A PROCESS AND AN APPARATUS TO ADJUST THE IGNITION TIMING OF AN INTERNAL COMBUSTION ENGINE

A process to adjust the ignition timing of an air-fuel mixture in a combustion chamber (6) of an internal combustion engine (2) , the process comprises determining a first quantity indicative of a pressure of the mixture for a cycle of the engine, determining a second quantity indicative of a speed of the engine (2), determining a third quantity indicative of a first temperature of a conditioning fluid, providing a heat exchange mathematical model for the combustion chamber (6), which maps the three quantities from the first to the third one onto a fourth quantity indicative of a second temperature of a wall portion (3, 5) around the combustion chamber (6), estimating the fourth quantity by means of the three determined quantities and by means of the mathematical model, and adjusting the ignition timing as a function of the fourth estimated quantity.