Experiment: Effects of mogas and alcohol

[joeboisselle]

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 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.

[mannanj]

Seems a terrible waste of Bacardi 151 Don't blow your shop up in the experiment!!!!

[Geico266]

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!

[joeboisselle]

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.

[TSwezey]

I hope the proseal holds because I want to run E85 in my plane.

[Dave Cole]

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.

[chaskuss]

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

[RV7ator]

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

[chaskuss]

Originally Posted by RV7ator

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

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

[David-aviator]

Originally Posted by Dave Cole

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.

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.