Effective 29 January 1998, the US EPA certified equipment from Engine Control Systems (ECS) under the Urban Bus Retrofit/Rebuild (UBRR) program. The certified equipment is a converter muffler which includes a diesel oxidation catalyst. The certification extends to petroleum fueled diesel Cummins L-10 engines and all other 4-stroke engines that were originally manufactured prior to and including 1993.
The ECS converter muffler has been certified for 18% reduction of particulate matter emissions. Since the 25% reduction was not demonstrated, the equipment can only be used under Option 2 of the UBRR program, i.e., for fleet emission averaging.
ECS equipment was previously certified for 25% PM reduction on 2-stroke DDC engines.
Source: US EPA