Abstract: The device comprises an induction pipe and an exhaust pipe interconnected by a connecting pipe. A closure member controlled in accordance with the conditions of operation of the engine is inserted in the connecting pipe. The connecting pipe is connected to the induction pipe downstream of a throttle valve member which is capable of assuming two throttling positions in the induction pipe in accordance with the position of the accelerator pedal of the engine.

Abstract: The device comprises a connecting pipe which interconnects the exhaust pipe and the induction pipe of the engine. Valve means are inserted in the connecting pipe and the portion of the connecting pipe between the valve means and the exhaust pipe and the portion between the induction pipe and the valve means are short and of large section. The section of the passage through the valve means, defined by a cylinder formed in a seat, is small relative to the section of the connecting pipe and the valve member which cooperates with the seat has a cylindrical end portion whose diameter is slightly less than the diameter of the cylinder and whose length is slightly greater than the length of the seat.