How to Choose a Nitrous System

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The principle is simple: Air and fuel plus ignition equals horsepower; therefore, more air and fuel equals more horsepower. It's the equation that nitrous systems manufacturers use to help produce incredible power gains-in some cases up to 400 extra ponies-in everything from sport compacts to dedicated race vehicles.

Still, many performance enthusiasts don't fully understand how nitrous systems make extra horsepower. More importantly, they don't understand how to tune their nitrous system for optimal performance.

Summit Racing Equipment sells nitrous kits and accessories from top nitrous system manufacturers like NOS, Nitrous Express, Zex, Edelbrock,  Trick Flow Specialties, and Venom. To help you get the most from your nitrous setup, we'll show you some nitrous system basics and share some basic tuning tips.

Nitrous Basics
An engine uses three ingredients to make horsepower: Fuel, oxygen (air), and spark (ignition). The engine produces power by mixing the fuel with oxygen, which acts as a catalyst. The spark then ignites the air/fuel mixture. As the air/fuel mixture burns, it expands and moves the pistons down in the cylinders. A nitrous system enhances this combustion process-and the resulting horsepower output-by altering the air/fuel mixture three different ways:

1. Nitrous changes the air/fuel mixture by increasing the oxygen level. By injecting your engine with nitrous oxide, you're essentially adding concentrated oxygen to your intake charge. Nitrous oxide consists of two parts nitrogen and one part oxygen. When your engine receives a shot of nitrous, the heat of combustion breaks the nitrogen and oxygen apart and allows your engine to use the oxygen molecules to burn more fuel. A nitrous oxide system essentially gives your engine the capacity to burn larger amounts of fuel by supplying the  necessary oxygen to burn this greater quantity of fuel.

2. Nitrous systems improve fuel atomization. Atomization- the process by which raw fuel is broken down into tiny droplets-helps the ignition spark burn fuel more quickly and efficiently. Atomization is necessary because fuel must be converted into a vapor before combustion can be achieved.  Like any other liquid, raw gasoline must go through the process of evaporation to become a vapor. Engine heat and fuel atomization are the key ingredients in accelerating this evaporation process. While the combustion process provides the heat, a properly designed nitrous system will deliver proper fuel atomization by spraying the fuel supply in very small droplets. This promotes quicker evaporation and faster combustion in conjunction with the increased oxygen levels.

3. Nitrous systems increase the density of the air/fuel mixture. When nitrous oxide is injected, it instantly changes from a liquid to an extremely cold gas. The nitrous vapors chill the temperature of the intake charge, including the gasoline, by as much as 65 degrees F. As you probably learned back in "Horsepower 101," a colder, denser intake charge promotes greater combustion and increased horsepower production.

It's important to clear up one common misconception about nitrous: NITROUS IS NOT A FUEL AND DOES NOT INCREASE POWER BY ITSELF. Nitrous is a great way to add the necessary oxygen to burn more gasoline, but it is not combustible by itself. To gain power, you must add more fuel. The way you introduce more fuel to the intake charge depends largely on the type of nitrous system you choose.

Nitrous System Styles
As you shop for your nitrous system, you'll find a wide range of styles for carbureted and electronically fuel injected engines. There are cheater systems, piggyback systems, plate systems, and fogger systems. The bottom line, however, is that all nitrous systems fit into one of three main categories: Wet, dry, or direct-port systems.

A dry nitrous system is generally the easiest way to add nitrous to fuel injected vehicle. Dry systems work with your existing fuel system to supply the needed fuel to make horsepower. Additional fuel is delivered one of two ways. The first way to "trick" the OEM fuel injection system into supplying more fuel to the engine. In these cases, the nitrous system is designed to modify your factory computer's fuel curve to get the necessary fuel delivered to your engine. A second way is to increase the fuel pressure to the injectors by applying nitrous pressure from the solenoid assembly when the system is activated.

Wet nitrous systems come with their own fuel components to introduce additional fuel to your intake system. These systems include a separate fuel solenoid and nozzle, which spray the fuel at the same location as the nitrous. In most carbureted applications, the fuel and nitrous is introduced just below the carburetor. In fuel injected systems, the mixture is sprayed just ahead of the throttle body.

The last type of nitrous system is the direct-port system. This system introduces the nitrous and fuel mixture directly into each engine cylinder. Generally, these systems will inject nitrous and extra fuel together through a common nozzle. Because individual nozzles are placed above each cylinder, direct-port systems are the most accurate and powerful. They have more tuning capabilities than other styles of nitrous systems, because each nozzle can be adjusted to control the nitrous and fuel flow to the individual cylinders.

The drawback to direct-port nitrous systems is the complexity of the installation. They are typically the most complicated system to install, because they required the intake manifold to be drilled and tapped to accommodate each nozzle. That's why these systems are usually reserved for race vehicles.

Nitrous oxide is one of the more popular power adders for race vehicles and street rides alike. It's generally affordable, easy-to-install, and delivers a power boost when you want it and normal engine operation when you don't. The result is less stress on your engine, better overall drivability, and superior fuel economy over cylinder head porting, supercharging, and other power adders.

Now that you've learned the basics, we'll show you how get optimum performance from your nitrous system. That's coming in Part II of Nitrous Know-How.