The auxiliary piston may function as {HEAD ~ a compression and ignition means} by moving rapidly toward {TAIL ~ its top dead center position} only when the working piston is close to its top dead center position 
by moving rapidly toward
The auxiliary piston may function as { HEAD ~ a compression and ignition means } by moving rapidly toward { TAIL ~ its top dead center position } only when the working piston is close to its top dead center position
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH