Backcountry Pilot

[EZFlap offline]

Split from Stinson STOL modifications -Z
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my Stinson my hourly fuel cost has more than doubled (largely due to ethanol in mogas forcing me to 100LL).

Myself and several others have posted on this subject previously, please forgive the repetition but it may make a big difference in this person's case.

Take the !($*%# ethanol out of the mogas.You will invest a little more of your own time, but your time has the potential to cut your fuel bill back in half as you mentioned. It's absolutely earth-shaking rocket science, and only those with a double master's degree in chemistry and nuclear physics can do this....

Put about 15 or 20% water into your mogas. Right from a garden hose. Mix it up really really well. Shake it, stir it, figure out some way to use a drill operated paint stirrer, drive over a really rough road... whatever. The water will absorb or chemically bond to the ethanol like a magnet. Then let the tank sit for a while, until the water and the mogas separate again. After some period of time, there will be two layers : The water-ethanol mixture on the bottom and the ethanol free mogas on the top.

Drain off this water-ethanol, and you are left with un-tested ethanol-free mogas that may meet your mogas STC after testing. Now all you have to do is test the gas for water (per common sense and FAR's) and for ethanol (to meet your STC). If you are using mogas that you tested and proved to be ethanol-free, I believe you are now complying with your STC and your insurance requirements.

The ethanol raised the octane rating of the mogas, and removing it will lower the final octane rating. So starting with premium grade ethanol-mogas will likely be necessary in order to arrive at mid-grade ethanol-free mogas. Please check on the minimum octane requirement for the Franklin because I don't know. The small Continentals are 73, but if your Franklin is 85 or something you might want to ask a real fuel expert what the octane of mogas is before they add ethanol.

Also, removing 5-8% ethanol from your gas means that you have lost 5-8% of the amount of usable fuel. However, you have still saved a very large chunk of money.

Your monetary investment will be a translucent white plastic fuel drum, a drain valve at the bottom (to remove the water-ethanol mixture), some way to mix the fuel, and some way to pump the fuel from the plastic tank into the airplane.

Now the good news... if you have a fuel distributor in your area and are willing to spend a little extra time, you can save a bunch more money by buying the gas there and signing a document certifying that it is for use in an off-road vehicle and not subject to the 30 - 60 cents a gallon road taxes.

[Vick offline]

EZ - I've heard what you're describing referred to as "washing" ethanol out of gas, but I've also heard elsewhere that it's not as simple as what you describe - that you end up removing other desirable additives in the process. Have you tried this yourself or is this procedure conjecture? I have a distinctively non-technical background so I'm at the mercy of legitimate scientists and engineers, I'm all ears if you speak from experience.

Then what to do with the waste ethanol? Can I pour it on the nearest cornfield to "put it back"?

[RDUStinson offline]

Then what to do with the waste ethanol? Can I pour it on the nearest cornfield to "put it back"?

You could invite a few friends over with mixers... but I hear they've poisoned the ethanol to prevent exactly that...

[EZFlap offline]

Hi Vick,

NO, I do not speak from hands-on personal experience. This was, however, described to me by a legitimate degreed biochemist who works for a major government testing and engineering facility. I'm not aware of any additives that are also washed out with the ethanol. But I believe the ethanol is bad enough that it warrants taking it out, regardless of whether it is required by the STC or if you lose a couple of otherwise nice additives.

Again, I am NOT technically qualified to say anything about fuel chemistry. I ain't got a degree or significant equivalent experience in that area. I only have it on good enough authority to trust my own aircraft to it, and would do so as soon as I can find a good enough deal on a good used 50 gallon plastic tank. If there is anyone on this forum who has the verifiable technical expertise in chemistry and/or fuels who can shed some light on this, I will cheerfully stand corrected if I'm wrong. I do know for a fact that the EAA and Petersen STC's are certified based on using water to absorb ethanol out of the fuel as part of the pre-flight test. So I am pretty certain the water will pull the ethanol out of the mogas.

What I do have is some reasonable experience in emergency power-off, off-airport landings (from flying sailplanes). So what I will say with great confidence is that if you switch from one kind of fuel to another, or modify your fuel, or modify anything in the engine compartment... you should spend half an hour flying around the pattern within glide distance of the runway, and give (whatever it is) a proof test. This is true with spark plugs, magneto work, new pistons, new propeller, oil change, etc. to include changing fuels.

[porterjet offline]

Hi Vick,

... you should spend half an hour flying around the pattern within glide distance of the runway, and give (whatever it is) a proof test. This is true with spark plugs, magneto work, new pistons, new propeller, oil change, etc. to include changing fuels.

The worst time to fly is right out of the shop. Take a perfectly good airplane in for a scheduled visit and who knows how it is going to come out. On the other hand I've collected several tools by doing a real good preflight before taxiing away.

[Tadpole offline]

Since we're on the subject I just found this video on EAA that our own Joe Norris did about testing mogas for alcohol.

http://link.brightcove.com/services/pla ... 2010108001

[hotrod180 offline]

....
Take the !($*%# ethanol out of the mogas.You will invest a little more of your own time, but your time has the potential to cut your fuel bill back in half as you mentioned. It's absolutely earth-shaking rocket science, and only those with a double master's degree in chemistry and nuclear physics can do this.... ...................
Drain off this water-ethanol, and you are left with un-tested ethanol-free mogas that may meet your mogas STC after testing. ......
If you are using mogas that you tested and proved to be ethanol-free, I believe you are now complying with your STC and your insurance requirements. ...............
So starting with premium grade ethanol-mogas will likely be necessary in order to arrive at mid-grade ethanol-free mogas............

This all sounds well & fine, except for the octane level. I see that you have qualified some of your instructions with the word "may", "I believe", and "will likely be necesary". It MAY meet your needs, or it may NOT. IMHO it will NOT meet the STC requirements- my EAA STC calls out use of 97 minimum index (EDIT: ooops, meant 87 octane) fuel meeting ASTM spec D-439 or D-4818, or 82UL avgas.Maybe modern day car gas still meets there specs, or maybe not- but it is generally considered acceptable for airplane use under this STC except in the case of ethanol contamination. The STC does not mention this home-distilled concoction which may or may not have a high enough octane to provide proper power, and more importantly prevent detonation.
You come up with a real way to test for the required octane & I'll withdraw my objections. BTW it would help your credibility on a post like this if you did speak from personal hands-on experience.

Eric

[RDUStinson offline]

The STC does not mention this home-distilled concoction which may or may not have a high enough octane to provide proper power, and more importantly prevent detonation.
You come up with a real way to test for the required octane & I'll withdraw my objections.

I share your concerns. For what it's worth, a girl in the state motor fuels lab here in NC told me they could perform octane testing for me were I to provide a sample of fuel which I had washed in this fashion. As far as missing additives, I have no idea, nor do I know what my aircraft engine requires...

[EZFlap offline]

This all sounds well & fine, except for the octane level. I see that you have qualified some of your instructions with the word "may", "I believe", and "will likely be nexesary". It MAY meet your needs, or it may NOT. IMHO it will NOT meet the STC requirements- my EAA STC calls out use of 97 minimum index fuel meeting ASTM spec D-439 or D-4818, or 82UL avgas.

So where do you get car gas that is 97 Octane and meets your STC? The highest octane rating I've seen on a gas pump is 91. 97 Octane car gas is probably dragster fuel or something.

Maybe modern day car gas still meets there specs, or maybe not- but it is generally considered acceptable for airplane use under this STC except in the case of ethanol contamination.

Stop right there, pardner... "generally considered acceptable for airplane use" doesn't exactly jibe with your other comments, and certainly does not sound like FAA approved language. MY suggestion about things that are generally considered acceptable seems to have annoyed you for that reason too. My engine is certified for use with 73 octane fuel. I think it is "generally considered" common sense that if you start with 91 octane car gas and take out the ethanol, you're still going to be well above 73 octane.

The STC does not mention this home-distilled concoction which may or may not have a high enough octane to provide proper power, and more importantly prevent detonation.

The STC probably doesn't mention a hundred other realities that have come to the forefront since they did their original testing. But I don't think the STC prevents you from taking steps to insure the fuel meets the no-ethanol requirement.

You come up with a real way to test for the required octane & I'll withdraw my objections. BTW it would help your credibility on a post like this if you did speak from personal hands-on experience.

OK, here's a way to do it like another post said.... Make up some test samples and have a lab test it for octane. He knows someone who can do the testing. I know someone who works for a major research institute in San Antonio who can arrange to do it. In reality, I'm sure that the octane ratings with and without ethanol additive are pretty well understood and known to fuel manufacturers. I'd guess that they already know the answer to this. So my second method of verifying these ideas is to find where this knowledge already is on file. If the numbers say that 91 octane car gas with 5% ethanol removed results in 75 octane, then testing in a lab would be worthwhile. If someone already has research that says 91 octane car gas with 5% ethanol "Washed" out of it lowers the octane of the gas to 86... then that will be common sense enough for me to go and flight test.

I don't have any hands-on experience with shooting Heroin in my arm, but I know enough to make an educated recommendation about its use (don't). I didn't witness the signing of the Declaration of Independence, but I am qualified to discuss the general concept with some amount of credibility.

[Tadpole offline]

So where do you get car gas that is 97 Octane and meets your STC? The highest octane rating I've seen on a gas pump is 91. 97 Octane car gas is probably dragster fuel or something.

Come to Colorado Springs, I think 91 is our lowest. I heard it's due to our MSL here that we have higher octanes at the pump. I could be completely wrong though, being all laid up on narcotics I'm not sure what is at the pumps anymore!

[EZFlap offline]

You guys are a blast

All this jousting and sparring keeps our brains sharp as we get older, so it's probably a good thing. Kinda like three takeoffs and three landings to meet currency... BCP-mandated minimum of three medium arguments and one all-out brawl every 90 days to keep access to the site?

But some of you mugs do take off the gloves and go for the throat a lot quicker than normal!

Down here at closer to MSL, 91 is premium gas and 87 is regular. I can see it going up as you increase altitude, but then again the Continentals are certified at 73 octane - how would that be safe at altitude?

[Tadpole offline]

Down here at closer to MSL, 91 is premium gas and 87 is regular. I can see it going up as you increase altitude, but then again the Continentals are certified at 73 octane - how would that be safe at altitude?

Man I have no idea, I'm an engine mechanic, but on turbines I don't get all this stuff. Maybe car engines work a bit different in that aspect?

I have my wife checking on the octanes we have here. It's only rumor that I heard the reason we have the higher octanes is due to altitude, but no idea.

[Tadpole offline]

K I was wrong, we have 85, 87, and 89 here. I was thinking it was the other way. Seems we have lower octane here. We were just in Indiana it was higher there...thought it was the other way around. I blame the narcotics! Ya!

[Glidergeek offline]

Vick
I know this horse has been beat way past death, but why do you feel you need to remove 4%-6% ethanol from your mogas?
Russ

[Tadpole offline]

Vick
I know this horse has been beat way past death, but why do you feel you need to remove 4%-6% ethanol from your mogas?
Russ

Doesn't the ethanol eat up the seals and stuff in the fuel systems?

[RDUStinson offline]

but why do you feel you need to remove 4%-6% ethanol from your mogas?

Simple answer: it's EXPRESSLY prohibited by any mogas STC on a certificated aircraft. I'll let others speak to the specific operational problems with ethanol, but I can tell you that I won't even put it in my lawnmower. (Although I'm fine with it in our new Subaru.)

[onceAndFutr_alaskaflyer offline]

Vick
I know this horse has been beat way past death, but why do you feel you need to remove 4%-6% ethanol from your mogas?
Russ

Not Vick, but for me, I feel no need to do so, unless I am going to put it in my airplane. For the same reason I conduct due diligence on making sure my maintenance is logged and my equipment is approved I don't want unapproved fuel in the tanks - because when I crash I want the insurance company to own the airplane, not me; and would prefer judgements against me be paid by someone else with the initials AVEMCO. For an old 55 model airplane I doubt ethanol at such a low concentration will do that much damage, but we are stuck with what is legal, not what is safe

[courierguy offline]

So where do you get car gas that is 97 Octane and meets your STC? The highest octane rating I've seen on a gas pump is 91. 97 Octane car gas is probably dragster fuel or something.

Come to Colorado Springs, I think 91 is our lowest. I heard it's due to our MSL here that we have higher octanes at the pump. I could be completely wrong though, being all laid up on narcotics I'm not sure what is at the pumps anymore!

Tadpole,
I believe it is the opposite. When I was flying a Subaru powered aircraft (1300 hrs) the engine guru said burn premium mogas at or below 2500' asl, and while at my field elevation (back then) of 6150' burn regular. As I recall, the higher altitude takes away or migates somewhat the pre ignition problem as the engine cannot develop full power. Others will correct me I'm sure if this is wrong.

I have yet to get an answer, now that I am flying behind the mighty Rotax 912S, as to whether I can burn regular mogas at my altitude, which is NEVER below 4500'. Buying 300 gallons at a whack saving 15 cents or so a gallon isn't a bad idea, not woth blowing an engine, but if I don't need it...?

[shorton offline]

What about "phase separation"? As I understand it that is when the fuel with alcohol absorbs all the water it can hold and you add just a little bit more. The whole batch goes into phase separation and you get a layer of sort of gas not fit to use, a layer of alcohol not fit to use, and a layer of goop that will plug up the entire fuel system.

I have seen this happen when you use "heet" to clear water out of your gas. It works if you have a little, but if you have too much you get the three layers of crap.

[EZFlap offline]

I have not heard of phase separation, but if it exists to the level you describe then it sounds like bad news. I'll have a chat with my chemist friend (no not the one running the narcotics lab) and see.