In order to further improve the aforementioned operations, it is preferred that an opening area of {TAIL ~ the first intake air passage} is reduced and an opening area of {HEAD ~ the second intake air passage} is enlarged 
In order to further improve the aforementioned operations , it is preferred that an opening area of { TAIL ~ the first intake air passage } is reduced and an opening area of { HEAD ~ the second intake air passage } is enlarged
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH