Abstract: Disclosed is a power-plant comprising an internal-combustion engine, a turbo-charger providing the supercharging of said internal-combustion engine and having a turbine and a compressor whose outlet communicates with an inlet of the internal-combustion engine and, through a by-pass duct, with a turbine inlet communicating with an outlet of the internal-combustion engine. An air flow sensor is installed at an inlet of the compressor. Arranged in the by-pass duct are an auxiliary combustion chamber and an air flow rate adjusting device for the air by-passed from the compressor to the turbine. The air flow rate adjusting device incorporates a throttling member linked with a drive used to change the position thereof and is provided with a comparison unit having a first input, a second input, and an output.