Vehicle air conditioning torque reserve via belt integrated starter generator

A method for controlling a powertrain of a vehicle comprising:

• responsive to a request for torque from an air-conditioning (AC) compressor, an available BISG torque from a belt-integrated starter generator (BISG) being insufficient to satisfy the request, and an absence of demand for negative torque from the engine to decelerate the vehicle, mechanically couple the BISG and an engine to a shaft of the AC compressor and retard spark timing of the engine,
• responsive to the request, the available BISG torque being sufficient to satisfy the request, and the absence of the demand, mechanically couple the BISG to the shaft without retarding the spark timing of the engine, and
• responsive to the request, the available BISG torque being sufficient to satisfy the request, and presence of the demand, wherein the demand exceeds a threshold value, mechanically couple the engine to the shaft without mechanically coupling the BISG to the shaft.

A control system for a powertrain, comprising

• one or more controllers configured to,
• responsive to a request for torque from an air-conditioning (AC) compressor, an available BISG torque of a belt-integrated starter generator (BISG) being sufficient to satisfy the request, and an absence of demand for negative torque to decelerate the powertrain, command transfer of the available BISG torque to the AC compressor, and
• responsive to the request for torque, the available BISG torque of the BISG being sufficient to satisfy the request, and a presence of the demand, mechanically couple a crankshaft of an engine to a shaft of the AC compressor without commanding transfer of the available BISG torque to the AC compressor.