Please don't call it "noss." Just...don't. Call it "nitrous," "juice," "squeeze," "spray" or "laughing gas." Call it "A-Stoff" or "T-Stoff" if you're feeling ironic and historical; even "N2O" is acceptable in a written discussion. But do not under any circumstances call it "noss" in the company of people who are familiar with nitrous oxide outside of their DVD collection. Nitrous doesn't warp space and time, it won't make your diamond-plate floorboards fall off, and it doesn't explode in green flame. But it does make anything it's injected into a lot faster than it has a right to be, and anyone who knows how to use it a force to be reckoned with. So, please...don't call it "noss."
If you're like most people, you're probably still wondering what "A-Stoff" and "T-Stoff" are. Back in WWII, Germany invested a lot of its resources in liquid-fueled rockets, which worked by combining a combustible fuel with a powerful oxidizer. The oxidizing agent reacted with those fuels by "donating" some oxygen atoms to them, either setting it on fire when the two came into contact -- T-Stoff, or hydrogen peroxide -- or helping that fuel to burn very hot and fierce, as with A-Stoff, or liquid oxygen. Nitrous oxide is composed of two nitrogen atoms and one oxygen atom; under the heat and pressure of combustion, the oxygen atom splits off, combining with fuel molecules in the combustion chamber. This allows the engine to burn more fuel, and instantly make more power. Injecting nitrous isn't dissimilar from turning your engine partly into a liquid-fueled rocket, and with much the same effect on ignition.
The obvious question at this point is "If N2O works by splitting off an oxygen atom in the cylinder to burn more fuel, why not just pump in pure oxygen? Why include the nitrogen?" Some of the first engines ever experimented with did indeed run on a mixture of pure oxygen and hydrogen gases, and they were tremendously powerful -- for about a half-second, before they exploded. Pure oxygen gas makes fuel want to explode when it gets remotely warm, as it tends to do while it's next to the intake valve, and when the piston's coming up in the cylinder. Remember, fuel doesn't "explode" in your cylinders: it burns and expands in a controlled manner. By bonding the oxygen atom to a pair of nitrogen atoms, the oxygen isn't released to burn the fuel until the cylinder gets very hot. This in-built safety mechanism in nitrous means that it's oxygen atoms are always just assisting in the fuel combustion, and never causing it before it's supposed to happen.
There are to basic types of nitrous systems: "dry" and "wet." Nitrous can't make more power by burning more fuel unless there's more fuel in the cylinder to burn. When you trigger the nitrous system, an electronic valve opens that allows the pressurized nitrous to spray into the engine. That has to be met simultaneously with more fuel, or the engine will run lean, overheat and send expensive bits of metal flying through the sides of the block. "Dry" systems inject only nitrous oxide, and depend on the oxygen sensors and fuel injection system to quickly detect the lean condition and inject more fuel to compensate. A "wet" system injects both fuel and nitrous at the same time, ensuring that the engine never runs short of either. Wet systems are generally safer in terms of not blowing up, have much higher power potential and are the only option on carbureted vehicles. Dry systems are cheaper, easier to install, and are generally acceptable for shots of 150 horsepower or less.
"Plate" nitrous systems are the simplest; they sandwich in between the intake and carburetor or throttle body, and use a set of spray bars to send nitrous or nitrous and fuel into the engine. They come in wet and dry varieties, and can support big power, but wet plate systems shouldn't be used on multiport fuel injected vehicles. The intakes on these vehicles are designed to carry air, not liquid fuel, and you could end up with fuel distribution problems and -- yet again -- an explosion. For these applications and very high-horsepower race engines, "direct-port" nitrous injection delivers the juice at the base of the intake, directly into each individual head intake port. Functionally similar to multipoint fuel injection, this approach ensures that each cylinder is getting exactly the right amount of nitrous or nitrous-fuel mixture.
In terms of system power potential, it generally goes: dry-plate, dry-direct port, wet-plate, wet-direct port. Dry systems are always limited by your fuel injector size: If your injectors can deliver 300 horses worth of fuel, and you're making 200 without nitrous, then you can only put a 100-horsepower nitrous hit through the motor before you run out of fuel. Wet systems are limited only by what your engine and driveline can handle without going Hindenburg. Many nitrous users will opt to install a device that automatically retards timing by a few degrees when they hit the nitrous button, just to reduce the odds of detonation. Too much nitrous and too much timing is bad, but too little nitrous is no better when it comes in spurts. Those huge clouds of fog you see nitrous cars spewing at the start line aren't -- just -- for show; they're valve purges used to eliminate air bubbles in the nitrous line. Purging lines before a race is important for consistent nitrous delivery. And it looks cool.
Those seeking to juice their way to legend will often install multiple "stages" of nitrous, splitting one big hit into two smaller, separately triggered hits for better control. Controlling the nitrous hit's power doesn't just help you keep your vehicle pointed straight and tires planted, it also helps your driveline to survive without the kind of massive, hammer-like shock load that breaks parts. Sure, it's fun feeling like you just got rear-ended by a truck when you press the go-fast button, but that kind of violence breaks transmissions and other driveline components, and puts undue stress on the engine. For these reasons, many opt to go with a more progressive "soft hit" nitrous system, which feeds in the nitrous-fuel mixture over a period of time rather than opening the flood gates all at once. It also gives the tires a moment to settle and bite in so they don't break loose when the full power comes on.
Speaking of which: If you want to win races, engage your nitrous the instant you have the traction to put the power down. More nitrous down more of the track makes for faster times. Forget the movies: as long as you have the traction, there's no such thing as too soon, kid.
"Nitro" is and always has been short for "nitromethane," the powerful, oxygen-containing fuel used in Top Fuel dragsters. It's not the same as "nitrous."
