Precious Metal Strategies for Catalytic Emission Control in New Generation 4-Stroke Two-Wheelers

Catalytic emission control for two-wheelers has been widely used in a number of markets around the world for many years. The successful application of catalysts to many two-wheelers, in particular those with 2-stroke engines, and the desire for cleaner vehicles are leading to increasingly tighter emission regulations worldwide for those vehicles. These facts, coupled with changing market forces, are shifting the focus of catalyst applications from 2-stroke engines to 4-stroke engines. Inherently cleaner, particularly for hydrocarbons (HC), 4-stroke engines until now have utilized very basic approaches to emissions control. Most have required no catalyst at all, relying only on adjustments to engine tuning. Some others have utilized secondary air injection (SAI) to reduce carbon monoxide (CO) emissions. But new regulations coming into force around the world in the next few years will almost certainly require catalytic emissions control on many or most two-wheelers with 4-stroke engines. This paper will describe some of the approaches being taken to reformulate and optimize existing catalyst formulations for future 4-stroke engine applications.