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Due to the importance of the pollution of cars, buses and tracks from Diesel engines, the “Centro Sviluppo Materiali” of Rome has studied a particular device for the electrostatic precipitation and the combustion of the particulate from exhaust gases (MEA). After the study and the construction of the device, many tests controlled by the Ministry of Transport both on engines of 2500 cc and 9600 cc have been undertaken. The reliability tests were carried out on a urban and extra-urban buses. The results of tests can be summarized as follows: a) the back pressure values obtained by using MEA are always lower than a standard silencer, while High Voltage Power Supply does not affect the other electronics on the vehicle; b) (tests made upon a 2500 cc engine), the decreasing capacity of the Bosch smoke has been lower at high revolutions per minute. Anyway reduction average value of the smoke has been about 60%.

From september 1988 a fleet test started in Italy on urban buses equipped with a single ceramic monolith filter plus a by-pass and Diesel fuel burners for regeneration. The operation of the particulate trap, during the normal bus running in the city, has been assessed in three different ways: 1. Continuous control, by means of a data acquisition system purposely designed, of the main parameters affecting regeneration (i.e. time between consecutive regenerations, temperature in three selected zones in the filter during regeneration,filter loading); 2. Periodic control of smoke opacity of the bus measured, with and without the filter, under free acceleration and when bus is accelerating from 50 to 65 km/h on proving ground; 3. Particulate collection efficiency of the trap by using a dilution tunnel with the engine operated at the test bench. Information carried out from the fleet tests and additional information deriving from laboratory results were used for the system improvement.