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Thread: O320 160hp 75% of power

  1. #1
    Alessandro's Avatar
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    Default O320 160hp 75% of power

    Good morning, I'm not used to fly Lyco, I have only Rotax engine experience and the 160hp on my Tripacer will be my first Lyco.

    Looking at the manual Piper wrote : "to determine the proper cruising RPM of 75% of power, fly the aircraft as near sea level as praticable at full throttle until maximum speed is reached. Note the RPM at top speed, level flight. Then reduce the maximum RPM by 10% and cruise at 90% of full RPM".

    I never heard this rule: why 90% of top RPM is 75% of power?? Is it correct only for 61" propeller (as std Tripacer 160hp) or for every pitch ?


    I found on web one more different rule to determine 75% in the lycoming: the rule of number 48.

    The sum of map and rpm must be 48: for example 2500rpm and 23map= 48


    What do you think about?

    Thank you.
    Alex.

  2. #2
    6PapaWhiskey's Avatar
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    Default Re: O320 160hp 75% of power

    If you have an Apple device (iPhone or iPad), there is an app called "Aircraft Power" for $0.99 on the app store that will calculate power percentage. Here is the web page for the app:

    https://phiaeroapps.webs.com/
    Tom P.
    Wagabond @ 08A

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

    Thank you, it seems that now on apple store there is only "truairspeed". I cannot find "aircraft power"...

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    6PapaWhiskey's Avatar
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    Default Re: O320 160hp 75% of power

    Sorry - it looks like this app is available only for the iPad.
    Tom P.
    Wagabond @ 08A

  5. #5
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    It's true!! Thank you for your suggestion!!

    Quote Originally Posted by 6PapaWhiskey View Post
    Sorry - it looks like this app is available only for the iPad.

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

    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.



    Attached Images Attached Images
    Last edited by Gilbert Pierce; 08-01-2020 at 09:26 PM.

  7. #7

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    Default Re: O320 160hp 75% of power

    I use a different formula. I try to cruise between 2400 and 2500 RPM at all times because anecdotal and some historical data has shown these 150 to 160 hp engines "like" that range. I'm still looking for factory Lycoming data that tells me anything more than the folklore available on the web. Theoretically, you can run it all day long at redline of 2700. I don't. I also don't run full oil. I run about 6.5 quarts with a spin on filter. If I didn't have the filter, I'd run 6 quarts. More than that and it leaks or burns or spits it out. I lean the fuel to achieve cylinder head temperatures that generate temps that many people have said will improve the the life of the engine. Again, I take this on faith as I have yet to run an engine out. Working on it. I try to maintain 330 degrees minimum, 400 degrees maximum Fahrenheit. You might try Aluminum-tape on your #1 and #2 cylinders to get them up to temp, and once you know what works, then add a baffle block to keep the front cylinder temps up. This will give your engine reliability. If your front cylinder heads are too cold compared with the back two, then you risk sticking a valve. Check it out. Most times, Lycs stick the front #1 or #2 exhaust valves because they run too cold. Push the throttle in to go as fast as you like and then lean to improve combustion physics to improve the life of the engine. Amazing engines. I try to take care of it. I don't like to run above 2600 for long periods, or below 2100 very long. Keep it humming. Oil temp should be 180 to 220 deg. F. This is all just my opinion.

  8. #8
    Alessandro'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.



    Thank you. It makes more sense respect to 90% of max rpm, as written on the Piper manual....


    Sent from my iPhone using ShortWingPipers.Org mobile app

  9. #9
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    Quote Originally Posted by Subsonic View Post
    I use a different formula. I try to cruise between 2400 and 2500 RPM at all times because anecdotal and some historical data has shown these 150 to 160 hp engines "like" that range. I'm still looking for factory Lycoming data that tells me anything more than the folklore available on the web. Theoretically, you can run it all day long at redline of 2700. I don't. I also don't run full oil. I run about 6.5 quarts with a spin on filter. If I didn't have the filter, I'd run 6 quarts. More than that and it leaks or burns or spits it out. I lean the fuel to achieve cylinder head temperatures that generate temps that many people have said will improve the the life of the engine. Again, I take this on faith as I have yet to run an engine out. Working on it. I try to maintain 330 degrees minimum, 400 degrees maximum Fahrenheit. You might try Aluminum-tape on your #1 and #2 cylinders to get them up to temp, and once you know what works, then add a baffle block to keep the front cylinder temps up. This will give your engine reliability. If your front cylinder heads are too cold compared with the back two, then you risk sticking a valve. Check it out. Most times, Lycs stick the front #1 or #2 exhaust valves because they run too cold. Push the throttle in to go as fast as you like and then lean to improve combustion physics to improve the life of the engine. Amazing engines. I try to take care of it. I don't like to run above 2600 for long periods, or below 2100 very long. Keep it humming. Oil temp should be 180 to 220 deg. F. This is all just my opinion.
    Thank you. Also with Rotax engine I always stay between middle and max oil level. With Lycoming I must learn to descend from high altitude to sea level, I used to fly engine with water radiator and thermostat, that helps to maintain correct temperature. No experience with air cooled.


    Sent from my iPhone using ShortWingPipers.Org mobile app

  10. #10
    Alessandro's Avatar
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    Default Re: O320 160hp 75% of power

    With your experience a Tripacer with a good 160hp (76 of compression), a good rigging (if we did it correctly...), 2 on board, full std tanks, 58 propeller could cruise at around 100 knots IAS ?

    If I look at number wrote it could.

    But I would like an opinion based on your experiences.
    Thank you.

    Ps: 100 knots with about 3 hours range + 1/2 h reserve would be a very good result for me!


    Inviato dal mio iPhone utilizzando ShortWingPipers.Org

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