Here is my last post on Nitrous
Dry Systems
For a dry system, you have a nozzle mounted approximately 6 inches in front of the throttle body. The nozzle injects only nitrous which is fed from the bottle, wherever it may be mounted. The additional fuel is provided through the fuel injectors requiring the computer to be essentially 'tricked' into thinking it has additional air coming in through the manifold (which essentially it does, but not in the way that it believes). The computer in turn tells the injectors to shoot more fuel into the cylinders. The injectors and fuel are under a load during nitrous injection, so it's a good idea to make sure your fuel pump and injectors can handle it. This will depend on what modifications are already done to your car besides the nitrous.
Pros: Does not have fuel flowing through the manifold so there is no worry of a puddling effect and a nitrous backfire in turn.
Cons: Relies on tricking the computer for its fuel supply. Anything that requires tricking the computer for such a vital element as fuel is not an intelligent way to approach anything, much less NITROUS INJECTION. Because the fuel is added through the injectors and the injectors all inject essentially the same amount of fuel and the nitrous is flowing through the manifold that does not apply equal air to all cylinders, the balance of air/fuel is going to be off. It'll be lean on some cylinders and rich on others.
Wet Systems
Wet systems are similar to dry systems. The only thing that is really different is the way the fuel is added to compensate for the nitrous. A wet system has a dual injection nozzle. It injects fuel along with nitrous into the air stream (6 inches in front of the throttle body), and the fuel is carried along with the nitrous into the engine compartment. This requires the dual injection nozzle to be connected to the fuel system. The fuel side of the injection nozzle is connected to a fuel solenoid, which is connected directly to the fuel rails, and the fuel solenoid opens at the same time the nitrous solenoid opens, which is when the system is armed and all conditions are met. You still must make sure you have a strong enough fuel pump to handle the fuel requirements of the nitrous injection.
Pros: Functions independently of the computer. The computer otherwise will not even know anything is going on during nitrous injection because of the way the fuel is supplied. Because the fuel and nitrous are added in together, the nitrous/fuel ratio will be the same, or at least very close to the same on each cylinder because the fuel and nitrous are flowing TOGETHER in the manifold.
Cons: Having fuel flowing through the manifold is not the safest thing in the world. Theoretically if you have enough air intake velocity (injection above 3,000RPM), you should not have to worry about a backfire, but that is not a sure science. If fuel puddles it can create a nitrous backfire that can damage the motor and/or intake system.
Direct Port Systems
Direct Port systems are very different from the dry and wet EFI systems. A direct port system has a nitrous injector and a fuel injector on EVERY cylinder. When the system is armed and fired both the fuel and nitrous injector do their thing. This method is safer because it bypasses the manifold entirely and does not rely on tricking the computer for its fuel supply.
Pros: Efficient. Safe. Powerful. By far the most advanced nitrous system on the market.
Cons: Expensive. By far the most expensive nitrous system on the market.
Nitrous oxide is a non-flammable compound of nitrogen and oxygen. At room temperature, nitrous oxide is a gas, but it is easily liquefied and stored under pressure. Technically, each molecule of nitrous oxide is comprised of two atoms of nitrogen bonded to one atom of oxygen. At temperatures above 565-575º F., nitrous oxide breaks down into separate nitrogen and oxygen molecules. When injected in a vaporous state to the intake air of an internal combustion engine, the resultant heat of compression (on the compression stroke of the engine) breaks down the nitrous oxide compound into inert nitrogen and free oxygen available to support the combustion of extra fuel. This means more fuel can be burned than air alone would support. Burning more fuel releases more heat, which creates more expansion of the working fluid (mostly nitrogen) in the cylinder for more pressure on the piston. The result is more power.
Air/fuel in nitrous
The chemically correct nitrous to gasoline ratio is 9.649:1, but that is too lean to run safely. The chemically correct air to gasoline ratio is 14.7:1, but at wide open throttle, we cannot run that lean without going lean. The problem is that every bit of oxygen does not find and mix with every bit of gasoline. Same goes for nitrous, you need a richer mixture to better the chances of the nitrous mixing with fuel. If a nitrous engine runs lean, it can destroy the engine in a matter of seconds. There must be enough fuel for the nitrous to react with, if there isn't, temperatures rise rapidly. The oxygen that couldn't react with fuel will oxidize any parts that get hot enough, and the next thing in line to burn is aluminum, so don't run lean
A NX 100 shot with a Gen II upgrade, MSD Window swtich, NGK TR6 plugs and that is all you need for a good nitrous kit.
