I didn't know that full-length videos by these guys were on Youtube, thanks for linking. Of course, they have published quite a bit of written work, and all of it is highly recommended, even if not an absolute point-of-view that everyone must take.
Paughco wrote:The main thing I got out of that discussion was that a parameter that you want to absolutely minimize for engine longevity is cylinder head pressure (CHP). [...] AVOID that area of peak EGT, and the slightly ROP zone, as that's where you get high CHP, as indicated by high CHT.
There is one big "but if" in this one, which at least in their written work they sometimes mention (no time for the videos right now). We
need pressure to produce torque, and thereby any usable power. In particular in the simulator world, we see a tendency of folks flying pretty high for naturally aspirated piston airplanes. At high cruise altitudes, where we are running the engine at its maximum output for the conditions, we actually
want to maximize the cylinder pressure to get maximum performance. The peak pressures will remain tolerable, as you really can't push the engine further with thin air. At sensible airspeeds, it is impossible to bring the CHTs harmfully high either.
Another point that is not too often brought up is the importance of ignition timing, which is often simply noted to be fixed in these engines. This is true obviously, but it still varies in between engine models, and not always hand-in-hand with rated RPM. Engines with relatively late ignition timing would generally speaking tolerate best power mixtures better, if everything else is assumed unchanged. Further, the issue of having fixed ignition timing is one big reason for that all this trickery with mixture is needed at all. For instance, automobile engines that vary their ignition timing dynamically as required, don't vary their mixture much at all for most part, albeit reasons for their design choices are entirely different. Anyways, where the timing is set precisely in any given airplane engine will surely have certain consequences on its nature.
-Esa