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