;452107 said:
Ok, hang on just a minute. I've been sitting at the bar and watching the dance for a long time here keeping my mouth shut, but enough is enough. It's time to take a step back from La-La land and get a cotton'-pickin' grip on reality for just a darn minute.
All comments here are from a double-degreed college-educated and laboratory-trained chemist and engineer currently earning a darn-fine living dealing with hydrocarbons and the combustion of such in internal combustion engines. If you don't like what you hear, don't believe it, I honestly don't care.
Go read the afore-mentioned quote at the top of this message, and then see my responses below.
Point #1: Cessna's comment about detonation margins and fuel flow volume is WORDED to appear to apply to all ethanol-containing fuels, but is ACCURATE only to fuels approaching 85% (or greater) ethanol content. 10% MOGAS does not equate to this statement. The key here is "ethanol-based fuels", and that covers A LOT of territory - if we are considering AGE85 or higher ethanol content, this statement is, for the most part, true. If we look at standard automotive highway-grade E-mogas, it is nowhere near accurate, and I challenge anyone to present hard data refuting my statement. If you can prove me wrong, I'll sit down and shut up. This forum is not the appropriate place for Chem 101, but this shall suffice as notice that you need to learn more than "fuel in, exhaust out".
Point #2, part A: This is fear-mongering at it's finest. Most of the mentioned problems are common to both 100LL AND any ethanol-based fuels, and have no relation to quantity of ethanol in the fuel, but rather to the fuel distribution system itself, and weather exposure in particular. Specifically - the "extreme corrosion of ferrous metals" is caused by water entrained in the fuel (let's not get started on solvation of water just yet - I'll address that in a moment). Let's all go back to our PSEL student days for just a moment, and remember our instructor teaching us to SUMP THE TANKS during our preflight inspection. Why was this done? Oh yes - TO CHECK FOR WATER. WITH 100LL. Let me repeat that - WATER IN 100LL. Yes, it's possible, just as in any fuel service. That's why we check after each fueling and before the first flight of each day. It happens. Be prepared.
Point #2, part B - formation of salt deposits - from where? The only place salt can enter the combustion chamber is in water-borne suspension or solvation. If it was suspension or minor solvation, we would already be seeing it in everyday use with 100LL for the obvious exposure that we already guard against. Salt (as long as we are talking about the vastly-most-common sodium chloride variety) is far more soluble in water than in hydrocarbon fuel, and is SPECIFICALLY filtered out at the refineries during hydrocarbon-chain based fuel synthesis from raw stock, for the simple reason that it causes severe corrosion at the refinery and they are FAR more worried about their $100M+ refinery than your $10K engine.
Point #2, part C - jelly-like deposits - I have to call BS on this, simply because any serious analysis of NTSB reports will utterly fail to find any significant proportion of engine-failure accidents proported to originate from "jelly-like deposits on fuel strainers". Again, I welcome anyone to prove me wrong here. It's easy to throw dust in the wind.
Point #2, part D - this is the only part of Point #2 that has any basis in fact. Natural rubber components do not react well to ethanol, showing a response to concentrations commonly accepted to begin at 3.5-4%. The most typical reaction to E-based MOGAS is softening of the rubber, deteroriation and flaking, followed by separation and complete failure after some hundreds of hours of exposure to E-10, or as little as a few dozen hours with AGE85. This applies to all natural rubber components of the aircraft fuel system, including (from start to finish) fuel filler cap seals, rubber fuel tank bladders, fuel tank sump drain seals, rubber fuel lines and hoses, engine-driven fuel pump diaphragms, and carburetor floats and seals. It should be noted that ALL OF THESE COMPONENTS have after-market material replacements available that are not affected by ethanol. I will not recommend any of them here, simply because you need to do your own homework.
Point #3 - in all my experience and education, there is exactly zero basis for this statement, with regard to the difference between 100LL and ethanol-based fuels (of any EtOH concentration). I eagerly await anyone who can present evidence otherwise. The ONLY possible exception would be for the use of natural rubber components in the electric fuel pump, which has been adequately covered under Point 2-D above.
Point #4 - This is only partially true, and depends on the equipment installed in the aircraft. For the case of the most common float-type senders, the only consideration is whether or not the float itself will be affected by the ethanol content. Any type of composite (plastic/rubber/foam) has the potential to be affected, unless you know from personal experience and education that it is impervious to ethanol attack. Metal floats are just as immune to ethanol-based inaccuracies as they are to 100LL-based inaccuracies, and for the same reasons. Electro-capacitance indicator systems are very accurate in their response to total fuel quantity in the tanks, but are sensitive to the fuel TYPE in that each particular fuel type has different chemical (and electrical) characteristics. If you have capacitive senders calibrated for 100LL and you switch to E-10, you MUST RECALIBRATE your senders. Likewise, if you go back to 100LL from E10, you MUST RECALIBRATE your senders. The response of the fuel capacitance senders will be different with different fuel compositions. THEY ARE NOT EQUALIVALENT.
(Further points listed in next post, system won't allow a post beyond 8 kilobytes length)
What have you discovered?
