View Full Version : Running a Rotax on E-85?

Bob Furr
07-08-2013, 12:47 PM
Well can it be done? I know it is about 100 octane. I know the cost per hour of operation for fuel alone is good with nearly a $1 gal discount on E-85. Any real world experience? I know that years ago the Ascender was flown from AZ to Oshkosh on alcohol fuel. Any suggestions? BTW try not to flame me... I am just trying to find a way past the problem of alcohol in fuel by embracing the possibility....Thanks Bob

07-08-2013, 01:33 PM
I looked at a web site that shows where you can buy ethanol-free fuel in the US. Omaha has 10, repeat 10, locations that sell ethanol free gas. You're lucky!

07-08-2013, 04:56 PM
First, of course, Rotax specifies a maximum of 10% ethanol.

It's certainly possible, but you'd have to make some significant changes to carburetor jetting. You'd probably have to replace all rubber seals and hoses with seals compatible with that concentration of ethanol. You will likely have problems with oil properly mixing with the ethanol (might not be an issue with oil injection, I don't know). You'll have problems with water dissolving in the fuel and then coming back out as the temperature drops, which plays havoc with the needle bearings used in 2-strokes. Finally, there would be a significant power loss since ethanol has a lower energy content than gasoline.

Bob Furr
07-09-2013, 05:32 AM
Actually what I am looking for is real world experience and I am guessing there really isn't much. Water separation from freezing is called fractional freezing and occurs at temps far below 32 degrees and I simply don't fly if it is that cold. What forms is a slush that goes back into mix once it warms back up. Not really a problem in the fuel tank. If you run the engine until the crankcase fully warms up not much of a problem there as fuel evaporates from the hot crankcase and leaves a protective coat of oil. There is a real question on premixing oil but I can sort that out with a simple test myself. As far as lower power... well I have flown model airplanes with both gas and alcohol fuels and can tell you that the alcohol seems to produce more power but at higher consumption rates. I do agree if you hold the fuel consumption rate down it will produce less power. On the comment about being lucky with multiple places to buy alcohol free gas I agree... but do not see that lasting long with the legislature here looking at forcing all gas to be sold with an alcohol mix. I am trying to be proactive and look at options before that happens. Any other thoughts? I am really looking for experience here.

Bob Furr
07-09-2013, 05:35 AM
BTW I have seen castor oil come out of solution in model plane fuels stored in an unheated garage here in the Midwest where winter temps can drop to -25. If I were running castor oil I would worry because the wax like solids do not go back into solution. I have never seen petro based or synthetic oils do the same thing.