noelawinslow Posted May 17, 2015 Share Posted May 17, 2015 I don't know if this has been discussed before, but I'm curious why it's not a more popular idea. I was talking to my brother in law the other day, and we have very different views on whether or not ethanol should be in gasoline in the first place. While he bemoaned its effects on his lawn mower and chainsaw, I asked him if he knew if it was possible to pull the ethanol from the gas after it's been added. After all, it's just gas + booze, right? Turns out you can use ethanols negative properties against it to purify your gas using phase separation, which is just a fancy way of saying water and gas don't mix. There's a couple points I haven't quite figured out yet. Mostly how to figure out the octane rating after removing the ethanol. Long story short, you add water to your gas tank (bear with me) and suck out the water/ethanol mix that will ensue from adding the water. Then, once it all settles, you can drain the mix from the bottom of the tank with either an aftermarket drain plug of some sort, or from the top via an inspection port if your car has one (like the z31's sender unit). The trick is to figure out how much water to add and how much water/ethanol to pull out before you start sucking gas instead. I ran some math, in my area gas is about 2.43. If you buy E10 at $2.43, and it's 10% ethanol, you get 9 gallons of pure gas for every 10 gallons of e10 you buy. That comes out to $2.70 per gallon after you pull the ethanol. But the upside is since gasoline has higher energy content, you'll get a couple extra mpg from the process. So if you get 24 mpg on 2.43 and 27 on 2.70, you'll still end up with basically the same ratio of $ to miles, which is more important to me than mpg. So for about 5-6 buck per fill up you can use pure gas instead of regular gas. Actually pulling the gas out seems like it'll be the fun part, but it seems the ethanol/water mix is a different color than the pure gasoline so if you rig up a clear hose and container to view the gas, you'll see when you've removed all the ethanol water mix. How much water do you use? Not much, really. Most places I've read say abou .45% to .5%. Add too much water and all you have to do is drain the water then the water/ethanol mix, which will sit at the very bottom of the tank. So in practice probably about 2.75 oz per gallon of gas for e10. Keep in mind e10 is a rough approximation of the actual ethanol content, so YMMV as far as how much water to use. I'd add the water first then the e10, since the station pump will help mix the water thoroughly with the e10. About 10 to 20 minutes of settling after you pump the gas should in theory separate most of the ethanol out. No big deal since it'll take about 10 minutes to access the fuel tank from the top of my z31 that I'm planning on testing this idea on. I don't see why this isn't done more often, is there any particular reason why not? Quote Link to comment Share on other sites More sharing options...
Namor Posted May 17, 2015 Share Posted May 17, 2015 Probably because the potential downsides outweigh the gains. Personally, I just go to a local gas station that sells ethanol free for anything seasonal. It's quite a bit more expensive, but it is worth it to me. Quote Link to comment Share on other sites More sharing options...
Phantom Posted May 18, 2015 Share Posted May 18, 2015 I've been running e10 forever and have never had an issue with any of my engine/ fuel systems except for the fuel lines to a '93 Mercury 2-stroke outboard where the fuel lines started to disintegrate. Sounds like a lot of hassle with little upside. Quote Link to comment Share on other sites More sharing options...
TimZ Posted May 18, 2015 Share Posted May 18, 2015 Seems like a lot of work to go through just to lower your octane by ~ 2 points. But hey - enjoy your "pure" gas. And your detonation. Quote Link to comment Share on other sites More sharing options...
djwarner Posted May 18, 2015 Share Posted May 18, 2015 Here is an article on the topic: http://www.mcnews.com/mcn/technical/2012decethanol.pdf His comments about restoring the octane rating is a bit off though. Octane measures the resistance to explosive detonation and an octane rating of 113 for ethanol cannot be resolved by some simple algebraic equation. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted May 19, 2015 Share Posted May 19, 2015 What you described is how you test ethanol percentage in e85. Also your gas tank has baffles, that makes it a lot harder to drain effectively. It's not worth the risk when you can just buy higher octane gas. Quote Link to comment Share on other sites More sharing options...
noelawinslow Posted May 21, 2015 Author Share Posted May 21, 2015 I recently ran into an issue on my z31 where rust got into the fuel lines, and I couldn't prove why. I looked inside the tank and it was clean. I postulated the alcohol content stripped some rust buildup from the tank and sent it through the pump. Made more sense because the pump won't hold pressure when it's shut off anymore either, so perhaps the particulates damaged the check valve while it worked its way into my fuel lines. Not too sure, but it made me wonder if it'd be worth it to make a conversion for some people/cars. On my S30 I'll run flex fuel if I can map it right, I don't inherently hate ethanol. Djwarner, thanks for the article, kept me awake during music appreciation. Quote Link to comment Share on other sites More sharing options...
Midri Posted September 23, 2015 Share Posted September 23, 2015 I recently ran into an issue on my z31 where rust got into the fuel lines, and I couldn't prove why. I looked inside the tank and it was clean. I postulated the alcohol content stripped some rust buildup from the tank and sent it through the pump. Made more sense because the pump won't hold pressure when it's shut off anymore either, so perhaps the particulates damaged the check valve while it worked its way into my fuel lines. Not too sure, but it made me wonder if it'd be worth it to make a conversion for some people/cars. On my S30 I'll run flex fuel if I can map it right, I don't inherently hate ethanol. Djwarner, thanks for the article, kept me awake during music appreciation. Just wanted to comment on this for science! Ethanol is actually a lot less effective a solvent than gasoline is. Gasoline, however leaves varnish which then makes things look dirty and thus it's not used as a solvent (though a byproduct, Diesel; can be used as a very effective solvent -- we actually use it a lot to clean engine parts and the more manly of the mechanics club wash their hands with it). So it stripping rust from your tank would make no sense. The reason ethanol is bad for older vehicles is it dries out older rubber/plastic compounds causing them to become brittle and crack. Quote Link to comment Share on other sites More sharing options...
jer305 Posted November 17, 2015 Share Posted November 17, 2015 (edited) Would you have to use your cars gas tank? Might be easier to separate in large gas cans or a spare tank. Edited November 17, 2015 by jer305 Quote Link to comment Share on other sites More sharing options...
djwarner Posted November 18, 2015 Share Posted November 18, 2015 Two points as side notes to this thread: After overhauling my L24, I was still a little slow compared to the original Motor Trend article 0-60 times. Since, my car suffers from dual DGV Webers, I decided to contact RedLine for suggestions. Their first comment concerned E10 fuel and how it runs lean. If you think about it, there is extra oxygen in the fuel and fewer hydrogen and carbon atoms to burn. Thus when going through a carburetor, there are fewer energy producing bonds to burn. Re-jetting two steps richer made a significant performance improvement. I ended up reducing my 0-60 time by a full second. If you have re-jetted your carbs in the last 4-5 years, you are probably running lean. Impressed, I also converted the DGVs from a progressive linkage to synchronous. While this wouldn't help full throttle operation, the car is now a delight to drive around town. The second item is my son's 2014 GT-R. He has adapted his car to run on E85. It involved changing the injectors, fuel pump, and manifold. Software required re-mapping, but the data logging during test drive is like having your own dyno. Nice feature with the GT-R is that you can switch maps as you fill up with different fuels. Why run E85 instead of 93 octane? How does 600+ hp at the rear wheels sound? As you might expect with the extra oxygen in the fuel and extra power, mileage will suffer. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 18, 2015 Share Posted November 18, 2015 I wonder if you could add diesel to E10 to get back to the energy content of old formula gasoline? The volatility loss might not let it work though. On the previous point about solvent effectiveness - it depends on what's being dissolved. On the idea of using phase separation with water to pull ethanol from E10 - you'll probably end up with less ethanol in the fuel but more water, and still some ethanol. And the hydrocarbon portion of the fuel will be fully loaded with as much water as it can hold. A few heating-cooling cycles in the tank and moisture from the air that gets pulled in will start phase separating to the bottom of your tank. Quote Link to comment Share on other sites More sharing options...
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