Injecting nitrous oxide into an engine increases the amount of oxygen in the combustion chamber, allowing more fuel to be burned to produce more power. Nitrous oxide also cools the intake air, increasing its density and allowing a higher mass of oxygen to fill the engine's cylinders.
Because the combustion of fuel requires a specific ratio of oxygen and fuel, the amount of oxygen supplied to the engine becomes the limiting factor in how much power can be produced. The rate of fuel flow can be controlled. Normally, engines combine fuel with atmospheric air containing 21 percent oxygen by volume.
Nitrous oxide contains 33 percent oxygen by volume. The oxygen is released when the nitrous oxide decomposes. This occurs when the nitrous oxide is heated to about 570 degrees Fahrenheit. The cooling effect on the intake air occurs because the nitrous oxide is stored as a liquid within the bottles at 1,000 psi. When it is used, it expands into a gas, causing a rapid temperature drop.
Although it is beneficial for producing power, running nitrous oxide continuously is impractical. A typical 5-liter engine consumes about 2,642 gallons of air per minute while running at 4,000 rpm, but it would only consume about 0.06 gallons of fuel. Thus, nitrous oxide is only used in short bursts when power is desired.