Glossary: Nitrous oxide

Whenever a car purrs rather loud, or even gives an energetic note from the silencer for that, most earthlings (or Muggles as the HP fans know it) think that the car has nitrous oxide in it… only a handful of us really know about its working.

The basics: The air/fuel mixture that enters the engine (regardless of the volume) is in the ratio of about 14:1 to 15:1(14 or 15 parts of air to 1 part of fuel). Exceptions are during starting/rapid acceleration, when the amount of fuel going into the cylinder is more(16:1 or 18:1). Now, if the fuel supplied is increased for the same quantity of air, then there wouldn’t be enough oxygen for all the extra fuel to be burnt completely, which means there is wastage of fuel. The oxygen content in the air is what supports the combustion of fuel and for a given kg of fuel, there only 210 grams of oxygen(21%) and that is very limited. Where as on the other hand N2O contains about 33%. If both combine, then there would be 51% oxygen. With 51% oxygen, the amount of fuel that can be combusted completely is more than 2 times which means there is almost twice the power from the same engine.

Nitrous oxide(N20) is non-reactive with most substances. However, once the temperature or pressure is raised, nitrous oxide can become a very volatile substance. When sufficiently heated(to around 300 degrees centigrade), N2O decomposes into nitrogen gas (N2) and oxygen gas (O2). When this decomposition occurs it is a highly exothermic reaction(chemical reaction that produces a large amount of heat). Thus the liberation of oxygen is made use of to give extra power by injecting extra fuel into the cylinders and thus more oxygen = more power.

To expand the explanation a bit… Nitrous oxide is an oxidizing agent which increases an engine’s power output by allowing more fuel to be burned than would normally be the case.
(Fact: N2O can be used to increase the power from as little as 0.5 hp to as much as 3,000 hp.)

Ok, we’ve talked enough of the basic working.

Let’s talk about the nitrous purge we all drool upon… Remember the scene in ‘The Fast and the Furious’ or in ‘NFS Underground’ where the car seems to spit out gases… An electrically operated valve is used to release gaseous nitrous oxide all the way up from the storage tank to the solenoid valve or valves that will release it into the engine’s intake tract. When this happens, for a moment the liquid N2O flashes to vapor as it is released… that’s purging.

Purging is not just for show off… Purging also has a purpose.. when the engine is purged, the N2O in the bottle is exerted on to the engine air intake tract to provide just the right amount of N2O in the engine to keep the combustion uniform when the N2O system is activated. Otherwise, when the system is suddenly activated the engine tends to bog a bit until the liquid N20 reaches the air intake. How cool is that!

Nitrous (as N2O is commonly or more popularly known) comes in two types…

1. Dry system
2. Wet system

In a dry nitrous system, the manifold is kept dry, the fuel is sprayed in through the injectors and nitrous is sprayed through the mass airflow sensor (MAF). This gives the vehicle’s ECU a signal that more fuel is required as the air is colder and denser than it should be, thus fooling the system to give in some extra fuel which is burnt more efficiently through the ‘extra air’ (the 1/3 mole of extra oxygen). This is how a Dry shot System works.

The wet system, on the other hand, gives out a spray of fuel along with air to maintain the proper air-fuel mixture, thus wetting the upper intake manifold - hence its name. Wet systems are difficult to install as any intake disorder can cause a backfire and can damage the engine. They are more expensive too.

Equipments such as these can be very harmful too… if you fit it on to an incapable engine or if a novice mechanic fits it into a capable engine it can only spell ‘Disaster’ with a capital ‘D’…

You can end up breaking your (car’s) pistons or ruining its camshaft or even worse… detonating your engine altogether!

You also destroy the poor, innocent Mother Earth and all your fellow-drivers with nitrogen… a very harmful green house gas, it has 270 times the effect of carbon dioxide on producing global warming

Anyway N2O rocks…