Abstract: A control system which controls engine air/fuel ratio while providing a measurement of efficiency in the catalytic converter coupled to the engine exhaust. A test period is completed when counts in transitions of a feedback variable derived from an exhaust gas oxygen sensor positioned upstream of the converter have reached a preselected count for each of a plurality of inducted air flow ranges. Converter efficiency is determined during the test cycle by comparing an integration of the feedback variable, after band pass filtering and rectification, to an integration of a downstream exhaust gas oxygen sensor after its output is band pass filtered and rectified.

Abstract: An air-fuel ratio control system for an internal combustion engine comprises a catalytic converter disposed in an exhaust line of the engine. The converter has an oxygen storage effect. First and second oxygen sensors are disposed in the exhaust line at positions upstream and downstream of the converter respectively. Each sensor varies the output in accordance the oxygen concentration in the exhaust gas flowing in the exhaust line. A first device is employed for deriving an air-fuel ratio feedback correction value in accordance with the output from the first oxygen sensor. A second device is employed for changing the air-fuel ratio feedback correction value of the first device in accordance with the output from the second oxygen sensor. A third device is employed for controlling the quantity of fuel fed to the engine in accordance with the air-fuel ratio feedback correction value derived by the first device.

Abstract: An exhaust emission control device for an internal combustion engine is provided with a main catalyst activated with heat of exhaust gas, a self-exothermic type auxiliary catalyst activated with electric current energy and a silencer, which are connected in series and in sequence from an upstream side to a downstream side in an exhaust system leading from an engine body. Thus, noxious components included in the exhaust gas can be converted and the gas is purified by using the main and auxiliary catalysts in combination but with the auxiliary catalyst being subject to less heat from the exhaust gas than the main catalyst.

Abstract: Trap for filtering particulates from diesel engine exhaust including filter cartridge arrangement having heat enhancement elements. In the case of exhaust gases flowing through a filter cartridge from inside to out and the cartridge having an inner tubular heater, heat enhancement elements include a heat insulator plugging the downstream end of the cartridge, a plurality of flow distribution rings which inhibit flow to the end of the cartridge thereby causing more even flow through the cartridge nearer the upstream end, and mechanism for controlling regeneration on-time as a function of vehicle system voltage and pre-energization heater temperature. In the case of a filter cartridge having flow from outside to in and having an outer heater, heat enhancement elements include a tubular, non-filtering, heat insulating sleeve about the heater and mechanism for controlling on-time as a function of vehicle system voltage and pre-energization heater temperature.

Abstract: A catalytic diagnostic apparatus for determining whether a catalyst of an internal combustion engine has deteriorated as disclosed. Air-fuel ratio sensors are placed at the upstream and downstream sides of the catalytic converter, and the output signal from the upstream air-fuel sensor is used to control the air-fuel mixture provided to the engine via the fuel injectors, in a conventional closed loop operation. Diagnosis of the condition of the catalytic converter is performed only when selected engine operating parameters fall within a predetermined diagnostic range. When the engine is operated in the diagnostic range, the condition of the catalytic converter is analyzed by calculating a deterioration index based on a comparison of the variation of the output signals from the upstream and downstream air-fuel ratio sensors.

Abstract: An air-fuel ratio control system for an internal combustion engine having a catalytic converter arranged in the exhaust system, a first air-fuel ratio sensor arranged upstream of the catalytic converter, and a second air-fuel ratio sensor arranged downstream of the catalytic converter, calculates an air-fuel ratio control variable, based on an output from the second air-fuel ratio sensor. An air-fuel ratio correction amount is calculated based on an output from the first air-fuel ratio sensor and the air-fuel ratio control variable. The air-fuel ratio of a mixture supplied to the engine is controlled based on the air-fuel ratio correction amount. The air-fuel ratio control variable is corrected in the rich direction such that the air-fuel ratio of the mixture supplied to the engine becomes richer, when deterioration of the catalytic converter is detected.

Abstract: An engine exhaust emission control system, in which a valve is set at a hydrocarbon adsorbing position to guide exhaust emissions to a bypass line including an adsorbent sieve for adsorbing hydrocarbons during a initial period of engine start-up, and the valve is switched over to a hydrocarbon purging position to guide exhaust emissions to an exhaust line and to divert a part of the exhaust emissions to the bypass line.

Abstract: An exhaust system for a spark ignition engine on an automotive vehicle including an exhaust filter disposed downstream of a spark ignition engine for condensing hydrocarbons in exhaust gases from the engine during a first time period after start of the engine, a bypass structure for bypassing at least a portion of exhaust gases around the exhaust-filter to heat the exhaust filter during a second time period after the first time period and evaporate the condensed hydrocarbons, and a catalytic converter disposed downstream of the exhaust filter to oxidize the evaporated hydrocarbons and reduce NO.sub.x in exhaust gases passing therethrough. A method is also provided.

Abstract: An air-fuel ratio control system for an internal combustion engine having a first and second groups of cylinders and first and second catalytic converters arranged respectively in first and second exhaust systems extending from the respective cylinder groups, includes first and second upstream oxygen sensors upstream of the catalytic converters, and a single downstream oxygen sensor downstream of the catalytic converters. The air-fuel ratios of air-fuel mixtures supplied into the first and second cylinder groups are controlled by the use of first and second air-fuel ratio control amounts based on outputs from the respective first and second upstream oxygen sensors and the downstream oxygen sensor, when the engine is in a predetermined operating condition.

Abstract: Engine air/fuel ratio is controlled in response to a comparison of an exhaust gas oxygen sensor output with a reference value. A correction voltage is generated which is related to a change in the midpoint between saturated output states of the sensor during a test period in which engine air/fuel operation is first forced rich and then forced lean of a preselected air/fuel ratio. The sensor output amplitude is shifted with the correction voltage to reduce variations between the reference value and the midpoint.

Abstract: The present invention provides an improved air-fuel ratio control system which eliminates a time lag of outputs of an outlet or second oxygen sensor at a high accuracy and adequately controls the air-fuel ratio, thus efficiently reducing an exhaust of harmful gases including HC, CO, and NOx and improving the fuel consumption. When an output voltage SOX of the second oxygen sensor is within a predetermined range between a first voltage E1 and a second voltage E2 including a reference voltage E0 corresponding to a stoichiometric air-fuel ratio, an update quantity DRSR of a rich skip amount RSR is equal to zero. When the output voltage SOX is in a range between a minimum output GSOXmin and the first voltage E1, the update quantity DRSR exponentially increases with the decrease in the voltage. When the output voltage SOX is in a range between the second voltage E2 and a maximum output GSOXmax, the update quantity DRSR exponentially decreases with the increase in the voltage.

Abstract: An improved exhaust emission control device is disposed in a motor bicycle of the type in which a muffler body, containing a catalyst for exhaust emission control, is connected to an exhaust pipe extending from the exhaust port of the associated engine, and the exhaust pipe is inserted into the muffler body through the front section thereof and extends through the inner space of the muffler body to the rear section thereof. The exhaust pipe is turned back in U-shape at the rear section to the front section of the inner space of the muffler body and the catalyst, supported by a partition wall which is disposed in the muffler body, is positioned in the vicinity of the opening of the exhaust pipe.

Abstract: Internal combustion engine air/fuel ratio regulation in which closed-loop air/fuel ratio control responsive to a pre-converter oxygen sensor feedback signal is further regulated in accord with a feedback signal from a post-converter oxygen sensor signal operative under certain engine operating conditions to provide an average actual engine air/fuel ratio signal. A pre-converter oxygen sensor rich/lean threshold is adjusted in accord with the post-converter signal to drive or maintain such post-converter signal within a preferred range corresponding to an average engine air/fuel ratio of stoichiometry.

Abstract: An ignition timing control system for an internal combustion engine which can perform fast catalyst warm-up operation and prevent stalling at the restart of the internal combustion engine at a low temperature is disclosed. This control system judges whether the engine is in the start state or not, whether the cooling water temperature is lower than the specified temperature or not, and whether the intake air temperature is higher than the preset temperature or not. When these judgments are all affirmative, the system further judges whether the time after the start has reached the control starting time or not, and then whether the engine is in the idle operation state or not. When these judgments are both affirmative, the system sets the target ignition timing retard amount and the ignition timing gradual change time according to the intake air temperature, and then actually performs the ignition timing control according to the target retard amount and gradual retard time.

Abstract: An electronic engine controller (EEC) is utilized to perform an onboard diagnostic test of a catalytic converter. An upstream oxygen sensor detects the exhaust gas entering the catalytic converter and an downstream oxygen sensor detects the exhaust gas exiting the catalytic converter. An air/fuel mixture is maintained at a first bias level until the exhaust gas produced by combustion of the air/fuel mixture is detected by the downstream oxygen sensor at which point the air/fuel mixture is altered to a second bias level and maintained at the second bias level until the exhaust gas produced by combustion of the air/fuel mixture is detected by the downstream oxygen sensor. An amount of time required for the upstream oxygen sensor to detect the exhaust products of the first bias value and for the second bias value is calculated, and similar values are calculated for the downstream oxygen sensor.

Abstract: When a preheater elevates internal combustion engine exhaust gas treatment means temperature above a threshold temperature and prior to and during engine cranking, supplemental air is provided to an internal combustion engine exhaust gas path at a controlled rate responsive to parameters indicating excess engine emission levels during an engine startup period.

Abstract: An air-fuel ratio control system for an internal combustion engine uses a dynamic model which is set as an approximation to a controlled object. The controlled object covers an operation sequence from a fuel injection valve to an air-fuel ratio sensor which is provided downstream of a catalytic converter for detecting an actual air-fuel ratio based on the exhaust gas downstream of the catalytic converter. The system derives a fuel injection amount to be fed to the engine by performing a state-feedback control in such a manner as to control the actual air-fuel ratio to a target air-fuel ratio. The system performs the state-feedback control using, as state variables, current and past input and output data relative to the dynamic model. Accordingly, the actual air-fuel ratio monitored on the downstream-side of the catalytic converter is controlled to the target air-fuel ratio without delay by directly deriving the fuel injection amount using the state-feedback control.

Abstract: An exhaust system for vehicles and other devices with internal combustion engines such as boats, airplanes, lawnmowers, tractors, and the like, includes a sound attenuating chamber having a single, common opening in an imperforate container providing access for exhaust gases both to and from the container while attenuating the exhaust sound thereof. The system maintains low back pressure during operation. Resonator tubes and optional sound absorbing material may be used in the chamber to control exhaust sounds. An optional, remote-operated, sound control valve upstream of the chamber allows individualized control of the exhaust sound by the vehicle driver. An optional baffle in the exhaust outlet and/or an optional helical insert in the exhaust pipe further deadens the sound. In a preferred form, the system is attached downstream of a catalytic converter and includes dual sound attenuating chambers and dual exhaust outlets at the opposite vehicle sides between the front and rear wheels.

Abstract: An exhaust manifold catalytic reactor and muffler for an automotive internal combustion engine includes at least one exhaust branch for conducting exhaust gases from the cylinder head exhaust ports of an engine to a hollow, generally cylindrical primary catalyst substrate for treating the exhaust gases flowing from the engine. The substrate has inner and outer surfaces which are generally cylindrical and which define an inner cavity. A housing connected to the exhaust branch places the exhaust gases in contact with the substrate and includes a generally cylindrical container having an outer wall and a transition section conducting the exhaust gases from the branch to the outer surface of the substrate such that the initial flow of the gases from the branch to the outer surface of the substrate such that the initial flow of the gases from the substrate is generally tangential.

Abstract: A secondary air supply control system for an internal combustion engine having at least one catalyst arranged in the exhaust system comprises an electric air pump for supplying secondary air to the exhaust system at a location upstream of the catalyst, and a catalyst temperature sensor for detecting the temperature of the catalyst. The ECU calculates a rate of variation in the temperature of the catalyst detected by the catalyst temperature sensor per a predetermined time interval, and controls an amount of secondary air to be supplied by means of the electric air pump, in response to the calculated rate of variation in the temperature of the catalyst.