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