J

joeboisselle

Well Known Member
As per another thread, I volunteered to see what the effects of mogas and alcohol have on proseal and common rubber parts found in aircraft fuel systems. Right now I have proseal soaking in Shell 92 octane unleaded with no alcohol, Bicardi 151 the highest alcohol content substance I could find without driving accross the state :D and Arco 92 octane with 10% ethenal added. I have an old carb I can dis-assemble tomarrow to remove its rubber parts. Any other ideas are welcome...




Here is the gas and alcohol sitting on the can in my shop, I turned the heat up to 75 deg.

 
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Fuel Test

Seems a terrible waste of Bacardi 151 :D Don't blow your shop up in the experiment!!!!
 
Could you get some E85 for a more closely matched test to what we will be using?

Good use for Bacardi though, just don't waste Captain Morgan! ;)
 
They don't sell e85 around here that I know of. If you want to send an ounce or two, I'd try it. I actually felt kinda bad pouring perfectly good rum onto a blob of pro-seal, but there's still plenty left. :D
 
E85 could cause problems

While you may succeed in using E10 in an aircraft engine, E85 will present problems that go well beyond seal compatibility. One of the biggest issues is a vapor pressure that can result in vapor lock under normal operating conditions.

Superior Air Parts offers a certified version of its popular XP-360 Experimental Engine, and this certified Vantage engine is approved for use of 91 octane auto fuel. That certainly sets Superior apart from the rest of the aircraft engine manufacturers, and I would not hesitate to use auto fuel in an XP-360. But, you should note that they do not include gasohol in their approval. The following is from the engine operating manual.

The Vantage series engine can operate and perform at a rated power with unleaded automotive fuel without alcohol of at least 91 Octane. ​
​
​
When operating with unleaded automotive fuel, use only 91 minimum octane premium grade fuel.​
​

 
Joe,
I would suggest you bond the ProSeal to a small piece of 2024-T3. You also need to test how well the Proseal to metal bond holds up in the presence of alcohol.
Charlie Kuss
 
Don't stop with the carb and proseal. Consider fuel senders (Stewart-Warner says "o.k."), gaskets here and there, the various hoses that could be used throughout FWF, o-rings and seals in pumps, fuel valves, tank caps, and gascolators - of all the different manufacturers that might be found in RVs - and aluminum and its various alloys. You can eliminate many test samples by knowing the material, but it's a ponderous job any way you approach thoroughness. Don't overlook time; some damage can take months to develop.

You might find it easier and more accurate to list every material along your fuel path (my gut says there's ~50) by extraction from parts and material lists from manufacturers (then hope they maintain conformance forever). Scratch off known goods, like viton and teflon, then inquire of material authorities on the doubtful or unknown.

Good luck.

John Siebold
 
RV7ator said:
Don't stop with the carb and proseal. Consider fuel senders (Stewart-Warner says "o.k."), gaskets here and there, the various hoses that could be used throughout FWF, o-rings and seals in pumps, fuel valves, tank caps, and gascolators - of all the different manufacturers that might be found in RVs - and aluminum and its various alloys. You can eliminate many test samples by knowing the material, but it's a ponderous job any way you approach thoroughness. Don't overlook time; some damage can take months to develop.

You might find it easier and more accurate to list every material along your fuel path (my gut says there's ~50) by extraction from parts and material lists from manufacturers (then hope they maintain conformance forever). Scratch off known goods, like viton and teflon, then inquire of material authorities on the doubtful or unknown.

Good luck.

John Siebold
Click to expand...

John
Seals and O-rings made from Viton or other Flourosilicones are impervious to alcohol and other additives found in unleaded fuels. Don at Airflow Performance told me that his fuel injection components use these seals. Late model Bendix/Precision Airmotive fuel injection systems with the orange colored seals are also made from Flourosilicones. The older style seals are black in color.
Charlie Kuss
 
Dave Cole said:
While you may succeed in using E10 in an aircraft engine, E85 will present problems that go well beyond seal compatibility. One of the biggest issues is a vapor pressure that can result in vapor lock under normal operating conditions.

Superior Air Parts offers a certified version of its popular XP-360 Experimental Engine, and this certified Vantage engine is approved for use of 91 octane auto fuel. That certainly sets Superior apart from the rest of the aircraft engine manufacturers, and I would not hesitate to use auto fuel in an XP-360. But, you should note that they do not include gasohol in their approval. The following is from the engine operating manual.

The Vantage series engine can operate and perform at a rated power with unleaded automotive fuel without alcohol of at least 91 Octane. ​
​
​
When operating with unleaded automotive fuel, use only 91 minimum octane premium grade fuel.​
​
Click to expand...

I bought a gallon of E85 last summer just to check its vapor pressure with the Hodges system. It came in at over 50 kPa, almost as good as 100LL at 62. Most mogas come in at 45-50, except winter blend in late spring.

With 100's of millions of autos in this country doing just fine on mogas, it is amazing no one has figured out how to set up a Lycoming to run on it without concerns of melting seals and other issues. The big problem around here is finding fuel without alcohol. But is it really that much of a boogy man? I have been using fuel with it for over a year, all year 'round, and have found the vapor pressure very safe for flight. It may be somewhat less than with no alcohol, I don't know for sure, but it has tested above the safe line with the Hodges meter.

So far, after using mogas with alcohol and occassional 100LL since 2003, the pro-seal is holding up OK.
 
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Dave Cole said:
While you may succeed in using E10 in an aircraft engine, E85 will present problems that go well beyond seal compatibility. One of the biggest issues is a vapor pressure that can result in vapor lock under normal operating conditions.

Superior Air Parts offers a certified version of its popular XP-360 Experimental Engine, and this certified Vantage engine is approved for use of 91 octane auto fuel. That certainly sets Superior apart from the rest of the aircraft engine manufacturers, and I would not hesitate to use auto fuel in an XP-360. But, you should note that they do not include gasohol in their approval. The following is from the engine operating manual.

The Vantage series engine can operate and perform at a rated power with unleaded automotive fuel without alcohol of at least 91 Octane. ​
​
​
When operating with unleaded automotive fuel, use only 91 minimum octane premium grade fuel.​
​
Click to expand...
All the negative vibes in the aviation world concerning alcohol as an additive in fuel needs to have a caveat associated with it. Now mind you, lest I start getting hammered on this subject, I want to say the below is my opinion only. You know the saying. . . "they are like *******'s, everyone has one!"

Well, here is my opinion on this line of thinking with Superior. It is liability and money that drives that type of statement. It is not driven by the technical issues associated with burning alcohol as a fuel in these or any other engines.

Companies that are in the business of making money are not going to go out on a limb with something new that they do not feel has been tested enough to cover their butts in case there is something that goes wrong with the new "whatever".

Superior is going to say the above referenced statement in their documentation just as Lycoming has said for decades now not to run engines LOP. Even though there is ever increasing anecdotal and documented proof showing that LOP operation is not as detrimental to an engine as was once thought Lycoming still states in their documentation not to run LOP. Why? Because financially they cannot afford to be wrong. So they err on the side of being conservative. Running LOP may save money on fuel for the owner but stating that it is ok is not going to ever benefit Lycoming in any way.

Not until there is indisputable proof from decades of operations in that environment will companies such as these succumb to the "new ideas" out there. In fact, by the time these companies accept the "new idea" it really is no longer new at all. They have too much at stake to jump on any new band wagons.

Superior's release of the 360 engine that burns 91 octane mogas fits this mold. Their entrance into the mogas burning engine business was not done in the infancy of research into that idea. It is being initiated in the mature stages, one might even say in the twilight, of the notion that burning mogas is ok.

They "all of a sudden" feel it safe enough to jump into the pool because years and years have passed since numerous other "braver" souls have already proven that it really isn't that bad of a deal to jump in! So now they feel safe about doing so. Or do they? "Wait! Now they have changed the water in the pool! We need to be careful here. Maybe if we just stick our toe in to test the waters. Maybe that would be safe!"
 
Idiot proof....

A problem using mogas vrs 100LL is pilot responsibility. Using mogas is not as simple as using 100LL.

100LL in a certified airplane is as near idiot proof as it can be. The fuel always has a safe vapor pressure and fuel systems are designed to be as cool as possible. Van's has done a good job of system design with this matter. Build it by the book, use 100LL and you won't have any problems, assuming the fuel is not contaminated.

Enter mogas. The issue of vapor pressure is a variable that must be varified by the pilot. It is most unwise to fuel up and fly without knowing the limits of the fuel. Vapor pressure has to be checked before each flight just as the fuel load must be sufficient for the trip. The issue of octane and fixed timing, or no knock sensing with variable timing, must also be understood and considered.

Saving money using mogas is very attractive, but it is not a totally free ride.
 
Experiment day 2

Ok, today I added several things to my experiment. I added a gasket from a carb, fuel cap gasket, clecos covered with proseal (someone asked for proseal on aluminum) a gascolator gasket and a simple rubber gromet.



David-aviator said:
I bought a gallon of E85 last summer just to check its vapor pressure with the Hodges system. It came in at over 50 kPa, almost as good as 100LL at 62. Most mogas come in at 45-50, except winter blend in late spring.

With 100's of millions of autos in this country doing just fine on mogas, it is amazing no one has figured out how to set up a Lycoming to run on it without concerns of melting seals and other issues. The big problem around here is finding fuel without alcohol. But is it really that much of a boogy man? I have been using fuel with it for over a year, all year 'round, and have found the vapor pressure very safe for flight. It may be somewhat less than with no alcohol, I don't know for sure, but it has tested above the safe line with the Hodges meter.

So far, after using mogas with alcohol and occassional 100LL since 2003, the pro-seal is holding up OK.
Click to expand...
David, this is exactly what I've heard over and over from mogas users. Little or no problems. Vapor has been a problem when you park the aircraft hot, get back in it a few minutes later for another flight and it locks up. (e85 was being used in most cases I've found) I've looked all over the internet for other cases and found one where a guy thought it was alcohol related o-ring failure in his carb in what was supposed to be alcohol free mogas. (EAA.org has a fuel tester for $25 that will show the presence of alcohol if you are unsure.) One other problem is a few people have noticed excesive rusting on exhaust valves. I suspect my little rubber bits and pieces are going to have to sit for a couple months, but I doubt I'll find anything out of the ordinary. Don't base you decisions on what I find I'm just having fun doing something else besides rivet pounding. I just can't afford/justify the $6 avgas price when alcohol free Shell is $2.55 down the street.
 
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experiment day 4

I inspected my little pieces today and thought I'd post an update. In the 92 grade mogas with 10% ethenal as well as the bicardi 151, the regular rubber gromet pieces were bloated up to twice there original size. But not in the regular 92 grade mogas. The clecos with 1 year old proseal... I found it easy to scratch them clean with a fingernail in all three. The blobs of proseal however, seemed about the same across the board, a little softer, but not much more than they originally were. The carb gasket pieces were the same as were the gascolator gaskets the fuel tank gasket was softer in all three, but not bloated like the other rubber pieces. So that makes little or no change so far in everything but the rubber gromet.
 
The one thing here that concerns me is the Proseal and it's bond to the aluminum - all other gaskets and seals can be exchanged for alcohol-impervious materials during the build process, but we don't have a known-good sealant for fuel with EtOH, do we?
 
You're right Greg, I think I'll whip up a new batch of proseal, apply it to a rough piece of aluminum and go from there. I'll keep this post... posted.
 
I'm all for saving a buck. That's one of the reasons I got rid of the CT210 and built an RV. I can save on fuel if I choose to run LOP - while I may or may not be trading off some additional engine maintenance, I'm not putting anyone else at risk. If I choose to run an unapproved fuel, I'm hoping that altitude/pressure/temperature/storage issues do not lead to an engine out situation. If it does, the risk now perhaps involves a passenger, someone on the ground, or even search & rescue volunteers.
It seems every winter I read about some climbers stranded on a mountain or sailors skirting a hurricane that somehow forgot that the risk they were willing to take expanded to others as soon as they called for help.
One of the main reasons for choosing an RV was the significant number flying and the expected high reliability. Same rationale for choosing a Lycoming. I tend to think of fuel in the same light.
Terry
 
joeboisselle said:
You're right Greg, I think I'll whip up a new batch of proseal, apply it to a rough piece of aluminum and go from there. I'll keep this post... posted.
Click to expand...

Joe - do a blind test as well, proseal on aluminum without any solvent, and maybe proseal on aluminum under 100LL, then you'll have three samples to be able to determine variations in bond strength to have a basis for comparison.
 
airguy said:
Joe - do a blind test as well, proseal on aluminum without any solvent, and maybe proseal on aluminum under 100LL, then you'll have three samples to be able to determine variations in bond strength to have a basis for comparison.
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What do you mean as far as no solvent, just proseal out by itself?
I'll get some 100LL monday, thanks for the input.
 
joeboisselle said:
What do you mean as far as no solvent, just proseal out by itself?
I'll get some 100LL monday, thanks for the input.
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Yes, just proseal on dry aluminum. Then you have some basis to determine the effect of ethanol vs 100LL on the bare, dry bonding. The question is not whether or not the ethanol affects the bond - it's whether or not the ethanol affects the bond MORE than the 100LL does. For that determination you need a dry blank.
 
You can get "pure" alcohol for some pharmacy. Tell them it's for an experiment. I used to buy it for other purposes. A word of wisdom, don't try it pure.
 
Ok here's your monday update. Nothing much changed from the last post, the only thing I see so far is everything in the alcohol (bicardi 151) is noticably softer than everything else, especially the proseal. But not so soft as I would say it would fail. Not yet anyway. Paul, my wife works as a tech in a pharmacy... and they still wouldn't give me any everclear.
 
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