Misunderstood, misused in action media, and often mistaken for an explosive, nitrous oxide is the mysterious power adder to those who aren’t in the know.
But what is this curious chemical compound? How does it work to produce such a powerful burst? Is it as dangerous as many have claimed? To help answer these questions, I reached out to the experts at Nitrous Oxide Systems (NOS), Nitrous Express and Edelbrock to learn the ins and outs of N2O.
First, what is nitrous oxide? From a chemical standpoint, it’s a compound made up of two parts of nitrogen and a single part of oxygen. It’s used in many places, legally, including amateur rocketry and medicine. Famously, it was suggested in 1914 patent by Robert Goddard, the American rocket pioneer, as an option for liquid-fueled rockets. It’s the choice for use as an oxidizer by many, because when compared to other oxidizers, it’s non-toxic, stable at room temperature, easy to store, and relatively safe to carry on a flight.
Its first use in an internal combustion engine was during World War II by the Luftwaffe in the Göring Mischung 1 (GM-1) engines which were used at high altitudes. It was then developed by Otto Lutz on the Bf 109E/Z fighter and eventually to other aircraft. The British also used a variant of nitrous injection in modified Merlin aircraft engines for the de Havilland Mosquito and the Supermarine Spitfire. This system eventually made its way to ground vehicles, providing the same performance benefits. It offers a boost of power when activated and as needed, with shots that increase horsepower with an associated jet size.
How does that work? How does nitrous oxide provide a boost of power? It’s done when one of the nitrogen molecules decompose to release the oxygen molecules and the remaining nitrogen molecules as the temperature of the combustion chamber increases. This increases the amount of available oxygen in the combustion chamber. It’s a similar idea as to how a supercharger or turbocharger works, but instead of shoving in more atmospheric air into the combustion chamber, it does it chemically. It also makes it an easier package to install on a car over a turbocharger or supercharger.
“Hot rodders and drag racers have been opting for juice over boost for many years,” says Keith Jessee of Holley Performance, the parent company of Nitrous Oxide Systems (NOS). “The initial expense is significantly less than superchargers or turbos, and the installation is much, much simpler.” Jamie Wagner, product manager of NOS, agrees, “The mechanical knowledge needed to install a nitrous kit is very basic. Sometimes it’s as minor an operation as removing four bolts, installing a nitrous plate between the throttle body or carburetor and the intake manifold, and installing a couple of hoses.” He’s right, as many carburetor kits from many manufacturers could be installed with just a half-inch open-end/box-end wrench, a flat blade screw driver, and a 10-inch adjustable wrench.
Mike Wood, CEO of Nitrous Express also adds that it’s far less expensive. “A modern nitrous system can be installed by the typical auto enthusiast in only a few hours. It requires little or no tuning and typically cost less than 10% of a complete, installed, and tuned turbo or supercharger set up.” Smitty Smith, the Technical Sales Coordinator at Edelbrock, adds, “Nitrous Oxide doesn’t even require a laptop like a turbocharger or a supercharger when tuning them.” What Smitty is referencing here is adjusting the amount of nitrous by changing of the jets that controls the amount of the liquid sprayed out of the system. Provided you monitor the lean or rich condition of the engine during and after nitrous injection, which you can do without the need of an O2 monitor. You will have to be able to ‘read’ a spark plug, though.
That’s where many beginners make their mistakes when it comes to nitrous oxide injection. There is a risk of both going too lean and going too rich on a nitrous injection system. “Usually when an engine runs too lean on nitrous cylinder temperatures start climbing,” says Keith. “In extreme cases the cylinder temps can get so hot the pistons start to get soft and melt, this of course is no good for obvious reasons.” Mike Wood adds, “Every nitrous system must have a fuel supply that matches its power capability. NX offers the Maximizer 5 progressive nitrous controller which monitors A/F ratios and will either add or subtract fuel if the situation demands it or completely shut the nitrous down if the addition or subtraction of fuel cannot remedy the situation.”
Of course, Hollywood hasn’t helped the image of nitrous. Not only in the use but how explosive it is. This isn’t the case and is very, very far from the truth. Nitrous oxide is an oxidizer, just like oxygen, and isn’t even a propellant for rockets unless you use a catalyst decompose the compound at temperature of 1,070°F (577°C). Without that, nitrous will combust at 1112°F (600°C) at 21.3bar (roughly 309psi). So, even at typical bottle pressures of 900 to 1000psi, you’d still need to create a flame temperature just under the requirement to melt aluminum (aluminum melts at 1218°F or 659°C). However, there is the risk of over-pressurization at 3000psi but most nitrous oxide bottles, especially the ones sold by the companies our experts represent, have a pressure relief device in the form of a burst disk that prevents this from occurring. This typically happens from overheating the bottle, but heating the bottle is an accepted practice provided you do it safely.
Jamie says on this, “At times, the nitrous bottle needs to be heated to get the pressure to a level needed for the tune-up.” That means the use of a proper bottle heater, as Mike explains: “Bottle heaters are a requirement if you want your nitrous system to perform consistently and produce the power it is rated for. Heating your nitrous bottle with an open flame is extremely dangerous and will eventually result in a catastrophic bottle failure resulting in serious or fatal injuries.”
Jamie adds, “The most popular heaters are the silicon based, heating element type, that are wrapped around the bottle and powered by either a 12volt DC or 110volt AC source. The issue with this type of heater is there are typically no thermostats or over temperature protection devices. If left unattended, it can cause over pressurization of the bottle.” If you get one that works well, there is an advantage as Smitty points out: “Edelbrock sells bottle heaters, and they work well when monitored and you keep an eye on the bottle pressure. The best bottle pressure is 900-950psi and you will be consistent run after run.”
One of the things you’ll notice from anyone who uses nitrous is the spray of nitrous in the form of a cloud called ‘purging’. “The main reason for purging your system is so that the nitrous gas is in its gas state and as close to the solenoids as possible,” explains Smitty. “If you did not purge the system, you would not have the nitrous in a gas state, and your mixture of nitrous and gasoline will not be what you think it is.” Jamie explains it a step further: “Nitrous has two states of existence – gaseous and liquid [it is stored in the bottle, primarily in a liquid state]. The gaseous phase of nitrous is what we use to make power with, as it has to be in a gaseous form to split the oxygen molecules from the nitrogen. As the nitrous is in a gaseous form and is not as dense as liquid, so it would take much more of it to make the power we all want if it stayed in its liquid state.”
On top of the extra oxygen nitrous brings, there is another advantage when used within or ahead of the intake manifold. By converting to its gaseous form into the manifold, the intake temperatures will drop and create a cooler, denser intake air charge. It’s a similar advantage in power making that TBI and carburetors give over port fuel injection. The state change of liquid to a gaseous form, as the atomized state of fuel and the conversion of the gaseous state of nitrous by it boiling, carries the heat in the intake away and into the combustion chamber.
It also can be used in conjunction with a additional power adder like a turbocharger or supercharger to make up for a lack of boost or, simply, to get the maximum power out of an engine as possible. However, doing the latter requires very careful tuning considering how much oxygen will be added as boost comes in or as you feed in nitrous during boost and the risk of going too lean. The AEM video above graphically shows how nitrous is used in Fredric Aasbø’s Papadakis Racing Corolla during a run.
Nitrous oxide is an amazing power adder that gets a bad rap thanks to inexperienced tuners, the dramatics of Hollywood, and the rumors spread by those who don’t know any better. However, as with any power adder, if you do it in a controlled effort and monitor your engine as you tune with nitrous, the gains you get out of it can be equal to that of a turbocharger or supercharger. Even as a gas or liquid, nitrous is a safe thing to use provided you monitor bottle pressure and the lean/rich condition of your engine as you use it. If you’re thinking about using nitrous, don’t shy away from it. You’ll be glad you did.