Engineering Question #3966

dave hack, a 36 year old male from brisbane asks on October 23, 2007,

Nitrous oxide when used in motorsport is often classed as "forced induction" although is it really forced induction? Does the pressure of the nitrous oxide (900psi in the bottle) allow more volume of air/fuel to be "forced" into the engine, or does it still rely on the engine "sucking" in the extra charge of air and fuel.

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The answer

John Jones answered on October 29, 2007

Nitrous oxide has two effects. The first major effect is that it decomposes in the cylinder to produce oxygen, thus allowing more complete combustion. The second effect is that the nitrous oxide is usually supplied as a liquid under pressure. When it is injected into the intake manifold, the liquid vaporises and cools, thus cooling the intake air and fuel and effectively increasing its density. Through this second effect, it does increase the amount of air/fuel that the engine takes in -- though this is due to cooling the intake rather than pressurising it.  This is not usually classed as forced induction, though.

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