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