[hecilopter]

With all the talk of raising GA fuel tax by .75/gal, I wonder how much effort/reward a company like Superior/ECI could get if they were to design a modified XP-360 engine to specifically run on Ethanol enhanced auto fuel.

I'm not an engine expert, but if they could change/modify appropriate seals, valves, etc. and come out with an XPA-360 (XP, Auto fuel) version of an engine, it seems like it would be a big seller.

Even if they could come out with an engine that you had to put a $5 per tank additive in to make it run on auto fuel, it would still be way worth it in the end if these GA fuel taxes get implemented.

 

[PJSeipel]

I know there are people who haul fuel between their local gas station and the airport, but how practical would that be if all of GA started doing it? The FAA would just come up with a way to tax MOGAS when used in an aircraft. Or they'd decide that the gas tax wasn't working and come up with a "yearly fee" that you had to pay instead. As long as they keep coming up with ways to spend more money, they're going to get us to pay one way or another.

PJ
RV-10 #40032

 

[sadams]

I am no expert, but the problems with ethanol go beyond effects on hoses, seals, and gaskets. If those were the only problems I'm sure it would be relatively easy to to make changes so that you could run on ethanol. The problems include the affinity for water, which can then come out of solution at altitude, causing the engine to run rough or quit, or even freeze causing a complete blockage of fuel. I'm sure others more knowledgable than me will know of other problems with ethanol.

 

[CFI1513840]

Fuel Tax

Another way to attack this problem is to get 500,000+ GA pilots to write to their congressman and senators to voice their opposition to the fuel tax increase. The problem is that the tax slams everyone equally, whether you call ATC once a year or ten times a day. Point out that most General Aviation aircraft do not need the expensive upgrades to the air traffic control system required by the airlines. It is only the demands of the airline hub and spoke system that require an upgraded ATC system. Why should pilots of light aircraft who use an insignificant chunk of ATC services pay for something we don?t need so that the airlines can show a profit despite their poor (some might say criminal) management practices?

For Senators: http://www.senate.gov/general/contact_information/senators_cfm.cfm

For Congressmen: http://www.house.gov/writerep/

 

[c177tx]

May be we will need to throw all the avgas into the Boston Harbor..

 

[Captain_John]

May be we will need to throw all the avgas into the Boston Harbor..

HEY!

It is just now beginning to get cleaner!

Let's throw it into Galveston instead!

CJ

 

[Rick6a]

.....the problems with ethanol go beyond effects on hoses, seals, and gaskets. If those were the only problems I'm sure it would be relatively easy to to make changes so that you could run on ethanol. The problems include the affinity for water, which can then come out of solution at altitude, causing the engine to run rough or quit, or even freeze causing a complete blockage of fuel. I'm sure others more knowledgable than me will know of other problems with ethanol.

I am probably even less knowledgeable than you when it comes to the technical aspects of burning ethanol but Lycoming engines have been modified for Brazilian aircraft and are designed to run on 100% sugar ethanol. According to this source up to 400 light planes there already use modified aircraft engines. http://www.bellona.org/english_import_area/energy/37677

I suspect the real problem is in fashioning an efficient production and distribution system for the U.S. market. Remember in this country, General Aviation in the aggregate accounts for a relatively tiny percentage of petroleum consumption. Somebody has to smell a real profit before investing untold millions of dollars to develop such a project. If it is ever done here, it is likely to be motivated by a commitment to supply 4 wheel vehicles first.

 

[GTechRV]

May be we will need to throw all the avgas into the Boston Harbor..

Oh my god. I just about fell out of my chair.
... while shouting "taxation without representation!" (hey - it fits)

As much as people detest them here, those auto-conversion kits are starting to look a little more practical now. If there is one thing joe-consumer is worried about, its gas prices. While they can pull one over on pilots, I don't think congress would even attempt a nominal raise on mogas anytime soon IMHO.

And if they manage to fanangle some law against mogas in airplanes, heres a great visual: 1920's rum-runners, except with mogas. Get it to the airport from the gas station and your safe!

 

[sadams]

Unfortunately I think the proposed increase also applies to mogas used in aviation: read page 36 here http://www.faa.gov/regulations_polic...l_Analysis.pdf

It says, "Subsection (a)(1) sets the tax rate for aviation gasoline to be 70.0 cents per gallon starting on the transition date, which is October 1, 2008 . . . . . . The 70.0 cent tax rate also applies to auto gasoline used in aviation."

So that will probably kill any savings from buying mogas at an airport. Now, will they have federal agents hanging out at your local airport watching for shady characters pulling gas cans out of their trunks? I guess we'll have to wait and see.

 

[RVbySDI]

I am no expert, but the problems with ethanol go beyond effects on hoses, seals, and gaskets. If those were the only problems I'm sure it would be relatively easy to to make changes so that you could run on ethanol. The problems include the affinity for water, which can then come out of solution at altitude, causing the engine to run rough or quit, or even freeze causing a complete blockage of fuel. I'm sure others more knowledgable than me will know of other problems with ethanol.

Count me as one of those "I am no expert. . ." people too. However, I do read as much as I can about these things. I do not understand where you are coming from with the idea that H2O will somehow "come out of solution at altitude. . .". Can you provide information on your reference to this idea? I am unfamiliar with this idea that water can somehow, at a specific altitude, come out of an alcohol solution. Can you please provide some reference information on this.

What I understand from the information I have read is that the difference in alcohol and gasoline in relation to H2O is in the fact that the water molecules chemically bond to the alcohol molecules. Because of this there is no separation of alcohol from water as there is in petroleum fuels. Meaning you cannot sump fuel and strain out any water that may be in the tank. Further that the H2O will pass through the combustion process bonded to the alcohol and this may cause a decrease in power, etc.

Of course as stated above, I am not an expert in any of this. If I am in error in any of these ideas I would ask that the "experts" reading this post point out my misconceptions and educate me on the correct information on these issues related to alcohol use as a motor fuel.

Concerning the issue of auto fuel burning engines. Would those who have the chemical engineering background provide some information on the real dangers of burning auto fuel in our airplane engines? I understand about detonation, vapor lock and octane levels in relation to compression ratio and the like but what is the most dangerous issue that has to be addressed if auto fuel is burned in a 8.5 to 1 or lower ratio compression engine? What about a 9.0 to 1, a 9.5 to 1 or a 10 to 1 ratio engine? As an example, if I chose to use a fuel injected engine with 9.5 to 1 compression pistons what would be the most critical danger in using auto fuel in such an engine?

Are there measures that will reduce or eliminate any of those dangers? Would running a 91 or 92 octane (based on auto fuel octane measurements) cause significant damage to engines or catastrophic engine failures in flight? What changes to the engine components, parts or design would need to be made before use of 91 octane fuel could be considered safe?

 

[Low Pass]

Count me as one of those "I am no expert. . ." people too. However, I do read as much as I can about these things. I do not understand where you are coming from with the idea that H2O will somehow "come out of solution at altitude. . .". Can you provide information on your reference to this idea? I am unfamiliar with this idea that water can somehow, at a specific altitude, come out of an alcohol solution. Can you please provide some reference information on this.
...

I'm no chemist, but bear in mind that the pressure and temp changes the solubility characteristics of liquids. I don't have the answer, but I can see it as a legitimate concern.

 

[briand]

Count me as one of those "I am no expert. . ." people too. However, I do read as much as I can about these things. I do not understand where you are coming from with the idea that H2O will somehow "come out of solution at altitude. . .". Can you provide information on your reference to this idea? I am unfamiliar with this idea that water can somehow, at a specific altitude, come out of an alcohol solution. Can you please provide some reference information on this.

What I understand from the information I have read is that the difference in alcohol and gasoline in relation to H2O is in the fact that the water molecules chemically bond to the alcohol molecules. Because of this there is no separation of alcohol from water as there is in petroleum fuels. Meaning you cannot sump fuel and strain out any water that may be in the tank. Further that the H2O will pass through the combustion process bonded to the alcohol and this may cause a decrease in power, etc
QUOTE]




I have to agree with you. Gas dryer bought in the little 12 oz. plastic bottles contains ethanol to do exactly what you stated. I doubt altitude would affect anything but I don't know.

 

[rtry9a]

I think the problem is with water turning to ice at higher altitudes w/ much cooler temperatures, not a chemical breakdown.

 

[WSBuilder]

Different States

I used to regularly run 92 octane mogas in my 180 hp (carburated) Mooney and 87 octane in my C140. Oil analysis and frequent plug inspection revealed nothing except cleaner plugs. IAS remained same. CHT's and EGT's the same as with avgas. It was inconvenient using cans, but a truckbed tank with transfer pump would make it easy. Contamination of fuel is an issue with using transfered mogas, but again, the truckbed tank can easily incorporate filters. One thing I don't know much about is the different blends of additives each state requires (thinks best?). I know cars using same brand/different states results in different gas mileage. Biggest issue I ever had with mogas was allowing too low idle rpm (600) which causes slow initial throttle response when ambient temps are >90 F. I just set the idle to 800 and no problem. EAA did extensive research on mogas, albeit in a C150 only and conclusively proved the viability of mogas and the myth of lead additives needed for aircooled engines. Keep it clean and save a bunch of money for flying more!

 

[WSBuilder]

Ice

I think the problem is with water turning to ice at higher altitudes w/ much cooler temperatures, not a chemical breakdown.

There is greater chance of ice when the water is NOT in suspension in the gas, but rests at the bottom of the sump/tank. When intermingled with alcohol the freezing point of the water is lowered and it remains liquid and burns in the cyclinders just fine, maybe slightly leaner. I tried to go flying in freezing temps and the sump drains were frozen. I added a couple ounces of alcohol to the tank and it unfroze the drains in a few minutes. You can use denatured alcohol or IPA from the store.

 

[joeboisselle]

If the new fuel tax is implemented the gas at my airport would be pushing the $6 a gal. range. That'd be $180 to top off my rv-4. As far as an extra hike in mogas taxes, you're never going to see it at $6 without the whole contry going into some sort of anarchy. I too am no expert, but I play one in my hanger... if you could replace any gaskets that might be damaged by mogas with gaskets that are made to be used with mogas, you shouldn't have a problem. (?) Also, a change in magneto (or what have you) timing, you should be able to use at least a 92 octane mogas with minimal or no detonation right?

 

[jiminy]

How do I build for future fuels compatibility

So, what in a current wing tank for a RV series plane needs to change to support MOGAS/Ethanol fuels as well as 100LL? Seems to me that the piping valves etc would be easily switched as they are more accessible than the insides of a tank..
Is the sealant compatible?
JD

 

[WSBuilder]

Materials Testing

So, what in a current wing tank for a RV series plane needs to change to support MOGAS/Ethanol fuels as well as 100LL? Seems to me that the piping valves etc would be easily switched as they are more accessible than the insides of a tank..
Is the sealant compatible?
JD

Great question. Anybody have some cured Pro-Seal they could immerse in alcohol and moniter for swelling or tensile breakdown?

 

[Greenley]

From what I understand, the issues surrounding gaskets, hoses, etc. are all related to old materials that we don't have in modern kitplanes, and junk in the fuel tanks that couple be broken loose by the ethanal and cause problems has not had much time to accumulate in new planes. What that leaves is the possibility at altitude of water coming out of solution bacause of cooling of the fuel. I have been flying mogas for 2 years and never seen this, but at higher altitudes maybe it is more likely. If so, why not simply put in a larger gascolator with a glass bowl so that you can check for that easily before every flight segment? I don't think even if water comes out it would be much so would this be a viable answer?
Bill Greenley
soon to be RV-10 builder

 

[RVbySDI]

I think the problem is with water turning to ice at higher altitudes w/ much cooler temperatures, not a chemical breakdown.

Well, the previous post that my reply is in reference to suggested that there would be a chemical breakdown at altitude. To address your statement, an alcohol solution is less susceptible to freezing than is pure water. Think about that radiator solution in your liquid cooled automobile. If that radiator were full of H2O it would freeze anytime that radiator reached 32 deg F. Mix a 50/50 solution of alcohol and water and the solution freezing point will drop down to far below freezing. So I still do not see where water that has bonded with alcohol can present a freezing risk at whatever altitude we fly.

If so, why not simply put in a larger gascolator with a glass bowl so that you can check for that easily before every flight segment? I don't think even if water comes out it would be much so would this be a viable answer?

This would not be a solution for alcohol based fuel as there would be no separation of water to see in the gascolator. The water would be bound to the alcohol and not separate from any of the fuel in the tank or the gascolator. This is one of those things "mired in very old, well set beliefs" that I refer to below. If we cannot see it how do we know for sure it is not there waiting to cause us problems? So it is very important that we be able to see it in the fuel somehow.

if you could replace any gaskets that might be damaged by mogas with gaskets that are made to be used with mogas, you shouldn't have a problem. (?) Also, a change in magneto (or what have you) timing, you should be able to use at least a 92 octane mogas with minimal or no detonation right?

These changes you mention are exactly the type of information I am interested in reading about. I have a hard time believing that there are such fundamental differences between an internal combustion (IC) engine that is liquid cooled or air cooled that propels a vehicle on the ground and an IC engine that is liquid cooled or air cooled that propels a vehicle in the sky.

I am interested in specific information such as you mention concerning the necessary changes of materials, practices, behaviors, designs or whatever else anyone can think of that would be necessary to allow us to use auto fuel. It appears to me that the arguments against the use of auto fuel are mired in very old, well set beliefs from those who have lived their entire aviation lives under a specific system that taught them that there is only one safe way to aviate. I cannot believe that the fuel in the tanks at the local gas station is inferior to that in the tanks at the air field. I really do not see how this can be.

For all those experts reading this post please continue posting your advice, opinions, facts, figures concerning this issue.

 

[RVbySDI]

So, what in a current wing tank for a RV series plane needs to change to support MOGAS/Ethanol fuels as well as 100LL? Seems to me that the piping valves etc would be easily switched as they are more accessible than the insides of a tank..
Is the sealant compatible?
JD

In my opinion it would be an issue of assurance that the proseal sealant (or whatever type used) is compatible with an alcohol based solution. Also, any gasket material used in the fuel lines, connector plates, sensor probes, valves would have to be compatible with alcohol as well. As far as the petroleum based auto fuel vs the petroleum based avgas I cannot see where there would be any differences in the way these two fuels would react to any of the materials used.

 

[WSBuilder]

I cannot believe that the fuel in the tanks at the local gas station is inferior to that in the tanks at the air field. I really do not see how this can be.

For all those experts reading this post please continue posting your advice, opinions, facts, figures concerning this issue.

Not an expert, but just recalling my experiences...

The volume of gas sold at a given airport may be much less than at the local Citgo. Octane levels degrade fairly quickly and tank contamination may turn 100LL into something less.

Not all 92 octane mogas contains alcohol. I'll have to refresh my memory which ones don't. Anyone?

Keep the two issues clear: mogas: good (at least for 200 hp and under), effect of constant diet of alcohol on a/c engine parts: ?

 

[Lycosaurus]

So, what in a current wing tank for a RV series plane needs to change to support MOGAS/Ethanol fuels as well as 100LL? Seems to me that the piping valves etc would be easily switched as they are more accessible than the insides of a tank..
JD

One notable item about our fuel system design, in comparison to automotive systems, is that the latter is sealed (relatively). Less risk of condensation, and therefore, moisture being absorbed by the alcohol.

Question is: How would you go about designing a sealed fuel system for aircraft? Haven't seen one yet (that is light).

Some interesting reading material, for those who are so inclined:

Water phase separation (nice read):
http://www.epa.gov/OMS/regs/fuels/rfg/waterphs.pdf

Autogas vs. Avgase (Part I)
http://www.aviationfuel.org/autogas/articles/Autogas%20vs%20Avgas.pdf

Autogas vs. Avgase (Part II)
http://www.aviationfuel.org/autogas/articles/Autogas%20vs%20Avgas%20Part%202.pdf

 

[joeboisselle]

Not all 92 octane mogas contains alcohol. I'll have to refresh my memory which ones don't. Anyone?: ?

I think Citgo and Arco are the only two in my area that have alcohol in all grades of gas. Arco for sure, they have a placard on every pump.

Anybody have some cured Pro-Seal they could immerse in alcohol and moniter for swelling or tensile breakdown?

I've got a cured blob of it, I can get some ethenal mogas for a week long soak if you'd like. Maby throw in some aviation grade gaskets with it. And set it in the freezer?

 

[WSBuilder]

I've got a cured blob of it, I can get some ethenal mogas for a week long soak if you'd like. Maby throw in some aviation grade gaskets with it. And set it in the freezer?

If you've got enough to do it, put some in pure alcohol as an accelerated test and then measure/feel it daily. The rest put in ethenal. Room temperature would also accelerate the test.

Have your report on my desk Monday!

 

[joeboisselle]

Now when you say pure alcohol, do I need to dip into my wifes bicardi 151, or what're you thinkin?

 

[erich weaver]

RV by SDI wrote:

"What changes to the engine components, parts or design would need to be made before use of 91 octane fuel could be considered safe?"


GAMI's electronic ignition that is awaiting certification is supposed to allow use of mogas in aircraft engines. See http://www.gami.com/prism.html


erich weaver

 

[Geico266]

I have been running a 50/50 mix of 100LL & 92 premium MOGAS (no alcohol) from a local Shell Oil station. My tank is a 100 gallon tank on a trailer with a 12V transfer pump I tow to the airport. That saves me $80 per 100 gallons of fuel. I fly about 150 hours a year that's a savings of $1,100 a year. That's hanger rent and condition inspection.

I have had small amounts of water in the sumps, never even enough to form a drop, or cause problems and I fly to 0F. Never any water in the gasolator. I assume it's condensation, but I keep my tanks full for storage all the time. Any comments about this would be appreciated.

There is a fleet of 4 RV4's at Tea, SD (KY14) that use nothing but 100% ethanol. They fly for the state ethanol board. Pretty interesting set up. The use standard Lycombs with 100LL primers. The engines won't start on ethanol, so they have to have the 100LL to get going then switch.

http://ezinearticles.com/?Flying-Aircraft-on-Ethanol&id=25803

Interesting conversation as always. Keep the info coming!

 

[Kyle Boatright]

I think we will see 92 UL at the avgas pumps one day, but that day may be waay into the future, because FBO's don't want to inventory three fuels (92 UL, 100LL, and Jet A). The problem with 92 UL is that some of the big-boy piston aircraft can't use that fuel, and those big boys represent the FBO's best chance to sell 100+ gallons of fuel at any one time.

I do not *ever* expect to see ethanol blends at aviation fuel pumps. The seal degradation issues are bad enough, but ethanol also has a lower energy content than gasoline. This means you suffer reduced range at a given speed, because you need to feed more fuel through the engine. This means re-jetting your carb, or at least adjusting the mixture, and doing the same kind of thing to FI systems, unless you want the engine to run lean all of the time. And that means you'll be over-rich if you run non-ethanol fuels. Damned if you do, damned if you don't. I don't believe the FAA is going to allow piston aircraft to be flown on fuels with different operating characteristics. That's asking for trouble.

Add to that the cost and hassle of transitioning all of the aircraft and aviation fuel distribution systems over to ethanol blends, and it'll be easier on everyone for the FBO's to pump non-ethanol 92UL.

And that will leave the big boys flying 300 HP Cherokee 6's, Malibu's, and several other highly stressed engines out in the cold.

 

[Geico266]

I have to ask a question here.

I thought I had gotten some bad 100LL at a cross country fuel stop and I called the FAA to see if they would want to check it out. Their comment to me was they have nothing to do with fuel quality. I about fell over, but that is what they said. They have no control or could care less about filter, tank, pump, maintence, ect.

Does anyone know for sure the FAA even cares about fuel quality?

 

[Low Pass]

I have to ask a question here.

I thought I had gotten some bad 100LL at a cross country fuel stop and I called the FAA to see if they would want to check it out. Their comment to me was they have nothing to do with fuel quality. I about fell over, but that is what they said. They have no control or could care less about filter, tank, pump, maintence, ect.

Does anyone know for sure the FAA even cares about fuel quality?

AFAIK, the FAA doesn't have anything to do with quality of fuel, and *I* for one darn sure don't want them in that segment of the business!! Buy name-brand fuel at reputable FBOs is my rule.

 

[WSBuilder]

Good Idea!

Now when you say pure alcohol, do I need to dip into my wifes bicardi 151, or what're you thinkin?

YOU can take a dip in the Bicardi AFTER you put the glob in some IPA (isopropol). A thorough test would use all different types, de-natured, etc. but IPA has a high solvent quality and will bracket on the extreme end. Since no one would pour pure IPA into their fuel tanks it's not relevant to anything real world, but it will tell you that there's a reaction potential. The other glob in the eth-fuel will be a real-world test, but it probably needs to be on a shelf somewhere for 6 months or longer. Thanks for doing this!

 

[ddurakovich]

Huh???

I'm sooooooo confused

I've followed this thread from the beginning when it was a simple question regarding using ETHANOL enhanced fuel in aircraft, watching it quickly morph into pure ethanol will not drop out at low temps, to ?????

My $0.02.... worth every cent you paid for it!

Ethanol enhanced fuels will drop water/alcohol with decreasing temperatures, but only AFTER the absorption of, or contamination with water. The higher the water contamination level, the more likely that the material will freeze. However, I would guess that the engine will quit from fuel starvation due to the high water content long before it freezes. Pretty much same effect in any case

Pure alcohol (Methyl, Ethyl, Isopropyl) will not freeze (within our operating parameters), and upon contamination with water will not kick out anything, right up to the point when the mixture freezes! However, the engine will have quit long before that due to fuel starvation as a result of the high water content

While testing gaskets and rubber seals for compatibility with alcohol is a start, the alcohol is probably the least of your worries in auto fuel. Most auto fuels today contain oxygenates to improve combustion, octane rating, etc. The most common is MTBE (methyl tertiary butyl ether), but other analogs are becoming popular. The ethers are SUBSTANTIALLY more aggressive solvents than the primary alcohols. This is what needs to be evaluated, but then you need to know what will be in there, which varies by geography, current legislation, etc.

I'm lucky in that the gas station across from the airport sells pure gasoline (no ethanol). I'm just not sure at this point if my O-360 at 180 HP will tolerate 93 Octane Auto, but I will find out soon! After that, I'm going to be looking hard at potential diesels, because I really believe that that will eventually be the only economic/technical alternative to Real Aviation Fuel that I'll be able to get my hands on.

 

[RVbySDI]

I have had small amounts of water in the sumps, never even enough to form a drop, or cause problems and I fly to 0F. Never any water in the gasolator. I assume it's condensation, but I keep my tanks full for storage all the time. Any comments about this would be appreciated.

Lycosaurus' previous post with links to several articles on this subject is very informative. The water phase article mentions the issue of water in 90/10 blended gasoline. It is a very interesting read. It does state that the alcohol in this blend can hold up to 3.8 teaspoons of water per gallon of fuel. That is a substantial amount of water that I don't think any of us would ever be exposed to. It also discusses the idea of condensed water and what it would take to have a measurable amount of water accumulate in a gas tank. I might suggest you click on his link and read the article.

Some interesting reading material, for those who are so inclined:
Water phase separation (nice read):
http://www.epa.gov/OMS/regs/fuels/rfg/waterphs.pdf

Autogas vs. Avgase (Part I)
http://www.aviationfuel.org/autogas...0vs Avgas.pdf

Autogas vs. Avgase (Part II)
http://www.aviationfuel.org/autogas... Part 2.pdf

Thanks Lycosaurus for the links to those articles. That is the type of information that I want to examine when evaluating this type of stuff.

 

[WSBuilder]

I'm just not sure at this point if my O-360 at 180 HP will tolerate 93 Octane Auto, but I will find out soon!

Like I said, my Mooney 0-360 did just fine year-round with 92 autogas, but each installation is different. I guess keeping avgas in one tank and ellicit car gas in the other might mitigate your initial concerns.

 

[joeboisselle]

It does state that the alcohol in this blend can hold up to 3.8 teaspoons of water per gallon of fuel. That is a substantial amount of water that I don't think any of us would ever be exposed to.

There's been alot of talk of water in e-gas on this thread, isn't this solved by sumping your tanks, and draining your gascolator?

 

[sadams]

It does state that the alcohol in this blend can hold up to 3.8 teaspoons of water per gallon of fuel. That is a substantial amount of water that I don't think any of us would ever be exposed to.

Under most conditions I agree that this is more water than you are likely to get in your tank. The problem is, how do you know how much water has made it's way into the fuel before you got it into your tank? Again, probably not that much, but you just don't know for sure.

 

[ddurakovich]

There's been alot of talk of water in e-gas on this thread, isn't this solved by sumping your tanks, and draining your gascolator?

The problem is thus:

Avgas has very little capacity to hold water, in the parts per million neighborhood. Even if temperatures go WAY down, there is little water to drop out after the initial "sumping".

Gasahol on the otherhand can hold quite a bit. Even after "sumping" the water/alcohol, at altitude it can drop substantially more if water is present. Without actually running the water content, you won't actually know

 

[RVbySDI]

There's been alot of talk of water in e-gas on this thread, isn't this solved by sumping your tanks, and draining your gascolator?

Well, no it isn't going to be solved by sumping because there will be no water showing up in the gascolator in an alcohol/gasoline fuel mixture. This is the issue with alcohol/gasoline fuel and that ever present "That is the way we have always done things" idea. With an alcohol mixture in the fuel there would not be any water to sump unless, according to the previously mentioned water phase article, the amount of water in the fuel mixture exceeded 3.8 teaspoons/gal. Up to that point the water would be in solution with the fuel and therefore would not be visible in the gascolator or in your fuel sampler.

 

[David-aviator]

There's been alot of talk of water in e-gas on this thread, isn't this solved by sumping your tanks, and draining your gascolator?

Nope. Alcohol absorbs water, you won't know it is there.

I don't think it is a huge issue with fuel injection. A little water will go through the system. Freezing could be an issue with a ton of water, but I don't know for sure. If the airplane is tied down outside through a heavy rain, like at an air show, water definitely is an issue. I tape the fuel caps shut to make sure no water gets in.

I do sump drain now and then, but I have never found a drop of water. With Subaru, running at 32 psi, I don't think about it much. It might even help cool the cylinder heads.

 

[RVbySDI]

Under most conditions I agree that this is more water than you are likely to get in your tank. The problem is, how do you know how much water has made it's way into the fuel before you got it into your tank? Again, probably not that much, but you just don't know for sure.

True, but when is the last time you were concerned with whether you had water in the gas tank of your car? When was the last time you tested for water in the gas tank of your car?

Again using the water phase article as reference (http://www.epa.gov/OMS/regs/fuels/rfg/waterphs.pdf), if the water is in solution with the fuel mixture there will be no damage to the engine and little, if any, performance change will be noticed, except perhaps a leaner fuel mixture that may exist. So unless the water is in the tank as a separate phase than the fuel the water will pose little problem for the engine. It can be a different story if you exceed the solubility of the water/fuel mixture and you send a slug of pure H2O through the cylinder. But again, this is highly unlikely in an alcohol/gasoline mixture as this mixture of fuel can hold more H2O in solution than can a pure gasoline fuel (.15 teaspoons/gal).

All of this worry about water in the fuel is really a non-issue. The aviation community has been concerned about it in the past because the gasoline we have used in the past had a very low tolerance for water in the fuel (.15 teaspoons/gal). Today, that is not so much of an issue with the oxygenated fuel (.5 teaspoons/gal) that can handle more water than in the past. And, with the advent of alcohol being used as an oxygenate for fuel the tolerance for water in the fuel is even greater than before (3.8 teaspoons/gal). Again, it is a non-factor except in extreme situations.

The other issues of lower BTU meaning fewer miles(hours)/gallon and perhaps the issue of vapor lock sound like more important issues than whether there is water in the fuel or not.

 

[David-aviator]

No drum beat...just an observation.

I am not financially connected with the EGG factory so this is just an observation based on experience, not otherwise motivated to say anything but to share information. In fact, I pay full price for everything I buy from them.

All engines are not totally perfect. The issue of mogas and Lycoming, power and Subaru are examples of it. I would like to be going a little faster, but that down side (which is going away with late engines) is more than off set by the advanced technology of the engine, especially with regard to fuel.

The H6 has a compression ratio of 10.7:1 and is very happy with 100LL or any mogas, with or without alcohol. This is possible because of knock sensing. I like to use 87 mogas for local flying because it is relatively cheap and always fresh - they sell so much of it. I know the ECU adjusts timing because I've measured it at take off power. 87 mogas results in a slightly retarded fire vrs 100LL. Obviously there isn't as much power but I can not detect it. The airplane comes off the ground quick.

I do believe the trend toward auto engines will continue because of the fuel issue more than anything else. As I mentioned in another thread, it is not a free ride, though. The pilot must understand vapor pressure and the limits of using mogas whether using it in an auto engine or Lycoming.

 

[sadams]

True, but when is the last time you were concerned with whether you had water in the gas tank of your car? When was the last time you tested for water in the gas tank of your car?

Again using the water phase article as reference (http://www.epa.gov/OMS/regs/fuels/rfg/waterphs.pdf), if the water is in solution with the fuel mixture there will be no damage to the engine and little, if any, performance change will be noticed, except perhaps a leaner fuel mixture that may exist. So unless the water is in the tank as a separate phase than the fuel the water will pose little problem for the engine. It can be a different story if you exceed the solubility of the water/fuel mixture and you send a slug of pure H2O through the cylinder. But again, this is highly unlikely in an alcohol/gasoline mixture as this mixture of fuel can hold more H2O in solution than can a pure gasoline fuel (.15 teaspoons/gal).

All of this worry about water in the fuel is really a non-issue. The aviation community has been concerned about it in the past because the gasoline we have used in the past had a very low tolerance for water in the fuel (.15 teaspoons/gal). Today, that is not so much of an issue with the oxygenated fuel (.5 teaspoons/gal) that can handle more water than in the past. And, with the advent of alcohol being used as an oxygenate for fuel the tolerance for water in the fuel is even greater than before (3.8 teaspoons/gal). Again, it is a non-factor except in extreme situations.

The other issues of lower BTU meaning fewer miles(hours)/gallon and perhaps the issue of vapor lock sound like more important issues than whether there is water in the fuel or not.

If you get a bunch of water in fuel without EtOH, it will separate out. You can sump it out, and the fuel will be essential water free. Add EtOH and things are different. Say you fill your tanks at 15 deg C, and there is 3 tsp of water per gallon in the fuel. You don't know how much water is there because you can't sump it out. So everything looks good and you take off and climb to altitude where it is now 2 deg C. Now instead of holding 3.8 tsp/ gal, the EtOH can only hold 0.2 tsp/gal. Now if you have 30 gal of fuel, you now have about a pint of water separated out of the fuel, which I believe is enough to ruin your day. Maybe not a major issue, but it is one to consider.

 

[garnt.piper]

Mogas tax

The Mogas substitution 'problem' was sidestepped here (Australia) a few years ago by removing the extra tax on Avgas, so that it was not much dearer than Mogas. The incentive for people to run Mogas disappeared. That said, we have a pretty big tax on Mogas anyway, so Mogas is now AUD$1.20-1.30/litre, while Avgas is AUD$1.45/litre! Ag operators tell me that in the same period Avtur has gone from AUD$0.45/litre to about AUD$1.30/litre, many are wondering why they went to turbine aircraft.
Our CASA (FAA equivalent) is on the way to cost recovery also, as is ASA (the ATC provider). We are saying the same things your are, why should GA pay for a system we don't use or need. We really only have two domestic airline operators in this country, plus international carriers, they obviously don't want to foot the whole bill.

 

[joeboisselle]

If you've got 3 tsp of water per gallon, and you've got say, 30 gallons on board, that's 16 Fl Ounces (1 pint, 2 cups .5 quarts 1/8 gallon) of water in your tanks. (yeah, I used my wifes kitchen coversion thingy) so if you're buring 10 gph (it's a good round number) that's .167 gallons of gas with .05 tsp of it being water, per minute. I agree, not a major issue, but one to consider.

 

[RVbySDI]

If you get a bunch of water in fuel without EtOH, it will separate out. You can sump it out, and the fuel will be essential water free. Add EtOH and things are different. Say you fill your tanks at 15 deg C, and there is 3 tsp of water per gallon in the fuel. You don't know how much water is there because you can't sump it out. So everything looks good and you take off and climb to altitude where it is now 2 deg C. Now instead of holding 3.8 tsp/ gal, the EtOH can only hold 0.2 tsp/gal. Now if you have 30 gal of fuel, you now have about a pint of water separated out of the fuel, which I believe is enough to ruin your day. Maybe not a major issue, but it is one to consider.

I am not sure where you are getting 0.2 tsp/gal at 2 deg C. According to the water phase article I am referencing, when a 90/10 ethanol blended fuel is at 2 deg C (35.6 F) that fuel mixture can hold up to 3.079 teaspoons of water per gallon of fuel in suspension. As I stated earlier, that would be a lot of water in the fuel before it would separate out.

Your statement that there were 3 teaspoons of water per gallon in the fuel at fill up would imply that this hypothetical pilot has just filled up from a tank that has some serious contamination issues. It would be my contention that any fuel tank that had that much water contamination would be more of a problem for fuel without alcohol than it would for those fuels with alcohol in it. It would most definitely be a bad tank of gas but it would be much worse without the alcohol even if you could see the water.

The only contention of merit with this comment is that without the alcohol a pilot would see the water when the fuel tank was sumped which would allow him to then act on that fact and possibly remove all of that water. However, if he could not remove all of that water his plane would be in some serious hurt. Without alcohol in the fuel the amount of water that could be maintained in suspension in the fuel would be far lower than in a blended fuel. So the risk would be greater for running this contaminated fuel without alcohol in the mix than it is with it. In your example of flying at 2 deg C (35.6 F) pure gasoline would only be able to hold .15 teaspoons of water in suspension and oxygenated fuel using MTBE would only hold .32 teaspoons before the water would separate. With either one of these fuel mixtures your 3 teaspoons of water are going to cause some serious problems. With the ethanol blended fuel those 3 teaspoons will just be burnt in the combustion process because at 2 deg C that blended fuel could still hold up to 3.079 teaspoons of water in suspension. The water would not separate out at this point. It is water in a separate phase than fuel that is the "scary" part of water in the fuel. As long as the water does not separate then there is little chance of a problem (I do say little instead of no risk because I do acknowledge that no endeavor is without risk. If there were enough water in the mixture to cause a drastic increase in the leaning of the fuel for example. Higher temperatures could result in some damage, if those higher temperatures were not dealt with and managed.)

My contention is that as long as the H2O remained in suspension while it was being consumed by the combustion process it would be a non-factor, at least concerning the idea of whether it would damage the engine or cause a catastrophic engine failure in flight. Further, since more water can be held in suspension in an alcohol solution than can be held in a pure gasoline or in a fuel mixture that uses some oxygenation agent other than alcohol (MTBE), then this fear would be unfounded when flying with a fuel mixed with alcohol.

With a higher ratio of alcohol to gasoline these numbers should be even higher and would mean that there would have to be an extremely serious water contamination occur with the fuel before it would begin to cause a serious problem.

Again, I say this because I feel that water contamination is not as serious an issue with blended fuels as is the issues of fuel consumption and vapor lock.

 

[rv6ejguy]

I've run street and race cars on M85 (85% methanol) and never worried about water in it. It absorbs what it can, any left over in an aviation situation is drained out on the preflight right.

The Po-seal could be a problem. tests will tell. The rest of the fuel system with small ethanol blends is not a big problem in my view. Go to Viton elastomers and gaskets and anodized aluminum. I found one rubber pickup hose which swelled to about 4 times its size. Replaced that and had no other problems. Used Bosch and Denso injectors and Bosch pumps- standard issue. Don't use bonded paper fuel filters however.

A little water going through the engine is no problem, ran water injection for years putting massive amounts through. Cleans off the pistons and chambers.

With fuel injection and proper fuel pump pickup layout, the vapor pressure is a minimal concern too. With carbs and high fuel lifts on a hot day, watch out.