BlueTec equals green for Mercedes-Benz: BlueTec system being used on buses in Europe; emissions technology coming to passenger cars and SUVs in U.S
The European Union’s stringent Euro 5 emission standards take effect in 2009 and compared to Euro 4, Euro 5 standards represent a further 43% reduction in nitrogen oxide (N[O.sub.x]) emissions. Earlier this year, the Mercedes-Benz Bus and Coach Unit delivered nearly 100 Citaro urban transit buses already meeting these stricter standards. These Euro 5 compliant buses feature DaimlerChrysler’s BlueTec diesel technology. Since early 2005, DaimlerChrysler has delivered over 20,000 Mercedes-Benz Actros, Axor and Atego heavy trucks with BlueTec diesel technology for Euro 4 and Euro 5 level emissions control.
Seven second-generation Citaro buses fitted with Euro 5 compliant Mercedes-Benz OM 906 LA/hLA engines were delivered to Verkehrsgesellschaft Breitenbach in Hamm, Germany. Another 90 similar Citaro buses are being delivered to Rotterdamse Elektrische Tram for service in Rotterdam, Netherlands.
There are two components to the BlueTec technology–enhanced engines and an integral exhaust gas aftertreatment system. For the Citaro application, the horizontally mounted, six-cylinder turbocharged diesel engine and its combustion processes have been optimized as far as possible to reduce emissions. This 6.4 L engine features electronic engine control, intercooled turbocharging and three valves per cylinder. The OM 906 LA/hLA engine in this application is rated at 279 hp with a peak torque of 830 lb.ft. at 1300 rpm.
In terms of aftertreatment, BlueTec is an umbrella term covering different technologies chosen for the operating characteristics of the particular application. It is modular so it can be used on trucks, buses, cars, SUVs and even hybrids, Mercedes-Benz said. Carbon monoxide and hydrocarbons emissions are reduced using diesel oxidation catalysts. Particulate matter is addressed though the use of a particulate filter, either as a separate element or integrated with one of the other BlueTec components. The installation of a larger sintered metal particulate filter in the buses is intended to ensure compliance with the more stringent Euro 5 emissions standard.
To meet Euro 5 requirements, N[O.sub.x] is reduced by a selective catalytic reduction (SCR) system with a urea-based injection system using an aqueous urea solution called AdBlue (thus the source of the name, BlueTec). When AdBlue, which is odorless, nontoxic and stored in an onboard tank, is injected into the pre-scrubbed exhaust, ammonia (N[H.sub.3]) is released. This causes the N[O.sub.x] to be reduced to nitrogen and water in the downstream SCR catalytic converter. Injection is controlled by the engine management system. To make the Citaro urban buses Euro 5 compatible, the size of the SCR catalytic converter was increased and the AdBlue injection quantity was adjusted accordingly. Incidentally, there are now around 1500 public-access AdBlue refueling sites in Europe, ranging from the Arctic Circle to southern Spain and from Ireland to Moscow. Several producers supply AdBlue.
The new Citaro buses can be distinguished by a front end that creates a visual link with the latest Mercedes-Benz touring coaches and rural service buses. The front-end flap and corner panels, including the headlamp housings, can now be opened, so the entire front end is accessible for routine maintenance and is easy to replace in the event of an accident. The rear end has also been modified.
The buses are fitted with disc brakes on all wheels, ABS and acceleration skid control (ASR), with a four-speed automatic transmission. The independent front suspension features lower wishbones and a standard-fit stabilizer. Finally, the turning circle is approximately 20 in. smaller than the first-generation Citaro bus.
The electronic self-leveling suspension system allows one side to kneel. Folding ramps and externally mounted, convenient request buttons make it easier for people with restricted mobility, older passengers and those with strollers. The 15 in. destination screens display the name of the next stop along with additional information, such as timetable changes and advertising. The Dutch buses also feature electrically extending wheelchair ramps, camera systems for monitoring the interior and digital bus-stop information and announcement systems.
On the lighter vehicle side, recognizing America’s demand for vehicles with good fuel economy without compromising utility, cargo capacity and performance, Mercedes-Benz has re-introduced several diesel-powered vehicles. It is now offering the E320 BlueTec luxury sedan, ML320 CDI SUV and R320 CDI Sports Touter.
These BlueTec diesels use a DeNOx catalytic converter rather than the more effective AdBlue injection process for N[O.sub.x] emissions. Therefore, these 2007 diesel models do not meet the emissions requirements of California, Maine, Massachusetts, New York, or Vermont and thus will not be available in these states.
According to DaimlerChrysler, the new-generation V6 diesel engine with CDI fuel injection technology yields up to 20 to 40% better fuel economy than comparable gasoline engines. The E320 BlueTec is the only diesel-powered luxury sedan available in the U.S. that can deliver an estimated 780 miles on a tank of fuel, the company said.