Generally not the case. Best power is between 12.5 air to fuel and 12.7 air to fuel. So, the EGT for that range is at about 1600 degrees. So, if the probe is in too deep or is too close to the port face you will get a EGT number that does not match the actual mixture ratio. A back up heated Oxygen sensor will be more accurate than an EGT gauge but more expensive. Both measure mixture strength although the Oxygen sensor is newer. In olden times there was only the EGT gauge.
The temp during combustion is what you want to know. So, the EGT tells you the temp of gasses leaving the chamber, so we must speculate on the chamber temps. Also the Oxygen quantity left in the exhaust flow allows us only to guess at what the temps in the chamber might be. So, adding more fuel in hopes of lowering EGT will run aground because there is always some extra Oxygen left in the flow which will raise the EGT When it unites with the added fuel.
The airplane is just a Dyno with wings. So, fly at top speed (best power) and lean to stumble then back rich to just smooth. The heated Oxygen sensor should show about 12.5 to one. The EGT should show 1600 degrees.
At best speed. going for highest power. Once have that data. add a killer ignition and repeat going for lowest fuel flow. This will get you the mixture that is just short of best power. Now repeat, but once at best speed just add fuel and watch for a speed increase. This will get you above best power . This will also get you into the highest chamber temps. So, just sit there for a few seconds. Now you have best power slightly rich of peak and best power slightly lean of peak. Temps come down with lean of peak operations because less fuel is being introduced.
Lynn E. Hanover .
In a message dated 7/30/2018 3:47:13 AM Eastern Standard Time, flyrotary@lancaironline.net writes: