what zex is, is a "dry kit," quoting pdhaudio:
DRY
By far the easiest to understand and use of all four types is the dry injection system so we will cover it first. Probably when you think of a street-car running nitrous you are thinking of this form of injection. Companies such as Zex and NOS have made dry systems extremely popular recently. Usually these systems are activated at wide-open throttle (WOT) and are almost as easy to use as just flooring the accelerator. A dry manifold injection system works by simply spraying only nitrous into the intake manifold. At this point, the cars fuel injectors must supply enough fuel to burn the additional oxygen.
Now, remembering what we learned earlier about fuel being the key to nitrous injection, we can see the biggest disadvantage to having a dry system. Because the cars fuel injectors are supplying the additional fuel the amount of power you can gain from a dry system is going to be limited. As a general rule of thumb you can only get a maximum of a 75 hp shot out of a dry system. Another common problem with dry kits is that they suffer from distribution problems, meaning that there is always the possibility that the cylinders will get an uneven amount of nitrous sprayed into them. This uneven distribution can cause the injection to be less potent. However, dry kits have some good advantages as well. As I mentioned above, dry kits are very easy to install and use so that means they are perfect for the nitrous beginner. Also if you opt for a Zex kit you get the benefit of a computer controlled safety module. Just be careful and do not let the safety features lure you into thinking that you are 100% safe from mishaps.
