A downhole heated fluid generation system includes an air subsystem having at least one of an air compressor and an air flow control valve; a fuel subsystem having at least one of a fuel compressor and a fuel flow control valve; a treatment fluid subsystem having a fluid pump; a combustor fluidly coupled to at least one of the air subsystem, the fuel subsystem, or the treatment fluid subsystem, and operable to provide a heated fluid into a wellbore; and a controller operable to receive an input representing a heated fluid parameter; determine a virtual heated fluid generation rate based at least partially on the heated fluid parameter; and control at least one of the air subsystem, the fuel subsystem, or the treatment fluid subsystem by the virtual heated fluid generation rate.