Abstract: A control system and method for a multi cylinder engine that employs a single sensor associated with only one of the combustion chambers for feedback control of that combustion chamber and for controlling the fuel/air ratio of the remaining combustion chambers. The control of the remaining combustion chambers is based upon the value of the feedback control upon the time of shifting between lean and rich mixtures. The reference value is selected, however, after the initial switch between rich and lean so as to permit time for stabilization. Engine protection is accomplished by cylinder diseabling. At that time feed back control is discontinued.

Abstract: Feedback control systems for engines employing combustion condition sensors. The feedback control is varied in response to various other parameters such as back pressure, engine speed, engine temperature, engine load and initial start-up operation so as to provide more accurate control under varying and transient conditions.

Abstract: Fuel vapor is produced in a fuel tank and absorbed in a canister. The absorbed fuel vapor is purged through a purge passage into an engine induction passage under predetermined engine operating conditions. The air/fuel ratio is learned for air/fuel ratio feedback control. The learning control is inhibited when the fuel temperature exceeds a reference value during the air/fuel ratio feedback control. In another aspect of the invention, a purge valve is provided in the purge passage. The air/fuel ratio correction factor is set at an initial value in response to a movement of a purge valve from its open position toward its closed position.

Abstract: Provided is an apparatus for detecting a volatility of fuel supplied to an engine, in order to ensure a more precise acceleration dependent fuel increasing-correction during air-fuel-ratio feed-back control. When the air-fuel-ratio feed-back control begins after engine starting (S4), a determination is made as to whether the engine is in a low exhaust-temperature state on the basis of an engine coolant temperature Tw (S5). When the exhaust temperature is low, an average value .alpha..sub.av of an air-fuel-ratio feed-back correction factor .alpha. is derived (S6, S7), and then the average value .alpha..sub.av is compared with a reference value (S8). In case that the fuel supplied to the engine is a heavy-gravity fuel of a low volatility, since there are great amounts of hydrocarbons HC in exhaust gases and with a great consumption of oxygen a control point of the air-fuel-ratio feed-back control, which point can be indicated by the average value .alpha..sub.av, shifts to a leaner side.

Abstract: An air/fuel control system for an engine (28) provides an air/fuel indicating signal linearly related to average engine air/fuel operation from a two-state exhaust gas oxygen sensor (44). Fuel delivered to the engine is modulated with a periodic signal (144). A reference value corresponding to a desired air/fuel ratio is subtracted from a rolling average of the exhaust gas oxygen sensor output to provide an error signal (148-152). A feedback variable (FV) for adjusting the engine air/fuel ratio is generated from a proportional plus integral controller having the error signal as its input (156). In this manner, average engine air/fuel ratio is maintained at the desired air/fuel ratio and the rolling average of the exhaust gas oxygen sensor output provides an air/fuel indicating signal.

Abstract: A circuit and method are provided for heating a dual heater oxygen sensor. One resistance element is of relatively low resistance such that the oxygen sensor is heated quickly and the other element is of relatively high resistance such that the oxygen sensor is heated and maintained at an optimal operating temperature. The circuit and associated method turn on a low resistance start heater that is in communication with the oxygen sensor given start-up conditions. Once the oxygen sensor has reached an operating temperature range a high resistance operating temperature heater is turned on and the start heater is turned off.

Abstract: A flexible fuel compensation system including a method of methanol boil-off compensation. The methanol boil-off compensation method includes an initialization routine, a run mode routine and a shutdown routine. The method will monitor a plurality of flags to determine when the methanol boil-off compensation should be used.

Abstract: An engine air/fuel control system modulates the flow of fuel delivered to the engine with a modulation signal (100, 144) The feedback variable generated (210-228) from a two-state exhaust gas oxygen sensor (16) corrects the fuel flow (156). During each of a plurality of pre-determined intervals, the fuel flow is biased with a rich offset (342). Amplitude of the modulation signal is corrected by a difference between the feedback variable generated during two successive occurrences of the predetermined interval (346-378).

Abstract: With an electronic control device for an internal combustion engine using an oxygenated compound mixed fuel, operating conditions of the engine are detected, and are utilized to determine fundamental control data for the engine, while the dielectric constant and the refractive index of an oxygenated compound mixed fuel supplied to the engine are detected, and the oxygenated compound content of the mixed fuel is calculated according to the dielectric constant thus detected. The refractive index, and the oxygenated compound content are utilized to estimate the distillation characteristic of the petroleum refined fuel in the mixed fuel. The fundamental control data are corrected by using first correction data determined from the oxygenated compound content and second correction data determined from the distillation characteristic.

Abstract: A fuel injection control system suitable for use with internal combustion vehicle engines fueled by compressed natural gas or the like. A conventional liquid-fuel closed-loop injection timing controller establishes the duration of each injection command signal by the combination of a P.I.D. controller responsive to the level of exhaust oxygen, an adaptive table which stores previously determined fuel delivery rate values for particular engine speed and load conditions, an injector supply voltage table which stores fuel delivery rate correction values which compensate for variations in injector operating potentials, and a two-dimensional correction table which provides correction values to compensate for variations due to fuel pressure and resistance variations in the injector actuators due to temperature variations.

Abstract: For stable air-fuel ratio control without hunting, an output condition of an air-fuel ratio sensor is monitored to decide whether or not a modern or advanced control using a dynamic model may be performed. The appropriateness of using the dynamic model may be determined by monitoring whether the output value of an air-fuel ratio sensor exists in a predetermined range or whether the air-fuel ratio sensor is maintained stably in an air-fuel ratio detectable state. When the sensor output condition is out of the predetermined range suitable for the modern control, an optimum feedback gain for performing the modern control is switched over to a lowered gain or the modern control is switched over into normal feedback control by proportional-and-integral control. By this control mode switch-over, most appropriate air-fuel ratio feedback control may be performed.

Abstract: An air-fuel ratio control system for an internal combustion engine controls the air-fuel ratio of a mixture supplied to the engine to a desired air-fuel ratio in response to an output from an exhaust gas ingredient concentration sensor. A first value of the desired air-fuel ratio is calculated based on the rotational speed of the engine and the load on the engine. A second value of the desired air-fuel ratio is calculated based results of determination on whether a vehicle on which the engine is installed has just started from a standing position thereof. A third value of the desired air-fuel ratio is calculated based on results of determination on whether the temperature of the engine is lower than a predetermined value. The largest value of at least the first to third values of the desired air-fuel ratio is set to a final value of the desired air-fuel ratio.

Abstract: A system for controlling an air/fuel ratio of an internal combustion engine supplied with a blended fuel of gasoline and alcohol and equipped with a blowby gas ventilator. An oxygen sensor is provided and an amount of fuel supply is corrected in response to the detected air/fuel ratio within a range having a lower limit set in the lean direction and an upper limit set in the rich direction. At engine starting, injected alcohol may not vaporize but leak into the crankcase and will then vaporize to pass into the air intake passage along with the blowby gas when the engine temperature rises, causing the air/fuel ratio to be become rich beyond the correction lower limit. For that reason, in this system, engine coolant temperature and alcohol content in the fuel are detected. And if the temperature is within a range defined from the alcohol boiling point when the alcohol content is above a reference value, the lower limit of the range is shifted in the leaner direction.