Nitromethane from RC Car Fuel?

[Richard L]

Originally Posted by JohnA

Washing up liquid eh?

Fairy any good?

If this keeps it suspended, I'd be tempted to try it myself.
But it will need a special tank I suppose, can't use the windscreen wiper bottle eh?

I will try fairy when I get some from home on Monday.

[Hitokiri]

Much has been said in this forum on Methanol, but here is an except from a great book by Graham Bell with respect to Nitro. Please excese typos, after typing it all I didn't feel like reading it over


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On Nitromethane from "Forced Induction Performance Tuning" by A. Graham Bell.

Table 12.4 pg. 185

Specific Gravity Fuel/Air Ratio Heat Energy
Nitromethane: 1.13 1:2 5000 btu/lb
premium unleaded .74 1:12 19,000
Methanol .79 1:4.5 12,500

Nitromethane use and blending:

Nitromethane is different again, and if you look at the fuel characteristeics table(table 12.4) you will see that it is not even assigned an octane number (becuase there are too many variables). yet it can easily double the power of an engine burning petrol/ This is possible through nitor's very special chemical composition, and owing to the fact that extremely rich mixtues can be burned satifactorily. In itself, nitromethane is a very poor fuel, but becuase it contains approximatly 53% oxygen by weight it permits the induction of large quantities of fuel into the engine for conversion to heat energy. Also because it burns so slowly it continues to allpy force to the pistons almost to the bottom of the power stroke.

In the past, nitromethane was burned in the most power drag machines in ratio's of 80-90% nitro and 10-20% Methanol, but today very little methanol is blended in, with most Top Fuel rails running 98% nitro. On the speedway scene and hill climbs, nitro is used (often illegally) in smaller percentages (usually 10-20%) as a power booster. Methanol is the base fuel, and acetone plus other doping agents may also me added (plus about .5% castor oil as an odour masking agent).

To deter detonation or other engine damange, it is always necessary to reduce the compression ratio when nitro is used. At all times air/fuel ration must be very rich. With 80-90% blend of nitro it may be as rich as two parts air to one part fuel. Using 20% nitro this would change to three or four parts air to one part fuel.

When blending nitro with other fuels, the safest method to avoid error is to mis according to volume. So, for a 20% nitro blend you would add one liter of nitro to four liters of methanol...

Igniting high percentage nitro is always a problem. Top Fuel dragsters run the equivalent of a mini welder delivering 1.2 amps to each spark plug. As higher percentages of nitro are burned, the combustion rate is reduced (unless a fuel ignition accelerator such as propylene oxide is added). Therefore, the spark advance must be increased, with most Top Fuel engines typically running a system locked on about 50 degrees advance.

Heading: Nitromethane Dangers

There is considerable risk to yourself and other associated with the use of nitro. After combustion, relativily large amounts of vaporized nitric acid are exhausted. The higher the nitro dose, the more acid vapour is released. When inhaled, nitric acid vapours cause a muscle reaction, making it impossible to breath. Therefore, use of the correct gas mask is essencial if the driver is in a position to inhale the exhaust gases. Certainly mechanics working around the car and those in the starting area will have masks. Some people have the idea that nitromethane is explosive. It isn't, but like any fuel it can be made shock sensitive. The following are the main causes of nitro becoming dangerous:

- the addition of hydrazine in fuel blending. Hydrazine is banned in many countrys because of the danger.
- The use of caustic soda or any other alkaline substance for cleaning fuel tanks or lines.
- The use of "unpicked" anodised aluminium fuel tanks. After anodising, the tank must be allowed to stand for a few days filled with a solution of 90%water and 10% vinegar. This serves to remove and deposits remaining in the tank after anodising.
- The use of excessive fuel pump pressure. Nitro is liable to become unstable when confined and subject to shock. Even though some dragsters routinely run 500psi fuel pressure, anything over 100psi should be considered dangerous.

Wen using more than 20% nitro, there is always a danger of a sump fire or explosion because of the large amount of fuel that finds its way past the rings and into the sump. The first signs of such a fire are yellowish flames appearing at any of the breathers. Therefore, it is important to keep an eye on the engine for at least 2-3 minutes after shut down.
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[janis]

@Hitokiri:

Thanks for taking the time to type all this. Very interesting read!

[EvoTio]

Yes, thank you. I also enjoyed this article.

[Richard L]

Hitokiri,

Thanks for coming to our rescue with more comprehensive information about Nitro.

[Richard L]

I have made a few more tests on water, methanol and nitro mix today.
(by volume)

First mixture W50/M40/N10, no separations - perfect mix:




Second mixture W50/M30/N20, visible separation -





Third mixture W50/M35/N15, very small visible separation (one blob)-





Convert the 50/35/15 by weight:

actual mass:
50/27.65/16.95

normalized % by mass:
52.85/29.23/17.92

If 300ml/minute is injected into the engine, you will get approximately 26.9g of oxygen. if you are pushing in 10kg of air into the engine, the nitro will be adding another 12.8% of oxygen. Doesn't seem possible, someone please check!

[hotrod]

Okay --- numbers check

10 Kg/min of air --- air contains 23.16% oxygen by mass.

That is a mass oxygen flow rate from the air of 2,316 gm/min
------------------------------

Nitromethane CH3NO2 sp gr = 1.139 (20 deg C)

Carbon 12.0111 x1 = 12.0111
Hydrogen 1.008 x 3 = 3.024
Nitrogen 14.0067 x 1 = 14.0067
nonoxygen mass fraction (29.0418)
Oxygen 15.9994 x 2 = 31.9988

Nitromethane Gram molar weight = 61.0406

Oxygen content by mass = 52.4221584%

At 300 ml / min of mixture and a mass fraction due to nitro of 17.92% that would yield 53.76 gm of nitromethane, containing 28.18 gm oxygen.

air flow supplies 2316 gm/min O2 + 28.18 gm/min of O2 from the nitromethane = 2344.2 gm/min.

I figure that out to be an additional 1.2022236 % oxygen.
You might be off by one decimal place Richard.

It looks to me that by mass, that injection rate of nitromethane would add about 1.2% oxygen by mass. That would be the equivalent to increasing air flow by 121.6 gm/min or enough oxygen for 2-3 hp.

Obviously at lower airflow rates, like mid range rpm the proportion of extra oxygen contributed by the water/methanol/nitro mix would go up proportionately. At a 5 kg/min air flow you would be adding 2.4% oxygen with your 300 ml/min injection. That would likely be a noticable increase in initial throttle response and low midrange torque. Also by effectively automatically leaning the mixture when the WI comes on it might be tailored to give a fail safe setup that would be lean when the water was working but a safe tune if the water spray was off.

As far as your mixes go. You might try adding a small portion of acetone to your mix. In gasoline alcohol mixes the addition of a higher alcohol like acetone helps any water stay in suspension. The same effect may help with your nitromethane. A mixed alcohol like 75% methanol + 25% ethanol may have some possibilities as well.

Larry

[Richard L]

That sounds much better - I was one decimal point out for sure, thank you. hotrod.

It would be interesting to work out injecting 300cc of pure nitro into a 10kg/min air stream. a quick calculation says 20-30hp? - a/f leaning could be a problem but if all turbo cars run rich under boost - the excess fuel may now be used for power?

At present, I can only managed to dessolve 15% of nitro into the mix. I will try adding ethanol and acetone and see if the nitro% can be increased.

[Richard L]

hotrod,

Have tried acetone but not successful. I have the following mix:

W50/M20/N20/A10, the nitro was in suspense and settle on the bottom of the flask a few seconds later.

Also tried:
W50/E30/N20, same result and nitro remained at the bottom of the flask.

It appears that I have to reduce water and increase methanol% to go beyond 15% of Nitro.

Any more ideas?

[hotrod]

Richard :

It appears that I have to reduce water and increase methanol% to go beyond 15% of Nitro.

Any more ideas?

Not at the moment, the simple solution would likely be to drop the water content slightly. Just out of curiosity have you double checked to be sure the bolus that is settling out is the nitro rather than the water ?? As I recall nitro is supposed to be infinitely soluable with methanol just as methanol is infinitely soluble with water. Seems at least possible that some water is coming out of solution rather than the nitro.

A long eye dropper to suck it up and test it for flamability comes to mind.

The other option would be to make a more complex system (not my prefered choice), one injection jet supplied with methanol/nitro and another with water methanol. If you controlled both with independent HSV's it would make some interesting combinations possible, but I'm not a fan of doing things the hard way unless absolutely necessary. You would also need a more advanced / flexible controller than I think most folks can afford.

I very strongly suspect that water is necessary as there is ample evidence that a small mistake with nitro mixtures will melt an engine or blow the block apart. I much prefer the safer approach of starting with a known safe water methanol mix and slowly add nitro and subtract water while monitoring effects on the engine.

If I had a mulitimillion dollar racing budget I might start from the other end, but prefer not to break any more equipment than necessary as it would all come out of my pocket. I think most everyone on this board is in that same boat.

All valid questions and if someone wants to bite the bullet and approach the problem from the sharp end of the stick I'm sure everyone here would be glad to hear the results of the tests.

Larry