Turbocharger with bypass valve providing complete bypass of the turbine for improved catalyst light-off

摘要

A turbocharger includes a turbine housing defining an exhaust gas inlet, and an exhaust gas exit. The turbine housing is integrated with a housing for a 3-way valve defining a primary through-passage that supplies exhaust gas directly to a catalyst. The exhaust gas inlet is connected to a bypass passage of the valve that allows exhaust gases to flow to the turbine before going to the catalyst. The valve includes a rotary element whose position is controllable to regulate flow through each of the primary through-passage and the bypass passage of the valve. The rotary element is rotatable over a first range of movement and a further second range of movement, the first range including a position in which the bypass passage is substantially fully closed. Over the second range the bypass passage is fully open regardless of the degree of opening or closing of the primary through-passage.