Cruise Performance - Efficiency Thread

[Bcone1381]

Group: This is me thinking/observing cruise performance....Cruising at any altitude.

• Whats best engine setting for cruise?
  • Define your goal.
• Max efficiency.
  • Do you want to fly slow?
• No
  • Going fast requires more Fuel Flow. How much fuel do you want to burn at this altitude?
• 8 gph
  • Then Experiment! Try different RPM's, MP at 8 gph.
  • What setting maximizes TAS while staying with in the boundaries of the Lycoming power chart (Max 5" over square)?
• That chart lets me go down to 1800 RPM. For example, 5" over square is 23"/1800.
  • Thats what I mean.

Observations and questions.

• I improved my cruise speed at 5.4 gph by 3% by slowing the RPM from 2200 to 1900.
• LOP
  • Is the LOP calculation that my EI Engine Monitor did at 2200 RPM still valid if I set 1900?
  • If my EGT stays about the same, is my LOP calculation is still accurate?
• Oil Consumption
  • I think my oil consumption goes up when I slow down the RPM to 1900 or 1800 rpm.
  • Max Efficiency may (key word) have a cost of increased oil consumption...needs more research.
• Do others see higher Oil Consumption at slower RPM's in parallel valve Lycoming engines?
• CHT's and Oil temps drop when slowing RPM down this much.
• Is it worth 3%?

Tell us why you use your "go to" power settings, what you know, curiosity you have, or what you don't know and want to learn. Personal experiences are important. I want to know both what you set along with why you choose it.