:An In-line hydrocarbon (HC) adsorber system was developed to reduce cold start HC emissions. The system comprises a first catalyst, adsorber unit, and a second catalyst for oxidation of desorbed HC. During cold start, exhaust gas is directed to the hydrocarbon adsorber using a fluidic flow diverter unit without any mechanical moving parts in the exhaust system. After the first catalyst lights off, the diverter is shut off and the major portion of the exhaust gas then flows directly to the second catalyst without heating the adsorber unit. After the second catalyst reaches light-off temperature additional air was added to oxidize the desorbed HC.The system attributes:NMHC emissions in ULEV range Straight line axial flow Reliable design Limited back pressure penalty The system was tested on a 3.8L U.S. vehicle.