A method, comprising: determining, at a controller for an engine system comprising an engine, the controller having one or more processors, a desired torque output (T desired) from the engine system in response to a torque request, wherein the engine is configured to generate torque at a flywheel, and wherein the engine system includes a belt-driven starter generator coupled to the flywheel by a belt; determining, at the controller, a current engine torque capacity (ET current); and when the desired torque output (T desired) is greater than the current engine torque capacity (ET current): (i) determining, at the controller, a maximum engine torque capacity (ET maximum); (ii) determining, at the controller, a current BSG torque capacity (BT current); (iii) commanding, by the controller, the BSG to operate as either a torque generator or a torque consumer based on a difference between the desired torque output (T desired) and the maximum engine torque capacity (ET maximum) and a state of a battery system configured to power the BSG; and (iv) controlling, by the controller, the engine and the BSG to collectively generate the desired torque output at the flywheel of the engine, wherein the BSG is operated, during the whole time period of the BSG being active, as either a torque generator or a torque consumer, such that the belt always has at least a desired minimal tension and an electric variable tensioner is not required to maintain the desired minimal tension of the belt determining, at a controller for an engine system comprising an engine, the controller having one or more processors, a desired torque output (T desired) from the engine system in response to a torque request, wherein the engine is configured to generate torque at a flywheel, and wherein the engine system includes a belt-driven starter generator coupled to the flywheel by a belt; determining, at the controller, a current engine torque capacity (ET current); and when the desired torque output (T desired) is greater than the current engine torque capacity (ET current): (i) determining, at the controller, a maximum engine torque capacity (ET maximum); (ii) determining, at the controller, a current BSG torque capacity (BT current); (iii) commanding, by the controller, the BSG to operate as either a torque generator or a torque consumer based on a difference between the desired torque output (T desired) and the maximum engine torque capacity (ET maximum) and a state of a battery system configured to power the BSG; and (iv) controlling, by the controller, the engine and the BSG to collectively generate the desired torque output at the flywheel of the engine, wherein the BSG is operated, during the whole time period of the BSG being active, as either a torque generator or a torque consumer, such that the belt always has at least a desired minimal tension and an electric variable tensioner is not required to maintain the desired minimal tension of the belt (i) determining, at the controller, a maximum engine torque capacity (ET maximum); (ii) determining, at the controller, a current BSG torque capacity (BT current); (iii) commanding, by the controller, the BSG to operate as either a torque generator or a torque consumer based on a difference between the desired torque output (T desired) and the maximum engine torque capacity (ET maximum) and a state of a battery system configured to power the BSG; and (iv) controlling, by the controller, the engine and the BSG to collectively generate the desired torque output at the flywheel of the engine,