The second intake air passage is closed when {TAIL ~ the first urging force} is smaller than {HEAD ~ the second urging force} 
The second intake air passage is closed when { TAIL ~ the first urging force } is smaller than { HEAD ~ the second urging force }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD