Abstract: A diagnostic apparatus for exhaust gas clarification apparatus for internal combustion engine diagnoses the individual catalyst independently by an air/fuel ratio sensor mounted before and after the individual catalyst. The individual catalyst is diagnosed by estimating the correlation of the output signals from the air/fuel ratio sensors mounted before and after the individual catalyst. The individual diagnosis operation is performed at distinctive operation regions adequate for their corresponding diagnostic mode. A by-pass route is provided for by-passing the exhaust gas from the upstream catalyst, and a by-pass valve switches the exhaust gas flow into the upstream catalyst or into the by-pass routes. A cross-correlation function calculation valve based upon outputs from air/fuel ratio sensors permits diagnosis of degradation of the overall catalyst.

Abstract: A combustion state detection system for an internal combustion engine in which a timing signal associated with the rotation of the crankshaft by a predetermined angle is detected and corrected, and a combustion state parameter is calculated from the timing signal. Further, the deviation of the calculated combustion state parameters for normal combustion is detected between the cylinders, and the correction amount of the timing signal is calculated. A reference cylinder is determined by the means for detecting the deviation. The deviation is detected between the combustion state parameter for normal combustion of the reference cylinder and the cylinder opposed thereto and the combustion state parameter for normal combustion of the remaining cylinders. The correction amount is calculated in such a manner as to control the correction amount to not more than a predetermined value or to zero from the detected deviation.

Abstract: In an apparatus of detecting a combustion state of an internal combustion engine, a combustion parameter value of the engine is calculated on the basis of measurement data concerning an engine speed, the value of the data concerning the engine speed is corrected with a correction value, the correction value is calculated to make the calculated combustion parameter fall within a predetermined range, and the correction value is set to a predetermined value when a predetermined condition is satisfied.

Abstract: It is intended to detect combustion state of an internal combustion engine over the entire range where positive torque is generated. Time required from a predetermined first crank angle to a second crank angle is measured by detecting a rotation angle of a ring gear or plate with engine speed detecting means 101. Then, a combustion state parameter is calculated from said required time by combustion state detecting means 102 with an established calculation method, and combustion state is determined by combustion state judging means 103. Engine speed correction means 104 determines and feeds back a correction value for the combustion state detecting value to correct the engine speed. At the moment, the correction quantity for correcting the required time is varied so that the normal combustion value of said combustion state parameter is at a predetermined value or less, or within a predetermined range.

Abstract: It is intended to detect combustion state of an internal combustion engine over the entire range where positive torque is generated. Time required from a predetermined first crank angle to a second crank angle is measured by detecting a rotation angle of a ring gear or plate with engine speed detecting means 101. Then, a combustion state parameter is calculated from said required time by combustion state detecting means 102 with an established calculation method, and combustion state is determined by combustion state judging means 103. Engine speed correction means 104 determines and feeds back a correction value for the combustion state detecting value to correct the engine speed. At the moment, the correction quantity for correcting the required time is varied so that the normal combustion value of said combustion state parameter is at a predetermined value or less, or within a predetermined range.

Abstract: A diagnostic apparatus for exhaust gas clarification apparatus for internal combustion engine is disclosed. The diagnostic apparatus can diagnoses the individual catalyst independently by means that an air/fuel ratio sensor is mounted before and after the individual catalyst, and that the individual catalyst is diagnosed by estimating the correlation of the output signals from the air/fuel ratio sensors mounted before and after the individual catalyst, and furthermore, that the individual diangosis operation is performed at distinctive operation regions adequate for their corresponding diagnostic mode.