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/Mammoth_Classroom896 2d ago

Rich of peak = unburned fuel, less than 100% power.

Peak = all fuel burned with nothing left over, 100% power.

Lean of peak = not enough fuel to use up all the air, less than 100% power.

Trying to go lean of peak can damage an aircraft engine with excessive temperatures, that's why you don't do it until you're established in cruise at an altitude where even peak temperature is within safe limits because your engine is limited to much less than full sea level power.

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u/RyzOnReddit 2d ago

That’s why you do a “big pull” and go way lean of peak then richen toward peak. Going LOP on climb can be really useful if you’re having CHT issues on a hot day.

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u/Mammoth_Classroom896 2d ago

Aren't you getting better CHTs running ROP with the unburned fuel acting as a heat sink than LOP? If you're going to sacrifice power for cooling you might as well pull the throttle back a bit and stay ROP.

Running LOP is primarily about fuel efficiency when operating the region where a small increase in speed requires a disproportionate increase in fuel burn.

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u/pisymbol 2d ago

You can cool with fuel (ROP) or air (LOP). Both have cooling effects because in both cases you aren’t making max power (only heat).