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This paper describes the development of an emissions upgrade kit for the DDC 6V-92TA MUI bus engine manufactured by the Detroit Diesel Corporation (DDC). It incorporates three components: a base engine upgrade kit, a diesel oxidation catalyst and an electric demand turbocharger. A particulate matter level of 0.09 g/hp-hour has been demonstrated and certification is currently being sought at the 0.1 g/hp-hour level under the US EPA's Urban Bus Rebuild/Retrofit Program.

This paper describes an integrated approach to the reduction of three pollutants; HC, CO, and NOx, as well as the soluble organic fraction of particulate matter emitted from engines operating with excess air. This technology is applicable to all lean burn engines and is particularly pertinent to natural gas, methane, and propane fueled engines due to the difficulty of catalytic oxidation of low molecular weight hydrocarbons, such as methane. The technology uses existing catalytic materials and combines a novel approach to thermal management of the catalyst bed. Additionally, a HC rich exhaust serves as a reducing agent for a deNOx catalyst as well as a source of chemical energy to heat the catalyst. This paper will detail the configuration of the catalyst system during testing, the test conditions under which the unit was run, and the results of emissions reduction and mechanical integrity tests.