However a SR22 pilot suggested that I could also try flying it at around 1370°F, since the SR22 has the best economy at that temp.
Somebody definitely needs to do some serious John Deakin reading!!!!
The absolute value of EGT has little relevance. What matters is the operating point relative to peak EGT.
I won't write reams (again!) but in a nutshell:
Peak EGT gives you best economy. Also called
stochiometric. Actually
25F LOP gives you the best economy / best MPG (for almost any normal petrol engine) but the efficiency curve is very flat around there so one doesn't have to be too precise.
100F ROP gives you the best power for the amount of air you've got to play with. This is relevant to a) generating sales brochure performance figures
or b) high altitude flight in non-turbo engines, say FL150+, where you are air-mass-flow limited, are already at full throttle, and just want the best power.
50F ROP (and the above mentioned 75F ROP is not far away from that) is the
worst place to set an engine to (on any continuous basis) because this is the biggest detonation risk area. In reality, one gets away with that because the big old Lycos/Contis don't detonate below some 85% power and some 450F+ CHT which is pretty hot.
Incidentally, fuel injection units tend to be set around
150F ROP with both throttle and mixture levers full forward - this is the takeoff setting and delivers the certified 100% power with a very rich mixture which produces a lower CHT through wasting some unburnt fuel. This is done because the lightweight air-cooled engine is structurally not capable of dissipating the heat that would be generated at the 100% power output if one was running stochiometric.
Apparently the SR22 and R172K have very similar engines
What is an R172K? The SR22 is about 300HP, Conti.