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old man emu

E10 petrol and water

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I don't know if I'm correct in this, but recently I made the following observation involving E10 petrol.

 

As you know, I've got an old Harley, and they say that if it doesn't drip oil, there's none in it. Well, I was putting a sheet of oil soaked plywood under the bike to protect the garage floor. It seems that the float valve got stuck, and overfilled the bowl. The excess fuel dripped down onto the plywood.

 

Now here's the observation. After a couple of days, I saw quite a few, large beads of water on the oily plywood where the pool of leaked fuel had been. There was no fuel left on the plywood. That got me thinking. Had the water been absorbed into a fuel by the ethanol in the E10 fuel, and been released when the fuel and ethanol evaporated?

 

If I'm correct, would that send alarm signals to you about using E10 in an aero engine?

 

Old Man Emu

 

 

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You are probably correct, but why would that be cause for alarm? E10 is not generally recommended in an aircraft for other reasons but the water will only come out of solution when the alcohol can absorb no more water.( or the alcohol evaporates) . It's always a good idea to run the carb dry on an aircraft, so no water should remain there.

 

On a bike like your Harley where the carb can be easily adjusted, running ethanol should be no problem. Any small amount of water will be absorbed and used. The engine will run cooler with alcohol in the fuel. Just does a bit less miles per gallon. Nev

 

 

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If I'm correct, would that send alarm signals to you about using E10 in an aero engine?

 

Old Man Emu

FYI, all Rotax engines are cleared for use with fuel containing up to 10% ethanol. However this does not necessarilly apply to the aircraft fuel system.

 

The ethanol will combine with any water in the tank and come out of solution, thereby lowering the octane value of the fuel. If you are using the minimum octane fuel for your aircraft, then this process will reduce the octane value to below min requirements and you would be well advised to drain the fuel tank.

 

Safe flying

 

Kev

 

 

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at least with motorcycle tanks you will not get rust holes appearing. the ethanol will absorb the water, hooray!...................................Really???....... can the water, absorbed by ethanol precipitate out and form ice???? as Ultralight says.. I would have thought that once in soultion it (water) would tend to stay in solution, But I'm not a chemist

 

 

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It has long been known that if you got water in a car fuel tank, then adding alcohol (usually methylated spirits - ethanol + menthanol ) would get rid of it by mixing and then this mixture would go through the combustion cycle and out the exhaust.

 

The problem with normally aspirated aero engines being fed petrol with ethanol and water, is that due to evaporative cooling at the fuel jet in the carburetor venturi, the water deposits as ice and blocks the fuel jet, leading to fuel starvation and lack of engine noise. Th1s situation is worsened if the fuel has cooled down to near zero temperatures in nthe outside air at altitude.

 

I believe that water injection as a means of boosting the power of an engine at power settings is not done through the carburetor, but somewhare else in the intake manifold. (I could be corrected on this point.)

 

OME

 

 

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I don't know what amount of water can be held in the ethanol or what the freeze point is of the saturated mixture. Many engines have a water methanol injection system. The RR dart has such a system and I can't remember any difficulty with icing. You should be able to look a Product data spec on the E10 fuel and get those details. I doubt that it would be a problem in normal temps we encounter.

 

Until the ethanol is saturated with water it stays in solution. The cold parts of a carburetter are where the fuel goes from liquid to gas which is downstream of the jet spray nozzle. This usually shows on the throttle butterfly . The venturi causes a lowering of temp too but it's not much P1V1/T1 = K Nev

 

 

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Interesting discussion. As part of the STC I got for the Auster to use Mogas there was a formal method for checking whether petrol has ethanol. Fill a container with water up to a line then add fuel and shake. The ethanol will mix with the water and increase the volume of that layer - separated out from the fuel - and you can directly tell the %ethanol from that as well. So, as far as this test is concerned the ethanol does not pick up the water from the tank.

 

 

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If the fuel you test already has some water absorbed what effect would that have? You are only testing for the presence of ethanol aren't you Ian? Nev

 

 

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FYI, all Rotax engines are cleared for use with fuel containing up to 10% ethanol.

Don't use E10 in an aero engine. The stuff promotes residue buildup, burns colder and has a slower flamefront than petroluem... it is not a good fuel for engines that aren't specifically designed for it. Keep in mind that 'tolerate' and 'designed for' are two different things, too.

 

Use no other fuel than the one recommended by your engine manufacturer or the experienced shop which has built your engine for you. If they say use Avgas exclusively, use that. If they say use 95RON mogas, use that. I find it hard to fathom that ANY manufacturer or LAME would actively recommend E10 for ANY engine.

 

Old Man Emu's original post

On oil soaked plywood and fuel dripping onto it, I think the petroleum would simply have evaporated and left the water behind to mix with the oil. Especially if you use mineral oil which will readily take on water; hence why it is good practice to regularly run engines to full operating temperature, to evaporate and get rid of any excess moisture accumulated.

 

Cheers - boingk

 

 

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A lot of E10 pumps have "not for use in aircraft" displayed. It will affect your mixture too unless your engine has a n adjustment that allows more rich selection than normal. Planes fly on PURE ethanol in brazil sometimes. You would have a lot less range because the fuel flow is about 160% higher at least. Nev

 

 

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If the fuel you test already has some water absorbed what effect would that have? You are only testing for the presence of ethanol aren't you Ian? Nev

I was assuming that as the ethanol combines with the water in this test and is a separate layer that the E10 does not soak up water

 

 

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Want to know how much water ethanol will hold? Try this simple experiment and you'll be amazed. Take a glass and fill it right to the brim with metho. The take another glass and fill it with water. Start pouring the water into the metho filled glass and stop when the glass overflows. That's how much water alcohol will hold.

 

https://www.youtube.com/watch?v=84k206qaVRU

 

 

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There is virtually no absorption of water by petrol. If you shake it there will be some fine drops suspended which will settle out pretty quickly leaving a clear surface of demarcation with the water on the bottom. I'm not sure that metho will mix with water completely nor does ethanol. Something that mixes with both has to be added to make it happen. ( as far as I know)... Nev

 

 

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Support Drive Aid - greedy people in Africa want to eat our fuel!

 

 

"hungry petrol tanks make me angry"

 

 

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I find this to be a very valuable discussion, thanks OME. There are some clearly different opinions, it would be good to get to the bottom of some of them, since fuel management, in all its forms, is a critical part of our pastime.

 

Interesting discussion. As part of the STC I got for the Auster to use Mogas there was a formal method for checking whether petrol has ethanol. Fill a container with water up to a line then add fuel and shake. The ethanol will mix with the water and increase the volume of that layer - separated out from the fuel - and you can directly tell the %ethanol from that as well. So, as far as this test is concerned the ethanol does not pick up the water from the tank.

Want to know how much water ethanol will hold? Try this simple experiment and you'll be amazed. Take a glass and fill it right to the brim with metho. The take another glass and fill it with water. Start pouring the water into the metho filled glass and stop when the glass overflows. That's how much water alcohol will hold.

https://www.youtube.com/watch?v=84k206qaVRU

The preceding two quotes seem to be contrary to each other but the science experiment on csscotthendry's video indicates that the ethanol does take the water into suspension (solution?) and reduce the total volume, so does this mean that the 'formal method' used for aircraft applications for detecting the presence of ethanol is flawed? If it is flawed where is this taught, and what is being done to correct it?

 

Don't use E10 in an aero engine. The stuff promotes residue buildup, burns colder and has a slower flamefront than petroluem... it is not a good fuel for engines that aren't specifically designed for it. Keep in mind that 'tolerate' and 'designed for' are two different things, too.

 

FYI, all Rotax engines are cleared for use with fuel containing up to 10% ethanol. However this does not necessarilly apply to the aircraft fuel system.The ethanol will combine with any water in the tank and come out of solution, thereby lowering the octane value of the fuel. If you are using the minimum octane fuel for your aircraft, then this process will reduce the octane value to below min requirements and you would be well advised to drain the fuel tank.

OK, so Boink has a good point in general aero engine terms but Kev is saying that Rotax has taken the ethanol into account for their engines specifically. The reason for my post here is because of something I learnt yesterday that confirms what Boingk says about residue build-up, I'll get to that in a moment, but what is wrong with a cooler burn? And the slower flamefront should be no problem on a 2T engine but perhaps you'd need to advance the ignition timing a bit on a 4T to prevent burning the exhaust valves?

 

I think Kev means the ethanol will come out of solution from the petrol (rather than the water) but would the octane value of the fuel, as a whole, be lowered? The whole lot, petrol, ethanol and water all goes into the combustion chamber.

 

in winter, the water can freeze out as well.

 

at least with motorcycle tanks you will not get rust holes appearing. the ethanol will absorb the water, hooray!...................................Really???....... can the water, absorbed by ethanol precipitate out and form ice???? as Ultralight says.. I would have thought that once in soultion it (water) would tend to stay in solution, But I'm not a chemist

I'm not a chemist either. OK, if Ultralights is right and this is true what are the practical effects? On a sub-zero day I'd be flying along and the water would freeze and fall out of suspension (or is it solution) from the ethanol, fall to the bottom of the tank and block the fuel pick-up? Would/does this actually happen? How can we do a practical experiment? Mix a little water with some E10 and chuck it in the bait freezer - what should we see? Ice in the bottom of the container?

 

The problem with normally aspirated aero engines being fed petrol with ethanol and water, is that due to evaporative cooling at the fuel jet in the carburetor venturi, the water deposits as ice and blocks the fuel jet, leading to fuel starvation and lack of engine noise....

 

The cold parts of a carburetter are where the fuel goes from liquid to gas which is downstream of the jet spray nozzle. This usually shows on the throttle butterfly . The venturi causes a lowering of temp too but it's not much P1V1/T1 = K Nev

So - which is right? Is carby icing more of a problem with ethanol in the fuel? Does it block the jets or the carby throat?

 

Fuel deterioration due to ethanol/which fuel supplier to use -

 

Something I learned yesterday. I have had to replace the fuel tubes regularly on my garden machines (line trimmer, blower, hedge trimmer etc), about each three years the tubes go hard and dark brown and very brittle and just fall off, bits into the tank, fuel runs everywhere, both the supply lines and the return lines from the pumper carbies. Met a very helpful bloke at the mower joint yesterday who really knew his stuff. The fuel lines are a thin yellow affair, 1/8" OD and 5/32" OD, Tygon is the brand and I think they're made from polyurethane. In years gone by the fuel tube used to last as long as the machine ...

 

So while the helpful fella was cutting me some new tubing I commented that it was probably the ethanol in the fuel which destroyed the fuel tube. As it turned out this bloke had some training in industrial chemistry and he's employed to test all their fuels and one of the tests involves an ethanol analysing machine. He said it wasn't/isn't only the ethanol that does the damage but also the lack of it. Well that got me listening as you'd imagine. What boingk said above is quite correct apparently, the ethanol not only grabs all sorts of nasties out of the air, it also comes with lots of them already in it when it's added into the fuel. When you leave your machine sitting for a while the ethanol evaporates out of the fuel and leaves all the greebies behind which vigorously attack your plastics and rubber gear (something for the fetishists there I guess). And also, when the ethanol has gone, apparently that's when the octane rating becomes lower and can damage your engine due to detonation.

 

The conversation went on to become a discussion of the good guys vs the bad guys in terms of fuel refineries and after a bit of persuasion I got some more valuable stuff out of him. Their company supplies several thousand lawn care machines to the local council on lease with full maintenance supplied, so they really care about anything that might deteriorate or otherwise adversely affect their machines and he said one of the biggest problems they had was fuel related so they now check all the fuel that goes into their machines, from dozens of different outlets.

 

He said wherever possible they use Shell fuel as it has proven to be the purest and always up to octane and never more ethanol than advertised. Next choice is BP. The Independents buy their fuel wherever is cheapest so they don't use them because you don't know what you might get this week. The one fuel they would never use is one of the biggest in Oz and surprised me but I must say I've noticed my car doesn't always run the same ...

 

I don't want to post it on public forum but if anyone wants to know whose fuel they won't use under any circumstances (they said they would rather the machines sat idle instead), you can PM me.

 

Oils ain't oils -

 

We always swore by Penrite green slime but I understand it's no longer available. I'll be using a 2T for the C2S so would like to hear opinions/experiences/facts about current 2T oils, and especially to do with different experiences/recommendations for liquid-cooled vs air-cooled 2Ts, thanks.

 

 

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The preceding two quotes seem to be contrary to each other but the science experiment on csscotthendry's video indicates that the ethanol does take the water into suspension (solution?) and reduce the total volume, so does this mean that the 'formal method' used for aircraft applications for detecting the presence of ethanol is flawed? If it is flawed where is this taught, and what is being done to correct it?

looking back I could have used better wording - the point I was making with the formal one is that the ethanol and water mix - but are separated from the fuel

 

This link has some info on the testing : http://www.eaa.org/autofuel/autogas/test_kit.asp

 

 

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HITC:

 

Great wrap up of the current debate. At first look, the method for testing for alcohol in fuel seems to contradict the science experiment, but...When you think about it, the test says that the layer of water under the fuel will increase if alcohol is present. This suggests to me that the water will absorb the alcohol out of the fuel which will make the water layer seem to increase and the fuel layer decrease. In the experiment we saw that although the water absorbed (some of?) the alcohol, the total volume still increased.

 

 

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looking back I could have used better wording - the point I was making with the formal one is that the ethanol and water mix - but are separated from the fuelThis link has some info on the testing : http://www.eaa.org/autofuel/autogas/test_kit.asp

Thanks for the link Ian, that's added lots to my understanding of this. I'll be ordering an EAA tester!

 

HITC:

Great wrap up of the current debate. At first look, the method for testing for alcohol in fuel seems to contradict the science experiment, but...When you think about it, the test says that the layer of water under the fuel will increase if alcohol is present. This suggests to me that the water will absorb the alcohol out of the fuel which will make the water layer seem to increase and the fuel layer decrease. In the experiment we saw that although the water absorbed (some of?) the alcohol, the total volume still increased.

Thanks cs.

 

Yes - I'd completely missed the point that the water pulls the ethanol out of the petrol solution, I thought the ethanol pulled the water into the petrol/ethanol solution. Even so, in the experiment the total volume decreased didn't it? But that still makes the 'formal test' introduced by Ian valid, because the total volume of water plus ethanol increases and the petrol/ethanol volume decreases, showing the presence of ethanol ... I think ... undecided.gif.79f63bc5f64db26a5ec24d3f27260923.gif

 

 

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HITC:

 

Yep. Another way to look at is: If there's no ethanol in the fuel then the water level shouldn't change because petrol and water don't mix.

 

 

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Ok, let me clear couple things:

 

1. water freezing - have you ever tried to freeze a bottle of strong alcohol (vodka, whiskey, etc) - you need a temperature far lower than you would experience anywhere in Australia. At about -20 C vodka usually gets a bit "oily" but still liquid, and that's about 35-40% alcohol, rest water (and for those unaware - ethanol is the alcohol we drink in all alcoholic drinks)

 

2. ethanol absorbing water - out of wiki: "Mixing equal volumes of ethanol and water results in only 1.92 volumes of mixture." So yes, ethanol will absorb some of the water or rather the mixture of alcohol and water will be of smaller volume than a sum of both, but still much bigger than any of them alone. So the described test will still work, as ethanol mixes better with water than with petrol, it will transfer from fuel into the water and you'll be able to see those 2 liquids separated.

 

3.

 

If the fuel you test already has some water absorbed what effect would that have? You are only testing for the presence of ethanol aren't you Ian? Nev

If you have water in your fuel that water will show as droplets at the bottom of the tank. Even if you do have water mixed in the fuel and do this test, the water will settle at the bottom of your container raising the initial water level, thus indicating a false alcohol content (if your fuel had no alcohol in it) or will just give you a higher alcohol percentage value if you do have alcohol in it.

 

Also since E10 fuel have 10% alcohol any water mixed with the fuel shouldn't get too much bearing on the test result itself.

 

As to the effect of all this on engine performance - I have no idea, but I assume since water won't burn you will effectively have less fuel in your cylinder for the same amount of air, and also you'll have water absorbing some of the explosion energy, so I'd guess your engine power will be reduced.

 

 

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You need enough FUEL to use all the oxygen. Non burning substances have a complex effect. To change them to vapour needs the latent heat of vaporisation to be added so this reduces the temperature of the gas but MASS is added too. There are now more molecules to bounce against each other and the container surfaces, so there is more force on the piston. It's not all minus.

 

In your discussions don't confuse dissolving with mixing. A "mixture" is easy to understand. and you get something with the properties of both (or more, if there is more than 2). Example the freezing point of ethanol and water mixed drops. Some dissolving gives or takes heat and has different properties depending on the "concentration" I have simplified this somewhat so may have some technical shortcuts but I hope you get the idea. Concentrated Urea dissolved in water goes cold and caustic soda gets very hot .Nev

 

 

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Cooler burning and slower flamefront equals less power per unit energy and a total consumption rate higher than standard for same performance. E10 will give a shorter range and less performance. Cooler burns will also have a tendacy to promote residue buildup and/or plug fouling.

 

On 2T oils, I'm particularly fond of Castrol 2T 'Race', specced to JASO-FC and about $10/L from Supercheap. Used it for over 12,000km in my Aprilia RS125 which put out 33hp from a tiny 124cc engine - that's 240hp/litre! On teardown saw no excess wear or residue buildup and in fact made it past the maximum recommended replacement interval with no problems whatsoever.

 

Cheers - boingk

 

 

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