Abstract: A system is provided for reducing detectable hydrocarbons in the exhaust gas of a diesel engine and for retarding the formation of sulfate including a housing having an inlet and an outlet, a first exhaust gas glow passage extending from the inlet to the outlet within the housing, a first catalyst bed positioned within the first flow passage, a second exhaust gas flow passage extending from the inlet to the outlet within the housing, and a second catalyst bed positioned within the second flow passage. Also provided is a valve for directing the flow of the exhaust gas through one of the first and second flow passages, and an electronic control for controlling the valve in response to engine load and exhaust gas temperature such that the exhaust gas is directed through the first flow passage and the first catalyst bed under low engine load and low exhaust gas temperature conditions and through the second flow passage and the second catalyst bed under high engine load and high exhaust gas temperature conditions.

Abstract: A unitary system for removing particulates from the exhaust gas of an internal combustion engine includes a main flow passage and a by-pass flow passage for conducting the exhaust gas from an inlet portion to an outlet portion of a housing which contains the system. A valve for selectively directing the exhaust gas through one of the passages is provided, with a particulate trap mounted in the main flow passage for trapping particulates within the exhaust gas when the exhaust gas is directed therethrough. A regeneration system is positioned intermediate the valve and the particulate trap with an oxidation catalyst being positioned downstream of the particulate trap and in both the main flow passage and the by-pass flow passage. Further, a control system is provided for selectively activating and deactivating the regeneration system in response to predetermined operating conditions of the unitary system.