Turbo-compound internal combustion engine

In a engine system including a internal combustion engine equipped with a turbo-charger and an auxiliary turbine integrated with said engine, the combination comprising:

• an exhaust passage leading from a combustion chamber of said engine to a turbine of said turbo-charger;
• a transfer passage leading from the turbo-charger turbine to a scroll of said auxiliary turbine;
• a first by-pass passage leading from said exhaust passage to said scroll;
• a second by-pass passage leading from said transfer passage to an exhaust conduit of said engine;
• a first waste gate responsive to the discharge pressure of a compressor of said turbo-charger which controls the communication between said exhaust passage and said first by-pass passage, said first waste gate being adapted to open upon the discharge pressure of said turbo-charger compressor reaching a first predetermined value;
• a second waste gate responsive to the pressure prevailing in said transfer passage which controls the communication between said second by-pass passage and said transfer passage, said second waste gate being adapted to open upon a second predetermined pressure prevailing in said transfer passage;
• and
• means defining first and second passages within said scroll which exclusively communicate with said first by-pass passage and said transfer passage, respectively.