A fuel injected dry manifold system uses a nitrous ONLY injector to deliver only nitrous oxide to the intake. A wet manifold system introduces fuel and nitrous into the intake manifold usually through a combined fuel and nitrous injector. With a dry manifold system, the additional fuel is supplied by increasing fuel delivery through the original fuel injectors when the nitrous system is activated. It is called a dry manifold system because there isn't any fuel present in the intake manifold.
