DragBikeMike
Serious Thumper
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SuzukiSavage.com Rocks!
Posts: 4210
Honolulu
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Gary, your reply is excellent, certainly not long-winded. It is a subject that has mystified me for many years. I know from personal experience just what a lean mixture can do. I have managed to stick valves, burn valves, melt holes in pistons, seize pistons, and most recently pull the top off a piston. All, I'm sure, due to lean A/F ratio.
What baffles me is my former training in A&P school and also the USAF. I was a recip engine mechanic in the AF. I was always instructed, just as you described in detail, that peak EGT occurs at stoichiometric, and EGT falls off either side of 14.7:1.
But all those melted parts I've accumulated over the years contradict that. Your reply to SoC also seems to contradict the premise that EGT is lower either side (lean or rich) of 14.7: "Depending on the mixture (air:fuel ratio) it will be between 1,600 (very lean) and 1,100 (very rich)".
I'm not denying your numbers because my personal experience supports very hot stuff goin on when mixtures are north of 12.5 at WOT. But the aviation industry couldn't possibly be wrong.
Your comment about CHT is excellent. Are you saying that when a mixture goes lean, and as a result the EGT goes down, the CHT is going up? Am I getting the two mixed up? Is it the CHT that's killing the engine?
This graphic from an aircraft engine manufacturer shows the CHT & EGT tracking. Peak CHT & EGT are right around 14.7. What the heck am I missing here.
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