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