In a system, a calculating unit calculates a control parameter required for control of an engine based on a valve opening parameter each time a calculating timing repeatedly appears, and stores the control parameter in a predetermined area of the system. A reflecting unit reflects the control parameter in the control of the engine each time a reflecting timing repeatedly appears. A preliminary estimated timing setting unit sets a preliminary estimated timing between an input timing of the switching request and an estimated timing. The estimated timing represents that the valve opening parameter is estimated to be switched from a first value to a second value in response to the input timing of the switching request. A preliminary correcting unit corrects the control parameter based on at least the switched second value of the valve opening parameter when the preliminary estimated timing appears.