defining {HEAD ~ the model variable} for {TAIL ~ the air mass flow} into the cylinder as a linear function of the inlet pipe pressure; and 
for
defining { HEAD ~ the model variable } for { TAIL ~ the air mass flow } into the cylinder as a linear function of the inlet pipe pressure ; and
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH