means for calculating the efficiency of the engine, wherein {HEAD ~ 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 
varies
means for calculating the efficiency of the engine , wherein { HEAD ~ 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 OTH OTH OTH OTH 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 OTH OTH OTH OTH OTH OTH OTH OTH