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For the development of a very high efficiency engine, the continuous monitoring of the engine operating conditions is needed. Moreover, the early detection of engine faults is fundamental in order to take appropriate corrective actions and avoid malfunctioning and failures. The in-cylinder pressure is the most direct parameter associated to the engine thermodynamic cycle. The cost and the intrusiveness of the dynamic pressure sensor and the harsh operating condition that limits its life-time, make the direct measurement of the in-cylinder pressure not suitable for mass production applications. Consequently, research is oriented on the measurement of physical phenomena linked to the thermodynamic cycle to obtain useful information for the ICE control.

For the development of a very high efficiency engine, the continuous monitoring of the engine operating conditions is needed. Moreover, the early detection of engine faults is fundamental in order to take appropriate corrective actions and avoid malfunctioning and failures. The in-cylinder pressure is the most direct parameter associated to the engine thermodynamic cycle. The cost and the intrusiveness of the dynamic pressure sensor and the harsh operating condition that limits its life-time, make the direct measurement of the in-cylinder pressure not suitable for mass production applications. Consequently, research is oriented on the measurement of physical phenomena linked to the thermodynamic cycle to obtain useful information for the ICE control.

In recent years, the motorcycle muffler design is moving to dissipative silencer architectures. Due to the increased of restrictions on noise emissions, both dissipative and coupled reactive-dissipative mufflers have substituted the most widely used reactive silencers. This led to higher noise efficiency of the muffler and size reduction. A dissipative muffler is composed by a perforated pipe that crosses a cavity volume filled by a fibrous porous material. The acoustic performance of this kind of muffler are strictly dependent on the porosity of the perforated pipe and the flow resistivity characteristic of the porous material. However, while the acoustic performance of a reactive muffler is almost independent from the presence of a mean flow for typical Mach numbers of exhaust gases, in a dissipative muffler the acoustic behaviour is strictly linked to the mass flow rate intensity.

In order to ensure a high level of performance and to comply with more severe limitations in term of fuel consumption and emissions reduction, a continuous supervision of the engine operating conditions, by monitoring several parameters, is needed. The growing use of turbocharger (TC) in ICE for automotive and industrial applications suggests to use the TC speed as a possible feedback of engine operating condition. Indeed, the turbocharger behavior is connected to the thermo-dynamic and fluid-dynamic conditions at the engine cylinder exit: this feature suggests that the turbocharger speed could give useful information about the engine cycle. In previous studies, a preliminary investigation of the relationship between the engine performance and the turbocharger speed of a four-stroke multi-cylinder turbo-diesel engine was carried out by varying the operating conditions of the engine such as fuel mass flow rate, EGR rate and back pressure at the turbine outlet.

A condition monitoring activity consists in the analysis of several information from the engine and the subsequent data elaboration to assess its operating condition. By means of a continuous supervision of the operating conditions the internal combustion engine performance can be maintained at design-level in the long term. The growing use of turbocharger (TC) in automotive field suggests to use the TC speed as a possible feedback of engine operating condition. Indeed, the turbocharger behavior is influenced by the thermo and fluid-dynamic conditions in the cylinder exhaust port: this feature suggests that the TC speed could provide useful data about the engine cycle. In this study the authors describe a theoretical and numerical analysis focused on the TC speed in a four stroke turbo-diesel engine. The purpose of this study is to highlight whether the TC speed allows one to detect the variation of the engine parameters.