| Porsche-O-Phile |
12-01-2009 03:49 AM |
This is something I'm keenly interested in as well - I'm even willing to go so far as to home-prepare de-ethanolized fuel if that's what it takes. I've done some limited research into this (there is considerable interest in this topic in the boating and experimental aircraft crowds, among others). I'm hoping that someone with a strong chemistry/petrochemical background can either confirm or deny the following tidbits of information I've been able to discern in sifting through various websites, blogs, etc.
1. Ethanol is corrosive to standard fuel system seals, hoses and other components (I think most here know this). I suspect (but can't prove) that it may have had something to do with the "unexpected combustion" of my 951 a couple of years ago (fuel hose deterioration).
2. Most pump stations now are selling "E10" fuel, meaning it can contain up to 10% ethanol (most people here already know this too).
3. Ethanol is soluble in water. This suggests an approach using distilled water mixed with pump-station gasoline might work. However I'm not certain that ethanol's affinity to water is greater than its affinity for hydrocarbons like gasoline. In other words, I'm not certain that simply adding a bunch of distilled water to a tank of gasoline and stirring it up would force much of the ethanol out of solution with the gasoline and into solution with the water, which could then be separated.
4. Supposedly gasoline can hold up to 13% water in liquid solution at standard temperatures. Some less-than-scrupulous gas stations deliberately use water as a "filler" by dumping water into their tanks, giving them an instant 13% profit margin, supposedly... Some people claim that under engine combustion temps/pressures this dissolved water can produce highly detrimental effects (corrosion, mostly) to internal engine and combustion chamber components. Others say it's fine and cite the use of water-injected engines as proof that it's no big deal.
5. I'm also not sure to what extent solubilities of ethanol-in-gasoline and ethanol-in-water vary as a function of temperature. Depending on what these are exactly, it might suggest that heating (or cooling) a tank of gasoline before mixing it with water might yield better results in stripping out the ethanol from the gas.
6. Assuming one could obtain "pure" gasoline (with the ethanol removed), there is still the possibility that water could disssolve into the gasoline again - either due to condensation on the inside surface of the tank or as a result of the de-ethanolizing process (you have to saturate the gasoline with water before you get enough water floating around not in solution that can be used to strip the ethanol out and settle to the bottom of the tank - the theory is that you'd get a layer of (water-saturated) gasoline floating on top of a layer of water with ethanol in solution in it at the bottom of your preparation tank/apparatus).
7. I suppose if it's shown that water-saturated gasoline is bad or worse for engines than gasoline with little or no water content dissolved in it, the de-ethanolized gasoline could then be run through a second apparatus to condense out or otherwise remove as much of the water as possible before using it.
8. Since ethanol increases octane (anti-knock) rating, stripping it out of gasoline would result in lower octane gas. To boost the octane rating again, one would need to add lead or mix with another substance to boost the octane rating - particularly in high-compression or forced-inducation engines. I know some 951 guys use toluene and/or xylene to do this. Supposedly a 1:3 mixture of xylene:gasoline gives a huge boost in octane rating (IIRC something like 10 points) and a voracious flame front spread inside the cylinder... Again, not directly confirmed by me though. Point is there are ways to boost the octane rating lost by removing the ethanol - but I also don't know if tossing toluene or xylene in a tank would be better or worse necessarily for fuel system hoses and seals, injectors, pumps, etc than the ethanol...
Hopefully someone with a good chem-e background can chime in about the feasibility of setting up a small-scale home de-ethanolizer using water.
Or, I suppose those of us with non-catylitic cars can just run 100LL avgas, which has no ethanol. ;)
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