Quote:
Originally Posted by abently
The RPM's can't be the same, because say you use 8Kw of power to cruise at 60km/hr, that 8Kw of power at 14.7:1 occurs at say 1500rpm, and at 17.7:1 occurs potentially at 1700rpm. Therefore shifting your cruise rpm into a lower bsfc zone.
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Most engines are putting out more power then needed at cruising speed tho, so say your car requires that 8kw/10hp to maintain speed, the engine is most likely putting out closer to 12kw/15hp, so with a lean burn engine you keep the same engine speed but cut out some of the fuel so it run leaner, you get a drop in power but it's a low load condition so you don't need that power.