| abstract |
An engine exhaust system and method of controlling hydrocarbon emissions are provided. The system and method are based on the use of two catalytic converter chambers, a first chamber containing a catalytic material and a second chamber containing catalyst as well as molecular sieves capable of adsorbing hydrocarbons during engine start-up and of having hydrocarbons desorbed therefrom when the catalysts reach an effective converting temperature. According to the invention, engine exhaust is selectively conveyed to each of the two converters in a manner such that initially produced hydrocarbon is withheld in the system by the molecular sieves in order to be recycled through the converters and brought into contact with the catalyst after an effective converting temperature has been attained. |