A “dry” nitrous system simply means that the fuel required to make additional power with nitrous will be introduced through the fuel injectors.
The second type of nitrous kit is the “wet” style of kit. These kits include carburetor plate systems and add nitrous and fuel at the same time and place.
The last type of system is the direct port system. It introduces the nitrous and fuel directly into each intake port on an engine. These systems will normally add the nitrous and fuel together through a fogger nozzle. The fogger nozzle mixes and meters the nitrous and fuel delivered to each cylinder. This is the most powerful and one of the most accurate types of systems.