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Thread: Avgas in auto engine

  1. #1
    overtime's Avatar
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    Shocked Avgas in auto engine

    My apologies if this topic has been covered before.

    Does anyone have real data on which to offer insights on using avgas in an auto conversion? I am running a Subaru EA81 in a Karatoo-based aircraft and wonder what impact avgas will have on the Subaru when I start making longer flights and refuel at airports that do not have auto gasoline.

  2. #2
    FlyingRon's Avatar
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    If that engine still has the oxygen sensor, you're going to kill it in short order with leaded fuel.

  3. #3
    overtime's Avatar
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    No oxygen sensor on this one. I started with a basic core and built up the engine with Bing carbs, manifold, SS exhaust from Stratus. Core had incomplete ignition system so I installed a Crane Cams unit.

  4. #4
    Chris In Marshfield's Avatar
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    I'm a member of the FlySoob group on Yahoo!, and the topic has come up a fair amount pretty recently. I think that what people are seeing is that lead buildup on the valves keeps the system from sealing up tight (lower compression), as well as the potential for sticky valves. I believe that most try to use autofuel where they can, and judicious use of Decalin/TCP when avgas is the only option.

    Here's a good thread to start with (presuming you can read posts in the group anonymously--I haven't tried):

    http://groups.yahoo.com/group/FlySoob/message/10478

    Best regards,
    Chris
    Christopher Owens (EAA #808438, VAA #723276)
    Germantown, WI
    Bearhawk Plans #991, Bearhawk Patrol Plans #P313

  5. #5
    overtime's Avatar
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    Thanks Chris. I appreciate the response and will definitely check out the link.

    Terry

  6. #6
    Kiwi ZK-CKE's Avatar
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    Subs run really nice on Avgas - I run the EJ20 in my Adventurer on it. The only proviso as mentioned earlier is around Oxygen sensors. Mine doesn't have one and it runs really sweet. There is no way I would want to be stuck with auto fuel on this beast - lugging jerry cans around isn't my idea of fun.
    "If it was supposed to be easy, everybody would be doing it...."

    Proud designer / builder of Avian Adventurer ZK-CKE.

  7. #7
    Chris In Marshfield's Avatar
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    Thanks for that bit of info, Kiwi. I agree jerry cans wouldn't be fun to have to carry around, especially in the plane that I'm building that carries at least 50 gallons of fuel!

    How much time do you have on your EJ20 with avgas? Do you use any additives in the fuel?

    I'm hoping that by the time I'm flying they'll have the unleaded avgas thing sorted out here in the U.S. Then I won't have to worry about it.

    Best regards,
    Chris
    Christopher Owens (EAA #808438, VAA #723276)
    Germantown, WI
    Bearhawk Plans #991, Bearhawk Patrol Plans #P313

  8. #8
    Kiwi ZK-CKE's Avatar
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    I've got 50hrs on my EJ, but the guy who built my PRU has built several hundred EJ engines for Gyrocopters, most running on Avgas. They have collectively accumulated many thousands of hours with no issues related to Avgas use. Other than the O2 sensor, there is absolutely nothing in the engine that objects to Avgas. The car Rally guys here in NZ run Avgas in their WRX rally cars as it offers better performance.
    An EA series engine will have even less problems - remember the EA81 was designed in the early 1970s, before unleaded fuel was widely available. Millions of running hours on high octane leaded fuel in the car fleet should give you some confidence. All you have to do is tune it with Avgas. Avgas is probably better for the older engines in many ways as its strict spec isn't subject to variations of performance additives and ethanol found in motor fuel, and which is known to cause problems. An interesting fact is the Subaru boxer engines were developed from an engine intended to power the Fuji FA200 light trainer aircraft built by the same company. I'm guessing the Sub designers were familiar with Avgas!....
    "If it was supposed to be easy, everybody would be doing it...."

    Proud designer / builder of Avian Adventurer ZK-CKE.

  9. #9
    overtime's Avatar
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    Thanks for the response. This type of real-world information is exactly what I was seeking. I am impressed with the results of posting a simple question. I will not likely be needing to refuel with avgas within the next few weeks but it is reassuring to know that the EA81 should happily convert this fuel into enjoyable flying.

    It would be really great if some photos of the engine installation on ZK-CKE could be made available. Having spent a great deal of time on my own installation, seeing how someone else did it could be quite instructive.

    Terry

  10. #10

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    I had an oxygen sensor in my Lycoming O-320 exhaust pipe that 'fed' an amplifier; when it sensed OX it lit a light on instrument panel that indicated a need for mixture adjustment. That worked fine. I recall replacing the sensor twice in over 500 hours using avgas. Even when it began to fail it didn't die suddenly, but became somewhat irregular. I just used sensors from NAPA auto store.

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