**Nomenclature**

In both plots, the interpolation lines and the corresponding R‐squared values are shown (they are the square of the correlation coefficients).The obtained R values are in all cases very close to the unity, giving a measure of the very high reliability of the relationship between the combustion indicators estimated via accelerometer transducer and computed by direct

A methodology was developed and validated, aimed at extracting from the signal of an accelerometer placed on a selected location of the engine block information about the combustion

Experimentation was performed on a two‐cylinder common rail diesel engine; two configura-

The analysis of the signals acquired in the engine complete operative field highlighted that it is always possible to select a frequency band in which in‐cylinder pressure and engine block vibration signals are highly correlated. Such a band has demonstrated to be reliant on the engine speed value, whereas load condition has a weak effect on the frequency band, in agree-

The accelerometer signals were filtered in order to remove all the vibration components due to sources other than the combustion. The obtained combustion‐related vibration contributions

in‐cylinder pressure measurements.

**Figure 16.** SOC and MFB50 for turbocharged engine.

94 Improvement Trends for Internal Combustion Engines

tions were tested: naturally aspirated and turbocharged.

ment with results obtained during previous investigations.

**4. Conclusion**

process in a diesel engine.

