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Old 09-25-2004, 09:17 PM   #1
I am: Boolean21
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Fuel Basics

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I don't know why but the issue of fuel has always interested me..perhaps
its the fire bug in me.

None the less I did some internet scouring to sum it up.

Because I'm lazy and didn't want to retype pages of text about certain
subjects I'll quote where necessary (and of course acknowledge the authors)

If this gets too long, (and I'm my A.D.D kicks in) I'll break it up into
parts...plus I'll make it available for download.

Where to start..well what is our fuel.

What exactly is nitro fuel.. its a mixture of nitromethane oils/lubricants
and methanol. Sometimes you get other additives which can be added bonus items from specific manufactures (such as friction inhibitors)

The main volume of the ingredient is Methanol. Which is a odourless
colourless liquid. Also poisonous to us humans, and very flammable. Flash point of Methanol is roughly 43F vs Nitromethane which is 94F. (different from ingnition points) Methanol by itself fuels engines, at a standard air / fuel ratio and this is where nitromethane comes in.

Good methanol is both anhydrous (free of water), and hydroscopic (absorbs water from air and is soluable in water). This is why if left in an
unsealed container for any duration of time, the fuel pulls moisture out of
the air, and contaminates the fuel. However the fuel will still burn when
diluted with water, it just won't burn well, thus you'd experience bear
like engine response.

So what is nitromethane. Well it was originally designed for top fuel
dragsters, but has been adapted for the r/c market.

An interesting thing about nitromethane is that it does not burn as
quickly as gasoline. In fact, there is not enough time to burn all of the
nitromethane between when the spark plug fires and when the exhaust valve opens. So the engine is pumping still-burning nitromethane into the exhaust pipe. That's why you see flames shooting out of the exhaust of a
drag-racing car.
Nitro methane is in the nitroparaffin family. There are three members of
that family all propane based...yes propane. (for those of you interested
nitroethane and nitropropane (two types of those))

basically nitromethane is a chemical reaction between nitric acid and

So how does nitromethane create power? Well its in the mix. Fuel/Oxygen
mix. Nitromethane burns up to 2 1/2 times the fuel in the same volume of
air..thus the increase power. (we'll touch on the nitromethane % later)

It also helps achieve a lower, more reliable idle. One good rule of thumb
for checking to see if a particular engine needs a higher nitro blend is to
start the engine, let it warm up for a few seconds, set throttle to full
idle and remove the glow driver. If it drops rpm, move up to a 5% higher
nitro blend. If there is no discernible drop, you should be fine right
where you are.

Increasing the nitro has the effect of increasing the compression ratio,
and each specific engine has an optimum compression level. Exceed it and performance will probably suffer, not gain, and the engine will become much less "user friendly."
The conclusion is that nitromethane provides extra oxygen above that
provided by combustion air and therefor improves hp output.

Lets talk about oils.

They are basically designed to do two things...cool the engine, by
lubricating and allowing heat to move away. Extending the life of your
parts by limiting friction..(which also reduces heat)

There are many different types of Synthetics....which you would not have to worry about unless you are making your own fuel. A great deal is trial and error, but thankfully fuel makers do all this R&D for you.

Many people complain of the oil residue left behind...yes it makes a mess
but this mess is telling you something. 1. its telling you that the oil is
not being burnt with the methanol...and 2. that there is enough to do the
job. You should wonder when there is no residue. Oil cannot burn off and
lubricate at the same time. We have to learn to live with it. As rc
trucks/cars we are lucky most will be expelled through the exhaust. The
remainder will seep through the engine doing what its supposed to do.

For many years, castor oil was considered the best model engine lubricant, providing exceptional protection even when the engine is overheated by a carelessly lean needle valve setting. Now modern synthetic oils have been developed that have the advantage of lower varnish and carbon buildup inside the engine than castor oil. However, the synthetic oils do not provide as much high-temperature protection. Along comes the blend of caster and synthetic. The caster provides the high end temperature protection while the synthetics provide the super lubricant ability.

Synthetic Oils

Strong Points
-Good Lubricity (It's "slick")
-Little to no carbon or vanish buildup inside
-Leave less oily mess on models
-Available in a variety of viscosities
-Totally soluble in nitromethane
Weak Points
-Most tend to cause corrosion if adequate inhibitors aren't added
-Burns off surfaces at about 100 degrees lower temperatures than castor oil
-Many types and qualities, making it hard to choose the best one
-Expensive - good ones cost almost twice as much as castor oil, increasing

the cost of the fuel.
-When used as the sole lubricant, a greater quantity is required, which

increases the cost of the fuel.

Castor Oil

Stong Points
-Great Lubricity
-Reduces the amount required, resulting in more power and better idle.
-Will tolerate internal temperatures about 100 degrees higher than any

-Almost 50% cheaper than good synthetics -
-reduces cost of fuel.
-Great natural rust and corrosion inhibitor

Weak Points

-Tends to cause carbon and varnish buildup in engine if cheap grade and/or

too much is used.
-Messier on model than synthetics
-Somewhat sensitive to extremely cold temperatures - mild separation in

solution, residue on model becomes almost "buttery" in consistency.
-Insoluble in nitromethane. In solutions above 40% - 50% nitro, will

separate unless some sort of co-solvent is used
-Generally available in only one viscosity
During my research phase I sent emails to Morgan and SIG. Neither returned my emails. I requested basic information on the chemical interaction between methanol and Nitromethane. Now I found most on other web sites, but shame!!!! for not having decent customer service!
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Old 09-26-2004, 02:46 PM   #2
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Wow, howe long did it take you to get that together? 8O

Great info though!

1978 VW Type 1 (Super Beetle) Convertible
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