Wet or Dry?
There are literally hundreds of nitrous systems on the market, but they all fall into two basic categories: wet and dry. Wet systems deliver both nitrous and fuel into the intake manifold. The most common wet system, by far, is the carburetor plate setup, which is mounted below the carburetor to facilitate injection of fuel and nitrous into the intake plenum. In fuel-injected applications, a plate or nozzle is usually mounted just behind the throttle body to accomplish the same task. Plate systems are popular for good reason-they're easy to install, and the level of power being added-the shot, as it's called-is easy to adjust via a jet change. Another advantage to this setup is that the plates are calibrated to provide a proper air/fuel ratio, making it less likely you'll run lean and damage your engine.
The top-of-the-line wet system is a direct-port arrangement, which you'll usually find on drag cars. We've gotten indepth in the subject elsewhere, so we'll only touch on the basics here, but the great advantage to this setup is that nitrous and fuel are injected directly into each intake runner. This means that copious quantities of squeeze can be fed into each cylinder for maximum power production. These systems are also very accurate, since the amounts of fuel and nitrous being delivered can be individually tuned for each cylinder. Installation, on the other hand, is much more involved.
Dry nitrous systems differ from their wet brethren in that they only provide nitrous, which is sprayed into the inlet tract (which stays dry of fuel, hence the name). The extra fuel needed is added through the engine's existing fuel injectors. One common way to do this is to revise the fuel curve in the factory's ECM; another is to bleed off a bit of nitrous to trick the factory fuel regulator into providing more fuel. But since there's only a single nozzle to install in the inlet tract, dry systems tend to be pretty simple to install.
Which system is for you? If you're running a carb, it's really a matter of what your goals are. For the vast majority of street/ strip cars, a plate system is gonna be your best bet. If you're looking to run bigger shots (350-plus, according to our sources) and plan on spending more time at the strip than on the street, it may be time to avail yourself of the benefits of a direct-port system. When it comes to EFI, a wet system takes a little more work to install, but it is easier to tune for higher horsepower levels since you're controlling both fuel and nitrous levels. Dry systems are simple to install, but you must have a return-style fuel system to use one. As with anything else, it pays to be honest about your goals and intended usage and do plenty of research before purchasing a system.
Jets are pretty simple devices, but since they do determine how much nitrous and fuel you're injecting into your engine, it's a good idea to make sure yours are in good shape-the bores can wear over time-and that the sizes are clearly marked. NOS' Precision SS jets are made from stainless steel for accuracy and durability, and the size is laser-etched into them.