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Thread: Percent Power Calculation

  1. #11
    OK Gary, I think I see what you mean. You have to add 0.17" MAP per degree ISA deviation to mantain any given % power setting. That ties up with my knowledge although I now think in centigrade so the addition is almost double.

  2. #12
    I run an injected 180HP engine with P-Mags, slightly pumped up. Here is a fairly accurate gauge for %HP; however, even though the outside air temperature and fuel flow are present, Advanced does not use them to enter into the power calculation.

    RPM 55%MP 75%MP
    2000 21.5 26.4
    2100 20.9 25.7
    2200 20.9 25.7
    2300 20.3 25.1
    2400 19.3 23.9
    2500 18.8 23.3
    2600 18.3 22.7
    2700 17.8 22.2

    I set 65% and lean to peak, at 9500' gives a consistant 186mph @ 7.4gph

    Give it a try, let me know if it works for you!


  3. #13
    RPM 55% 75%
    2000 21.5 26.4
    2100 20.9 25.7
    2200 20.3 25.1
    2300 19.8 24.5
    2400 19.3 23.9
    2500 18.8 23.3
    2600 18.3 22.7
    2700 17.8 22.2

    This is for my injected 180hp with p-mags. 65% power leaned to peak gives me at 9500' 186mph and 7.5 gph.

    Gary Brown

  4. #14
    I say again, I must still be missing something regarding the chart data. You say “notice the difference between 10,000 ft and 2,000 ft is about 8HP for a given setting”. If I start at 2000 feet on the right side of the chart and look at the intersection with the 2700 rpm line, I read 187HP in the middle of the chart. If I go to the 10,000 ft vertical line and again move up to the 2700 rpm line, I now read 140HP. This is a reduction of (187-140) 47HP, not the 8HP that you quote, if I am interpreting the chart correctly.

    Further, the AFS manual, on page 58, states that for an O-360, the delta HP with altitude at 8000 ft is 9.1 HP. We all know the rule of thumb that normally aspirated engines cannot exceed 75% power above 8,000 ft. For an O-360 rated at 180HP, this would be a 25% reduction, or 45HP, not the 9.1 HP in the manual example. The chart I posted above for an IO-360 A model supports this as well; maximum power at 8000 ft. is indicated as 150 hp, reduced 25% from a sea level maximum of 200HP.

    So I think I must be missing something, can you please explain your numbers? How did you get them?

    What is the problem with supplying the actual equation used by the software so your customers can decide whether the display is accurate enough or whether they should disable it? Thus far, you have not provided me with the information I need to make this decision. Is this too much to ask?
    Highest Regards,

    Noah F
    Rhode Island

  5. #15
    Does anyone have the numbers for the percentage HP for the Lycoming IO360A1B6 engine that I could use. The numbers in the manual as a starting point seem to be a little off. Thanks for any help.

  6. #16
    Try the data from my IO390. This comes very close to your angle valve 360. Use also the HP delta and make sure you have no set points without data.
    Lancair 390 OE-CCM
    AFS 4500EEA - AFS Pilot
    Austria / Europe

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