An Introduction to Nitromethane

By Brock McPherson

Top Fuel drag racing is a crazy world. For those uninitiated, in a drag race, two vehicles line up and see who can complete a quarter mile in less time. It’s practically an American tradition at this point, having been massively popular since the hot rodding scene of the 1950s. It makes sense, that some would take it more seriously than others. The fastest and most dangerous level of drag racing is Top Fuel.

There are restrictions on just about every part in those cars, yet they still find ways to make 8000 horsepower and blow through a quarter mile in under five seconds. Though, these ridiculous speeds didn’t appear out of thin air. Plenty of engineering went into these cars to make sure that they can make these absurd quantities of power.

One of the biggest constants in Top Fuel drag racing is the fuel. One of the additives to this race fuel is a part time cleaning solvent/part time rocket fuel known as nitromethane.

So what makes nitromethane so common in Top Fuel drag racing?

Nitromethane is an oxidizer, meaning that it carries oxygen in its molecules. Regular gasoline requires oxygen to combust, but Nitromethane is a monopropellant, which means that it’s capable of combusting using only the oxygen it contains.

The oxygen present in nitromethane alters the ideal air to fuel ratio of an engine, which allows the engine running it to use more fuel per cycle. When running normal gasoline as fuel, the best possible ratio is 14.7 pounds of air per 1 pound of gas. When all the air has to come from outside the car through the intake, that limits the power of a car, especially on bigger and thirstier engines like V8s. Running pure nitromethane, however, the ideal ratio is around 1.7 pounds of air to each 1 pound of fuel. This means that the engine can burn roughly 8.7 times more fuel per cycle and so generate more power.

Nitromethane isn’t without its problems, however. There are reasons that pure nitromethane is only viable in drag racing. One of the main reasons is that it’s just too expensive for regular use. For the amount of fuel a team would burn through on each pass, it just isn’t economical to use at any lower level.

Another reason is the reliability. Most Top Fuel teams don’t even run pure nitromethane because mixing fuels makes the engines less likely to lose the use of some cylinders during a pass. This high of a percentage of nitromethane is only even possible now due to improved ignition technology, and any ignition that’s old or not built for this kind of abuse will fry itself quickly.

The final major reason why it isn’t used in any other forms of racing is the mpg. As stated earlier, that the biggest strength of nitromethane is its ability to dump much more fuel into the engine at a time than regular gasoline. This also means that it absolutely guzzles gas, to the extent where if running a high enough mixture of nitro, the vehicle may not even be able to travel further than the quarter mile. Unless a pit crew can refuel a car fast enough to make up for the time it would have gained running pure nitromethane, it’ll never be viable in anything other than the highest levels of drag racing.

These drawbacks don’t make nitromethane bad, it’s still one of the most effective ways to add power to a car, but anybody not competing in Top Fuel drag races may want to consider alternatives, like turbochargers, superchargers, or nitrous oxide.