Engineering Explained: How NOS Works

Contrary to popular belief, if your car is topping out at 140mph, NOS is not a necessity. There are other ways of increasing power, but few are as cheap and easy to implement (albeit, if the engine can handle it)

Remind me later

The purpose of a nitrous oxide system is to increase the power output of an engine. It does this by increasing the amount of fuel that can be burned, by increasing the oxygen supply. To get an understanding of how nitrous systems work, let’s first take a look at the components involved.

1. Nitrous Bottle

A bit self explanatory, this tank holds the N2O pressurised in liquid form.

2. Nitrous Feed Line

Because nitrous tanks are often located in the rear of the vehicle, a feed line is used to supply liquid nitrous to the nitrous plate for injection.

Engineering Explained: How NOS Works - Tuning

3. Nitrous Plate

The nitrous plate is installed between the throttle body and the intake manifold and is where both additional fuel (in wet nitrous systems) and nitrous are injected. There are solenoids for both N2O and fuel, which inject when the engine is operating at wide open throttle. Note that this is only one example of the various methods of injecting nitrous.

4. Fuel Rail Adapter

This mounts between the fuel line and the fuel rail, allowing for the nitrous plate to tap into the fuel line.

5. Brass Jets

These small brass fittings have orifices to allow for various amount of nitrous or fuel flow through them. The larger the orifice, the more fuel or nitrous will flow, and thus the engine will produce more power. A fitting is selected based on the desired power output. This fitting is installed between the nitrous/fuel lines and the fitting connecting to the nitrous plate solenoids.

Nitrous Plate - Blue N2O Solenoid On The Left, Red Fuel Solenoid On The Right
Nitrous Plate - Blue N2O Solenoid On The Left, Red Fuel Solenoid On The Right

6. Electric Things & Stuff

Obviously where things get technical. Sensors, relays, and wires are used to connect to the throttle position sensor as well as solenoids on the nitrous plate. This particular setup activates nitrous when the engine is at wide open throttle.

7. Purge Valve

Purge valves are not required for a nitrous system and they are often used simply to draw attention; however, they do serve a small purpose. The valve allows you to directly vent from the feed line to the atmosphere. The goal is to eliminate any gaseous nitrous that may be in the feed line between the nitrous bottle and the nitrous solenoid. This ensures that liquid nitrous will be sprayed immediately into the nitrous plate when you hit wide open throttle.

Brass Jets: 35-136 N2O Jets Shown
Brass Jets: 35-136 N2O Jets Shown

So how does it work?

1. For this particular system to operate, the engine must be at wide open throttle. Once there, a sensor receives a signal from the TPS sensor that signals for the fuel and nitrous solenoids to open up, allowing for flow.

2. As the liquid nitrous is injected, it changes state to a gas due to the lack of pressure in the surrounding air. When it changes to a gas, it drops in temperature to -88.5 degrees Celsius. This is actually one of the ways it helps to increase horsepower. As it cools the intake charge, it allows for more air in the cylinders, enabling you to burn more fuel.

3. The oxygen atom attached to N2O has a strong bond, but this can be broken with heat. As the piston compresses the intake charge (as well as during combustion), the resulting heat breaks the oxygen atom off the N2O molecule.

4. Now that the oxygen atom is isolated, it is freed up to be used in combustion. It combines with the additional fuel to create extra heat and pressure, increasing the amount of power the engine generates.

Here’s a video further explaining nitrous systems, including the difference between wet and dry setups: