Method and apparatus for determining a normal combustion characteristic for an internal combustion engine from an accelerometer signal

A control system for an internal combustion engine, said control system comprising:

• an accelerometer sensor mounted to said internal combustion engine at a location where said accelerometer sensor can detect oscillations that correlate to a combustion characteristic;
• a calibration table in which is stored, in association with a predetermined operating condition, a reference accelerometer signal collected from a calibration engine and an associated combustion characteristic derived from data collected by a calibration sensor when operating said calibration engine;
• an electronic engine controller programmed to receive a real-time accelerometer signal from said accelerometer and to cross correlate it with said reference accelerometer signal for said predetermined operating condition, to determine a real-time combustion characteristic from a combustion characteristic stored in said calibration table in association with said reference accelerometer signal;
• and
• a signal wire for transmitting said signal from said accelerometer sensor to said electronic engine controller.

A calibration engine comprising:

• an engine block comprising at least one combustion chamber defined by a cylinder, a piston and a cylinder head;
• a calibration sensor associated with said engine for detecting a combustion characteristic;
• an accelerometer sensor mounted to said internal combustion engine at a location where said accelerometer sensor can detect oscillations that correlate to said combustion characteristic;
• a data storage device for storing data associated with a predetermined engine operating condition, said data comprising a reference accelerometer signal collected from said reference accelerometer sensor, and a value associated with said combustion characteristic collected from said calibration sensor;
• and
• wiring to respectively connect said accelerometer sensor and said calibration sensor to said data storage device.