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New Diesel exhaust gas aftertreatment systems, with combined DPF*) and deNOx (mostly SCR) systems represent a very important step towards zero emission Diesel fleet. These combined systems are already offered today by several suppliers for retrofitting of HD vehicles. Reliable quality standards for those quite complex systems are urgently needed to enable decisions of several authorities. The present report informs about the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles and NOx), which was started in Nov. 2006 with the objective to introduce the SCR-, or combined DPF+SCR-systems in the VERT verification procedure. Examples of results for some of the investigated systems are given. These investigations included parameters, which are important for the VERT quality testing: besides the regulated gaseous emissions several unregulated components such as NH3, NO2 and N2O were measured.

A light duty truck with a naturally aspirated engine was equipped with a DPF (changing the exhaust pipe and eliminating the muffler) and operated on fuel doped with a cerium based additive in various concentrations. Tests were carried out on chassis dynamometer using the European urban cycle, but also under city driving conditions with maximum speeds up to 50 km/h and exhaust gas temperature up to 300°C. Under these conditions, it was observed that filter regeneration was always possible at relatively high particulate accumulation in the filter, while the effect on fuel consumption (as measured over the emission test cycles) was not detectable, compared to baseline data of the vehicle. Change in driving conditions from slow urban to highway with highly loaded trap led to spontaneous trap regeneration at higher temperatures, without effect on fuel consumption. This paper documents the operation of a fully passive DPF system for diesel light duty vehicles.

The first two of a series of traps retrofitted on a pilot fleet of 110 buses of the Athens Bus Corporation were removed for examination after 100,000 km of revenue service. These buses were gradually equipped with the ELBO Trap Oxidiser since the beginning of 1989 and are constantly operated on Cerium based fuel additive. The physical properties and the chemical composition of filters and ash residues were analysed by the filter manufacturers and the fuel additive producer. The results have shown that after two years of operation the filter material remained intact and the ash deposits (consisting mainly of CeO2) exhibit a limited interaction with the cordierite. More than 94% of these deposits are filtered by the monoliths and could be removed to a large extent with the application of conventional methods.