Forcing more air into your engine so it burns more fuel is the basic concept behind superchargers and turbochargers. Another way to achieve this type of power boost is to change the actual content of the air charge. That's what happens when you add nitrous oxide, similar to the gas used by dentists to dull your senses. When injected into your engine, however, the effect is anything but dull. That's because it raises the oxygen concentration of the air from a typical figure of 20 percent (at sea level, less at higher altitudes) to a much higher level, so the engine can burn more fuel and produce more power.


The big advantage of nitrous is that it provides power on demand at the touch of a button. Otherwise, you don't even notice it's there. Also, a nitrous system is a lot less expensive and generally easier to install than a turbo or blower.

An extra bonus of nitrous oxide is the lowering of the intake temperature. When released from a pressurized bottle, the temperature of nitrous oxide drops to around minus 125 degrees, which can cool the overall intake charge by as much as 65 degrees, resulting in even more horsepower.

Direct Port

Nitrous systems consist of two basic types: dry manifold and direct port. The less expensive dry manifold design uses a single nozzle mounted in the throttle body or a plate underneath the carburetor, so it's also fairly easy to install. The direct-port systems have a fogger nozzle in each intake runner for a more complete and efficient distribution of nitrous oxide gas. This setup requires a more elaborate (and expensive) arrangement of tubing and a distribution block.

A simple injector spray-bar plate nitrous-oxide system is fine for street performance and certain classes of racing. When you need to add more than 350 horses, though, a direct-port system is the way to go. The extra tube-bending work required typically costs about $250 for most applications.

Dry Manifold

Both systems require a bottle of the go-juice to be mounted in the trunk. To get consistent performance when you're running nitrous (which is vital if you want to win drag races) you'll need to keep the bottle at the proper pressure. That means you'll need a gauge to monitor the pressure and a bottle warmer to bring up the temperature safely. Depending on how often you hit the happy button for some "squeeze," you'll need to periodically refill the canister. If you're injecting a considerable amount of nitrous, you may also need to upgrade your fuel system with a better (or supplemental) fuel pump.


Using nitrous requires correct technique, too. Never, ever hit the button unless you're at full throttle, or you'll damage the engine. While nitrous oxide may be the closest thing we have to a magic horsepower wand, it is not without its perils. Probably the most common nitrous-induced problem is an excessive lean condition. By introducing a great deal more oxygen into the combustion chamber, nitrous upsets the air/fuel ratio. If a corresponding measure of extra fuel is not added at the same time, the engine will run extremely lean, which results in detonation, elevated temperatures, and other serious problems.

Some nitrous companies have introduced computer-controlled systems that sense the oxygen content and compensate accordingly, a big plus when using nitrous in combination with a turbo or supercharger (for true hot rodders, too much power is just about right). Depending on the manufacturer, a system may use the vehicle's factory computer to correct the fuel/air ratio, or be tied directly into the injector drive circuit. On the latter, the system's control unit reads the oxygen sensor output and adjusts the injector pulse width itself, so the factory computer operates much as it would otherwise. Safety checks are included in the control module's programming, so if the oxygen sensor signal falls outside acceptable limits for too long, the nitrous system will shut down and an error code will be displayed.

Another problem sometimes encountered with nitrous oxide is simply overdoing it. If you have a high-mileage, somewhat tired old mill full of cast parts, it doesn't make sense to add a custom 200-hp nitrous system. Many nitrous kits are adjustable, so you can set them up to provide an additional 50, 100 or even 350 horsepower. For massive amounts of power, you'll need to upgrade your engine with high-performance parts. There are nitrous kits, however, that are designed specifically for bone-stock engines.

Specs & Stress

Even though most manufacturers have a safety margin designed into their engines to allow for increases in horsepower, there are no guarantees when you exceed the factory specs. Since you control the amount and frequency of use, you can determine the amount of stress on your engine and allow it to operate under normal conditions most of the time.

By the way, don't try inhaling automotive-grade nitrous, thinking it's the same as your dentist's "laughing gas." It has sulfur dioxide in it, which can burn your lungs. Save the squeeze for your vehicle, and get your grins from hitting the throttle.



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