In this paper we address the problem of computing silent paths in an Finite State Machine (FSM). These paths are characterized by no observable activity under constant inputs, and can be used for a variety of applications, from verification, to synthesis, to simulation.First, we describe a new approach to compute the Timed Transition Relation of an FSM. Then, we concentrate on applying the methodology to simulation of reactive behaviors. In this field, we automatically extract a BDD--based behavioral model from the RT or Gate Level description. The behavioral model is able to ``jump'' in time and to avoid the simulation of internal events. Finally, we discuss a set of promising experimental results in a simulation environment under the Ptolemy simulator.