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Q2 engine fuel options
- Thread starter SethInMI
- Start date
The FAA has said that 100LL will not go away until a suitable and approved replacement is in place. If your are still concerned that it will go away anyway (not that the government is ever wrong), you can run lower octane fuel in those engines using an electronic fuel injection/ignition system like SDS or EFII. Lycoming doesn't approve of this because they haven't tested it, but others have and since it's experimental, you can test it yourself.
glider_rider
Active Member
I've spoken to Lycoming support about this subject and I believe they do know that IO390 runs just fine on premium mogas. They must have tested it. Of course detonation margin is smaller, therefore my CHT yellow line is set at 375 deg. No problems whatsoever.
Fascinating. So many rabbit holes to go down in this experimental world. If you run FI system, how do you handle various octane fuels? I know auto engines have knock sensors and can automatically adjust the spark advance to lower the power for lower octane fuel. Do these FI systems have a user controlled setting for that?
SDS has complete mapping of the ignition timing available to the user plus an octane select switch option on the new EM-6.
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According to Lycoming your angle valve eats 100 octane. https://www.lycoming.com/sites/default/files/attachments/SI1070AB%20Specified%20Fuels.pdf
George Braly's GAMI 100 fuel has been issued a blanket STC for all piston engines rated for 100LL - but no one seems to be willing to discuss it. Not enough paid lobbyists.
The way I read the Lycoming document the 390 takes ASTM910 fuel.
Here is the spec for that:
https://www.aviation-fuel.com/pdfs/avgas100llspecsastmd910_2011.pdf
The "100" item in the Lycoming spec is not no-lead fuel. It is the normal lead fuel. So 100LL is less lead than the 100 in the table.
But yes, some -360 angle valve engines are in that table for no lead gas.
Here is the spec for that:
https://www.aviation-fuel.com/pdfs/avgas100llspecsastmd910_2011.pdf
The "100" item in the Lycoming spec is not no-lead fuel. It is the normal lead fuel. So 100LL is less lead than the 100 in the table.
But yes, some -360 angle valve engines are in that table for no lead gas.
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Carl Froehlich
Well Known Member
Here I apply my rule #4, “if something does not seem right there is reason to assume I don’t know the whole story”.
I suspect this comment on AOPA’s website might capture the underlying issue:
“In short, the STC process is proprietary by its very nature, and engine manufacturers and fuel distributors simply want to learn more about the GAMI fuel. Although there is no legal requirement for GAMI to pursue an American Society for Testing and Materials (ASTM) fuel specification, some suggest it should do so. And while GAMI has reportedly incorporated many ASTM testing standards in pursuit of its FAA STC approval, the company remains hesitant to go through such a cumbersome and complicated process that could take years. I believe having some type of industry consensus—not necessarily an ASTM standard—would be very helpful in moving the GAMI fuel forward”.
I also read the current cost estimate of the GAMI fuel is ~$1 more per gallon than 100LL.
My IO-360-M1B and new IO-540 engine (on order) have 8.5 pistons to provide option to burn ethanol free premium mogas. I’d rather burn Swift 94 but no FBO in my area can be convinced to offer it.
Carl
