The flow in turbocharger compressors and turbines for automotive engine application is highly unsteady in nature, as it responds to the intake and exhaust manifolds of the internal combustion engine. The optimization of the turbocharger system is therefore a very difficult task, since only steady flow maps are generally provided by turbocharger manufacturer.For several years a specialized components test facility operates at the University of Genoa, particularly suitable to test turbochargers under steady and unsteady flow conditions. The test bench has been continuously upgraded in order to study components under pulsating flow condition by using different layout configurations. A recent set-up makes it possible to study turbocharger compressor under unsteady flow condition by using a rotating valve pulse generator system. Measurements of pressure signals downstream the compressor, instantaneous mass flow rate and turbocharger rotational speed are performed.In the paper the effect of both pulse characteristics (frequency - i.e., engine rotational speed -, amplitude and mean value) on compressor performance is analyzed. In particular the attention is focused on the surge limit position under unsteady flow operation.