This paper focuses on the preliminary design of aproportional solenoid aimed at controlling the lowpressure stage of a two stage pressure regulator forCNG applications.In particular, the dynamic performance of a two stagepressure regulator is firstly studied in the wholeoperational field of a four stroke, four cylinder sparkignition engine, equipped with a simplified lowpressureCommon Rail type collector serving fourPWM actuated single stage injectors.Then, with the aim of developing an electro-magneticdirect actuation, the dynamic performance of thesecond stage needle is adopted to drive the design ofa spires type, cylindrical coil proportional solenoid. Inparticular, both the steady and the transients stepsneeded to complete the preliminary design arehighlighted, and the influence of some relevant designparameters (such as the coil geometry and the air gap)on the actuation characteristics are evidenced.Finally, the proportional solenoid is introduced into astandard electro-magnetic control circuit, and itsdriving capabilities, its dynamic performance and itslimit of applications are determined for different actualoperating conditions of the second stage needle.