Understanding how energy-conversion mechanisms, i.e. turbine power, heat transfer and total internal irreversibilities are affected by mass flow rate pulse characteristics, i.e. amplitude, frequency and temporal gradient, is a key technological factor to improve turbocharger turbine efficiency under pulsating flow conditions. In this work, the turbocharger turbine response to pulse shape is studied by comparing two different mass flow profiles, characterized by a 5% difference in amplitude, via a Detached Eddy Simulation (DES). With increasing amplitude, an exergy-based post-processing analysis shows a 1.5% increase in turbine power, and the growth of total internal irreversibilities by 7%, 8% and 3% inside the exhaust manifold, volute and turbine, respectively. The Bejan number distribution demonstrates that viscous dissipation, due to higher velocity gradients, is responsible for the increase of total internal irreversibilities. Furthermore, pulse amplitude effect on heat transfer is larger at the exhaust manifold compared to the volute. Under pulsating flow conditions, isentropic efficiency is demonstrated to provide inconsistent results rather than an exergy-based efficiency, which requires no phase correction. The analysis of secondary flows inside the volute highlights the formation of pairs of counter-rotating vortices, which interfere with the correct alignment of velocity triangles by adding a vertical component to the velocity field at the rotor inlet in the direction of the turbine axis of rotation.