Close-coupled catalytic converter system

An in-line engine exhaust system comprising:

• a close-coupled housing having an inlet and outlet end;
• a first catalyzed structure having an inlet and outlet end centrally located within the housing, the catalyzed structure comprising a honeycomb structure having a cellular peripheral region having a plurality of cells running longitudinally parallel between the inlet and outlet ends of the structure, the peripheral region surrounding an open core central region also running longitudinally parallel between the inlet and the outlet ends of the structure;
• a second catalytic converter structure having a light-off temperature, located downstream from the first catalyzed structure, such that an exhaust gas stream is formed connecting the engine and the second catalyzed structure through the housing, and such that the open core provides a substantially unobstructed flow path for exhaust gases in the exhaust stream from the engine to the second catalyzed structure;
• and,
• flow diverter connected to a secondary air source and disposed in the housing for diverting engine gases away from the open core prior to the second catalyzed structure attaining its light-off temperature.