Abstract: A system comprising an engine with a low pressure ratio having an inlet and outlet; a turbocompressor consisting of a turbine having its exhaust side connected with the engine outlet via a gas line, and a compressor having its inlet side connected via an air line with the engine inlet, which turbine and compressor are mounted on a common shaft. A combustion chamber is incorporated in a line communicating with the air and gas lines and provided with a fuel system. An air control valve and a fuel control valve are arranged to control the delivery of air and fuel into the combustion chamber. This is connected to a turbocompressor speed control circuit intended to maintain a predetermined speed during prestarting to provide independent operation of the turbocompressor and the combustion chamber. The turbocompressor speed control circuit is connected with an engine speed pickup.