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Alcohol/RC Plane Fuel Injection

Old 09-20-04, 08:27 PM
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Alcohol/RC Plane Fuel Injection

I was flying my friends RC Plane and noticed the fuel for it was a Methyl Alcohol/Nitromethane blend with lubricants in it. I instantly though it would make a good injection fuel. Would using Nitromethane in an alky injection system be overkill?
http://www2.towerhobbies.com/cgi-bin...&I=LXJM38&P=ML
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Old 09-21-04, 10:35 AM
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Bad idea. Nitromethane's big advantage is that it can be burned pig rich because it contains a lot of oxygen (you can technicially burn it without any oxygen) so you can run it around 2:1 AFRs. Because nitro has about the same amount of energy per weight as gasoline, the fact that you can stuff 6-7 times as much fuel per unit of air into an engine means big power potential.

There's two problems. First, nitro has an incredibly low octane. Yes, low. This is why they mix it with methanol, to reduce its tendency to pre-ignite. It's also why they use it in RC airplanes... the mild compression plus the glow plug is enough to light nitro.

The second problem is the fact that nitro has a lot of oxygen tied up in the molecules; introducing it in an engine tuned for gasoline will make it go lean. People have tried and melted NA piston engines because of that. Think of what that would do to a turbo rotary.

Bottom line is, don't mess with nitro unless you know what you're doing or are willing to kill a lot of engines learning.
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Old 09-21-04, 10:44 AM
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Besides the cost of burning up a few engines trying to get mixtures right, there is also the cost of the fuel. Straight nitromethane costs $45 a gallon. Then figure in that your air fuel ratio is 2:1 instead of the normal 13:1, and you see you will need to burn 6 times as much of the stuff than you do your normal gasoline. This means tremendous operating costs for nitro fuels.

What will methanol do to the housings and seals? Alchohols tned to wash the lubricating oils off metals, so what would it do to a rotary that needs extra oil in the combustion chambers and on the seals?
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Old 09-21-04, 11:35 AM
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Well, alky in a rotary is defintely possible (evidence the drag guys) but damned if I know what it entails.

I bet nitro in a rotary would be possible too, as in top-fuel style, not as in mixing with gasoline. Might have to try that someday for ***** and giggles.
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Old 09-21-04, 01:28 PM
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I'll jump in here with a question. It is recommended for cars that have to pass emissions testing each year that you put alcohol in an almost empty tank and take it for the emissions test then refill your tank with 87 octane after you pass the tests. I understand the concept, very little CO or hydrocarbons in the exhaust but how do you get around the internal lubrication? Are methanol and gasoline about equal in octane rating?
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Old 09-21-04, 03:13 PM
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Yeah, I started reading up on it and realized the that it ignites at low tempetures.
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Old 09-21-04, 04:44 PM
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RC airplane fuel also has alot of castor oil mixed in.
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