{HEAD ~ means} for calculating the efficiency of the engine, wherein {TAIL ~ 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 
wherein
{ HEAD ~ means } for calculating the efficiency of the engine , wherein { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL 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