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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › How to rehab bad nitro fuel
11-21-2016 03:56 PM  3 years ago
dgoss999

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UK - Lancashire

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Water in fuel..
Is it not rather the moisture in the fuel freezes in the carb and eveything ices up as the metanol vapourises and looses temperature.

Once the carb warms up it all unblocks until the next time it freezes!!

DG..
"Believe none of what you hear, and only half of what you see." • Benjamin Franklin
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11-21-2016 04:29 PM  3 years ago
AirWolfRC

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Carb. ice could explain a rather sudden stoppage.
A hotter plug won't help there.
And once you get to investigate . . . the evidence has evaporated.
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11-21-2016 06:48 PM  3 years ago
Leif

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USA

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Water in Fuel
The problem with trying to separate water from methanol-based fuel is that methanol has a high affinity to absorb water.

Freezing doesn't work as the water is fully mixed with the alcohol. The water molecules aren't in close promimity to each-other, so they won't form a solid lattice as they would in pure water.

Boiling off doesn't work either, as both methanol and nitro-methane have lower boiling points than water. If you tried "distilling", you would end up boiling off the methanol and nitro-methane, and you would be left with the oil and water.

In the lab, we used to dry solvents by running them over a bed of dry alumina. However, since the fuel contains oil that would get captured in the alumina and would gum up the works.

I can only think of ONE thing that might work. Adding pure sodium metal to the fuel would probably work, as the sodium would react with the water, removing it from the mix. This is one of the tricks that is used to produce 200 proof ethanol. Sodium is used to remove the last traces of water as it has a higher affinity (more reactive) to water than methanol. So if you can raid the local High-school chemistry lab and get your hands on some sodium you could give that a try.

Otherwise the dilution idea is probably the only feasible one. Add a bit of the old fuel (less than 10% mix) to new fuel would probably work. Alternatively you could just use the stuff to help light the woodpile on damp days......

Leif
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11-21-2016 07:14 PM  3 years ago
reddragon

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Brooklyn, N.Y.

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Works on gas, but methanol is hydroscopic more correctly hydrophilic,(water loving) so maybe not.
Hygroscopic.
Wayne - Fly it like you stole it! You're in good hands with Runryder!
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11-21-2016 07:16 PM  3 years ago
motorrc

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canton ohio usa

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just trying to remember my high school chemistry-I believe adding sodium to water is a very exothermic reaction-I'm a little afraid everything would go up in one giant fireball.if it doesn't fit, make it fit.
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11-21-2016 07:22 PM  3 years ago
motorrc

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ps why would the fuel(water) ice up in the carb but not in the fuel container, assuming I froze the fuel container to remove water.if it doesn't fit, make it fit.
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11-21-2016 07:35 PM  3 years ago
JuanRodriguez

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The Villages, Florida

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Ice buildup caused by the venturi effect of the carburetor.....

That's why airplanes using a carburetor have "carb heat" to melt off any ice buildup in the carb's venturi......

Do a google search on "venturi effect" to learn more about it....
Been there, done that and old enough to know better.....
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11-21-2016 07:54 PM  3 years ago
CostaRicaHeli

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Costa Rica, Central America

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I mixed an old gallon of fuel that wasn't working well (some unexplained flameouts, difficulty starting) with good new fuel to no ill effects. It was no more than 5 to 1 ratio (new to old).Franz
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11-22-2016 11:20 PM  3 years ago
motorrc

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canton ohio usa

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Juan, full scale airplanes don't use methanol as fuel.

My point was, if I can't freeze the water out of methanol when it is in the container, why would it freeze in the carburetor? (It either freezes in both places or neither, since the same rules of chemistry apply)
if it doesn't fit, make it fit.
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11-23-2016 12:14 AM  3 years ago
JuanRodriguez

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The Villages, Florida

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Juan, full scale airplanes don't use methanol as fuel.
No they don't but the venturi effect is the same whether its methanol or aviation fuel....

Again, do the search I suggested and you'll learn how the venturi effect can cause the moisture in methanol to ice up.......

You don't get the venturi effect by sticking a gallon of RC fuel in a freezer.....
Been there, done that and old enough to know better.....
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11-23-2016 12:33 AM  3 years ago
revmix

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NJ

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carb icing is due to atmospheric conditions
in other words the cause is the weather (humid air) & not the fuel
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11-23-2016 12:45 AM  3 years ago
JuanRodriguez

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The Villages, Florida

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Atmospheric conditions yes...... along with temperature drop in the carb's venturi.......ie, the venturi effect I've been alluding to......

https://en.wikipedia.org/wiki/Carburetor_icing
Been there, done that and old enough to know better.....
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11-23-2016 12:50 AM  3 years ago
revmix

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NJ

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venturi effect
yeah, the culprit is the moist-air but not the fuel itself
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11-23-2016 12:59 AM  3 years ago
AirWolfRC

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When you decrease the pressure of a volume of air, (venturi effect in the carburetor) the air mass cools (PV=nRT), the relative humidity increases because colder air can't hold as much water vapor as warmer air, and if the temperature decreases enough, water vapor in the air mass will condense (dew point). If the air mass gets cool enough (freezing), you get carb ice.

If you question that first part, think of an air compressor.
When you compress the air, it gets hot.
When you release the pressure, the air gets cold.
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11-23-2016 01:08 AM  3 years ago
revmix

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NJ

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sure, the air flows thru the carb inlet (icing), the fuel is through the nozzle
wet-fuel causes engine hick-ups or stoppage
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11-23-2016 01:09 AM  3 years ago
motorrc

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canton ohio usa

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yes, I get it now!

Thanks for the comments and keep em coming!
if it doesn't fit, make it fit.
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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › How to rehab bad nitro fuel
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