A turbine housing for an engine turbocharger includes a turbine outlet port fluidly coupled to an expansion mechanism, a waste port fluidly coupled to a collector, and a valve assembly rotatable between a first position blocking the turbine outlet port and a second position blocking the waste port. The valve assembly directs exhaust gas through the waste port in the first position and directs exhaust gas through the turbine outlet port in the second position. The valve assembly is in the first position during engine start-up to direct exhaust gas from the engine through the collector and into a catalyst. The valve assembly is in the second position a predetermined time following engine start-up to direct exhaust gas from the engine to the expansion mechanism.