How It Works - Nitrous Oxide Systems

February 2014

Stephen Kim Jan 24, 2014 0 Comment(s)
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Spark Plugs

A common mistake for nitrous newbies is using the wrong type of spark plug. The heat range of a plug refers to the temperature of the ceramic material surrounding the electrode. Since the spark plugs must maintain a certain temperature to stay clean, using plugs with the wrong heat range can result in plug overheating or fouling. Additionally, many late-model engines run leaner air/fuel ratios than older muscle cars, which require larger plug gaps and a projected plug nose to help ignite the air/fuel mixture. This can cause misfires in a nitrous application, as the ground strap is too long to dissipate the heat produced by the nitrous oxide. "With a projected nose plug, the ground strap can act as a glow plug, retaining too much heat from cycle to cycle, which sets the conditions for pre-ignition. The solution is using a non-projected-nose plug with a shorter ground strap," Kyle explains. "The plug gap will also need to be reduced as the amount of nitrous is increased, allowing the ignition system to fire the plug against the increased cylinder pressure. The ideal heat range of a plug depends on the application and amount of nitrous used. The more nitrous an engine sees, the colder plug it needs."

Nos Time Based Progressive Controller 2/12

Cam Specs

Some racers argue that nitrous makes so much power on its own that cam specs aren't very important in a nitrous engine. On the flip side, optimizing the valve events for heavy doses of nitrous beyond 300 hp ensures squeezing as much power out of the nitrous pills as possible. "Nitrous allows you to burn more fuel, and that in turn makes more heat and power. If you make more heat, you must get that heat and exhaust out of the chamber," Kyle explains. That usually requires opening the exhaust valve earlier and holding it open longer with a nitrous motor than in a naturally aspirated configuration. Exactly how much the cam specs need to be changed is directly proportional to the volume of nitrous an engine uses. Many nitrous cams have wider lobe-separation angles than naturally aspirated engines, but the exhaust valve opening and closing points are more important than LSA figures.

Nos Pro Shot 3/12

Bottle Pressure

Nitrous oxide is a gas at room temperature, which means it needs to be stored inside the bottle at extremely high pressure to keep it in a liquid state. Bottle pressure is directly related to bottle temperature, so cool ambient temperatures will compromise performance. "Maintaining a constant pressure is one of the most important aspects of tuning a nitrous system for proper performance, and 950 psi is considered the ideal operating range. Since bottle pressure is what controls the amount of nitrous the engine is receiving, inconsistent bottle pressure can result in inconsistent performance," Kyle explains. "If the pressure falls off too fast during a run, the system will go rich, since the nitrous system will continue enriching the air/fuel mixture even though the flow of nitrous has been reduced. This causes a car to slow, or in the worse case scenario, damages parts. Ambient temperature of 80-90 degrees Fahrenheit is ideal for maintaining consistent bottle pressure, so in conditions cooler than that, we recommend using an NOS electric bottle heater."

Nos Refills 4/12


Due to the heat required to convert nitrous oxide from a liquid to a gas, nitrous oxide dramatically cools the temperature of the incoming air intake charge by 75 degrees or more. Consequently, it didn't take fans of forced induction to recognize this benefit. Even in an application where a supercharger or a turbocharger functions as the primary power adder, injecting a very small dose of nitrous can substantially increase horsepower due to its intercooling effect. "In forced induction combinations where there isn't space for a traditional air-to-air or air-to-water intercooler, a small 50-shot of nitrous can be used in lieu of an intercooler with great results. It can also help mask an intercooler that has been maxed out beyond its cooling capacity," Kyle explains.

Power Management

Thanks to the dramatic increases in low- and mid-range torque that a nitrous system offers, one of the great benefits of nitrous in a street car is how hard it hits. However, this isn't always desirable in a drag car, especially in small-tire racing classes. Fortunately, there are many ways of managing nitrous flow to ensure that the tires stay hooked. One of the most effective methods is running a multi-stage nitrous system. By installing two sets of solenoids, a dual-stage system allows limiting nitrous flow off the line to enhance traction, and then increases nitrous flow once a car is farther down the track. So instead of spraying 400 hp worth of nitrous all at once, the first stage can be limited to 200 hp, with a second stage injecting an additional 200 hp later on in the pass. Furthermore, NOS offers several progressive controllers that electronically ramp up the flow of nitrous based on a user-defined period of time. They work by pulsing the solenoids on and off to increase or decrease nitrous flow. "For example, racers can set a progressive controller to flow 25 percent of the nitrous off the line, then ramp it up to 100 percent 2 seconds into a run once there's more traction available," Kyle explains.

Nos Plate System 5/12


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