Cruise leaning

N56404N56404
in General Discussion

For those that have an engine monitor, where do you like to run your engine at cruise. I'm operating an O-360. Lycoming manual says best economy is peak EGT and best power is about 175 ROP. I tend to run about 65-70% power and at peak EGT. That results in about 8.5 gph. I'm usually not in a big hurry.

Comments

  • MikeJJMikeJJ

    Hi N56404,

    I too run 65-70% and peak EGT in the leanest cylinder. However many times I also lean by ear and feel. Honestly, in my O-360-A4A at altitudes below 4000 feet, I do not see that much difference in economy.

    For best economy, Lycoming notes:

    "Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting. ​NOTE: When leaned, engine roughness is caused by misfiring due to a lean fuel/air mixture which will not support combustion. Roughness is eliminated by enriching slightly until the engine is smooth.​"

    Regards,

    Mike

    • Michael Jay Jones (MikeJJ)
    • Piper Owners Aviation Director, Forum Moderator, Author
    • Commercial, Instrument, CFI - Airplane
    • Commercial Helicopter, Remote Pilot - UAS
    • FAA Wright Brothers Master Pilot
    • 50+ years in aviation, and still learning!


  • cherokee383cherokee383

    I will run my O-320 at about 70-75% and will lean the mixture until I notice the RPM going up. Once it gets to its 'peak' I'll leave it there and that seems to get me the best cruise mixture setting. I do it in the O-360 powered plane at the flight school I maintain, and it yields similar results. No need to over complicate these simple engines.

    Hope this helps.

    Kyle LaMontagne

    AP/IA, PPL

    1974 PA-28-140

    N41383

  • N56404N56404
    https://piperowner.org/talk/discussion/comment/1449402#Comment_1449402

    I agree. Your process would lead me to believe you operate at "best power". If you did monitor EGT via an engine monitor, I bet it would be right at the book value of about 175 ROP.

  • FickertFarmsFickertFarms

    Use the Lean Assist on the 275 to ROP. Running about 9GPH at 75% power, but to be honest still dialing those numbers in. Right now longest flight is just over an hour to the farms from home plate and training time with the CFI for insurance before I can take the fam for $200 ice cream and thrown rolls.

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