Abstract: A method for controlling air-fuel ratio of an engine coupled to an emission control device uses an upstream linear exhaust gas sensor and a switching downstream exhaust gas sensor. During stoichiometric operation, both sensors are used for feedback control. During operation away from stoichiometry, the downstream sensor feedback is disabled.

Abstract: A method for controlling air-fuel ratio of an engine coupled to an emission control device uses an upstream linear exhaust gas sensor and a switching downstream exhaust gas sensor. During stoichiometric operation, both sensors are used for feedback control. During operation away from stoichiometry, the downstream sensor feedback is disabled.

Abstract: A method and apparatus for monitoring an EGR system during normal vehicle operations is disclosed. An EGR valve located in an EGR passage controls the flow of exhaust gas to an intake manifold, and a sensor disposed in the air intake manifold downstream of air and EGR confluence point, monitors temperature of the mixture. A controller calculates a correlation function between a calculated desired EGR flow and the output of the manifold temperature sensor. If the value of correlation function is lower than a reference level, the monitoring system deterioration of EGR flow rate is indicated.

Abstract: An EGR control system provides on-line adaptation of the EGR valve Start to Open value during normal vehicle operations. The adaptive logic determines whether the valve position output signal reaches a predetermined minimum output signal value within a desired predetermined time window defined by upper and lower time values. If outside the window, the initial duty cycle value applied to the EGR valve is increased or decreased as appropriate to force the output signal to reach the minimum value within or at the boundaries of the time window.

Abstract: A method and apparatus for protecting an engine from overheating. The apparatus comprises a cylinder head temperature sensor operably coupled to sense the temperature of the cylinder head and a control system operably coupled to the cylinders and the cylinder head temperature sensor such that when the temperature of the cylinder head exceeds a maximum level the control system deactivates one or more of the cylinders and rotates the deactivation of one or more engine cylinders such that no one cylinder is constantly fired thus providing engine cooling by drawing fresh air through the deactivated one or more cylinders.

Abstract: A closed loop fuel control system for controlling air/fuel ratio in response to exhaust gas oxygen signals includes a selective hysteresis function to prevent high frequency switching after a noise spike. This improves fuel control system noise protection without introducing permanent time delays.

Abstract: Apparatus and method are disclosed for monitoring catalytic converter efficiency in treating exhaust gas from an internal combustion engine having fuel control means for controlling the air/fuel ratio at which fuel is supplied to the engine in response to a fuel flow control signal. During normal operation mode, control signal means generate the fuel flow control signal based at least in part on output signals from first and second EGO sensors exposed to the exhaust gas upstream and downstream, respectively, of the catalytic converter. During a test operation mode, preferably initiated and carried out during substantially steady state or normal operation of the engine, the output signal from the upstream EGO sensor is replaced by a zero mean value periodic function test signal. The output signal of the second (i.e., downstream) EGO sensor is compared to a stored value corresponding to minimum acceptable efficacy of the catalytic converter.

Abstract: An on-board oxygen sensor monitoring system includes measuring a first limit cycle of air/fuel controller operation, changing operating parameters of the air/fuel controller and measuring a second limit cycle with the new calibration of the controller. A time constant of the oxygen sensor is calculated as a function of the first and second limit cycle periods and compared to a maximum response rate.

Abstract: An exhaust gas oxygen sensor downstream of a catalytic converter is used to control a closed loop air/fuel ratio control system. A measured limit cycle frequency at various engine speed/load conditions is compared to stored benchmark limit cycle frequencies as functions of engine speed/load conditions. If the measured frequency is higher, the catalytic converter is considered to be degraded.

Abstract: An on-board catalytic converter efficiency monitoring system uses an exhaust gas oxygen sensor downstream of a converter to enable closed loop air-fuel ratio control. The period of the air-fuel limit cycle is used to determine a time constant parameter of the feedback loop. A parameter in the fuel controller is changed to induce another air-fuel limit cycle frequency. The period of this new air-fuel limit cycle provides additional information with respect to the time constant of the feedback loop. Because it is possible to make other changes to the parameters of the fuel controller, different frequencies can be induced and additional parameters of the feedback loop time constant can be determined. With n different frequencies produced by n different fuel controller parameters it is possible to solve for n different time constants. The system can be used with either one or two EGO sensors depending upon the desired parameter to be solved.

Abstract: Air/fuel ratio control for an internal combustion engine includes the use of a first exhaust gas oxygen sensor (EGO) upstream of a catalytic converter and a second exhaust gas oxygen sensor downstream of the catalytic converter. The output of the first EGO sensor is passed through a high pass filter and then combined in a summer with the output of the second EGO sensor. The output of the summer is applied to a proportional and integral controller which then provides an output used to generate the fuel control signal.

Abstract: An ignition control system for controlling ignition knock while maintaining minimum spark for best torque (MBT). Both knock control and MBT control are simultaneously utilized. During knock control, engine cycles are counted between successive knock detections. When the count is less than a first value, a retard signal is generated. An advance signal is generted when the count is greater than a second predetermined value. These retard and advance signals are accumulated as knock trim signals in RAM storage locations as a function of engine speed and load operating points for each cylinder. During MBT control, MBT trim signals are generated by determining convergence of an average difference in indicated mean effective pressure for each cylinder. These MBT trim signals are stored in another RAM as a function of speed and load operating points. Base ignition timing is then corrected by both the knock trim signal and corresponding MBT trim signal at each speed and load operating point.

Abstract: A control system and method for optimizing power in a combustion cylinder of an engine. An ignition timing reference is offset during each learning interval. Differences in indicated mean effective pressure (IMEP) which result from the timing offset are calculated. When a determination is made that the offset timing reference is converging towards an optimal value, the timing reference is updated.