An engine assembly includes an internal combustion engine with an engine block having at least one cylinder. An intake manifold and an exhaust manifold are each fluidly connected to the at least one cylinder and define an intake manifold pressure (pi) and an exhaust manifold pressure (pe), respectively. A controller is operatively connected to the internal combustion engine and configured to receive a torque request (TR). The controller is programmed to determine a desired fuel mass (mf) for controlling a torque output of the internal combustion engine. The desired fuel mass (mf) is based at least partially on the torque request (TR), the intake and exhaust manifold pressures and a pressure-volume (PV) diagram of the at least one cylinder.