Design and Implementation of An Oxidation Catalyst for A Spark Ignited Two Stroke Snowmobile Engine

The primary goal of this project was to design and implement an oxidation catalyst specific to a high-performance spark ignited two stroke engines to reduce vehicle-out emissions. The primary challenges of two stroke catalysis at high loads include controlling the catalytic reaction temperature as well as minimizing the increase in exhaust back pressure due to the addition of a catalyst. Reaction temperature is difficult to control due to high HC and CO concentrations paired with an excess of oxygen in the exhaust stream. By limiting catalyst conversion efficiency, the reaction temperatures were controlled. Two stroke engines are also inherently sensitive to changes in exhaust back pressure and therefore location and sizing of the catalyst are key design considerations. Because of these challenges significant effort was directed toward developing the two-stroke specific catalyst design process. Through these efforts several key outcomes were reached including a better understanding of how to size and locate a catalyst in an existing two stroke exhaust system while maintaining minimal performance losses as well as insight into the wash coat development process and methods to promote catalyst durability. In total three actively coated catalyst samples were successfully tested over a range of engine speeds and loads. The catalyst samples showed significant HC reductions ranging from 30 to 96 percent across the engine operating range and CO reductions ranging from 10 to 97 percent in a significant portion of the operating range. Peak power loss also remained less than 1.5 percent for all catalyst samples.