This slight opening and closing creates {HEAD ~ a shock wave} that aids the atomizing air and fuel mixing in the intake system prior to normal intake valve opening and enhances {TAIL ~ the scavenging} of combustion gases during the exhaust cycle 
enhances
This slight opening and closing creates { HEAD ~ a shock wave } that aids the atomizing air and fuel mixing in the intake system prior to normal intake valve opening and enhances { TAIL ~ the scavenging } of combustion gases during the exhaust cycle
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH