Abstract: A dynamic combustion characteristic sensor suitable for the detection of the timing of peak combustion pressure or the occurrence of knock in an internal combustion engine comprises an engine headbolt having a piezoelectric disc affixed to the surface of the bolt head. An insulator holds an inner terminal electrically connected to the upper side of the piezoelectric disc and is held by its lower periphery, along with a surrounding electrically conducting outer terminal by a vertical annular wall rising from the surface of the bolt head. The annular wall and outer terminal provide electrostatic shielding and a ground reference for the inner terminal, which is connected electrically by a shielded connector to a charge amplifier with a double pole high pass filter with a half power frequency of 0.5-1.0 Hertz to block signals generated by thermal strains in the engine.

Abstract: In a combustion timing control system of the type wherein peak combustion temperature is sensed and combustion initiation timing is adjusted in closed loop to maintain peak combustion pressure at a desired constant crankshaft rotational angle, the combustion pressure signal is processed in apparatus having differentiating elements with a first time constant, smoothing integrating elements with a second time constant and further elements effective to vary both first and second time constants inversely with crankshaft rotational speed, wherein signal to noise ratio is optimized over the entire range of said speed.

Abstract: A spark ignited internal combustion engine includes apparatus effective to generate a signal from knock-induced and other ringing vibration bursts with amplification over a wide passband around the characteristic knock frequency. The signal is demodulated to obtain the envelope pulses of the knock and other vibration bursts and filtered in a low pass filter having a half power frequency from 60-200 Hertz. The output of this filter, in which other pulses are significantly attenuated with respect to knock pulses, is further processed to obtain a knock control signal which controls spark retard apparatus to limit knock intensity.

Abstract: An electrical pressure signal that varies directly in magnitude with changes of fuel line pressure at the fuel injector is raised to a selected mathematical power. This signal is then differentiated to detect the negative rate thereof that occurs at the point of inflection upon the start of fuel injection and a "start of fuel injection" output signal is produced in response to the detection of the point of inflection as indicated by the negative rate.