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EGT

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Aircraft Systems, Commercial Pilot, Flight Instructor, General Aviation, Private Pilot, Student Pilot

The EGT temperature increases as you lean the mixture until the optimum fuel/air ratio is achieved. Why does further leaning cause the temperature to begin decreasing?

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2 Answers



  1. John D Collins on Nov 27, 2014

    At peak EGT, theoretically all of the gas is combined with the available oxygen in the air. This mixture is called the stoichiometric mixture and is approximately 15 to 1 air to fuel. In practice, not all the fuel can be consumed at this mixture. Regardless, excess fuel in richer mixtures cool the combustion, so richer mixtures reduce the EGT. A rich mixture with an EGT of roughly 100 degrees F cooler than peak will usually produce the most power, but the power curve is fairly flat with richer mixtures. On the lean side of peak EGT, the mixtures do not have sufficient fuel to combust with all the available air. As the mixture leans further, the power produced is directly proportional to the fuel flow and therefore the power curve drops rapidly with the reduced fuel flow. Lower power means less heat and the excess air also acts as a coolant.

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  2. psequeira on Nov 27, 2014

    Thank you so much John!

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