Control apparatus for naturally aspirated gasoline engine

A control apparatus for a naturally aspirated gasoline engine including a first throttle provided in an intake passage of a gasoline engine, a surge tank comprising a specific capacity provided downstream of said first throttle, a second throttle provided in the intake passage downstream of said surge tank, and an EGR apparatus including an EGR passage used to recirculate a portion of exhaust gas discharged from said gasoline engine back to said intake passage between said first throttle and said second throttle and an EGR valve provided in said EGR passage,

• the control apparatus comprising:
• a controller comprising at least one processor configured to:
• control the quantity of fresh air supplied to said gasoline engine by adjusting the degree of opening of said second throttle while keeping said first throttle fully open and to adjust the degree of opening of said EGR valve so as to achieve an EGR rate adapted to the operation state of said gasoline engine when the operation state of said gasoline engine falls in a low load range;
• control the quantity of fresh air supplied to said gasoline engine by adjusting the degree of opening of said first throttle and the degree of opening of said second throttle while keeping the EGR valve fully open and to control the quantity of EGR gas so as to achieve an EGR rate adapted to the operation state of said gasoline engine when the operation state of said gasoline engine falls in a middle load range higher in load than said low load range;
• and
• control the quantity of fresh air supplied to said gasoline engine by adjusting the degree of opening of said first throttle while keeping said second throttle fully open and to adjust the degree of opening of said EGR valve so as to achieve an EGR rate adapted to the operation state of said gasoline engine when the operation state of said gasoline engine falls in a high load range higher in load than said middle load range.