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Thread: O320 160hp 75% of power

  1. #11
    Pacer42Z's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by Gilbert Pierce View Post
    Manifold pressure on a fixed prop doesn't do much good in my opinion. I removed my MAP gage

    Lycoming says 75% power is at 2450 rpm at sea level. For every 1000 above sea level add 20 rpm. i.e. at 4000' msl you would use 2530 rpm for 75% power. Here is a chart I carry in the airplane.

    Leaning to best power I typically see fuel flows 0.5 to 1.0 gallons per hour less than the chart shows.



    This is great info. I always keep 2,500 RPM, but according to the chart, at higher altitude I’m only running about 65% Power. I’ll try next time if I can get 2,600 RPM with my 58” pitch prop.

    Juergen
    Pacer N3342Z

  2. #12
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by Pacer42Z View Post
    This is great info. I always keep 2,500 RPM, but according to the chart, at higher altitude I’m only running about 65% Power. I’ll try next time if I can get 2,600 RPM with my 58” pitch prop.

    Juergen
    Pacer N3342Z
    If I remember correctly we miss about 1 inch of MAP every 1000 ft of altitude.




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  3. #13
    tloes's Avatar
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    Default Re: O320 160hp 75% of power

    The 90% rule comes from the rpm-related loading of a "fan". Power is a cubic function of RPM with fans. If you reduce rpm to 90% of maximum, you are also reducing power by 0.9 x 0.9 x 0.9 = 73% of the original power.
    Todd Loes -- Waterloo, IA
    (PA22-150 N3568Z)

  4. #14
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by tloes View Post
    The 90% rule comes from the rpm-related loading of a "fan". Power is a cubic function of RPM with fans. If you reduce rpm to 90% of maximum, you are also reducing power by 0.9 x 0.9 x 0.9 = 73% of the original power.
    Thank you!


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  6. #16
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by Pacer42Z View Post
    This is great info. I always keep 2,500 RPM, but according to the chart, at higher altitude I’m only running about 65% Power. I’ll try next time if I can get 2,600 RPM with my 58” pitch prop.

    Juergen
    Pacer N3342Z
    Juergen, at 2500 rpm and about 2000 ft, which speed you have with 58" prop? Your N3342Z is it a Tripacer? Thank you.

  7. #17
    Pacer42Z's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by Alessandro View Post
    Juergen, at 2500 rpm and about 2000 ft, which speed you have with 58" prop? Your N3342Z is it a Tripacer? Thank you.
    Alessandro, you gave me the perfect excuse not to work in the garden today and rather go flying. Attached are pictures at 2,000 feet, 3,000 feet and 6,500 feet each showing the indicated and true airspeed running the engine at 2,500 RPM. My airplane is a converted Tri-Pacer with 160 HP. I also have many other modifications on it. Here is a link to a YouTube video showing my Pacer: https://www.youtube.com/watch?v=OktsmuHiWKM . In most of my videos on my YouTube channel I keep one camera on the instrument panel, so you can see more different altitudes and OATs and I almost always run 2,500 RPM. However, in some of the videos I have my 6.00x6 tires with wheel pants and some videos I have 22" Desser tires. They slow me down by about 4 to 5 knots.

    I'm afraid though, it will not give you a direct comparison to your Tri-Pacer.

    Juergen
    Pacer N3342Z
    Attached Images Attached Images

  8. #18
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by Pacer42Z View Post
    Alessandro, you gave me the perfect excuse not to work in the garden today and rather go flying. Attached are pictures at 2,000 feet, 3,000 feet and 6,500 feet each showing the indicated and true airspeed running the engine at 2,500 RPM. My airplane is a converted Tri-Pacer with 160 HP. I also have many other modifications on it. Here is a link to a YouTube video showing my Pacer: https://www.youtube.com/watch?v=OktsmuHiWKM . In most of my videos on my YouTube channel I keep one camera on the instrument panel, so you can see more different altitudes and OATs and I almost always run 2,500 RPM. However, in some of the videos I have my 6.00x6 tires with wheel pants and some videos I have 22" Desser tires. They slow me down by about 4 to 5 knots.

    I'm afraid though, it will not give you a direct comparison to your Tri-Pacer.

    Juergen
    Pacer N3342Z
    Thank you very much!!
    Your ‘22/20 is very fast!!
    And you have a very good panel!

    I think that tricycle will be at least 5 knots slower.
    But the speed isn’t really important for me, just curiosity, the problem is that I haven’t yet the permit to fly and I can only imagine everything...........

    Now I watch all your videos!!




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  9. #19

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    Default Re: O320 160hp 75% of power

    Is there a formula that would correct the rpm for a given altitude based on the temperature?

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