I agree that metal melt at particular temperatures - But that's what CHT is for.
Like EGT, CHT is just a measurement in a single spot. Thing is, you've gotten that EGT probe up to 1550+F (which is metal), so that means that there's exhaust gasses of at least that temperature coming out of the exhaust port, going over the exhaust valve (which is what burns), etc. GAMI/Deakin/whatever are quick to point out all the variances in EGT, and that's sort of correct, but I spent a lot of hours running engines on dynos with EGTs on each cylinder, the same engines over years and multiple installs/removals, and I didn't observe a whole lot of variance in EGT based on each installation. There's still value in that number. How do you operate turbines? EGT is a big part of that.
So if you're running hotter, that 1600+F that you're seeing on EGT is translating into more heat going into the exhaust valves, exhaust system, turbo... The turbos all have limits on temperature, but those might not make it into the POH if the OEM decided that in cert testing it wasn't necessary based on the prescribed power settings. Don't believe that has an effect on things? That's fine, I don't care, I'm not paying the bills on your plane. Incidentally that's why I don't teach this stuff anymore or respond to questions about engine operation on here or other places, because everyone responds with "But GAMI and Deakin say..." and then decide they like the GAMI/Deakin answer better than mine because mine would prescribe more limits on operation, even if it's being nicer to the machinery.
In which case, if those are the opinions you care about, why ask me? This goes back to the half-serious side of my original post above. I've paid enough maintenance bills (about $500k worth for aircraft I've been in charge of) and spent enough time operating engines under all conditions to see results. If you don't care about the machinery, that's fine. I won't say that everything I do is based on being kind to the machine - it's not - but I also can state outright when I'm doing something because I care about going fast or there's a bigger picture involved. I don't even participate in engine debates on the MU-2 group and aside from working for a piston aircraft engine manufacturer as an engineer, I worked for a turbine aircraft engine manufacturer as an engineer. Operate however you want.
OK, I'm a big fan of efficiency... So I have questions about this.
Which Contis are the "D rocker" ones?
The ones for which the rocker box covers look like the letter "D".
When you were at 365 CHT vs 380, roughly where would you be on the EGTs relative to peak?
What do you think was the cause of the extra efficiency?
Wouldn't those values change with OAT?
Don't remember what the EGTs were relative to peak. Something on the LOP side. Once I learned how my engines ran I selected a fuel flow that I would target, and then trim based on CHT. Remember that I haven't flown the 310 in over 4 years, and the 414 was a different beast (haven't flown that in over 2 years).
These engines are more efficient at lower CHTs (to a point). That effect is clearly shown on a dyno. I won't pretend to understand all of the specifics as to why, but I imagine it probably has something to do with optimal clearances.
Yeah, they'd probably change somewhat with OAT. That was mostly a summer number - basically in the summer if I was at 380F CHT and leaned a bit further (stabilized at 365F or so) then I'd find the same speed. In the winter I'd probably be at 365F anyway. Again, this was on the 310 which I spent a lot of time optimizing all around, so I won't claim that will apply on your Mooney anyway (which as I recall has a cross-flow head design anyway, and may respond differently).