The revisions in the United States Clean Air Act of 1990 and recent regulatory actions taken by the California Air Resources Board and European Economic Community require the development of automobiles with much lower tailpipe emissions. A significant portion of the total pollutants emitted to the atmosphere by motor vehicles occurs immediately following the startup of the engine when the engine block and exhaust manifold are cold, and the catalytic converter has not yet reached high conversion efficiencies. An effective, energy efficient strategy for dealing with cold start hydrocarbon using carbon-free hydrocarbon traps and heat exchange related TWC catalyst beds has been successfully tested on a wide variety of current model vehicles. In each case U.S. FTP 75 total hydrocarbon emissions were reduced between 45 - 75% versus the vehicle's stock exhaust system.
