The hole is preferably selectively exposed to a discharge pressure for a small portion of {TAIL ~ the cycle}, and to an intermediate pressure for a second small portion of {HEAD ~ the cycle} 
The hole is preferably selectively exposed to a discharge pressure for a small portion of { TAIL ~ the cycle } , and to an intermediate pressure for a second small portion of { HEAD ~ the cycle }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD