Hi Kevin,
The engine type certificate states that the "well type head thermocouple" limit is 445 deg F. There is no EGT limit. When I talked to Aerospace Logic about how they set their limits on their EGT for Franklins, they told me they set it as follows:
Low Limit - 1250
Normal 1430-1489
Warning 1575
High 1625
All in deg F.
As you know, egt are really of value when you look at them as relative numbers. If one is exceptionally high or low, it can be indicative of a problem. I generally see about a 75-100 deg spread in mine.
Interestingly I find that when I use multipoint EGT to lean on a carburated engine, I will see a rpm drop before I see any one cylinder egt drop. I have seen this in Franklins, Lycomings and Continentals. I'd be interested in others observations. I would guess it is partially due to the nature of carb'd engines vs FI? Because of this, I lean by RPM/and my butt,( ok, my ear too...maybe that is why I get comments about not knowing the difference?) more than by EGT. I use egt to richen after I see the RPM drop. Also use it for trouble shooting, and general engine operation.
Larry
