9 January 2006

Mercedes-Benz unveiled two new diesel car models during the North American International Auto Show 2006 in Detroit: the E 320 BLUETEC and a full-size diesel SUV named Vision GL 320 BLUETEC. The E 320 BLUETEC will be launched this fall in the US market. The Vision GL 320 BLUETEC is still a concept vehicle with no market launch date.

Both vehicles use the same V6 diesel engine developing 155 kW (211 hp) and 540 Nm torque. The engine features 4 valves per cylinder, a common-rail fuel injection with piezoelectric injectors, a variable geometry turbocharger, and exhaust gas recirculation (EGR). The fuel economy is 6.7 l/100 km (35 mpg) in the E 320 and 9.4 l/100 km (25 mpg) in the Vision GL 320, thus representing a fuel saving of 20-40% compared to gasoline engines with similar power rating.

The E 320 will be launched in 50 states in the fall 2006, said DaimlerChrysler. To be offered for sale nationwide, the car must be emission certified to the Tier 2 / California LEV II standards, which have not yet been met by a diesel car. Both the E 320 and the Vision GL 320 are fitted with diesel particulate filters (DPF). However, the NOx emission control system in the E 320 and the Vision GL 320—even though marketed under the same name BLUETEC—is based on different technologies.

The E 320 utilizes a NOx adsorber-catalyst (NAC) system. The emission control system includes a close-coupled diesel oxidation catalyst (DOC), followed by the NAC converter, a diesel particulate filter, and an SCR (selective catalytic reduction) catalyst. The role of the SCR catalyst remains unclear; there is no urea injection in the E 320 model. The aftertreatment system reduces NOx by up to 80%.

The Vision GL 320, on the other hand, uses a urea-SCR system for NOx aftertreatment. The emission system includes a close-coupled DOC/DPF unit, followed by a urea solution injection nozzle and the SCR catalyst in the underfloor position. The urea consumption is around 0.1 l/100 km (1-3% of diesel consumption). The urea solution tank is designed so that it only needs to be refilled during regular, scheduled maintenance.

DaimlerChrysler also unveiled a BLUETEC Jeep Grand Cherokee engineering concept at the Detroit Auto Show. The BLUETEC Jeep features a urea-SCR NOx aftertreatment system.

DaimlerChrysler has been an outspoken supporter of urea-SCR technology. In Europe, over 10,000 commercial vehicles such as the Actros, Axor and Atego trucks have been fitted with BLUETEC urea-SCR systems. The name BLUETEC is obviously related to AdBlue, the European trade name for urea solutions. In the USA, however, urea-SCR technology has not yet been approved by the EPA due to potential compliance issues related to the replenishment of urea.

Source: DaimlerChrysler