Future of 100LL AvGas

[jmartinez443]

Originally Posted by Randy Walls

I find it hard to belive that 10% Ethanol in unleaded is so bad. If all of the horrible things that are supposed to happen are true, Interstate 90 should be littered with dead cars all winter. I wish someone smarter than me would seriously evaluate the effects of E-10 fuel in airplanes. I know higher concetrations of ethanol or metanol in concentration can cause problems but I really wonder about 10% ethanol.

The problem with that arguement is that cars are not subjected to temperature and pressure changes the same way that aircraft are.

Also, ethanol absorbs water which is released under the right circumstances. Not sure you'd like iced over fule lines at 10K.

I was watching a history channel show on Pikes Peak racers yesterday, and yes those cars were running special fluids to prevent breakdowns. For instance, normal break fluids would boil at the ambient pressure at 14k feet.

You can find some interesting articles about ethanol in airplanes at http://www.aviationfuel.org/autogas/articles/. This site is run by the EAA.

[David-aviator]

Originally Posted by jmartinez443

The problem with that arguement is that cars are not subjected to temperature and pressure changes the same way that aircraft are.

Also, ethanol absorbs water which is released under the right circumstances. Not sure you'd like iced over fule lines at 10K.

Seems like in our society, anyone who gets an article published is an expert on the subject and we then use that information as gospel for the rest of eternity.

If ethanol absorbs water why don't fuel systems freeze up when the temperature is below 32F? When's the last time your auto fuel system froze up? If it doesn't freeze up in an auto, why would it in an airplane?

I just don't buy into boogy man information that gets restated and restated and meanwhile some of us are out flying around OK with the stuff. If you've had a problem with it, report it. But lets stop reporting what has not been proven or backed up by experience.

[the_other_dougreeves]

Originally Posted by David-aviator

If ethanol absorbs water why don't fuel systems freeze up when the temperature is below 32F? When's the last time your auto fuel system froze up? If it doesn't freeze up in an auto, why would it in an airplane?

Basically, because the freezing point of the gasoline/water/EtOH mixture is less than 32F. Adding EtOH to water is like adding antifreeze to water - it depresses the freezing point. 50/50 water / antifreeze mixtures don't freeze at 32F, right? EtOH tends to keep water in solution rather than letting it separate out into a separate phase. EtOH can be like Prist - it keeps the water in solution rather than letting it separate out and form ice in the fuel system (generally regarded as Bad).

Mogas is formulated for specific climatic conditions. This means changing the vapor pressure among other things. This blend is frequently updated at the refinery and/or gasoline terminal where trucks fill up to take gasoline to stations.

I suspect that during colder conditions, some amount of additive is used to keep water in solution (like Prist with jet fuel). If you took Mogas that wasn't blended for cold conditions, added water and then cooled it to, say 10F, you might get ice formation as the fuel is atomized or even out of bulk solution.

TODR

[jmartinez443]

Originally Posted by David-aviator

I just don't buy into boogy man information that gets restated and restated and meanwhile some of us are out flying around OK with the stuff. If you've had a problem with it, report it. But lets stop reporting what has not been proven or backed up by experience.

David, it is true that I have not personally had experience with ethanol-laced fuel in an aircraft. And from your accounts, it seems that everything is fine and you feel comfortable with it. However, that does not invalidate the information in the available literature. Below please find an excerpt from one of the articles I referenced. Take it for what it's worth.

"Now we come to the really hard part: The fuel distribution system in all of the older aircraft. When
the fuel man mistakenly delivered some ethanol-containing fuel to my farm, I had three stalled
tractors and an old pickup that never ran right again. The ethanol fuel ruined all of the fuel hoses,
caused numerous leaks and necessitated the replacement of two fuel pumps and 11 fuel filters.
Now if you think your old aircraft will handle ethanol better than my old tractors, guess again.
Several years ago, another state tried ethanol in one of its Cessna aircraft. In a flight of less than
900 miles, the mechanic claimed that they had to change the composite carburetor float seven
times. There were also leaks and problems from other fuel system components."

[dreamer]

These Lycomings use 100% Ethanol and are certified.
You can convert yours.
See: http://www.aeroalcool.com.br/english/index_en.htm
You can't use cost comparison as they show because it refers to fuel cost in Brazil. But on technical side, there is nothing new on using ethanol in aviation.

[jmartinez443]

Originally Posted by dreamer

These Lycomings use 100% Ethanol and are certified.
You can convert yours.
See: http://www.aeroalcool.com.br/english/index_en.htm
You can't use cost comparison as they show because it refers to fuel cost in Brazil. But on technical side, there is nothing new on using ethanol in aviation.

I don't know about that site; it also claims that Brazilians invented airplanes .

[hevansrv7a]

from:http://www.bp.com/sectiongenericarti...ontentId=57723
Some engines benefit from the use of lead to help protect vulnerable engine valve seats. These could otherwise rapidly wear away, leading to loss of compression/engine failure. However, it must be said the use of lead can also give rise to problems such as spark plug fouling and attack on certain valve metallurgies.

And from:http://en.wikipedia.org/wiki/Avgas
Many general aviation aircraft engines were designed to run on 80/87 octane, roughly the standard for automobiles today. Direct conversions to run on automotive fuel are fairly common and applied via the supplemental type certificate (STC) process. However, the alloys used in aviation engine construction are rather outdated, and engine wear in the valves is a potential problem on automotive gasoline conversions. Fortunately, significant history of mogas-converted engines has shown that very few engine problems are actually caused by automotive gasoline.

And from TC:http://www.tcmlink.com/visitors/care...engoperhdr.cfm
Current aircraft engines feature valve gear components which are designed for compatibility with the leaded ASTM D910 fuels. In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead. The result can be remarkable, with cylinder performance deteriorating to unacceptable levels in under 10 hours.

[David-aviator]

Originally Posted by jmartinez443

David, it is true that I have not personally had experience with ethanol-laced fuel in an aircraft. And from your accounts, it seems that everything is fine and you feel comfortable with it. However, that does not invalidate the information in the available literature. Below please find an excerpt from one of the articles I referenced. Take it for what it's worth.

"Now we come to the really hard part: The fuel distribution system in all of the older aircraft. When
the fuel man mistakenly delivered some ethanol-containing fuel to my farm, I had three stalled
tractors and an old pickup that never ran right again. The ethanol fuel ruined all of the fuel hoses,
caused numerous leaks and necessitated the replacement of two fuel pumps and 11 fuel filters.
Now if you think your old aircraft will handle ethanol better than my old tractors, guess again.
Several years ago, another state tried ethanol in one of its Cessna aircraft. In a flight of less than
900 miles, the mechanic claimed that they had to change the composite carburetor float seven
times. There were also leaks and problems from other fuel system components."

Well, I guess its a good idea not to use it in old equipment. I've heard farmers don't like the stuff but they sure are not shy about producing it for everyone else...

[jonbakerok]

Originally Posted by hevansrv7a

from:http://www.bp.com/sectiongenericarti...ontentId=57723
Some engines benefit from the use of lead to help protect vulnerable engine valve seats. These could otherwise rapidly wear away, leading to loss of compression/engine failure. However, it must be said the use of lead can also give rise to problems such as spark plug fouling and attack on certain valve metallurgies.

And from:http://en.wikipedia.org/wiki/Avgas
Many general aviation aircraft engines were designed to run on 80/87 octane, roughly the standard for automobiles today. Direct conversions to run on automotive fuel are fairly common and applied via the supplemental type certificate (STC) process. However, the alloys used in aviation engine construction are rather outdated, and engine wear in the valves is a potential problem on automotive gasoline conversions. Fortunately, significant history of mogas-converted engines has shown that very few engine problems are actually caused by automotive gasoline.

And from TC:http://www.tcmlink.com/visitors/care...engoperhdr.cfm
Current aircraft engines feature valve gear components which are designed for compatibility with the leaded ASTM D910 fuels. In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead. The result can be remarkable, with cylinder performance deteriorating to unacceptable levels in under 10 hours.

I recently completed what was probably the fourth top-end overhaul on a 1974 Harley Sportster that I bought last year. With 9.5:1 compression and hemi heads, it was designed to run on 97 Octane leaded premium, but it's obviously been run on unlead for at least 30 years. The stock valve seats on this engine are merely ground out of the raw cast-iron heads -- they aren't even steel inserts. Although you can buy "no-lead" hardened valves and seat inserts for it, most people don't bother.

So what did I find when I pulled the heads? The factory original valve seats were still perfectly servicable after normal grinding for a new set of valves. The valves I replaced were NOT hardened "no-lead" valves, and I didn't waste my money on hardened replacements.

So much for "Valve Recession" theory.

[bjustus]

Someone mentioned earlier that alcohol in fuel can hold water in solution to be released later and potentially cause problems in flight.

Hopefully one of you is a chemistry guru and can explain this to me. I'm confused because I thought the test for alcohol was to put a certain amount of water in a container, add the fuel, wait a few minutes and if the water content appeared to INCREASE then you have alcohol? The fuel tester I have is graduated in a way that supports this.