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<<How much O2 (as a percent) of the exhaust stream do you think there is in
the exhaust stream ?

50F Rich of peak   xx %  ???
50F Lean of peak   xx %  ???
~ 20%?   ~ 10%  ~ 50%   ~ 5%  ~ 2%   ~ 1 %   ???
That is a starting point.>>

According to Lycoming (who doesn't publish actual air/fuel ratios on their
generic chart, and without digging into my old data base) peak EGT occurs at
about 96% power.  This equates to approximately stoichiometric air/fuel
ratio, about 14.5.  50 LOP is at about 93% power, or another 3% drop in
power.  At 50 ROP the free oxygen will definitely be less than 1%, maybe 500
to 1,000 ppm.  At peak EGT it will be only a little higher, but probably
still less than 1%.  Leaner than that the oxygen will rise in approximate
proportion to the power loss.  So at 50 LOP it will rise, say from a 1%
baseline, 3% of the 20% original value, or as an estimate will be about
1.6%, probably less.  To bracket it I would predict an oxygen content
between 1 and 2%.

Gary Casey
ES project

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