Abstract: In manufacturing an exhaust pipe of two-passage construction, a metallic plate having a first end and a second end respectively elongated in a longitudinal direction of the exhaust pipe is prepared. The metallic plate is bent into a substantially S shape in cross section. It has a diametrically extending central partition plate and a substantially semicircular peripheral wall on each lateral side of said partition plate in such a manner that a groove of substantially V shape in cross section having a substantially closed end on a radially inner side and an open end on a radially outer side is formed at each diametrically outer portion of the partition plate. A target is provided so as to elongate along the groove in a manner to extend substantially radially outward from the closed end. A welding arc is generated between the target and a welding gun disposed on a side of the open end such that the substantially closed end and the target are welded together.

Abstract: In manufacturing an exhaust pipe of two-passage construction, a metallic plate having a first end and a second end respectively elongated in a longitudinal direction of the exhaust pipe is prepared. The metallic plate is bent into a substantially S shape in cross section. It has a diametrically extending central partition plate and a substantially semicircular peripheral wall on each lateral side of said partition plate in such a manner that a groove of substantially V shape in cross section having a substantially closed end on a radially inner side and an open end on a radially outer side is formed at each diametrically outer portion of the partition plate. A target is provided so as to elongate along the groove in a manner to extend substantially radially outward from the closed end. A welding arc is generated between the target and a welding gun disposed on a side of the open end such that the substantially closed end and the target are welded together.

Abstract: In manufacturing an exhaust pipe of two-passage construction, a metallic plate having a first end and a second end respectively elongated in a longitudinal direction of the exhaust pipe is prepared. The metallic plate is bent into a substantially S shape in cross section. It has a diametrically extending central partition plate and a substantially semicircular peripheral wall on each lateral side of said partition plate in such a manner that a groove of substantially V shape in cross section having a substantially closed end on a radially inner side and an open end on a radially outer side is formed at each diametrically outer portion of the partition plate. A target is provided so as to elongate along the groove in a manner to extend substantially radially outward from the closed end. A welding arc is generated between the target and a welding gun disposed on a side of the open end such that the substantially closed end and the target are welded together.

Abstract: An evaporative fuel-purging control system for an internal combustion engine includes a mass flowmeter arranged across a purging passage of the engine for measuring a flow rate of a mixture of evaporative fuel and air being purged. A desired flow rate of the mixture is set according to operating conditions of the engine. The desired flow rate of the mixture is compared with a measured flow rate of the mixture obtained by the mass flowmeter, and the opening of a purge control valve arranged across the purging passage is controlled based on results of the comparison.

Abstract: An evaporative fuel-purging control system for an internal combustion engine includes at least one flowmeter arranged across a purging passage for outputting a detection parameter indicative of a flow rate of a gaseous mixtured purged through the purging passage, and a purge control valve arranged across the purging passage for controlling the flow rate of the gaseous mixture based on a control parameter indicative of a control amount for the purge control valve. One of the detection parameter and the control parameter is corrected based on a value of the one of the detection parameter and the control parameter assumed when the other of the detection parameter and the control parameter assumes a value corresponding to a state in which the flow rate of the gaseous mixture is equal to the minimum value.

Abstract: An evaporative fuel-purging control system for an internal combustion engine incorporates a flowmeter arranged across a purging passage for outputting an output value indicative of the flow rate of a mixture of evaporative fuel and air being purged through the purging passage. Abnormality of the flowmeter is determined, based on a value of the output value therefrom assumed when the purging of the gaseous mixture is stopped. Alternatively or in combination, abnormality of the flowmeter is determined, based on a value of the output value therefrom assumed when the purging of the gaseous mixture is resumed after stoppage thereof.

Abstract: A starting fuel supply control system for an internal combustion engine having a purging passage connecting between a canister and an intake passage for purging a mixture of evaporative fuel from a fuel tank and air therethrough into the intake passage, and a purge control valve arranged across the purging passage for controlling the flow rate of the evaporative fuel to be supplied to the intake passage. An ECU detects a flow rate of an evaporative fuel component in the mixture flowing in the purging passage, and sets an amount of fuel to be supplied to the engine at the start thereof, based upon the detected flow rate of the evaporative fuel component.

Abstract: An evaporative fuel-purging control system for an internal combustion engine having a canister in which evaporative fuel from a fuel tank is absorped. Purge control valves are arranged between the canister and the intake system of the engine for controlling the flow rate of evaporative fuel supplied from the canister to the intake system. An ECU is responsive to an output from an exhaust gas ingredient concentration sensor arranged in the exhaust system of the engine for calculating an air-fuel ratio correction coefficient, based upon the output from the exhaust gas ingredient concentration sensor and controlling the air-fuel ratio of a mixture supplied to the engine by the use of the air-fuel ratio correction coefficient. The ECU calculates an average value of the air-fuel ratio correction coefficient, and is responsive to the calculated average value for controlling the purge control valves.

Abstract: A mass flowmeter outputs an output value indicative of the flow rate of a gaseous mixture containing evaporative fuel and being purged into the intake system of an internal combustion engine. A calculated value of the flow rate of the mixture is obtained based on a plurality of operating parameters of the engine. The actual flow rate of the mixture and/or the actual flow rate of the evaporative fuel are/is calculated based on the output value from the mass flowmeter and the calculated value based on the engine operating parameters. The concentration of the evaporative fuel is calculated from the calculated actual flow rates of the evaporative fuel and the mixture. The calculated actual flow rate is compared with a desired flow rate value, and a purge control valve is controlled based on results of the comparison. A basic amount of fuel supplied to the engine is corrected based on the calculated actual flow rate of the evaporative fuel.

Abstract: An evaporative fuel-purging control system for an internal combustion engine having a canister in which evaporative fuel from a fuel tank is adsorbed. One or more purging control valves are arranged across a purging pipe extending between the canister and an intake system. An ECU integrates an estimated value of a flow rate of evaporative fuel supplied to the engine, which is estimated as a purging flow rate in the purging pipe, in accordance with engine operating conditions when a specific one of the purging control valves is opened to thereby obtain an integrated purging flow rate value, and subtracts a predetermined decremental value from the integrated purging flow rate value when the specific one purging control valve is closed. When the integrated purging flow rate value is equal to or smaller than a predetermined lower limit value, the ECU decreases the flow rate of the evaporative fuel supplied to the intake system, based on the integrated purging flow rate value obtained above.

Abstract: A device for measuring a flow rate of a mixture of evaporative fuel and air supplied to an internal combustion engine comprises a plurality of flowmeters arranged in a purging passage connecting between a canister and an intake passage of the engine for purging the mixture of evaporative fuel and air therethrough into the intake passage. The flowmeters have different output characteristics relative to concentration of the evaporative fuel in the mixture. At least one of the concentration of the evaporative fuel in the mixture and the volumetric flow rate of the mixture are detected based on outputs from the flowmeters. In an air-fuel ratio control system incorporating the above device, the weight per unit time of evaporative fuel supplied to the intake system is calculated from the detected concentration of the evaporative fuel and the detected volumetric flow rate of the mixture.

Abstract: An evaporative fuel-purging control system for an internal combustion engine comprises a mass flowmeter and a differential pressure type flowmeter arranged in a purging passage of the engine for measuring a flow rate of a mixture of evaporative fuel and air being purged. The flowmeters have different output characteristics relative to change in the concentration of evaporative fuel in the mixture from each other. Output values from the flowmeters are compared to obtain a difference or a ratio therebetween. Failure of at least one of the flowmeters is detected based upon the difference or the ratio.

Abstract: An evaporative fuel-purging control system for an internal combustion engine, which controls purging of a mixture of evaporative fuel from a fuel tank and air comprises a purge control valve arranged across a purging passage for controlling the flow rate of evaporative fuel from the fuel tank to an intake passage. The flow rate of evaporative fuel is detected and compared with a desired flow rate commensurate with an operating condition of the engine. The valve opening of the purge control valve is controlled in response to results of the comparison. The change rate of the valve opening is varied according to the concentration of evaporative fuel in the mixture. Specifically, the change rate is decreased as the evaporative fuel concentration is higher.

Abstract: An air-fuel ratio control method for an internal combustion engine. The air-fuel ratio of an air-fuel mixture supplied to the engine is feedback-controlled to a predetermined value in response to an output from the exhaust gas ingredient concentration sensor. The temperature of at least one component part of the engine, which should be controlled, is estimated based on the detected temperature of exhaust gases, engine rotational speed, and engine load. The air-fuel ratio of the air-fuel mixture is inhibited from being feedback-controlled but enriched, when the estimated temperature of any one of the at least one component part of the engine is higher than a corresponding predetermined value.

Abstract: A method of controlling the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine including the step of interrupting the feedback control of the air-fuel ratio responsive to a detected value of the concentration of an exhaust gas ingredient after a high load operating condition of the engine in which a detected load on the engine is above a predetermined reference value has continued over a predetermined time period. Calculation is made of a value of a parameter dependent on a ratio of a time period over which the detected load on the engine continued to be above a predetermined value to a time period over which the detected load on the engine continued to be below the predetermined value. The predetermined time is set based on the calculated value of the parameter dependent on the ratio. The predetermined value may be equal to the predetermined reference value, or alternatively may be smaller than the predetermined reference value.

Abstract: A method of controlling air-fuel ratio of a mixture supplied to an internal combustion engine in a feedback manner responsive to an output signal from an exhaust gas concentration sensor. The air-fuel ratio of the mixture is controlled to a desired value by means of proportional control and integral control. The proportional control is inhibited, when the value of the output signal has changed from a lean side to a rich side with respect to a predetermined reference value while the engine is operating in one of a predetermined high load condition and a predetermined high rotational speed condition.

Abstract: A method for controlling the flow rate of supplementary air supplied to an internal combustion engine via at least one supplementary air passage bypassing a throttle valve arranged in the intake air passage, by means of at least one control valve arranged across the at lease one supplementary air passage. The valve opening of the control valve is decreased with a decrease in the engine rotational speed, when the throttle valve is detected to be in a substantially fully closed position and at the same time the engine rotational speed is higher than a predetermined value which is higher than an idling speed of the engine. Preferably, the at least one supplementary air passage comprises a plurality of air passages, and the at least one control valve comprises a plurality of on-off valves arranged across respective ones of the air passages. One or more of the on-off valves are selectively opened in response to the extent of engine warming-up and/or an increase in engine load.