In this paper we extend Real Time Process Algebra by the silent step τ. We start by giving the operational semantics and we find a characterizing law of which the soundness and the completeness is proven. By adding the integral construct we can interpret symbolic (untimed) process terms as timed processes. We investigate the resulting τ-equivalence and come to a delay bisimulation with a stronger root condition. Finally we test the applicability of this notion of real time abstraction by proving the PAR protocol (Positive Acknowledgement with Retransmission) correct.