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A trap oxidiser system using exhaust gas throttling as main regeneration system, coupled to a by-pass control of ceramic temperature, was installed on five experimental buses of the Athens bus fleet. Cerium Naphthenate was also used as fuel additive at different concentrations, in order to ensure safe and reliable regeneration at relatively low temperatures. The behaviour of the systems was constantly monitored through data loggers, during regular on-road operation. In order to examine the performance of all available materials, parallel tests were carried out using wall flow ceramics of different configurations and foam type ceramic monoliths. The paper presents the evaluation of the results obtained after 9 months of systems operation, with an accumulated minimum of 45,000 km of useful life per system.

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.