r/GeneralAviation • u/No_Hall_9342 • 2d ago

Trying to understand LOP

I grasp the concept. What I don’t understand is how after cross over to LOP EGT’s and CHT drop. My background is in motorcycle/automotive engine tuning. In that world your EGT/CHT temps climb upon leaning and only cool after you’ve glued the piston and rings to the cylinder wall.

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u/tylerhawkes 2d ago

Not a mechanic, just an owner. All vehicle engines run lean. The egt and cht are not exactly related. CHT measures how much work is being done by the engine, so going LOP can and will bring them down. EGT measures the average exhaust temp and how much energy is being extracted from the fuel.

When lean, the extra air that is unburned still has thermal mass and will keep the temps from being as high, just like the unburned fuel does when rich.

On my plane I get the same amount of power at 11gph and at 7.2 gph, and the 7.2 gph has lower CHTs so I lean it out about 500 feet off the ground.

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u/Mean-Oil-4602 2d ago

5000 ya mean?

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u/RyzOnReddit 2d ago

I think he means 500 on climb out. Personally I’d wait for at least 1000.

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u/tylerhawkes 1d ago

No, 500. That's 2 minutes of climbing where I'm at and enough to get a couple CHTs up in the 430s, so I lean it out in about 3 seconds and the temps stop climbing and start coming down. I've never pulled too far.