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Bertram31.com General Bulletin Board
Water in Ethanol fuels
Posted By: Peter
Date: Monday, 24 April 2006, at 12:02 p.m.
I have been thinking about the way the water phase-separates from the gas in the new ethanol fuels. I have been a proponent of fitting some sort of sump to any new fuel tank to allow drawing off the water bottom. This sump doesn't have to be a drain in the bottom of the tank, but rather could be a pick up tube that extends to the very bitter-bottom of the tank, while the fuel pickups which supply gas to the motors are held an inch and a half or so above that. This would be a way that should be C.G. OK. You would have to cap the sump when not in use, and hook up some sort of a portable pump to the sump-pickup-drain to pull the water out when needed, but that shouldn't be hard to manage.
However, another issue is rattling around in my thoughts. When water gets into the old style gas it just settles to the bottom with the gas floating on top. The gas is essentially unchanged. So you draw off the water bottom and you are good to go.
With ethanol in the fuel the water stays in solution with the ethanol until it reaches a certian point, a sort of water-saturation. Then with just a little bit more water some water and ethanol separate out. The gas that is floating on top of the water is now NOT the same as it was before. It is fundamentally different because at least some of the ethanol has been removed from it, lowering its octaine rating...leading to potential for knock (pinging) which leads to other bad stuff like holes in the pistons. And what ethanol does remain in the gas is still at the water saturation point. Do the very next couple of drops of water that find their way into the fuel repeat the process?
Does this lead to further degradation of the remaining fuel and instantly a new potential corrosive ethanol/water bottom in the tank... even though you just drew off the water bottom only moments before? Just how much water and ethanol phase-separate out for each measure of water beyond the saturation point?I have not seen definitive discussions regarding this, but my simple logic tells me something like this must be the case.
I personally would still fit some sort of sump in any new tank because the ethanol puddle in the bottom of the tank is potentially hazardous to the tank and the motors. BUT ALSO I think we should get into the habit of using up nearly all of the gas in the tank before refueling. This way the little bit of "water-saturated" fuel remaining in the tank mixes with large quantities of NEW fuel with NEW ethanol and the total water percentage in the entire tank is lowered ...hopefully below the point for phase separation.
And all of that is just fine as long as the marina or gas station doesn't have any water in the fuel they are selling you. Just as in the case discussed above, the retailer might draw off the water bottom in his storage tank, but what he has left in his storage tank is NOT the same as fresh ethanol/gas. First it has lower octaine and second if there is ANY water in the tank bottom at all, the remaining fuel HAS TO BE water saturated, just waiting for one more drop of moisture to make a brand new puddle in the bottom of his tank or yours.
(If the fuel was not completely water-saturated a puddle could never form in the first place since the ethanol would have held the water in solution.)When his water-separating filters get wet, the entire tank load is suspect. Just changing the filters may not be enough to assure that he is selling you good fuel.
Oh yeah, and then there is the part where the water-saturation point is temperature sensitive... running gas through the venturi in the carb can lower the temp of the fuel/air mixture as much as 40 degrees. How will this effect the engines when the fuel is near to water saturation point?
If anyone knows any more than I do about this situation, or where to find real answers to these questions I'd love to be informed!
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