Effective immediately, all new Mercedes-Benz large buses and coaches from EvoBus GmbH will be equipped with Blue-Tec diesel technology. The complete range of urban and rural buses and touring coaches will thus be available with this pioneering technology to coincide with the launch of the Euro 4 emissions standard. Blue-Tec effectively combats environmental pollution, especially in major cities and conurbations, and also noticeably reduces fuel consumption, which is a very important economic factor in these times of rising fuel prices.

Blue-Tec diesel technology with efficient filtering

The first Mercedes-Benz Citaro urban buses underwent practical trials with new Blue-Tec diesel technology around one year ago. Since then, they have impressively demonstrated their effectiveness in everyday operations. The OM 906 hLA and OM 457 hLA turbodiesel engines used in the test (both Euro 4-compliant) consumed approximately 6 % less fuel on average than previous Euro 3 engines. This corresponds to annual fuel savings totalling hundreds of thousands of euros for a medium-size transport company. Series production of Citaro regular-service buses with Euro 4 engines has been under way for quite some time — and deliveries of the first buses equipped with OM 906 hLA Euro 5 engines (also with Blue-Tec diesel technology) began a few months ago.

In Blue-Tec vehicles that conform to the EU emissions standard Euro 4, particulate emissions and fine dust particles in the exhaust gas are reduced by up to 94 % compared to the early 1990s, while nitrogen oxide emissions are lowered by up to 76 %. A reduction of up to 86 % is possible in the case of Euro 5. All large buses and coaches from Mercedes-Benz within the EU, as well as in other countries, will now be equipped with Blue-Tec diesel technology.

Nitrogen oxides transformed into nitrogen and water vapour

Blue-Tec diesel technology from DaimlerChrysler is based on a combination of enhanced engine technology and an exhaust-gas treatment process. The highly efficient combustion within the engine generates extremely low emissions that are almost as clean as filtered exhaust when it comes to particulates. The nitrogen oxides are then converted to harmless nitrogen and water vapour with the help of an integrated after-treatment system based on the SCR principle, which involves the addition of the Ad-Blue aqueous reducing solution in a catalytic converter.

The vehicle’s engine electronics control the injection of the appropriate amount of Ad-Blue from a separate tank into the hot exhaust gas, where it is converted into ammonia. This, in turn, initiates the desired chemical reaction. Blue-Tec technology is geared to the future, as it not only complies with the Euro 4 norm but can also meet the Euro 5 norm (which will come into effect in 2008/2009), without any need for additional treatment or filter systems. What is more, Blue-Tec is also capable of meeting the even more stringent EEV (Enhanced Environmentally-friendly Vehicle) emissions standard.

Cleaner combustion, reduced consumption

A key element of Blue-Tec diesel technology, with its increased economy, involved the comprehensive further development of Mercedes-Benz diesel engines. Efforts here focused on a further reduction of engine-out emissions with a clear emphasis on combustion that leads to the lowest level of particulate emissions possible, while also reducing fuel consumption in comparison to other processes. All of this is accomplished while still maintaining the high standards of reliability and durability typical of Mercedes.

Secure supply of Ad-Blue

The Ad-Blue infrastructure at public filling stations has already reached an advanced stage of development (see www.findadblue.com). Company fuelling facilities and special Ad-Blue stations can also be established without any problems. Vehicles fill up with Ad-Blue via a second filler neck located right next to the primary fuel tank filler neck. While filling up with diesel, drivers can simultaneously pump Ad-Blue into the SCR tank. Ad-Blue consumption in conjunction with Euro 4 engines equipped with Blue-Tec diesel technology amounts to roughly 2–4 % of diesel fuel consumption. Consumption with Euro 5 diesel engines is approximately 5.5 % of the amount of diesel fuel consumed. A full tank of Ad-Blue will thus last as long as at least two to three tanks of diesel — for a touring coach, this corresponds to several thousand kilometres of driving; for a regular-service bus, it is the equivalent of several days of normal service in any case, and in most cases is sufficient for a whole week.

Blue-Tec has long since proved itself as an effective technology. It was presented at the IAA Commercial Vehicle Show 2004 in a Mercedes-Benz Actros heavy-duty truck. More than 40,000 Mercedes-Benz-trucks equipped with Blue-Tec diesel technology have been delivered to customers since the beginning of 2005 and are now operating successfully throughout Europe. These days, most Mercedes trucks for long-distance road haulage are ordered with Euro 5 engines.

Blue-Tec plus particulate filter equals compliance with the EEV emissions standard

Blue-Tec diesel technology’s ability to meet the demands of the future is being demonstrated at the FIAA 2006 by an engine that is already designed to meet the EEV (Enhanced Environmentally-friendly Vehicle) emissions standard. This voluntary standard, which is even more stringent than Euro 5 (valid from 2008/2009), can currently only be met by natural-gas-powered engines. Mercedes-Benz will begin delivering EEV-compliant Citaro urban buses to those customers who request them in the second quarter of 2007.

The exhaust gas limit will be met through the combination of the OM 906 hLA Blue-Tec diesel engine and a particulate filter. The sintered metal filter is manufactured by Purem, which is a DaimlerChrysler subsidiary. With Blue-Tec, the particulate filter and the SCR catalytic converter are accommodated together in one housing. The Citaro will also be available as an EEV-compliant model with the larger OM 457 hLA engine at some stage in 2007.

Alternative natural gas drive system

Along with its very economical diesel drives for buses, Mercedes-Benz has for years also been offering the Citaro with a low-emission natural gas drive system. The standard M 447 hLAG natural gas engine with a lambda control unit and oxidation-type catalytic converter fully meets exhaust gas limits as stipulated by Euro 4. The engine is also available with EEV certification as an option.

Particulate filter retrofitting at a fixed price

Since 1997, Mercedes-Benz has been offering urban and rural buses with Euro 2 and Euro 3 engines that come with a particulate filter as an additional option. More than 50 % of German customers have taken advantage of this offer. Because of the importance of such filters in scheduled operation today, Mercedes-Benz offers an extensive range of retrofitting solutions for urban and rural buses currently in service with Euro 3 engines and some Euro 2 engines. These solutions can be obtained via the Omniplus service network in Germany. Only those particulate filters that have been tested and approved are used here. The retrofitting solutions help make older vehicles in the fleet more environmentally friendly and contribute to reducing overall emissions.

Engine line-up for Mercedes-Benz buses and coaches (Euro 4/Euro 5)