Airflow system for engine with series turbochargers

An internal combustion engine, comprising:

• an intake manifold;
• an exhaust manifold;
• an engine block defining at least one cylinder, the cylinder being configured to receive compressed air via the intake manifold, the exhaust manifold being configured to receive exhaust flow from the cylinder;
• a first turbocharger including a first turbine coupled with a first compressor, the first turbine being configured to receive exhaust flow from the exhaust manifold, the first compressor being configured to supply compressed air to the air intake manifold;
• a second turbocharger including a second turbine coupled with a second compressor, the second compressor being configured to compress air drawn from atmosphere;
• a first conduit providing fluid communication between the first turbine and the second turbine;
• a second conduit providing fluid communication between the second compressor and the first compressor;
• a wastegate valve fluidly coupled with the exhaust manifold, the wastegate valve being movable between a first position and second position, the first position allowing fluid flow exhausted by the engine to bypass the first turbine, the second position restricting fluid flow exhausted by the engine from bypassing the first turbine;
• and
• a third conduit providing fluid communication between the second compressor and the wastegate valve,
• wherein the wastegate valve is moved to the first position at times when compressed air in the third conduit is at least a predetermined pressure.

A method of controlling airflow to an internal combustion engine having an air intake manifold and an exhaust manifold, the method comprising:

• imparting rotational movement to a first turbine and a first compressor of a first turbocharger with exhaust air flowing from the exhaust manifold of the engine;
• imparting rotational movement to a second turbine and a second compressor of a second turbocharger with exhaust air flowing from an exhaust duct of the first turbocharger;
• compressing air drawn from atmosphere with the second compressor;
• compressing air received from the second compressor with the first compressor;
• supplying compressed air from the first compressor to the air intake manifold;
• and
• supplying compressed air from the second compressor to a wastegate valve to control flow of the exhaust air from the exhaust manifold to the first turbine.