Pete Epple Technical Editor
September 10, 2010
Photos By: Team MM&FF, Courtesy Of Zex, John Zeilinga

Since the first automobile hit the streets, people have been trying to find ways to make them faster. Power adders have helped performance-based automotive enthusiasts and racers achieve astronomical power levels, and nitrous oxide is one of the most affordable and easiest ways to add power when you want it.

In an internal combustion engine, the incoming air supplies oxygen, which is mixed with fuel, compressed, and then ignited in the combustion chamber. This results in a powerful release of energy and heat, which causes the downward force on the pistons that makes torque and horsepower. Therefore, supplying more oxygen offers the ability to burn more fuel (by maintaining the proper air/fuel ratio), and ultimately equals a rise in the horsepower potential.

As many of you know, nitrous oxide injection is a simple and efficient way to add more oxygen to the combustion process. In the most basic terms, nitrous oxide (N20) is two parts nitrogen and one part oxygen. It is condensed and stored as a liquid, and instantly turns into a gas when it's introduced into the atmosphere.

Once the blend of nitrogen and oxygen enters the combustion chamber, the heat from the ignited fuel (about 570 degrees Fahrenheit) breaks the chemical bond, releasing both the nitrogen and oxygen molecules. The oxygen released can be used for combustion, allowing more fuel to be burned, which creates higher levels of cylinder pressure, resulting in more power. It would be unsafe to store and then simply inject pure oxygen into the cylinders because of the risk of fire.

For most street/strip applications, the vast majority of nitrous kits are simple to install, and can be done in less than a day in your garage or driveway. Also, there are a few options when it comes time to pick your nitrous kit.

Single-port nitrous kits inject nitrous oxide (dry) or nitrous oxide and fuel (wet), from either a single nozzle or a plate, into the intake stream. For the engine to make more power and the air/fuel ratio to be correct, extra fuel has to come from somewhere. In an EFI application, tuners can increase fuel pressure (or adjust pulse width of the injectors) to supply the needed fuel. Some kits apply nitrous pressure to the fuel rail when the system is activated, which causes an increase in fuel flow through the injectors when the system is initiated. In a carbureted application, simply running larger jets will do the trick.

In a wet system, the nozzle or plate injects fuel with the nitrous oxide to prevent a lean condition. When the nitrous oxide's chemical bond breaks during combustion, the extra fuel is there with all the oxygen to burn and create more power. These systems often have better atomization of the fuel and nitrous due to the fact that they normally share the same injection point.

"Plate systems offer excellent nitrous distribution," explains Matt Patrick, product manager for Zex. "In a carbureted application, there is usually not as much plenum volume as in an EFI application. The nozzles in an EFI system inject a very high-velocity plume of nitrous directly into the air and fuel stream. This creates a homogenous nitrous/fuel mixture, which is when nitrous oxide is the most effective."

The scalability of nitrous oxide is a huge benefit to running one of the many available systems. Kits can range from as low as 10 extra horsepower to multiple stages in excess of 2,000 hp. The kits we've been discussing for street/strip applications are generally in the range of 250 hp or lower.

When it's time to make some serious power, a direct-port system is the way to go. A direct-port nitrous system incorporates individual nitrous and fuel lines that are installed in each runner of the intake manifold. This allows an even supply or flow of nitrous oxide and fuel to each cylinder. These systems can be very complex, and the intake manifold must be drilled and tapped for the nozzles, as well as routing the rest of the system's plumbing. This also offers the ultimate in tuneability since each cylinder can have its own jetting.

"Direct-port nitrous systems are superior in high-flowing applications," Patrick adds. "Being designed for such high-flow rates, the direct-port systems work best at or above the 300hp level. Below these nitrous levels, a nozzle system or a plate system offers more efficient nitrous delivery."

One of the other benefits to nitrous-oxide injection is the cooling effect. When contained under pressure, nitrous is in liquid form, but its property changes to a gaseous state prior to being injected into the engine. When nitrous oxide is introduced into the atmosphere, phase change occurs. Nitrous exits the nozzle or plate at about -127 degrees Fahrenheit, and the pressure change causes it to flash boil. The cloud you see when a purge solenoid is opened is the moisture in the air freezing as the nitrous leaves the system. When nitrous is injected inside the intake manifold or intake runner, the temperature drop from the expanding gas increases the density of the incoming air, which adds to the available oxygen for combustion.

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