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Thread: Flex Fuel engines

  1. #21

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    How many of the folks do you see on these threads that are developing modifications to their fuel tanks, lines and engines to run the stuff without destroying them? I can't recall any of them.
    Ahem.

    Aluminum tank.
    Braided line on the fleshy side of the firewall, automobile fuel line on the noiser side.
    Fuel filter in addition to the gascolator.

    Then again, my engine isn't certified and is designed to run on automotive fuel in the first place. I'm fortunate that we have a high test ethanol free gas station convenient to the airfield, but I'm sure at some point some 100LL is going to go into the tank. If I need some juice at some distant field I'm not scavenger hunting; I'm gonna put up to ten whole gallons of Super Aviation Fuel in and go!
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  2. #22
    steveinindy's Avatar
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    Aluminum tank.
    Not to add fuel to the fire (pun not intended), but I believe you know my opinion of bare aluminum fuel tanks and their limitations with regards to my particular field of work. If I'm mistaken, shoot me a PM and we'll discuss it to avoid a further derail of this thread.

    Then again, my engine isn't certified and is designed to run on automotive fuel in the first place. I'm fortunate that we have a high test ethanol free gas station convenient to the airfield, but I'm sure at some point some 100LL is going to go into the tank. If I need some juice at some distant field I'm not scavenger hunting; I'm gonna put up to ten whole gallons of Super Aviation Fuel in and go!
    Yeah, the whole fuel debacle (including the current uncertainty of the 100LL replacement efforts should the EPA get a wild hare up its collective arse) is another primary reason why I decided to go with a Jet-A powered engine for the second design (the LSA being the first design) we have been working on.
    Last edited by steveinindy; 05-19-2012 at 02:29 AM.
    Unfortunately in science what you believe is irrelevant.

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  3. #23
    Aaron Novak's Avatar
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    Quote Originally Posted by Frank Giger View Post
    Ahem.

    Aluminum tank.
    Braided line on the fleshy side of the firewall, automobile fuel line on the noiser side.
    Fuel filter in addition to the gascolator.

    Then again, my engine isn't certified and is designed to run on automotive fuel in the first place. I'm fortunate that we have a high test ethanol free gas station convenient to the airfield, but I'm sure at some point some 100LL is going to go into the tank. If I need some juice at some distant field I'm not scavenger hunting; I'm gonna put up to ten whole gallons of Super Aviation Fuel in and go!

    Frank,
    Aluminum tank not a wise choice when going with ethanol blends, unless its 1100 or 3003, and even then you have to be VERY careful selecting fitting alloys. Automotive applications that use various ethanol blends typically stick to polymers (plastics), steel ( believe it or not ), certain nickle based alloys, and pure aluminum for their systems. What do you mean by "automotive fuel line" anyway?

  4. #24

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    Interesting topic!

    I think there are some key elements that get the conversation going in different directions. First off we in the aviation world have a EPA problem with 100LL, we also have a cost problem due in part to technical issues and driven by a very low volume customer base. One solution that started off the thread was the fact that some Rotax 912 engines are available that can use current auto gas, i.e. 10% ethanol. Let's assume we could develop a whole series of new aviation engines that would run just fine on the current auto gas. That would satisfy EPA and bring the fuel cost per gal closer to what we are paying to drive our cars. That would be great for all the guys who can afford to buy a new airplane or have their current "old bird" upgraded with a new fuel system and engine. We'd still have a huge number of folks left out to dry simply because they can't afford to do that big a modification. Then there's the distribution thing. Today most airports carry 100LL and Jet A, if you can fly (legally & technically) with current auto gas you still have a big problem finding it at any airport. Now if the whole GA fleet could magically operate on today's auto gas then all the 100LL tanks and pumps could be "changed" to auto gas and we'd all be happy.

    Unfortunately, we don't have many engines today that can run on auto gas with 10% ethanol, and there are a whole bunch of segments in GA outside of us "low and slow" guys who really need high performance fuel. I think EAA in the form of it's membership is doing what it can do to experiment with aircraft and engines using something other then 100LL. Steve is going Jet-A and Frank is lucky enough to have auto fuel near his home base. Both are good examples of homebuilders finding solutions that work for their missions. The rest of us stuck with older certified aircraft are flying on 100LL and hoping that a solution is found that will allow us to continue to fly at some sort of affordable cost.

    Joe

  5. #25
    Jim Heffelfinger's Avatar
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    As this is not a new thread and has had many iterations over the last few years. I comment in brief.<br>
    1. Anyone thinking they have mogas that is alcohol free better not make any significant bets on that. Nearly all US auto fuels have ethanol. Assume it does and be surprised if it does not. Asking the gas station will get an unreliable answer. Test for it.
    2. Ethanol is being used by the blenders because it's really less expensive - Because subsitities that were designed for infrastructure development for the supposed huge shift to flex fuel auto sales - that didn't happen. We now have a mandated (Feds) glut of ethanol in the US and high corn prices.<br>
    3. If 91 octane fuel was available at the pump without ethanol it would solve a number of issues . Not only allowing the planes with STC for mogas to use it but also all the Rotax and other Rotax type engines would be happier. That includes boaters, off road vehicles and 2 cycle garden equipment. The high performance boat guys are going to the airport and buying 100LL because it doesn't have ethanol.
    4. Airports that had Mogas have stopped carrying it as the ethanol free fuels are hard to find if not at all available. One ethanol-free fuel would bring back those airport services.
    5. Don't expect to see a true flex fuel engine in a plane - ever. No one is going to invest in that technology for such a tiny market. (auto-conversions excluded)<
    6. The world wide supply issue for 100LL has a number of engine manufacturers looking at Jet A for piston power.
    7. Flex fuels have less power per volume and dramatically effect HP/pound.

  6. #26

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    Jim,

    Lots of good thoughts! I might take issue with item 2, the real cost of ethanol is understated if your just looking at a cost per gallon comparison of with vs without ethanol. Everyone who buys food that contains any corn product is subsidizing the ethanol program. It's another cost pass through to the average consumer, the price of corn has gone up a whole lot since the ethanol program started. Now there are a bunch of plus and minuses that are really hard to track on this one so you can take any position on it and find figures to support that position. That was actually pointed out to George W. when the issue came up and his response was that this would be "short-term" while we switched to "switch grass". The idea being that you can produce ethanol from just about any plant and using Brazil as the model, you could produce the rare material without investing in fertilizer and expending a lot of fuel to acquire that material. Since we know have established corn-based ethanol, we've also established a political constituency to keep this in place.

    As of now, I think that converting to Jet-A is the only viable solution for GA, but it kills most of the current fleet.

    Joe

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