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The results of an extensive investigation developed on the wastegated radial flow turbine of a small automotive turbocharger are presented in this paper. Test rig measurements were performed to point out the influence of the by-pass opening on turbine performance. The analysis was extended both to steady and pulsating flow conditions, and controlled values of the main parameters of generated unsteady flow were obtained by a new dedicated turbine feeding line. A specific test method was followed in order to prevent inaccuracies in the definition of the waste-gate opening. The hypothesis assuming the turbine impeller and the waste-gate as two independent nozzles was studied in steady flow conditions. Turbine measured pulsating performance, which generally resulted higher than steady flow, was compared with the values supplied by analytical predicting models based on the quasi-steady flow assumption.