Damage from ethanol?

[john in illinois]

Here is a model T running on E-85.

http://www.mtfca.com/discus/messages...tml?1317161361

[Jim Brierley]

Interesting thread! My opinion is, why ask for trouble? We run methanol at Bonneville and it will eat the rubber (?) in braided stainless fuel lines if left in too long. We also have to increase the carb jet size a lot to get it to run right.

[steve s]

There was some confusion in the earlier thread regarding the concern over alcohol-water separation. It's true that Dry Gas type products contain methanol and work by dissolving the water into the gasoline. Also, it is true that both methanol and ethanol are completely miscible in any proportion with water. I believe that it's also true that both of those alcohols are completely miscible with gasoline. But, when you have the three-component system (water, alcohol, gasoline) there are serious miscibility limits and phase separation into different layers can occur, depending on temperature and proportions.

For example, to get the amount of alcohol into your tank by adding Dry Gas to the proportion comparable to what's already in 10% ethanol gasohol would require a gallon of Dry Gas (in a Model A tank), or about ten bottles! Not surprising if that caused issues.

Steve

[Old182]

Methanol and ethanol are completely miscible in water and will be partially extracted from the gasoline if water is present. But the phase separation event is dependent on temperature, hydrocarbon composition, type of alcohol and any additives that may present. For a 10% ethanol fuel at say, 60*F, it would tolerate about 0.7% (700 ppm) water before phase separation (assuming 26% aromatics, normal). The fuel would then consist of a bottom layer of mostly ethanol + water and a top layer of perhaps some ethanol but mostly gasoline. Ethanol has an (R+M)/2 octane value of ~115 and the alcohol/water layer would be somewhat rich in octane, but the gasoline layer would be octane deficient and may not meet spec. Because alcohols contain oxygen (the reason EPA demands it be put into gasolines), Jim has to fatten his jets to accommodate the chemically correct air-fuel ratio of 6.45:1 for methanol compared to 14.7:1 for straight gasoline. Oh, and just like Jack Daniels and ice, once the ethanol and water have mixed, you can't get them apart (without distillation). Sorry for the nerdiness.

[Rusty Homestead Fl]

The only part I understood was the Jack Daniels on ice. lol.

[Old182]

Sponsored Links (Register now to hide all advertisements)

Oh. The same goes for Old Grand Dad and Rebel Yell.

[steve s]

Originally Posted by Old182

Methanol and ethanol are completely miscible in water and will be partially extracted from the gasoline if water is present. But the phase separation event is dependent on temperature, hydrocarbon composition, type of alcohol and any additives that may present. For a 10% ethanol fuel at say, 60*F, it would tolerate about 0.7% (700 ppm) water before phase separation (assuming 26% aromatics, normal). The fuel would then consist of a bottom layer of mostly ethanol + water and a top layer of perhaps some ethanol but mostly gasoline. Ethanol has an (R+M)/2 octane value of ~115 and the alcohol/water layer would be somewhat rich in octane, but the gasoline layer would be octane deficient and may not meet spec. Because alcohols contain oxygen (the reason EPA demands it be put into gasolines), Jim has to fatten his jets to accommodate the chemically correct air-fuel ratio of 6.45:1 for methanol compared to 14.7:1 for straight gasoline. Oh, and just like Jack Daniels and ice, once the ethanol and water have mixed, you can't get them apart (without distillation). Sorry for the nerdiness.

Speaking nerd-to-nerd, doesn't 0.7% correspond to 7000 ppm? Also, when you say the alcohol/water layer would be somewhat rich in octane, you don't really mean that the actual octane molecules in the gasoline will preferentially partition into the alcohol phase, right? Assuming you're referring to the octane rating of the alcohol/water layer, don't you think that the water would pull the octane rating down a lot?

THanks.

Steve

[Old182]

Hi Steve. Yes, I believe you're right - pencil must've slipped a decimal (add 4 places to % to get ppm). That would mean you need quite a bit of water before phase separation, although we've seen cloudiness begin with much less water. Regarding the octane, ethanol-laced gasoline can be produced as "sub-octane", say 83 or 85 (R+M)/2 if the ethanol concentration is known beforehand (but ethanol cannot be shipped in pipelines and must be mixed at the terminal, away from the refinery). So if, for example, all the ethanol came out of the gasoline with the water, what's left would be essentially the octane of the base fuel: 83 or 85. Because ethanol is a polar material, it will preferentially go with the water and so will its octane benefit. I think we're in agreement that the "octane molecules" of the gasoline would not separate with the ethanol since the compounds that make up the composition of the gasoline are non-polar and would stay with the gasoline. And yes, the water/alcohol mixture would not be something you'd want to run through your engine. The point was an illustration only (sorry for the confusion), although the comment about the off-spec gasoline layer would be true. Fortunately, there is usually very little water in our fuel tanks and the ethanol will actually help to dry it out by pulling the water into the fuel and sending it to gasoline heaven along with the burned gasoline. Heck, we do add alcohols to gasolines all the time in the form of dry gas, be it small quantities of methanol, isopropyl or some other alcohol. Thanks for the correction and comments. Joe