENCY, the comprehensive vehicle fuel consumption reduction programme. The diesel engine in the CDI BlueEFFICIENCY models profits from this innovative approach: for BlueEFFICIENCY the Mercedes-Benz engineers make use of the potential in all areas of development in order to reduce weight, wind resistance and rolling resistance further and organise energy management in vehicles still more efficiently.

Thomas Weber, member of the Board of Management of Daimler AG and responsible for Group Research and Mercedes-Benz Cars Development commented on this in the summer of 2009: “Mercedes-Benz car models are very economical and clean as it stands today. Our BlueEFFICIENCY models – we will have 58 of them on the market by the end of the year – are a good example. Just how successful this concept is is shown by the new E-Class, which combines ultramodern engines and the world’s best Cd figure in this vehicle category with other pinpoint measures intended to optimise the vehicles, including lightweight design and intelligent energy management. In the sum of these efforts we attain 23 percent greater efficiency compared with the previous model.”

The Mercedes-Benz diesel passenger car success story has gained new momentum owing to BlueTEC – not only in the North American market. For as of September 2009 Mercedes-Benz has been offering this now complete BlueTEC model range also in Europe: along with the new W 212 series E-Class Saloon E 350 BlueTEC, the ML 350 BlueTEC 4MATIC, GL 350 BlueTEC 4MATIC and R 350 BlueTEC 4MATIC, which had already been on sale in the USA for a year. The environment-friendly BlueTEC technology lends these SUVs additional attractiveness in Europe. In spring 2010 the G 350 BlueTEC followed. And so a genuine classic – the G-Class, a success since 1979 – meets the particularly clean 21st century Mercedes-Benz diesel drive.

The new E 350 BlueTEC features a V6 diesel engine which delivers 155 kW (211 hp) and makes maximum torque of 540 Newton metres available from 1600 rpm. The fuel consumption of this model, fitted with a seven-speed automatic transmission, is 7.0 litres per 100 kilometres (combined NEDC consumption). For the BlueTEC model the V6 engine was reengineered in detail, among other things in order to reduce the in-engine raw emissions and meet the legal requirements in regard to on-board diagnosis (OBD). The emission control system has a close-coupled oxidising catalytic converter and a diesel particulate filter positioned in the area of the firewall – this shortens the regeneration periods.

The heart of the BlueTEC system is two SCR (Selective Catalytic Reduction) catalytic converters with an upstream AdBlue® injector. Monitoring and diagnosis of the complex exhaust gas aftertreatment are handled by several sensors including a differential pressure sensor, oxygen sensor and NOX and temperature sensors. For the service fluid AdBlue® the E 350 BlueTEC gets an additional 25-litre tank fitted with a diaphragm pump, valve, pressure and temperature sensor, as well as electric heating. It prevents the 33-percent urea solution from freezing at low temperatures. Refilling of the tank should take place during regular maintenance service. Owing to this complex technology the exhaust emissions of the E 350 BlueTEC are at EU6 level.

But the efforts of Mercedes-Benz to make the diesel drive cleaner with BlueTEC are not limited to six-cylinder models: with the E 250 BlueTEC study, specifically designed for the North American market, in spring 2009 Mercedes-Benz showed a way to combine the BlueTEC technology of the E-Class with a four-cylinder with optimised fuel consumption. In the study the Mercedes-Benz combined the all-new four-cylinder diesel with BlueTEC. The result is the most economical and cleanest diesel model in this vehicle category which, with its range of as much as 44 miles per gallon (equivalent to 5.3 litres per 100 kilometres), attains a fuel efficiency better than that of most hybrid vehicles in the US market. Thanks to highly effective emission control, the E 250 BlueTEC does better than required by the American Bin-5 and ULEV emission standards, which are among the toughest in the world. At the same time, thanks to its high torque of 500 Newton metres, seven-speed automatic transmission and Lanchester balancer shaft, the refinement and performance of the four-cylinder is on a level with that of six-cylinders.

Just as much as new engines, the BlueEFFICIENCY package of the W 212 E-Class also conduces to the remarkable reduction in the fuel consumption of the diesel models, as demonstrated by the new four-cylinder diesel engine in the E 250 CDI BlueEFFICIENCY. With an output of 150 kW (204 hp) and 500 Newton metres of torque from 2.1 litres displacement it develops seven percent more output and 25 percent more torque than the current V6 diesel engine in the E 280 CDI with its displacement of three litres. At the same time it uses about 23 percent less fuel. With 5.3 litres per 100 kilometres (combined NEDC consumption) it is distinctly more economical than comparable saloons in this performance class. The CO2 emissions of the new four-cylinder diesel models come to 139 grams per kilometre or up to 24 percent below the figures for the CDI predecessors.

Engineers from all Development departments have optimised parts and components to save fuel through less weight, new design, improved function or efficient energy management. The work in the wind tunnel was highly successful. With a drag coefficient of 0.25 the new E-Class is the most aerodynamically efficient executive-class saloon in the world. It beats the previous model’s very good Cd by another four percent. The aerodynamics are improved, for example, by an automatically controlled fan louvre which regulates the flow of air in the engine compartment on demand.

Other BlueEFFICIENCY measures included newly developed tyres with up to 17 percent less rolling resistance and the energy-saving control of alternator, fuel pump, air conditioner compressor and power steering.

With the new generation of four-cylinder diesel power plants in 2009, Mercedes-Benz introduced the fourth generation of its tried-and-trusted common-rail direct-injection system into series production. One of its hallmarks is a 400-bar increase in the maximum rail pressure, which now stands at 2000 bar in the 220 CDI BlueEFFICIENCY and the E 250 CDI BlueEFFICIENCY. This increased pressure potential is essential for raising engine output up to 150 kW (204 hp) and maximum torque to 500 Newton metres, while distinctly reducing untreated emissions.

Newly developed piezo injectors are key components in the latest CDI engine generation. They use piezo-ceramic properties to change their crystal structure – and therefore their thickness – in a matter of nanoseconds when electrical voltage is applied. The new injectors are equipped with a stack of thin piezo-ceramic layers (called the “piezo stack”) to enable them to achieve a sufficient overall lift from the very small lift per layer. In contrast to the systems commonly used to date, this lift activates the nozzle needle directly, so that the fuel injection can be adjusted even more precisely in line with the current load and engine-speed situation – for example by means of precise multiple injections, which have a favourable effect on emissions, fuel consumption and combustion noise. Moreover, the engine runs much smoother at idle than its predecessor. Crucial to peak output and to full-load consumption (with respect to emissions) is the maximum ignition pressure – at 200 bar the new four-cylinder diesel from Mercedes-Benz is tops in the passenger car diesel engine sector.

In the new diesel engines for the E 220 CDI BlueEFFICIENCY and E 250 CDI BlueEFFICIENCY, Mercedes-Benz also realises two-stage turbocharging with demand-related control, for the first time in production passenger car diesel engines. The major advantage of this sophisticated technology is improved cylinder charging, and therefore high torque even at low engine speeds. Fuel consumption is also reduced. When the car is driven, this concept makes itself felt by harmonious driving characteristics with no turbo lag, a favourable torque curve across the entire engine speed range, great responsiveness and noticeably improved performance.

But depending on application other techniques also find use, for example in the E 200 CDI BlueEFFICIENCY, which features a single-stage variable-nozzle turbocharger. Since the engine output is smaller, a smaller turbocharger could be chosen to obtain very good drive-away characteristics.

Other special features of the new four-cylinder diesel engines include cooled exhaust gas recirculation for NOX reduction, a rear-mounted camshaft drive and the controllable water pump.

Dieter Zetsche, Chairman of the Board of Management of Daimler AG and Head of Mercedes-Benz Cars, made an altogether favourable review of BlueEFFICIENCY in March 2010, citing the current four-cylinder CDI models of the E-Class as example: “We have significantly reduced consumption and emissions with our BlueEFFICIENCY offensive. Our new models boast an excellent ratio of performance to CO2 emissions, thereby achieving an outstanding degree of efficiency.”

The presentation of the E 300 BlueTEC HYBRID, the first series-produced diesel hybrid passenger car from Mercedes-Benz, at the International Motor Show in Geneva in 2010 marks a critical new stage in the development of the diesel engine in Mercedes-Benz cars. The E 300 BlueTEC HYBRID pairs a 2.2-litre four-cylinder diesel engine developing 150 kW (204 hp) with a powerful hybrid module. Its 15 kW electric motor, positioned between the internal combustion engine and the 7-speed automatic transmission, assists the diesel engine when the car is accelerating (boost effect), although it is also suitable for driving using electric power alone. It is also used for the recuperation of braking energy in alternator mode.

The E 300 BlueTEC HYBRID consumes 4.1 litres of diesel fuel per 100 kilometres (CO2 109 grams per kilometre). The diesel hybrid will be launched as Saloon and Estate at the end of 2011.

In summer 2010 Mercedes-Benz included the first BlueTEC model of the S-Class in its range, the S 350 BlueTEC. With combined fuel consumption of just 6.8 litres of diesel per 100 kilometres (NEDC) – corresponding to CO2 emissions of 177 grams per kilometre – the new diesel model is eleven percent more economical than its predecessor. At the same time, the power output is up ten percent at 190 kW (258 hp) and torque is 15 percent higher at 620 Newton metres. The S 350 BlueTEC already complies with the emission levels which are planned for 2014 with the introduction of the EU6 standard.

The new S-Class diesel model already features Active Blind Spot Assist and Active Lane Keeping Assist, the innovations for active safety. The S 350 BlueTEC thus combines outstanding safety and high comfort with the effortlessly superior performance of an eight-cylinder vehicle and simultaneously boasts very good fuel consumption and emission values.

In autumn 2010 the S 250 CDI BlueEFFICIENCY then caused somewhat of a sensation: this S-Class Saloon is the first 5-litre car in the luxury class and the first model with a four-cylinder in the more than 60-year success story of the S-Class. The highly efficient turbodiesel achieves fuel consumption of only 5.7 litres per 100 kilometres in the NEDC cycle, which equates to CO2 emissions of 149 grams per kilometre. This makes the new S 250 CDI BlueEFFICIENCY the first vehicle in its class to undercut the 150 gram mark for CO2 emissions.

To ensure hallmark S-Class comfort, dynamically controlled engine mounts feature as an innovation in the new S 250 CDI BlueEFFICIENCY. The rigidity and damping of these mounts, which are interlinked with the engine management system via databus, alter according to engine speed, load and vehicle speed, thus preventing the transmission of unwanted vibrations and noise from the engine to the body.

With an eye to the 125th anniversary of the invention of the automobile by Carl Benz in 1886, Dieter Zetsche, Chairman of the Board of Management of Daimler AG and Head of Mercedes-Benz Cars, referred to the S 250 CDI BlueEFFICIENCY as a component part of the future of the automobile in September 2010: “ The invention created by Daimler and Benz changed the world and affected virtually every aspect of daily life. Now we are inventing the automobile for the second time, and the effects will again be revolutionary.”