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Thread: Which engine

  1. #11
    Senior Member Eric Page's Avatar
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    Default Re: Which engine

    Quote Originally Posted by alexM View Post
    ...there are builders who just want to follow a known formula so they can get in the air. They don't want to work out the bugs of a cooling system or make a cowl from scratch. The build process can drag on for long enough so it's easy to see the logic there too.
    Yep, exactly. I spent a ridiculous amount of time researching and diving down rabbit holes on alternative engines of every description before I finally took a step back and analyzed why I was building the plane in the first place. The answer was because I wanted a Kitfox to fly, not because I wanted to spend a couple of years chasing parts and fixing problems I don't know anything about. That realization, and the discovery that Kitfox Aircraft sells a very complete firewall forward installation kit for the Rotax 912iS (used on their S-LSA product) made the decision to use that engine a no-brainer.

    I'd echo Alex's main point. If you're deeply interested in the experimentation aspect of this endeavor, and you're willing to endure some pain and trouble to achieve your vision of the perfect Kitfox -- or, if you're very knowledgeable about the type of engine you're planning to use -- then an "non-traditional" engine choice makes some sense. But, if you want a reliable plane to fly in a reasonable amount of time and with a minimum of hassle -- or, if you think you might sell the plane within a few years and want to have an easy time of it -- then a well-supported "mainstream" engine is probably a better choice.

    Here's a cautionary tale. Alex and I have a mutual acquaintance who put one of the automotive conversion engines on his Kitfox. Because it's not an engine that had been used on a Kitfox before, he had to build the cowling from scratch. He had both coolant and oil leaks in flight, an engine stoppage due to a broken reluctor gear (on the ground, thankfully), and some kind of problem (ECU?) that made the engine refuse to start in the middle of a cross-country trip. He trailered it home, removed the engine and sold the plane.
    Eric Page
    Building Kitfox 5 Safari
    Member: EAA, AOPA, ALPA
    ATP: MEL / Comm: SEL, Glider / ATCS: CTO
    Map of Landings

  2. #12
    Senior Member
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    Default Re: Which engine

    Quote Originally Posted by Eric Page View Post

    Here's a cautionary tale. Alex and I have a mutual acquaintance who put one of the automotive conversion engines on his Kitfox. Because it's not an engine that had been used on a Kitfox before, he had to build the cowling from scratch. He had both coolant and oil leaks in flight, an engine stoppage due to a broken reluctor gear (on the ground, thankfully), and some kind of problem (ECU?) that made the engine refuse to start in the middle of a cross-country trip. He trailered it home, removed the engine and sold the plane.
    I thought it was ECU too, but he has since told me it was seized up tight. I'm electing to not trash on an engine manufacturer here, as he was patient zero so it was bound to have some teething problems. I flew right next to that plane in formation for 2-3 hours total and it performed well. I came to the conclusion there is nothing wrong with (at least some) car engine conversions, but you have to keep the runny stuff inside. "Most of the time" isn't good enough.
    Kitfox 5 (under construction)
    Citabria (sold)
    Commercial SE/ME, CFII

  3. #13

    Join Date
    Jul 2021
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    Peachtree City, GA
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    Default Re: Which engine

    Quote Originally Posted by mitch View Post
    you are building the airplane for you, not for the next guy. I feel if you are going to devote that chunk of your life & labor to the project build it the way you want it.
    Mitch
    Major Ditto!

  4. #14

    Join Date
    Oct 2019
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    Pickerington, OH
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    Default Re: Which engine

    Good thread. I’m in the same camp right now. Firewall forward kits are 4-6 months out right now so gotta plan ahead. Was leaning toward the Edge package because of my mission (base airport 3000’ in hot desert conditions, plan ok mountain flying and I ain’t no lightweight and neither is my lineman copilot). Wanted more ponies but not interested in a snowmobile motor. Thinking 915 or Edge EP912STI, and leaning toward the Edge of I can get more reliability reports from builders.

  5. #15
    Senior Member efwd's Avatar
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    Default Re: Which engine

    Can't help but notice, your putting some weight behind "reliability" in your inquirey. Why are you not asking about reliability of the ROTAX?
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  6. #16
    SSFoxBuilder's Avatar
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    Default Re: Which engine

    Factory Rotax 915 if you want that kind of horsepower with simplicity, reliability, and longevity. There is no substitute for the r&d Rotax puts into their engines and the support/communication they provide. I'll pay a few extra dollars and take the weight penalty all day long to ensure I have a reliable engine.
    Dustin
    915is/AP430 powered Kitfox SS7

  7. #17

    Join Date
    Feb 2021
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    South Jordan, UT
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    Default Re: Which engine

    Quote Originally Posted by SSFoxBuilder View Post
    I'll pay a few extra dollars and take the weight penalty all day long to ensure I have a reliable engine.
    In today's aviation environment there are actual alternatives to a 'factory' engine. Experimental aviation is the lifeblood of general aviation and those who try new things advance the state-of-the-art. Nevertheless, I have to agree with you; which is why I'm choosing the Rotax 915.

  8. #18
    SSFoxBuilder's Avatar
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    Default Re: Which engine

    Unfortunately, what many people take for granted is the reliability aspect. Over 90% of experimental aviation incidents/accidents are a direct result of a loss of power, and the majority of those are powerplants or subsystems that have been modified from their original design. Until you are faced with an engine-out situation, you do not have the ability to fully appreciate what that exactly means, for you and your family. When we are talking experimental it's important to know what we are getting into. If someone is going to build you an engine it's a worthwhile question to ask about their qualifications/training....how many aircraft engines have they built....how many of those engines are still flying....
    I guess my point is, know exactly what you are getting. There are "engine builders" out there claiming to be the know-it-all on performance upgrades or enhancements, when in reality some may have had several engines not make it to 100hrs without leaving the pilot with minimal options. Just my .02.
    Dustin
    915is/AP430 powered Kitfox SS7

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