in fig6 a 6 c the arrangement of the intake system with electric and check valves according to the second embodiment of the present invention is shown specifically fig6 a 6 c illustrate the steps for combustion mode transition from si to hcci mode at the first step for fig6 a in si mode both intake valves 24 26 may be open for the cold air to flow into cylinder 28 by means of throttle 34 and check valve 38 being positioned as shown to have a high volumetric efficiency before the start of combustion mode transition from si to hcci hot air throttle 36 may open first as illustrated in fig6 b the delay time from the opening of hot air throttle 36 to the time of cam profile switching for fig6 c is provided for the low temperature air if any present in hot intake duct 40 to flow into cylinder 28 this delay time can be controlled by temperature measurement in hot intake duct 40 thereafter referring to fig5 b 5 c 6 b and 6 c the switching of cam profiles for cold intake valve 24 from lift curve 31 to lift curve 33 and the switching of cam profiles for exhaust valves 27 from lift curve 30 to lift curve 32 changes the combustion mode from si to hcci mode after cam profile switching check valve 38 may be closed automatically as shown in fig6 c because of the lower pressure in cold intake duct 42 due to throttling by cold air throttle 34 to control the overall air fuel charge temperature thus completing combustion mode transition from si to hcci mode referring next to fig7.