Abstract: A fuel mixture control system, for example a fuel injection system, has a control device which accepts signals for final correction of the fuel mixture. In particular, the final correction is made on the basis of engine roughness which is used as a measure of the degree of lean burning of the engine. The engine roughness is determined digitally by forming second differences of engine period in sequential digital counters whose contents are shifted after each counting period. The final counter is counted down at an rpm-dependent frequency. The digital datum related to engine roughness is examined for two conditions, i.e., for whether it exceeded a set-point value and for the nature of its algebraic sign. In one of the four possible states of combination of these conditions, the mixture is slightly enriched, whereas in the other three states, it is leaned out to a maximum degree.

Abstract: The fuel injection control pulses of an internal combustion engine may be shortened or lengthened to provide operation of the engine at a definite fuel-air ratio. When operation takes place in a leaned-out region, the engine suffers dynamic instability, resulting in rapid fluctuations of the rotational crankshaft velocity, superimposed on regular, periodic changes due to compression changes.The crankshaft speed is tested at two different locations of the angular path by passing markers in front of an inductive transducer. The output signal from this transducer gates the counting input of a digital counter which is supplied with a pulse train at a constant, high frequency. A flip-flop alternately causes upward and downward counting in the counter so that a net difference of counted pulses is formed after each two successive counting periods.

Abstract: The fuel supply control pulses of an internal combustion engine may be shortened or lengthened to provide operation of the engine at a definite fuel-air ratio. When operation takes place in a leaned-out region, the engine suffers dynamic instability, resulting in rapid fluctuations of the rotational crankshaft velocity, superimposed on regular, periodic changes due to compression changes.The maximum and minimum crankshaft speeds are measured at two different locations of the angular path by passing markers in front of an inductive transducer. The output signals from this transducer are fed to a gating circuit which controls the counting modes of a digital counter which is also supplied with a clocking pulse train at a constant, high frequency. The gating circuit causes alternate upward and downward counting in the counter so that a net difference of counted pulses is formed after each two successive counting periods.

Abstract: Engine control based on the smooth or rough running of the engine is performed by obtaining a signal indicative of crankshaft rotation and by digital measurement of the period of revolution. The periods of three successive revolutions are compared to obtain a second differential, related to acceleration and hence to combustion chamber pressure. This second differential is compared digitally to a nominal value, taken from an rpm-dependent function of the engine smoothness, derived by frequency synthesis of the frequencies from individual stages in one or more of the counters.