Visit The Dirt Forum for More Information

Author Topic:   Not that you would use it but here are some Nitro charts when adding Nitro to alky.
Dirt Administrator

Total posts: 3279
posted September 04, 2001 10:37 AM UIN: 16262997
A note. The Dirt Forum does not condone cheating in any way, but for everyone's sake, we want everyone to be educated. We feel this is a good way to learn about possibilities of our sport. That is the sole reason this is posted.



NOW that we are considering the use of Nitromethane it may be as well to get one well held idea out of the way before we go any further . . . that is that more power and therefore more performance can be obtained by simply adding more Nitromethane to the fuel tank. Nothing could be further from the truth, friends!

In actual fact this is perhaps one of the quickest ways of running into serious mechanical trouble.

The actual name Nitro in itself to most people sounds explosive and at once the idea of using this fuel leads the imagination to think of it getting into the cylinder head end then being exploded by the spark, thus producing a violent explosion in the engine, the extra power then doing more work and so giving the extra performance.

The introduction of more Nitro-methane to the fuel is not just that of the addition until enough power is obtained, but rather that of well controlled amounts used in relation to the other factors.


Recommended jet diameter increases (guide only) for Nitro - methane / Methanol fuel mixes over those used for straight Methanol fuel.

% Nitro in Methanol
per volume












Jet diameter
over Methanol per volume above












Chart 2 indicates the increase in jet size to allow the increased amount of fuel to flow as the ratio of Nitromethane to fuel is increased.

These figures in all cases provide a mixture on the rich side since as previously pointed out, these fuels are relatively insensitive to mixture ratio compared to petrol, and the consequences of running weak mixtures with these fuels is likely to be more serious than with petrol since the power level will be so much higher, also the thermal stresses.

Note how with 40 per cent nitromethane mixture the jet size has increased by 1.41, or put another way by 40 per cent on the diameter, which as mentioned before means an actual fuel flow of twice the original amount, so by comparison with petrol we now have four times as much fuel required by the engine.

At 80 per cent mixture the fuel flow rate has be-come three times the rate and therefore six times greater than petrol, hence the need to check the fuel pump and fuel lines to make quite certain they can cope with this requirement.


Now, as before, it is necessary to know the dangers involved with the use of nitromethane mixtures so

that the necessary precautions can be taken and understood, reducing them to a degree that makes the use of such fuels acceptable under the circumstances in which we normally operate.

Provided you know the dangers you can work with these fuels and come to no harm, but if you do not, then it is possible through lack of simple precautions to suffer, so bear them in mind at all times.

After combustion, mixtures containing nitromethane exhaust relatively large amounts of nitric acid in vapor form, making the use of a proper gas mask essential by the driver, and for those close to the car in the start area.

The reason for this is that nitric acid, when inhaled, causes a muscular reaction making it impossible to breathe.

Little imagination is required to see the dangers involved with this possible event taking place, and in fact there have been cases of drivers becoming almost unconscious due to the bad fitting of face masks.


The mandatory use of fire suits adds to the generally held view that with nitro-methane mixtures the fire risk is increased, but this is not so.

If you care to test this you can do so as follows. Take a small amount of petrol, about one teaspoonful say, and place in a small tin lid and then ignite. It will catch fire almost with a bang.

Now take the same amount of methanol and after the tin has cooled down, repeat the exercise observing the almost lazy manner in which it ignites, burning with a blue colour, the edges of the flame lined in places in yellow and orange.

Now take the same amount of nitro-methane, 98 per cent if you like, and repeat the experiment and see how difficult it is to ignite, burning with a green tinted flame in a reluctant manner.

This is due of course to the respective flash points of the three fuels, petrol being the lowest at between zero and 40 degrees F. approximately, methanol at 67 Degrees F., and nitromethane at 110 degrees F.

In other words with petrol you have a major fire risk and far less so with nitromethane mixtures.

The real problem with nitromethane is its ability to release high power, especially when ignited in a confined space.

Associated with this is its liability to be affected by shock.

Dropping a can of nitromethane will not cause an explosion, as the can, due to its construction of light weight material, will not have sufficient rigidity, but an amount in a very solid thick-walled container may.


There are three main possible causes of nitromethane becoming shock sensitive and they are as follows:

The use of hydrazine as an additive, which, be it noted, is barred by regulations in the USA for that very reason.

The use of caustic soda or any other alkaline, used for cleaning out a tank or fuel lines.

Alloy tanks, which before anodizing, have been cleaned with such a substance and have retained a small deposit.

To avoid any such possible troubles the tank must be filled with water and 10 per cent vinegar, plus a little ordinary household washing-up liquid, and left to soak for several days.

One final note of warning concerning burning nitromethane and methanol is that they can burn almost unseen in daylight, and you may well have a carburetor or injector ignited by a backfire without appreciating the danger.

Back to the Archives