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Thread: Round air filter vs flat filter

  1. #1

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    Round air filter vs flat filter

    Round air filter or flat ? Anyone know which is better and why?

  2. #2
    S2D's Avatar
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    the one thats on the airplane you have. Cause its already there and paid for and if you switch, it costs money and someone will come out with proof that the one you just sold cheap works better.

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    Crash's Avatar
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    Filter

    Piper would not have changed to the round filter for the last 30 years of PA-18 production if there was not an issue with the square one. I see more surface area on the round filter, a good thing. In a driving rain it is less likely to ingest water into the engine. Charlie Center says in tests they did for the FAA certification on their O-320 conversion that it turned up a 100 RPM more with the round filter on take off. You can buy the round ones at NAPA cheap. I would say if you have a choice, you should go with the round filter set up. Crash

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    T.J.'s Avatar
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    delete

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    SuperCub MD's Avatar
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    Quote Originally Posted by T.J. Hinkle
    After checking the Piper Parts book, I think the round filter is not legal on a float equipped Cub. Is this a correct assumption?
    Yup. Someone has the STC for a round filter and floats, can't remember who.

  6. #6
    Rookie's Avatar
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    STC SA912NW by Kenmore air installed on my airplane in 1980.

    Description of Type Design Change: The Fram CA-122PL induction air filter is eligible on Piper models listed above when Edo model 89-2000 seaplane floats are installed.

    The "models listed above" are PA-18S "150" and PA-18AS "150".

    Unfortunately, no floats these days, the fittings were not retained during a rebuild from 1985, completed in 1995 (!!).

    -->Aaron

  7. #7
    Crash's Avatar
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    Float STC

    You guy have too much time on your hands. Crash

  8. #8
    StewartB
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    I think this is an excellent question. I agree with S2D in that if I had one I'd keep it and find something else to spend the money on. In my case, I didn't have either, needed one or the other for my 12, and ended up with one of each. I'm using the round, for exactly the reason Crash stated. I asked Charly, and he told me the 100 rpm story. Done deal.

    What are all you experimental guys using if you start with nothing and have a choice?
    SB

  9. #9

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    Don't all the CC Topcubs on Floats use the round filters?

    Frank

  10. #10
    behindpropellers's Avatar
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    My friends '78 on wip amphibs still has the round filter?
    http://www.supercub.org/upload/BehindPropellers/cc.jpg

    ?

  11. #11
    SuperCub MD's Avatar
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    The round filter thing is if you install EDO 2000's per Piper specs. If you are installing some other STCed floats, that is a whole different thing.

    Aaron,
    Does the STC include doing anything to the airplane physically, like enlarging or relocating drain holes in the cowl scoop, or is it just paperwork? I've always been curious why Piper made such a fuss over the round filter on floats.

  12. #12

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    Re: Round air filter vs flat filter

    Quote Originally Posted by green horn
    Round air filter or flat ? Anyone know which is better and why?
    As far as cleaning the air, bigger is better, that is probably why they changed it. The round filters cost more but last longed.

    As far as positively affecting the power stroke of the engine, I have heard that the flat filters are better.

    Like the man says, run what you have, never heard any problems with either.

  13. #13
    Rick Papp's Avatar
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    Does anybody have a spare dome for the round filter type sittng around the shop that they would be willing to part with? I lost mine on the trip back from New Mexico. Duct tape is holding it on for now. Rick

  14. #14

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    Altee Dodge has the domes.

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    delete

  16. #16
    cubpilot2's Avatar
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    From my recollection the issue had to deal with any aircraft using a paper air filter during float operations, as the paper could become saturated, turning to mush and be ingested into the engine.

    I installed the Bracket "foam" filter on my cub and considered the case closed

    I have removed several of the round paper units that had been on floats that were pretty "sorry looking".
    Ed

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