A technique relating to such a mode of control of valve timing is disclosed in JP-A No. 6-101508. This prior art technique controls negative pressure in the intake pipe minutely at an optimum value, and controls the timing of closing the intake valve on the basis of parameters indicating the operating condition of the engine including cooling Water temperature, intake air temperature and time dependent changes in the engine in addition to a map showing a function of engine speed and load to reduce
pumping loss.