Abstract: The invention relates to a method for the cylinder-selective control of an air/fuel mixture to be burnt in a multi-cylinder internal combustion engine, in which the lambda values for different cylinders or groups of cylinders are separately sensed and controlled, and also relates to a multi-cylinder internal engine suitable for carrying out the method. In accordance with the invention, the lambda values of the individual cylinders or groups of cylinders are simultaneously controlled to different required values using an integrating I-control proportion with variable integrator slope and/or a differentiating D-control proportion.

Abstract: An air-fuel ratio control system for a multi-cylinder internal combustion engine is equipped with an exhaust emission control catalyst disposed in an exhaust passage of the engine, air-fuel ratio control means for controlling an air-fuel ratio of at least one of the plurality of cylinders, and an exhaust gas temperature sensor operating as catalyst temperature detection. During a cold start of the engine, the air-fuel ratio control means achieves one of rich-state and stoichiometric operation in all of the cylinders until the temperature of the exhaust emission control catalyst reaches a predetermined temperature. After the temperature of the exhaust emission control catalyst has reached the predetermined temperature, the air-fuel ratio control means starts lean-state operation in a first portion of the plurality of cylinders while maintaining rich-state operation in a second portion of the plurality of cylinders.

Abstract: A separate irregular-running determination is carried out for each cylinder bank. Each ascertained irregular-running value is compared to a lower and an upper threshold value, the upper threshold value being set in such a way that all irregular-running values below it are not caused by combustion misses. A defect is signaled in one of the exhaust trains when, for at least one of the two cylinder banks, an irregular-running value is ascertained lying between the lower and the upper threshold value, and the difference between the irregular-running values of the two cylinder banks exceeds a threshold. This method makes it possible to ascertain a defect in one of the two cylinder banks very early.

Abstract: The engine of the present invention has a plurality of cylinders that are divided into a first group and a second group. An air flow meter for detecting an amount of air supplied to the engine is provided downstream of an air cleaner in an intake system. A crank angle sensor for detecting a rotational speed of the engine is provided adjacent to a crank shaft. The amount of air distributed to the first group and the amount of air distributed to the second group are calculated based on the detected amount of air and the detected rotational speed of the engine. The amount of fuel injected into the first group and the amount of fuel injected into the second group are corrected according to the calculated amounts of air distributed to the first and second groups.

Abstract: A defect recognition device is provided for internal-combustion engines, as well as a process for operating an internal-combustion engine having at least two exhaust gas trains, with one lambda probe respectively being in each exhaust gas train. A joint measuring device detects the supplied air and a joint timing device apportions the fuel. The lambda probes, which generate a continuous signal for the lambda value of the exhaust gas, are used to provide improved defect recognition. The defect recognition device recognizes a defect when the signals supplied by the lambda probes deviate from one another.

Abstract: An air/fuel control system (8) and method for an engine (28) having two engine banks coupled to a single catalytic converter (50) uses first and second exhaust gas oxygen sensors (44, 55) coupled to respective first and second exhaust manifolds (56, 57) and various engine operating parameters. During a first set of engine operating conditions, air/fuel control system (8) maintains the exhaust air/fuel ratio oscillations of the two bank in phase with one another. During a second set of engine operating conditions, air/fuel control system (8) maintains the exhaust air/fuel ratio oscillations of the two bank 180 degrees out of phase with one another. When transitioning, emission impacts are minimized.

Abstract: A method and system for generating an inferred EGO sensor signal for use in monitoring operation of a catalytic convertor in an asymmetrical Y-pipe vehicle exhaust system utilizes current engine airflow and engine speed readings as address inputs for a look-up table of predetermined time delay values. The addressed time delay values are used to retrieve previously stored upstream EGO sensor signals corresponding to the time delay values. An inferred EGO sensor signal is then generated based on the retrieved EGO sensor signals, thus providing an inferred EGO sensor signal which accounts for the exhaust transport delay down the different respective exhaust pipe legs.

Abstract: In a horizontally opposed type engine, right and left exhaust pipes are provided for right and left cylinder banks, respectively and a collecting pipe is disposed to collect gases these two exhaust pipes. Further, in a two-stage catalytic converter system, two main catalysts are provided for the two exhaust pipes, respectively, and a subsidiary catalyst is provided in the collecting pipe. An oxygen sensors is provided in each of the exhaust pipes on the upstream side of it's main catalyst. The air-fuel ratios of both the banks are controlled simultaneously on the basis of the output of one of the sensors, and the air-fuel ratio of the other bank is corrected on the basis of a difference between the outputs of the two oxygen sensors. Accordingly, the air-fuel ratios of both right and left banks can be controlled appropriately, without the use of an auxiliary oxygen sensor. As a result, it is possible to improve the purification capability of the auxiliary catalyst in the collecting pipe.

Abstract: An air-fuel ratio control system for an internal combustion engine includes a pair of cylinder banks, a pair of exhaust passages connected to the cylinder banks, respectively, a common exhaust pipe where the exhaust passages join each other at their downstream ends, a pair of catalytic converters provided in the exhaust passages, respectively, a pair of main air-fuel ratio sensors provided in the exhaust passages upstream of the catalytic converters, respectively, a pair of auxiliary air-fuel ratio sensors provided in the exhaust passages downstream of the catalytic converters, respectively, and a catalytic converter provided in the common exhaust pipe. The system derives an air-fuel ratio feedback control correction value for each of the cylinder banks based on outputs of the auxiliary air-fuel ratio sensors.

Abstract: A system for estimating air/fuel ratios in the individual cylinders of a multicylinder internal combustion engine from the output of a single air/fuel ratio sensor installed at the exhaust system of the engine. A mathematical model is first designed to describe the behavior of the exhaust system which accepts the output of the air/fuel ratio sensor. An observer is designed to observe the internal state of the mathematical model and calculates the output which estimates the air/fuel ratios in the individual cylinders of the engine. In this configuration, when engine speed becomes high, the observer matrix calculation is discontinued, because it is difficult to ensure a time enough for calculation. Similarly, at a low engine load etc., the calculation is discontinued. Apart from the above, when a desired air/fuel ratio changes frequently such as when air/fuel ratio perturbation control is conducted, the desired air/fuel ratio is input to the observer as a second input.

Abstract: An air/fuel control system (8) and method for an engine (28) having two engine banks coupled to a single catalytic converter (50). First and second exhaust gas oxygen sensors (44, 55) are coupled to respective first and second exhaust manifolds (56, 57). A feedback signal is generated by a PI controller responsive to an average (104-120) of the first and second sensor outputs (44, 45). An adjustment signal is generated (440-448) by another PI controller responsive to a difference between the first and second sensor outputs (44, 45). Fuel delivered to the first engine bank (300a-306a) is adjusted by a first modified feedback signal generated by adding the adjustment term to the feedback signal (450-454). And, fuel delivered to the second engine bank (300b-306b) is adjusted by a second modified feedback signal generated by adding the adjustment term to the feedback signal (460-462).

Abstract: An oxygen sensor deterioration-detecting system for an internal combustion engine having a plurality of groups of cylinders groups, an exhaust system having a plurality of exhaust passages extending, respectively, from the cylinder groups, and catalytic converters arranged in the exhaust system, and a plurality of upstream oxygen sensors arranged, respectively, in the exhaust passages at locations upstream of the catalytic converters, includes a single downstream oxygen sensor arranged in a confluent portion of the exhaust passages at a location downstream of the catalytic converters, for detecting the mixed air-fuel ratio of exhaust gases emitted from the cylinder groups.

Abstract: An air/fuel control system (8) and method to maintain the air/fuel ratio of each engine bank (28) out of phase with one another. A feedback variable is generated (410-428) in response to a comparison of a difference in exhaust gas oxygen sensors (44, 55) from respective left and right engine banks (56, 57) to a reference (104-120). Separate feedback variables are generated for each engine bank by phase inverting the feedback variable between the banks and adding an adjustment signal (450-462). The adjustment signal is generated from a PI controller responsive to a comparison of the sum of the left and right exhaust gas oxygen sensors (44, 55) to a reference (440-448).

Abstract: With a V type engine, the exhaust air-fuel ratio is detected for each bank, and is also detected downstream of a catalytic converter which takes the combined exhaust flow from each bank. An air-fuel ratio feedback correction coefficient .alpha. is proportional-plus-integral controlled separately for each of the banks based on the air-fuel ratio detected for each of the banks, while a correction value PHOS for a proportional portion is set commonly for each of the banks, based on the air-fuel ratio detected downstream of the catalytic converter. Here the correction value PHOS is converted to separate correction values PHOSR, PHOSL for each of the banks corresponding to a change rate of the air-fuel ratio feedback correction coefficient .alpha. to an initial value, and the proportional operating amount of the proportional-plus-integral control which is carried out separately for each bank, is corrected based on the converted correction values PHOSR, PHOSL.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine, for example, a V-type engine, for accurately controlling the air-fuel ratio of a first cylinder group and that of a second cylinder group. The air-fuel ratio control apparatus is arranged such that air fuel ratios of respective cylinder groups are controlled to be phase different to prevent changes in rotational speed and improve the effect of a trinary catalyst.

Abstract: Air/fuel ratio in an internal combustion engine is controlled so as to test the operation of an exhaust gas oxygen sensor. The engine is divided into two banks, each bank including an intake bank of cylinders, an exhaust path, and an exhaust gas oxygen sensor in the exhaust path. Air/fuel ratio control signals are used in connection with each of the two banks, the control signals being 180.degree. out of phase with each other.

Abstract: A control apparatus and method for maintaining equal air flow among cylinders and independently controlling the air/fuel ratio of each individual cylinder, in an internal combustion engine having variable valve control. An air fuel controller generates valve control signals for each individual cylinder by sampling the exhaust gas oxygen sensor, and correlating the samples with corresponding combustion events. The valve lift for each variable lift valve is corrected to operate each cylinder at the desired air flow and air/fuel ratio. The variable valve lift can be accomplished in a camshaft type system incorporating a lost motion mechanism or similar device, or a system incorporating direct electrohydraulic or electromechanical valve actuation without a camshaft. The system and method can provide further flexibility in cylinder to cylinder air/fuel ratio control by combining it with a variable pulse width electronic fuel injector capability.

Abstract: This invention relates to an engine provided with a plurality of cylinder banks, exhaust manifolds for collecting exhaust from each bank, an exhaust branch pipe for combining the flows from the exhaust manifolds, and a three-way catalyst interposed in the exhaust branch pipe. An air-fuel ratio sensor is interposed in the exhaust manifold for each cylinder bank, and feedback control of the air-fuel ratio of each bank is performed based on the air-fuel ratio detected by the sensor of a specific bank such that this air-fuel ratio varies with a predetermined amplitude about the theoretical value as center value. The rich and lean times of the air-fuel ratio of the other banks are also measured from the output of the sensor at each bank, and feedback control is corrected for each bank such that the rich time is equal to the lean time for any bank.

Abstract: The exhaust gases of a two-bank internal-combustion engine are guided, by way of exhaust gas collectors, to a central expansion chamber of a housing. From there, they flow through main catalysts arranged on opposite ends of the housing, before they are guided into the open air by way of end mufflers.This exhaust system provides a space-saving arrangement of all components required for an optimal emission control, and low exhaust gas back pressure, and meets all acoustic requirements.

Abstract: Disclosed is an apparatus for detecting deterioration of a catalyst of an internal combustion engine having a plurality of cylinder banks in such a manner that the deterioration of the catalyst can be assuredly discriminated regardless of the presence of deviation of a control phase with respect to each cylinder bank. The influence of change of the air/fuel ratio can be eliminated considerably by reducing the air/fuel ratio correction coefficient for a right bank, or by also using the correction coefficient for the left bank as that for the right bank to cause the phases of them to be synchronized with each other, or by dither-controlling the right bank. Therefore, the change of the air/fuel ratio with respect to the left bank can be assuredly detected while necessitating one sub air/fuel ratio sensor.

Abstract: In the method for the adapted precontrol and feedback control of the air/fuel mixtures to be supplied to the two fuel-metering devices of an internal combustion engine, which has two separate exhaust-gas channels with a lambda probe and a catalytic converter in each channel, a common value of the precontrol manipulated variable and a common lambda desired value are determined for both fuel-metering devices. On the other hand, values of a control manipulated variable are determined separately for each fuel-metering device and values of precontrol adaptation variables, which are dependent upon the values of the control manipulated value, are determined and are superposed separately one after the other on the common precontrol value. This method makes it possible to manage with a single device for both cylinder banks which are to be operated in a stereo lambda control.

Abstract: An exhaust purification system has an upstream exhaust gas sensor and a downstream exhaust gas sensor disposed downstream of a catalytic device. Each sensor detects an oxygen concentration in exhaust gases and provides an output which inverts between a lean state, representative of a lean air/fuel ratio, and a rich state, representative of a rich air/fuel ratio, according to oxygen concentrations. The upstream exhaust sensor is determined to have deteriorated when an output from the upstream exhaust sensor is kept in a predetermined correlation with an output from the downstream exhaust sensor while the output from the downstream exhaust sensor remains the same.

Abstract: In an exhaust system for an internal combustion engine, including an upstream catalytic converter and a downstream catalytic converter, emission levels of exhaust gas are detected at positions upstream from the upstream catalytic converter, between the upstream and downstream catalytic converters, and downstream from the downstream catalytic converter, respectively. An air-fuel ratio is feedback controlled based on an emission level detected by the first emission sensor or feedback controlled based on an emission level detected by the second emission sensor when the engine operates in a specific vehicle operating condition. Deterioration of the downstream catalytic converter is detected based on an emission level detected by the third emission sensor while an air-fuel ratio is feedback controlled based on the emission level detected by the second emission sensor.

Abstract: An exhaust system for an automobile engine having two groups of cylinders has a catalytic device. Deterioration of the catalytic device is detected based on an oxygen level in exhaust gas passed through the catalytic device. A feedback control of an air-fuel ratio is conducted for the cylinder groups all together, based on either of the air-fuel ratios determined, based on emission levels of exhaust gas discharged, for one of two of the groups of cylinders, only when a specific vehicle driving condition is detected.

Abstract: An air-fuel ratio control device comprising an O.sub.2 sensor arranged in an exhaust passage, an air-fuel ratio feedback correction amount calculating unit for calculating an air-fuel ratio feedback correction amount in accordance with an output of the O.sub.

Abstract: An air-fuel ratio control device for an engine having two or more cylinder groups, such as a V-type engine or a horizontally opposed engine, wherein the air-fuel ratio control device controls the air-fuel ratio of cylinder groups in accordance with the output of upstream air-fuel ratio sensors and a downstream air-fuel ratio sensor. The upstream air-fuel ratio sensors are disposed in the individual exhaust passage connected to the respective cylinders upstream of the catalyst converter. The downstream air-fuel ratio sensor is disposed in the common exhaust passage downstream of the catalyst converter. The air-fuel control device usually controls the air-fuel ratios of individual cylinder groups in accordance with the output of the respective upstream air-fuel ratio sensor.

Abstract: An air fuel ratio control system for an internal combustion engine, comprising: an internal combustion engine having a plurality of cylinders, and exhaust passages corresponding to the respective cylinders; a plurality of oxygen sensors arranged in the respective exhaust passages to detect the composition of exhaust gas from the respective cylinders; and a control unit for independently controlling an air fuel ratio of the respective cylinders based on outputs from the oxygen sensors.

Abstract: An engine control system for an internal combustion engine is equipped with dual air-fuel ratio feedback control systems for feedback controlling air-fuel ratios for two groups of injectors. The system includes a common air flow rate sensor, common to both groups, for detecting a common air flow rate introduced into the cylinders and an individual air-fuel ratio sensor for each group of injectors for determining an air-fuel ratio related value for its respective air-fuel ratio feedback control system. A feedback correction value for correction of fuel injection is determined from the air-fuel ratio ralated values for each air-fuel ratio feedback control system. An air flow rate is corrected based on the feedback correction values for correction of fuel injection for the dual air-fuel ratio feedback control systems. Virtual fuel injection rates for the two groups of injectors are then determined from the corrected air flow rate.