Control system for internal combustion engine

A control system for an internal combustion engine in which a variable intake mechanism changes an amount of intake air drawn into cylinders thereof as desired, the control system controlling an amount of fuel to be supplied to a combustion chamber, comprising:

• operating condition parameter-detecting means for detecting an operating condition parameter indicative of an operating condition of the variable intake mechanism;
• first estimated intake air amount-calculating means for calculating a first estimated intake air amount as an estimated value of the amount of intake air according to the operating condition parameter;
• air flow rate-detecting means for detecting a flow rate of air flowing through an intake passage of the engine;
• second estimated intake air amount-calculating means for calculating a second estimated intake air amount as an estimated value of the amount of intake air according to the flow rate of air;
• load parameter-detecting means for detecting a load parameter indicative of load on the engine;
• and
• fuel amount-determining means for determining the amount of fuel according to the first estimated intake air amount when the load parameter is within a first predetermined range, and determining the amount of fuel according to the second estimated intake air amount when the load parameter is within a second predetermined range different from the first predetermined range, wherein the first predetermined range and the second predetermined range are set such that they do not overlap each other, and
• wherein said fuel amount-determining means determines the amount of fuel according to the first estimated intake air amount and the second estimated intake air amount when the load parameter is between the first predetermined range and the second predetermine range.