Abstract: A portion of the exhaust gas of an internal combustion engine is returned to the induction manifold through an exhaust gas recycling line. This recycle line contains one or more orifice plates to create a measurable pressure drop when gas is flowing. The gas flow through the recycle line may be interrupted in controlled manner by a valve, particularly a magnetically actuated valve. The pressure drop across the orifice plate or plates is sensed by pressure-responsive electrical switches which provide input signals for a logical circuit that energizes a signaling device to warn the operator of a malfunction in the exhaust gas recycling system.

Abstract: A portion of the exhaust gas of an internal combustion engine is returned to the induction manifold through an exhaust gas recycling line. This recycle line contains one or more orifice plates to create a measurable pressure drop when gas is flowing. The gas flow through the recycle line may be interrupted in controlled manner by a valve, particularly a magnetically actuated valve. The pressure drop across the orifice plate or plates is sensed by pressure-responsive electrical switches which provide input signals for a logical circuit that energizes a signaling device to warn the operator of a malfunction in the exhaust gas recycling system.

Abstract: A sensing means is provided to monitor combustion of fuel and air supplied to an internal combustion engine, for example by sensing ignition pulses, combustion pressure, or cylinder temperature. Signals, as sensed, are compared and if one of these signals is extreme with respect to an average and, at the same time, the temperature of a catalytic reactor in the exhaust system becomes excessive, supply of the combustible fuel-air mixture to the specific cylinder is interrupted. To permit starting with unequal heating of cylinders, interruption of supply of the combustible fuel-air mixture is cancelled during starting, as sensed, for example, by closing of the starting switch, or low temperature in the engine system.

Abstract: The output of an oxygen sensor is fed in parallel to the inputs of amplifiers having amplification in different portions of the sensor output range and having different gain. The amplifier outputs are combined in a summing circuit. The result is to smooth out the characteristic of the measurement and to produce a signal that can drive an indicator to provide a meaningful indication in terms of air number. The temperature of the oxygen sensor must be regulated or compensated for for good results.