Nitrous Oxide, Nitrous, or simply NOS is a chemical compound (N2O) that when introduced to a car’s engine increases horsepower performance. Typically, nitrous is not used in competitive drifting, instead, nitrous oxide is most commonly used in drag and street racing applications - drifting requires delicate use of horsepower to control drift angle but there are drifters that use nitrous like Japanese drifter Shuichi Yoshioka in his Nissan S15 Silvia. “The car has only 400ps (395hp). If two cars go into a curve at the same speed, the car that has more horsepower has more control. I use NOS to get more power,” says Shuichi Yoshioka.

When nitrous is injected, temperature inside the engine is about 572 degrees F, nitrous breaks down and nitrogen and oxygen are released. The extra oxygen creates additional horsepower by allowing more fuel to be burned and the nitrogen helps control the combustion process by reducing cylinder pressure. In addition, nitrous has an intercooling effect that reduces intake charge temperatures by 60 to 75 degrees F, further increasing performance.

Potential horsepower gains with nitrous:

4 cylinder engine extra 40-60 HP
6 cylinder engine extra 75-100 HP
8 cylinder engine extra 125-200 HP

Nitrous oxide is 2 parts nitrogen and 1 part oxygen (N2O) and is stored as a liquid in nitrous oxide tanks or bottles. Alone, nitrous is non-flammable; however, the oxygen present in nitrous causes fuel to combust more rapidly – this is how nitrous creates horsepower gain.

When nitrous is injected into an inlet manifold this cooling feature causes a reduction in air/fuel charge temperature, increasing air density, and increasing the cylinder’s volumetric efficiency – increased cylinder efficiency means more horsepower.

The term NOS is derived from the abbreviation of the company Nitrous Oxide Systems who is one of the pioneering companies in the development of nitrous oxide injection systems for aftermarket automotive performance. More recently, the term NOS was made popular with the film The Fast and the Furious.

Nitrous equipped cars will “purge” the nitrous delivery system prior to a race to ready the nitrous system. A separate electrically operated valve is used to release air and gaseous nitrous oxide trapped in the delivery system. This brings liquid nitrous oxide all the way up through the plumbing from the storage tank to the solenoid valve that will release nitrous into the engine’s intake tract.

When the purge system is activated, one or more plumes of nitrous oxide will be visible for a moment as the liquid flashes to vapor as it is released. The purpose of a nitrous purge is to ensure the correct amount of nitrous is delivered the moment the system is activated otherwise the car will lag for an instant until liquid nitrous oxide reaches the intake.

The best time to use nitrous is at wide-open throttle only, unless you have a progressive controller. Due to the tremendous amount of increased torque, you will generally find best results, traction permitting, at early activation. Nitrous can be safely applied above 2,500 RPM under full throttle conditions.

It is possible to hold the nitrous button down until the bottle is empty, but 15 continuous seconds at a time, or less, is recommended.

The best position to mount a nitrous bottle is at a 15 degree angle with the valve end higher than the bottom of the bottle. The valve end of the bottle should point to the front of the vehicle and the valve knob and label should face straight up.

How long will the bottle last largely depends on the type of nitrous kit and jetting used. For example, a 125 HP Power Shot kit with a standard 10 lb. capacity bottle will usually offer up to 7 to 10 full quarter-mile passes. For power levels of 250 HP, 3 to 5 full quarter-mile passes may be expected. If nitrous is only used in 2nd and 3rd gears, the number of runs will be more.

The most reliable method to know how much nitrous is left in the bottle is to weigh the bottle to determine how many pounds remain. When a nitrous bottle is near empty a surging effect is normally felt.

The way to get the most out of your nitrous bottle is to keep bottle pressure around 900-950 psi. Most nitrous bottle have a pressure gauge that allows you to monitor this. If you live or operate a nitrous system in colder temperatures, it is recommended to purchase a bottle heater kit. Generally, ambient temperatures of 80-90 degrees F will allow for best power potential of nitrous kits.

There are no benefits to chilling a nitrous bottle. In fact, chilling a nitrous bottle lowers pressure dramatically and causes a lower flow rate of nitrous causing a fuel rich situation - reducing horsepower.

There are benefits to using nitrous with turbo and supercharger applications. In turbo applications, turbo lag is completely eliminated with the addition of a nitrous system. In addition, both turbo and superchargers compress the incoming air, thus heating it. With the injection of nitrous, a tremendous intercooling effect reduces intake charge temperatures by 75 degrees or more. Boost is usually increased as well, adding to even more horsepower.

Two types of nitrous systems are plate injection systems and direct port injection systems. The advantages of a plate system are ease of installation and removal, ability to change jetting combinations quickly, and in most cases, provide you with all the extra HP you will ever need (75 to 350 more HP).

Direct port type systems are recommended for in-line type engines like the Toyota Supra’s 2JZ-GTE or the Nissan Skyline’s RB26DETT engine to maximize nitrous distribution. Direct port injection is also desirable when the system is hidden under the manifold or when you need over 350 horsepower gain.

One of the advantages of using nitrous compared to other performance options is cost. Dollar for dollar, you can’t buy more performance with less money than nitrous. With a nitrous system, performance and reliability can be had for a much more reasonable price while still retaining the advantage of a stock engine for normal driving conditions. Plus, nitrous offers tremendous gains in torque without having to rev the engine to excessive rpm’s. These factors help your engine last longer than many other methods of boosting horsepower.

The danger of using nitrous oxide is detonation. Detonation is the result of too little fuel present during combustion (lean) or too low of fuel octane. An engine running with nitrous oxide depends heavily on the proper air to fuel ratio to prevent detonation from occurring. Too much ignition advance can also causes detonation.

In general, most nitrous kits are engineered for stock type engines using premium type fuels and minimal decreases of ignition timing. In racing applications, where higher compression ratios are used, a higher fuel octane is needed along with more ignition retard.