Editing Nitrous oxide (section)

===Internal combustion engine===
{{Main|Nitrous oxide engine}}

In vehicle [[racing]], nitrous oxide (often called "[[Nitrous oxide engine|nitrous]]") increases [[engine power]] by providing more oxygen during combustion, thus allowing the engine to burn more fuel. It is an oxidising agent roughly equivalent to hydrogen peroxide, and much stronger than molecular oxygen. Nitrous oxide is not flammable at low pressure/temperature, but at about {{convert|300|C}}, its breakdown delivers more oxygen than atmospheric air. It often is mixed with another fuel that is easier to deflagrate. 

Nitrous oxide is stored as a compressed liquid. In an engine [[Inlet manifold|intake manifold]], the [[heat of vaporization|evaporation]] and expansion of the liquid causes a large drop in intake charge temperature, resulting in a denser charge and allowing more air/fuel mixture to enter the cylinder. Sometimes nitrous oxide is injected into (or prior to) the intake manifold, whereas other systems directly inject it just before the cylinder (direct port injection).

The technique was used during [[World War II]] by [[Luftwaffe]] aircraft with the [[GM-1]] system to boost the power output of [[aircraft engine]]s. Originally meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, technological considerations limited its use to extremely high altitudes. Accordingly, it was only used by specialised planes such as high-altitude [[reconnaissance aircraft]], [[schnellbomber|high-speed bombers]] and high-altitude [[interceptor aircraft]]. It sometimes could be found on Luftwaffe aircraft also fitted with another engine-boost system, [[MW 50]], a form of [[Water injection (engine)|water injection]] for aviation engines that used [[methanol]] for its boost capabilities.

One of the major problems of nitrous oxide oxidant in a reciprocating engine is excessive power: if the mechanical structure of the engine is not properly reinforced, it may be severely damaged or destroyed. It is important with nitrous oxide augmentation of [[petrol engine]]s to maintain proper and evenly spread [[operating temperature]]s and fuel levels to prevent [[pre-ignition]] (also called detonation or spark knock).<ref>Cline, Allen W. (January 2000) [http://www.contactmagazine.com/Issue54/EngineBasics.html "Engine Basics: Detonation and Pre-Ignition"]. ''CONTACT!'' Magazine</ref> However, most problems associated with nitrous oxide come not from excessive power but from excessive pressure, since the gas builds up a much denser charge in the cylinder. The increased pressure and temperature can melt, crack, or warp the piston, valve, and cylinder head.

Automotive-grade liquid nitrous oxide differs slightly from medical-grade. A small amount of [[sulfur dioxide]] ({{chem|SO|2}}) is added to prevent substance abuse.<ref name="Automotive gas">{{cite web|url=https://www.holley.com/support/faq/?category=NOS |work=Holley |title=Holley performance products, FAQ for Nitrous Oxide Systems |access-date=18 December 2013}}</ref>