means for calculating the efficiency of the engine, wherein said control means varies an opening of said throttle means for varying {HEAD ~ the engine speed} about {TAIL ~ an engine speed} setpoint read from said engine map 
about
means for calculating the efficiency of the engine , wherein said control means varies an opening of said throttle means for varying { HEAD ~ the engine speed } about { TAIL ~ an engine speed } setpoint read from said engine map
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH