NOS, short for nitrous oxide systems, is built around one key ingredient: nitrous oxide (N2O), a colorless gas made of two nitrogen atoms and one oxygen atom. The gas itself is manufactured from ammonium nitrate, and the system that delivers it to your engine includes a pressurized bottle, solenoids, fuel lines, and spray nozzles. Whether you’re curious about the chemistry of the gas or the hardware bolted under your hood, here’s how it all works.
What Nitrous Oxide Is Made Of
Nitrous oxide is a simple molecule with the formula N2O. Each molecule contains two nitrogen atoms bonded to one oxygen atom, giving it a molecular weight of about 44 grams per mole. At room temperature it’s a colorless, slightly sweet-smelling gas. It’s the same substance used in dentist offices as a sedative and in whipped cream canisters as a propellant.
The reason it works as a performance booster is that oxygen atom. When nitrous oxide gets hot enough inside an engine’s combustion chamber, roughly 750 to 950°C (about 1,380 to 1,740°F), the molecule breaks apart into nitrogen gas and a free oxygen atom. That extra oxygen allows the engine to burn more fuel per combustion cycle, which translates directly into more power. The nitrogen acts as a buffer, absorbing heat and helping prevent detonation.
How Nitrous Oxide Is Manufactured
Commercially, nitrous oxide is produced by heating ammonium nitrate, the same compound used in fertilizer. A concentrated solution of ammonium nitrate and water (80% to 93% concentration) is heated to approximately 250°C (about 482°F). At that temperature, the ammonium nitrate thermally decomposes into nitrous oxide and water vapor. The reaction releases energy on its own, making it self-sustaining once it gets going.
The raw gas then goes through a series of purification steps to remove byproducts like ammonia and nitric acid, which form from a competing reaction that happens at the same temperature. After scrubbing and drying, the purified nitrous oxide is compressed into high-pressure cylinders where it’s stored as a liquid under pressure, ready for use in automotive, medical, or food-grade applications.
Components of a NOS System
The gas is only one part of the equation. A complete nitrous oxide system includes several mechanical and electrical components that work together to deliver a precise spray of N2O into the engine at exactly the right moment.
The core components are:
- Nitrous bottle: A high-pressure aluminum or steel cylinder that stores liquid nitrous oxide, typically mounted in the trunk. A siphon tube inside ensures liquid (not vapor) feeds into the supply line.
- Solenoids: Electrically controlled valves that open and close the flow of nitrous oxide, and in some setups fuel as well, when you activate the system.
- Supply lines: High-pressure braided hoses or hard lines that carry nitrous from the bottle to the engine.
- Jets: Small, precisely drilled orifices that meter the exact amount of nitrous oxide (and fuel, in wet systems) entering the intake. Swapping jet sizes is how you change the power level.
- Nozzle or plate: The delivery point where nitrous is sprayed into the intake manifold or directly into the intake runners.
- Activation switch: A button on the steering wheel or a throttle-triggered switch that tells the solenoids to open.
Wet vs. Dry Nitrous Systems
Not all NOS setups deliver fuel the same way, and the distinction matters for both performance and reliability.
A wet system sprays both nitrous oxide and extra fuel through the same plate or nozzle. When you hit the activation switch, two solenoids open simultaneously: one for the nitrous supply, one for a dedicated fuel supply with its own pump. The jet sizes installed in the plate determine how much of each gets delivered. Wet systems are popular because they’re self-contained. The fuel enrichment is built into the kit, so there’s less risk of running lean (too little fuel for the amount of oxygen), which can destroy an engine quickly.
A dry system sprays only nitrous oxide through the nozzle or plate. The extra fuel needed to match that additional oxygen comes from the engine’s existing fuel system. On fuel-injected cars, this is typically done by increasing the injector pulse width through a signal modifier or engine management tune. Dry systems are simpler to install since there’s no separate fuel plumbing, but they depend entirely on the stock fuel system’s ability to deliver enough extra fuel on demand. If the fuel system can’t keep up, you’re back to the lean condition that causes engine damage.
Why It Makes More Power
An engine’s power output is fundamentally limited by how much oxygen it can pull in per cycle. More oxygen means you can burn more fuel, and burning more fuel releases more energy. Nitrous oxide is roughly 36% oxygen by weight, compared to atmospheric air at about 23%. When the N2O molecules break apart from combustion heat, that released oxygen effectively makes the engine behave as if it has a much larger displacement or a forced-induction setup like a turbocharger.
There’s a secondary benefit too. Nitrous oxide is stored as a liquid under pressure, and when it’s released into the intake, it rapidly expands and cools the incoming air charge. Cooler air is denser, which means even more oxygen molecules packed into each cylinder. This cooling effect alone can add a measurable bump in power before you even account for the oxygen content of the gas itself.
The power gains depend on jet sizing and system configuration. A mild street kit might add 50 to 75 horsepower, while aggressive race setups can add 300 or more. The tradeoff is that your engine’s internals, fuel system, and ignition timing all need to handle the extra stress. Running a nitrous system that’s too large for your engine’s components is one of the fastest ways to bend connecting rods or crack a piston.