Originally Posted by
alex90
Interesting Chuck! I am quite surprised to hear your thoughts on this! So you're suggesting that they may have been running slightly ROP and that caused damage? That is surprising indeed! I may be reading what you linked wrong, but I don't see that significant a temp change between LOP and ROP. I was always under the impression that ROP operations would always enable a slight element of cooling from excess fuel going in. Interesting!
Alex you have the message, no confusion at all. Look at the graph again CHT peaks before EGT; so, if you lean till peak EGT then richen the mixture slightly 'so the extra fuel can cool the valves or cylinder heads' (my parentheses, not yours) then you are achieving the exact opposite.
The reason why the CHT peaks first is the fuel burns the fastest at that fuel/air (Stoicometric ratio sp?) and because of the fixed ignition most of the heat goes into the cylinder head and not into pushing the piston down. (Ineffective crank angle plays a part here, transferring linear motion to rotating motion.) Peak EGT slows the combustion and most of the heat/energy is used to force the piston down the cylinder. The cylinder head has to absorb less heat and thus runs cooler.
Below 75% power, if you are scared of LOP operation, then do your engine a favour and stay at peak EGT.