What Grade Fuel do You Use?

The longer power stroke of the Atkinson Cycle allows for more efficiency. It doesn't directly reduce pumping losses, except in the sense that you have a more efficient engine so less air is needed. A smaller Otto Cycle engine would also have less pumping loss in this regard.

Tom

 

I think 'misleading' or not is more a matter of reference point. If one uses throttle setting (TPS on ScanGauge-II) as controlling engine output, then output does change significantly with atmospheric pressure. But if one use intake manifold pressure (MAP) as the controller, there is much less change. The biggest factor is that at higher altitude, the highest manifold pressures (and therefore highest engine outputs) are no longer available.

I normally don't watch MAP, but did so on a rolling highway yesterday. The vast majority of the trip, pressure was between 4 and 9 psi. Those numbers correspond to elevations of 34,000 and 13,000 feet, respectively.

Climbing a residential hill at low speed, pressure did reach 13.5 psi just before being forced to downshift. Sea level air is 14.7 psi, so this operating point would not be possible at high altitude.

 

Live in southern Colorado. Use 85 with not a bit of problems.

 

I do enjoy looking back on history. 13 years and the saga still continues.