Device for detecting defective combustion in an internal combustion engine

The combination of a device for initiating the ignition of an internal combustion engine and a device for detecting combustion defects and modifying the ignition advance of the engine if said defects are detected, said combustion defect detecting device comprising a detector for placing on the cylinder head of the engine and a system for utilising signals delivered by said detector and comprising means for temporarily storing in the course of each cycle data relating to each cylinder of the engine, and means for comparing the data relating to each cylinder, stored in succession in the course of a cycle, with corresponding data obtained in the course of the following cycle, the utilization system comprising means connected to the detector for converting analog data delivered by the detector into digital data and said temporary storing means comprising as many shifting registers connected in series as the engine has cylinders, said registers being connected to a switching circuit which is connected to an output of said comparing means so as to be controlled by the output signal of said comparing means, said switching means being capable of selectively connecting a first shifting register with an output of the converting means and with an output of a last shifting register, the last-mentioned output being furthermore connected to means for adding a threshold value and connected to said comparing means.