INTERNAL COMBUSTION ENGINE SYSTEM

PROBLEM TO BE SOLVED: To provide an internal combustion engine system which maintains the optimum operation state of an internal combustion engine and decreases the load on a supercharger.SOLUTION: An engine ECU 60 of the internal combustion engine system 10 detects a limited opening angle of a throttle valve 34a, wherein a negative pressure applied between a compressor wheel 52 and the throttle valve 34a in an air intake path 31 is not greater than a critical negative pressure value P. In addition, the engine ECU 60 compares the limited opening angle of the throttle valve 34a with the optimum opening angle of the throttle valve 34a, which is determined according to the state of a diesel engine 20, and sets a target opening angle of the throttle valve 34a to the optimum opening angle , when the optimum opening angle is the limited opening angle or more but on the other hand, sets the limited opening angle to the target opening angle when the optimum opening angle is less than the limited opening angle .