A one-dimensional turbine performance model was investigated under real engine exhaust environment. The model is capable of performance prediction under pulsating boundary conditions and twin-entry scroll configurations. The discrepancies between experimental and simulated results were less than 20%. This turbine model was further coupled with a one-dimensional engine code and an in house engine performance prediction software was developed. The maximum discrepancy of the whole engine model was 3.5%. A joint engine-turbine design method was further developed based on this model and thus turbine geometries could be considered in the engine design process. A newly designed twin-entry turbine was coupled with the turbocharged engine. The engine power and brake specific fuel consumption could be improved by 2.7% and 1.6%.