Unlike conventional turbomachinery, an automotive turbocharger’s turbine is operated under unsteady hot and pulsatile flow due to the inherent nature of reciprocating engine. Although the turbine is integrated with exhaust manifold in real application, some experiments and numerical studies ignore its presence. In this study, we aimed to investigate the effects of upstream complex exhaust manifold on the prediction of pulse flow turbine performance via Detached Eddy Simulation (DES). Heat transfer was incorporated and the exergy based approach was used to quantify the heat transfer associated losses. Our primary results showed that under the investigated turbine stage, although the presence of exhaust manifold influences the prediction of heat transfer and internal irreversibilities in the scroll significantly, it does not significantly affect the prediction of turbine power, heat transfer and irreversibilities at the downstream components.