Quote:
Originally Posted by drmiller100
look up lean burn. the basic idea is you are cruising down the freeway at 60 mph. lean the mixture down to 20 to 1, requiring more throttle to keep the flames lit. at the same time, advance the timing a BUNCH (30 degrees plus).
do it all right, EGT's drop, economy goes up. Do it wrong, you get detonation.
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Lean burn in the sense you described can only be used in certain types of engines and used efficiently only in a certain window of conditions. It does work (increases FE) to an extent, but that is primarily because a 20:1 AFR requires ~35% less fuel to maintain. The efficiency of the engine doesn't really increase so much by way of a wider throttle opening.
The lean burn by way of power reduction in a window of operation also has the effect of increasing throttle (VE) resolution, thus making it a bit easier to drive efficiently.
A very steady cruise on a flat surface is the ideal situation for this type of reduced power operation.