Wet nitrous oxide kitis are the most common type of nitrous oxide system used today and it is my preferred choice. It is called a wet system because the additional fuel required by the nitrous oxide is provided by the nitrous kits setup. This is done by routing a additional fuel supply to a fuel solenoid valve which fires the fuel into the engine when the system is activated. Wet nitrous oxide kits are by far the easiest to install and understand as a simple fitting guide for adding additional fuel apply to pretty much all cars where as a dry system does not. Wet nitrous systems could also be described as a feature of a direct port nitrous oxide system, which is described in more detail below.