Therefore, this paper presents an innovative methodology for instantaneous turbo speed estimation. The presented algorithm is based on the analysis of the signals coming from one accelerometer mounted on the compressor diffuser, or from one microphone facing the turbocharger. The estimation methodology can be divided in 2 steps. The first step consists in the estimation of turbocharger speed mean value, performed through a proper spectral analysis of the acquired signals (accelerometer or microphone). The second step is a time-based processing, that starts from the estimated mean turbo speed to refine signal filtering and determine the instantaneous turbo speed. The scheme of the overall estimation procedure is reported in Figure 5. The developed methodology proved to be effective in all the operating conditions taken into account in this work. Further investigations are currently being performed to implement the methodology in a Rapid Control Prototyping system, the goal being to develop an optimal turbocharger control strategy based on instantaneous turbo speed estimation.