Abstract: An engine misfire detector comprises an opto-electric sensor for monitoring light produced by combustion inside a cylinder. The sensor is connected to a variable gain amplifier having a gain control circuit for controlling the amplifier gain. The output of the gain control circuit is compared with a threshold in a comparator to provide a misfire detection signal. The transfer function of the gain control circuit includes an integral term.

Abstract: A control system for an internal combustion engine has an ignition timing control device and a combustion duration control device such as a mixture controller. Sensors detect the start and end of combustion which are compared with a look-up table of target values for the engine speed and load to provide error signals. The processed error signals provide corrections which are added to base values from look-up tables of ignition timing and mixture and supplied to the control devices so as to tend to eliminate the error signals, so that the engine runs with its designed start of combustion and combustion duration values.

Abstract: A method of monitoring combustion within a cylinder of a reciprocating piston internal combustion engine comprising deriving first and second electrical signals representative of light intensity within the cylinder by means of first and second optical transducers of spaced spectral response, said first and second optical transducers observing the combustion event at a common location, or at closely adjacent locations, and, establishing a signal representing the ratio of said first and second electrical signals, said ratio signal being used as, or to obtain, a control parameter for an engine control system. The invention also resides in apparatus for monitoring combustion in accordance with the above method.