One way to judge the popularity of a part or process is by the number of labels it acquires over the years. In the case of nitrous oxide, it has been called squeeze, spray, juice, fast gas, on the bottle, bottle fed or the single-syllable word nos. But no matter what you call it, nitrous oxide injection is the simplest, easiest and cheapest way to go fast that exists in hot rodding today.
What It Does
Nitrous oxide is a gaseous mixture of two parts nitrogen and one part oxygen (N2O). The gas helps make power in two ways. While nonflammable, its single oxygen molecule is used as an oxidizer to allow more fuel to be burned to create more heat and pressure during the combustion process. That is why nitrous must be accompanied with additional fuel. If additional fuel is not added, the engine will run lean, creating excessive combustion temperatures that will cause detonation and, eventually, severely damage the engine.
Nitrous oxide is stored at 800 to 1000 psi as a liquid, but injecting it into an engine converts the liquid nitrous to a gaseous state. That conversion reduces overall inlet-air temperature by absorbing heat, contributing to increased power by making the air/fuel mixture more dense. Inlet-air temperatures can drop by as much as 60 to 75 degrees Fahrenheit during the process. That’s important when you consider that power is increased by one percent for every 10-degree Fahrenheit drop in inlet-air temperature.
During combustion, at a temperature of 575 degrees Fahrenheit in the combustion chamber, oxygen separates from the nitrogen molecules and is available to help burn additional fuel. The nitrogen molecules act as a buffer to combustion, slowing the burning process to a more manageable rate as opposed to a violent explosion that is extremely hard on pistons, rods and crankshafts. That’s why nitrous oxide is used as opposed to pure oxygen.
How Nitrous Systems Work
A crucial element of nitrous-oxide injection is the input of additional fuel. Nitrous companies eliminate mixture guesswork by offering matched systems that mate known nitrous levels with safe amounts of gasoline. That’s why, at least for first-time nitrous users, the best bet is to use a matched system from one of the major manufacturers rather than a cobbled-up system.
To give you an idea of how a nitrous system works, take a look at the accompanying illustration. The nitrous tank stores the pressurized liquid nitrous until it’s ready for use. When the bottle’s valve is opened, pressurized nitrous exits on the upstream side of the nitrous solenoid. A matching gasoline solenoid is tapped into the engine’s fuel-delivery system and supplies the necessary fuel. In a plate-type system, both the fuel and the nitrous are introduced into the engine via a plate with small orifices drilled into spray bars, one for nitrous and one for fuel. For activation, most nitrous systems combine an arming switch, which merely powers the system, with a second momentary switch, which is usually a button placed on the shifter handle. The momentary switch completes the electrical circuit to open both solenoids. That introduces the combination of nitrous and fuel into the engine—and then it’s time to hang on!
What Can Happen
The foremost concern of any hot rodder is whether nitrous might be harmful to his engine. If installed and tuned properly for a particular application, nitrous will not harm an engine—although burned pistons and engine explosions are the reality checks that do play a part in the use of nitrous oxide. The gas makes serious cylinder pressure, however, and if enough cylinder pressure is added to an otherwise stock engine, it will fail. But basic 75- to 150hp kits are compatible with even stock engines and don’t present a danger to engine life if used properly.
That’s not to say that nitrous won’t hurt an engine if you decide to ignore the rules. Nitrous can bend connecting rods if triggered at too low an rpm, especially if the car is in high gear, since the additional power is more than the internal components can handle. Nitrous Oxide Systems (NOS) suggests not hitting the nitrous below 2500 rpm for the typical plate system. In addition, too little fuel pressure can also create a lean situation that has spit out many a head gasket or worse. Ignition timing also plays an important part in nitrous tuning. Timing should be retarded according to the manufacturer’s recommendations. We know of one heavily nitroused EFI engine that runs with 0 (zero) ignition lead to keep the engine out of detonation.
But don’t let these warnings intimidate you. Nitrous has been proven to be a safe, reliable and powerful addition to the hot rodder’s horsepower arsenal. Like any other power producer, though, it must be treated with the respect it deserves. And the best part is that there’s a system designed just for what you want.
