Volkswagen introduced the all-new Passat in 2011 at the Detroit Motor Show in the USA. It is a new midsize sedan designed exclusively for the American market and will be built at a completely new plant in Chattanooga, Tennessee. The second-generation 2.0l TDI~? engine familiar from Europe was extensively modified and further developed for the new Passat, in order to comply with the American BIN5/ULEV emission limits. For this purpose the engine’s untreated emissions had to be lowered and, in combination with exhaust emission control by selective catalytic reduction (SCR), compliance with the emission limits throughout the car’s operating life ensured. An effective measure for lowering the engine’s untreated emissions has proved to be the low-pressure EGR system (LP EGR) [1] introduced on the first-generation 2.0l TDI~? BIN5 engine. In the course of ongoing development of the LP EGR system, work continued on reducing pressure losses in the system, and charge-air cooling was converted from air to water cooling. Water-cooled charge-air cooling enabels intake pipe temperature control independent of ambient temperature, and due to the elimination of throttling and the associated reduction in volume improves road dynamics. Systematic elimination of throttling restrictions in the gas system, combined with improved turbocharging, led to a significant drop in fuel consumption and optimal road performance. As a means of stabilizing untreated emissions in the engine, cylinder-pressure control of combustion was carried-over from the first-generation 2.0l TDI BIN5 engine. Thanks to the closed-loop control of the indicated mean pressure and the centre of combustion with the pressure sensor integrated into the glowplug, it was possible to minimize the influences of fluctuating fuel quality and component tolerances. The exhaust system was completely revised in order to achieve maximum NOX conversion in the SCR catalytic converter. The coating of the diesel oxidation catalyst (DOC) / diesel particulate filter (DPF) module was modified to ensure an optimal NO2-NOX ratio over lifetime. Improved thermal response and an increase in the stationary temperature in the SCR catalytic converter at low loads were achieved by thermal insulation of the exhaust system. In order to obtain highly uniform NH3 distribution, a mixer has been integrated into the SCR system. Optimization of the coating minimized aging and de-activation of the SCR catalytic converter. The SCR system concept was adopted from the Passat ‘BlueTDI’ complying with Euro 6, as introduced in Europe in 2009 [2]. The tank is matched to the vehicle geometrically and located in the rear section of the vehicle. The tank and the feed lines to the injector can be heated to ensure the supply of AdBlue even at very low ambient temperatures. The requirements to be satisfied by the OBD system are determined by the tough current Californian standards for the 2013 model year, especially the more stringent exhaust gascorrelating threshold diagnoses. New functions were developed as a means of satisfying these diagnostic requirements. With the new second-generation 2.0l TDI~? BIN5/ULEV engine for the new Passat, which has been matched completely to the needs of the American market, combined with the low level of emissions, Volkswagen sets new standards for road performance and fuel consumption in a midsize automobile.
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