[Y]et it is the hottest component in the engine and highly stressed so it is useful to know how it correlates with CHT and EGT.
There is a scientific term for rubbish. It's: "rubbish". Like the usefulness of knowing there's a correlation between CO2 levels and at the number of pirates.
Now, the APS hypothesis brought to us here by Walter Atkinson is "valve temperature does NOT track EGT...[the NACA report with thermocouple in the valve] is definitive evidence the two are not in any way way related" is not supported by that report or any other piece of literature I have seen.
Except for the fact that valve temperature does not track EGT.
The part of that report you and Walter both cite as definitive is the valve temp peaking slightly rich of EGT.
"Slightly". Now there's a scientifically precise term.
But it does not follow that valve temperature does not track EGT.
True - it does not follow in principle.
However, valve temperature does not "track" EGT in fact.
The correlation with EGT alone is a very good proxy for valve temperature as a function of mixture.
And the correlation with CHT alone is an even better proxy for valve temperature as a function of mixture, because valve temperature more closely "follows" the CHT curve. One wonders at the scientific justification for preferring the EGT curve over the CHT curve as the "proxy".
Now to illustrate the absurdity of Walters logic let us test the APS teachings against it as well:
Quote:
"EGT is NOT the indication you're looking for. Pay attention to the CHT, and the valves take care of themselves.com." John Deakin; Fried Valves
Refer to figure 8 again. The CHT as represented by rear spark plug bushing. As a function of mixture it is going DOWN as the valve temp is still going UP. Now according to what you and Walter are saying this would be "definitive evidence" that CHT "does NOT track valve temperature and the two are in no way related". But of course, all it really means is that CHT - as a function of mixture - does not correlate with valve temperature as well on its own as it does when combined with EGT.
Gosh, I wish I'd read this first, because I'm now embarrassed to realise this is just a pisstake! We know what the NACA report says about the rear spark plug bushing measurement.
Got me a beauty, oggers! (You're not a Pastafarian, by the way?)