private double GetEngineEfficiency(int rpm)
{
// efficiency drops with increasing rpm
double retval = 1.00;
retval -= ((double)rpm / 100000) * 4;
/*if (rpm >= 7000) retval = 0.65;
else if (rpm >= 6000) retval = 0.70;
else if (rpm >= 5000) retval = 0.75;
else if (rpm >= 4000) retval = 0.80;
else if (rpm >= 3000) retval = 0.85;
else if (rpm >= 2000) retval = 0.90;
else if (rpm >= 1000) retval = 0.85;*/
return retval;
}