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How is fuel flow related to mixture for rich mixture values?

In piston engines at fuel/air mixtures above 0.095, the expected relationship between fuel/air mixture and fuel flow appears to break down. Here is a plot of ENG_FUEL_FLOW_GPH vs. RECIP_MIXTURE_RATIO (data collected by simconnect) for the Flysimware Chancellor:

fuelflow-vs-mixture.png

As fuel/air ratio rises above 0.095, EGT continues to fall as expected, but the fuel flow abruptly stops rising and begins a gradual decrease. The pattern becomes more exaggerated at excessively rich mixtures. At around 0.110 fuel/air ratio, the fuel flow decreases more rapidly, and above 0.120, the decrease is even faster. Here is a plot from the stock G36 Bonanza:

fuelflow-vs-mixture-widerrange.png

It appears that fuel flow is serving as some kind of proxy for engine power or perhaps fuel burn rate at very rich mixtures. Why does this happen? Is there a way to tune fuel flow for more realistic values at high mixture ratios?

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