Turbocharged engine and method of operating turbocharged engine

A turbocharged engine comprising:

• an intake port including a downstream end connected to a combustion chamber;
• a surge tank in communication with an upstream end of the intake port;
• an exhaust port including an upstream end connected to the combustion chamber;
• an exhaust passage in communication with a downstream end of the exhaust port;
• a turbocharger including a turbine installed in the exhaust passage, and a compressor that rotates together with the turbine;
• a control valve that controls a supercharging pressure of the turbocharger;
• an intake passage that guides air discharged from the compressor to the surge tank;
• a throttle valve installed in the intake passage;
• and
• a controller configured or programmed to control operations of the control valve and the throttle valve;
• wherein
• the controller is configured or programmed to control the throttle valve to set a maximum opening degree of the throttle valve to an opening degree less than a full-throttle opening degree, such that a compressor efficiency of the compressor is higher than a full-throttle compressor efficiency when an engine operation range is in a full-load operation range.

A method of operating a turbocharged engine including a turbocharger that supercharges air in an intake passage of an engine including a throttle valve, the method comprising:

• determining whether or not an engine operation range is in a full-load operation range;
• controlling a supercharging pressure of the turbocharger to a predetermined supercharging pressure with a control valve when the engine operation range is not in the full-load operation range;
• and
• controlling the supercharging pressure of the turbocharger to a predetermined supercharging pressure with the control valve, and controlling the throttle valve to set a maximum opening degree of the throttle valve to an opening degree less than a full-throttle opening degree, such that a compressor efficiency of a compressor in the turbocharger is higher than a full-throttle compressor efficiency when the engine operation range is in the full-load operation range.