Patent ID: 8396649

Claim:
A method of processing a vibration signal collected from a vibration sensor mounted on an engine component outside of a combustion chamber to reconstruct in-cylinder pressure data for an engine cycle of an internal combustion engine, the method comprising the steps of: (a) collecting said vibration signal from said vibration sensor during said engine cycle and transmitting said vibration signal to a data acquisition unit; (b) processing said vibration signal in a computer processing unit by: (i) filtering said vibration signal to produce filtered data with frequencies in a frequency range associated with combustion effects inside said combustion chamber; (ii) processing said filtered data for said engine cycle to produce processed data that is corrected for errors introduced by charge decay and sensor sensitivity by applying at least one correction factor determined as a function of an estimated motoring pressure associated with said engine cycle, being the same engine cycle from which said vibration signal was collected; and (c) in said computer processing unit reconstructing said in-cylinder pressure data from said processed data for at least a portion of said engine cycle.