Patent Document ID: 20140336956
Application ID: 14272980
Patent Flag: 0

Claim One:
1. A method of real-time evaluation of at least the pressure in the combustion chamber of an electronically controlled spark plug ignition engine by sensing the ion current flowing through the spark, comprising the steps of: refining a mathematical model of the electrical and physical spark plug ignition system and combustion chamber of the engine through a calibration campaign of tests conducted on a test engine purposely equipped with specific sensors of combustion chamber pressure, ambient temperature, air/fuel ratio or correspondent throttle setting, and of other engine control settings, covering the respective ranges of variability of said parameters and/or settings, by iteratively testing the interactive performance of correlation coefficients of related terms of a mathematical expression of said model and comparing the expressed pressure value with the real pressure value as measured by a sensor; storing in a matrix or look-up table a set of time invariant correlation coefficients of said terms when the residual mismatch between the estimated pressure value generated by the mathematical model compared with the measured value remains within a maximum spread; and sensing the ionization current in the running engine, measuring or calculating at least one or more significant features of the waveform of the sensed ionization current and processing any or more measured or calculated feature values together with said matrix of time invariant coefficients and with a set of actual values of said parameters other than pressure and/or of said control settings of the running engine for producing an evaluated value of the combustion chamber pressure.