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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Nitrous oxide systems are also nearly maintenance-free. Most are tested to extreme levels to ensure great long-term reliability. "Often there are issues on the electrical side of the system that cause problems," Patrick adds. "If the system is not installed properly and wires are spliced incorrectly, problems can arise.

"The weather and vehicle storage conditions can also affect the electrical side of the system. Over time, the connections can corrode and cause activation failures."

We also recommend periodic inspection of the lines, bottle condition and mount, and the solenoids and underhood hardware.

Tuned Up
Because nitrous has the ability to seriously alter the air/fuel ratio, tuning is extremely important. It's very easy to cross the boundaries of what is safe (lean or rich), and engine failure can occur if your engine and nitrous oxide system are not properly tuned.

"There are many factors that go into tuning a nitrous setup," explains Steve Johnson, owner of Induction Solution, which has years of nitrous tuning experience. "Nitrous systems and engine parameters really need to be tuned on an individual basis for optimal results. Some of the bigger companies will throw out blanket tuning rules, but with today's fuels, cylinder heads, camshafts, and intake manifolds, you really need to tune each setup specifically.

"The best thing you can do is thoroughly read the instructions that come with the kit. Following the manufacturers guidelines will give you a solid starting point for making power." Then take baby steps, first going with a small shot or horsepower increase. And check the spark plugs often, whether dyno or track testing.

Before you install your nitrous system, make sure your engine is in good working order, and know if existing engine components may need to be changed or adjusted. Depending on the system and the amount of nitrous and fuel you are injecting, ignition timing advance may need to be reduced and the spark plugs swapped for ones with a colder heat range. Spark plug gapping may also need to be closed up to prevent a misfire due to increased cylinder pressure.

"There are definitely things that need to be monitored," Johnson adds. "The octane of the fuel, heat range of the spark plugs, timing, and bottle pressure all need to be watched to ensure the combination is running properly."

A properly filled nitrous bottle with proper pressure is what supplies the constant flow of nitrous oxide to the engine. Bottle temperature and pressure are directly related and need to be monitored for consistent results.

Additionally, since bottle pressure is critical, temperature becomes very important. Stored in the bottle, nitrous oxide is a compressed gas-so when the bottle temperature rises, so does the pressure.

According to NOS, its kits are designed to work best between 900 and 1,000 psi of bottle pressure with optimal pressure at 950 psi. This is achieved with a bottle temperature of 85 degrees. If the pressure is too high, the initial hit will be much harder, but the bottle pressure will reduce dramatically and the vapor pressure inside the bottle will not regenerate itself fast enough to supply a constant flow of nitrous for the rest of the run. On the other hand, low bottle pressure will result in a softer initial hit with less pressure fall off over the course of a run.

Companies offer different versions of bottle heaters that give users the ability to control bottle temperature and pressure.

When a 10-pound nitrous bottle is properly filled, it should weigh 24 pounds, 12 ounces. It is very important that nitrous bottles are not overfilled. The bottle is designed to hold a specific amount of liquid-nitrous oxide with room for expansion as the liquid converts to its gaseous state. Over-filling the bottle can result in pressure levels above what the bottle can contain. Though the bottle's valve is designed with a pressure relief valve, too much pressure can cause the bottle to burst, resulting in serious injury or death.

Proper bottle mounting is also important. The pick-up tube in a nitrous bottle generally runs straight through the center of the bottle until the last 5 or 6 inches. At this point, it will turn approximately 45 degrees towards the bottom back section of the bottle. This ensures the pick-up tube remains submerged in the liquid nitrous oxide. If the bottle is mounted incorrectly, the pick-up tube may not be submerged in the liquid nitrous, and nitrous vapor will be pushed through the system. This will cause inconsistent power levels throughout passes at the track.

Your nitrous bottle valve should also be shut off when not in use, with the system purged. "Pressure in the system when it is not in use can cause damage to the plungers in the solenoids," Johnson adds. "If the solenoids fail and nitrous flows past the seals, nitrous in the intake manifold can cause a backfire when the engine is started."

Activating the nitrous system inside the proper operating window also is very critical. Engaging the nitrous at low rpm can result in a nitrous backfire and severe engine damage. With lower amounts of nitrous, the system should be activated no lower than 2,500 rpm. As the amount of nitrous increases, so should the rpm of when it is engaged.

The system should only be operated at wide-open throttle. Loading the intake plenum with nitrous and fuel under part throttle can also result in a nitrous backfire.

As nitrous systems become more advanced, there are components that can be added for more control of the overall system. Progressive injection controllers give you the ability to manage when and how much nitrous and fuel is being injected into the engine at any specific time. It allows you to ramp in the power, which can be helpful on the street or at the track.

If the system is capable of 300 hp, with a progressive controller, the system can be tuned to inject a smaller amount of nitrous and fuel first, and scale up to full power at a rate dictated by the tuner. These controllers are great in situation where traction is limited or with multiple-stage nitrous systems due to the torque spike when each stage is activated.

More horsepower definitely makes the hot-rodding world go round. When you want affordable power gains at the push of a button, nitrous oxide is the best way to go. It's relatively low initial cost and ease of operation make it a great power adder.

Bang For Your Buck
Nitrous oxide is one of the best bang-for-your-buck performance upgrades. Its simplicity, ease of use, and great performance gains make it an incredible way to add more power on demand!

When you look at the cost of a typical nitrous kit compared to a supercharger or turbo, which offers a better bang for your buck? A supercharger or turbo kit is often a one-time purchase, and the power is there whenever you want. Unfortunately, the up-front cost is much higher than a nitrous-oxide kit. Let's say the average supercharger kit is about $5,500, and the average cost of a nitrous kit is about $700. If you use a 100hp or 125hp shot, you'll get about four to five quarter-mile passes out of a 10-pound bottle before it needs to be refilled. The average cost to fill a 10-pound bottle is about $35. If $5,500 is our spending limit, how many times can we refill the nitrous bottle before it equals the cost of the supercharger kit? Once you spend the $700 on the nitrous kit, you're left with $4,800. With $4,800 to spend on refills, you'll get about 137 refills. If you go to the track about once a month and average 50 passes year, you can make your $5,500 last almost 14 years!

The downside is our calculations are based on track-only use. The supercharger will be there whenever you want the extra power, but as you know, there can be problems related to blowers. Nitrous allows you to maintain 100-percent stock-type driveability and mpg when the gas is not flowing. If you were looking for the same level of performance and nitrous oxide was your power adder of choice, street use would greatly reduce the length of time before the costs equalized.

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