Abstract: In a fuel blending ratio detecting method, a first blending ratio of the methanol in the fuel supplied to an internal combustion engine is detected by a blending ratio sensor; an air/fuel ratio feedback compensation coefficient computed on the basis of an output of an O.sub.2 sensor is used to compute a feedback learned value, and the current blending ratio compensation coefficient is multiplied by this value to compute the next blending ratio compensation coefficient so as to obtain a second blending ratio; the current blending ratio compensation coefficient is multiplied by a peak mean value of the computed feedback compensation coefficient to compute the next blending ratio compensation coefficient so as to obtain a third blending ratio; and the first, second or third blending ratio is selected according to the operating conditions of the internal combustion engine.

Abstract: In an operation control method of an engine using a mixed fuel of a mixture of a plurality of fuels having different properties, operation condition of the engine being controlled according to a detection signal from a fuel blend ratio detector for detecting the blend ratio of the plurality of fuels in the mixed fuel, and when a malfunction occurs in the detection by the fuel blend ratio detector, the engine is provided with blend ratio storage for storing a plurality of emergency blend ratios for ignition timing control and for air fuel ratio control, and operation condition of the engine is controlled according to the plurality of emergency blend ratios.

Abstract: A method includes a step of calculating an estimated blending ratio of a mixed fuel supplied to a combustion chamber of an internal combustion engine and a following equation is effected in this step to derive the estimated blending ratio:B(t)=k*B(t-1)+(1-k)*Bs(t-n)where t is an integer,n is a first delay coefficient set according to an operation parameter and a type of the engine,B(t-1) is an estimated blending ratio derived in the preceding cycle,Bs(t-n) is a blending ratio obtained by use of said blending ratio sensor in a cycle which was effected n cycles before the current cycle, andk is a second delay coefficient set according to a operation parameter and the type of the engine.

Abstract: In a fuel blending ratio detecting method, a first blending ratio of the methanol in the fuel supplied to an internal combustion engine is detected by a blending ratio sensor; an air/fuel ratio feedback compensation coefficient computed on the basis of an output of an O.sub.2 sensor is used to compute a feedback learned value, and the current blending ratio compensation coefficient is multiplied by this value to compute the next blending ratio compensation coefficient so as to obtain a second blending ratio; the current blending ratio compensation coefficient is multiplied by a peak mean value of the computed feedback compensation coefficient to compute the next blending ratio compensation coefficient so as to obtain a third blending ratio; and the first, second or third blending ratio is selected according to the operating conditions of the internal combustion engine.

Abstract: A fuel blending ratio detecting method is provided which includes a feedback computing compensation coefficient K.sub.FB on the basis of an air/fuel ratio responsive output V.sub.o of an O.sub.2 sensor, computing a feedback learned value K.sub.LRN on the basis of the feedback compensation coefficient K.sub.FB at intervals of a predetermined period, and multiplying the current blending ratio compensation coefficient K.sub.B by this feedback learned value K.sub.LRN to compute the next blending ratio compensation coefficient K.sub.B. Thus, the quantity of fuel supplied to the internal combustion engine can be always controlled accurately on the basis of the computed blending ratio compensation coefficient.

Abstract: A fuel blending ratio detecting method is provided wherein a feedback compensation coefficient K.sub.FB is computed on the basis of an air/fuel ratio responsive output V.sub.o of an O.sub.2 sensor, and a current blending ratio compensation coefficient K.sub.B is multiplied by a peak mean value K.sub.PEAK of the current and preceding peak values of the computed feedback compensation coefficient K.sub.FB to compute the next blending ratio compensation coefficient K.sub.B. Thus, the quantity of fuel supplied to the internal combustion engine can be always controlled accurately on the basis of the computed blending ratio compensation coefficient.

Abstract: A fuel blending ratio detecting method computes a control blending ratio on the basis of blending ratio information generated from a blending ratio sensor or air/fuel ratio information generated from an O.sub.2 sensor, and when the engine is stopped, the control blending ratio detected at that time is stored in a backup memory as a memory blending ratio. At the time of re-starting the engine, the memory blending ratio can be used as the control blending ratio B for a predetermined limited period.

Abstract: An air-fuel ratio feedback control method for a multi-fuel internal combustion engine using a dual O.sub.2 sensor system is provided, in which the concentration of oxygen in exhaust gas on the upstream side of an exhaust gas purifier is detected, a value corresponding to the detected oxygen concentration is compared with a first target value, and the air-fuel ratio is feedback-controlled in accordance with the result of the comparison. The mixture ratio of at least two fuels is detected, and a second target value is set in accordance with the detected fuel mixture ratio. On the other hand, the concentration of oxygen in the exhaust gas on the downstream side of the exhaust gas purifier is detected, and a value corresponding to the detected downstream-side oxygen concentration is obtained. The first target value is corrected in accordance with the difference between the obtained value and the second target value.

Abstract: Provided according to the present invention is a vehicular engine cooling apparatus comprising cooling fan means for cooling at least one of an engine and an environment of the engine, the engine being operated with use of any of two or more different fuels and a mixed fuel formed of a combination of the different fuels. This apparatus further comprises a mixture ratio sensor for detecting the mixture ratio of the two or more different fuels, and a controller for actuating the cooling fan means in accordance with the fuel mixture ratio detected by the mixture ratio sensor, after the engine is stopped. Preferably, the cooling fan is operated only during a predetermined operating time set in accordance with the fuel mixture ratio and the temperature of at least one of the engine and the environment of the engine.

Abstract: In an engine using fuel mixture of gasoline and methanol, the present control system compensates a detection value of a blend ratio sensor with a detection value of a knock sensor, or causes trouble detecting means to detect a failure of the blend ratio sensor and memories the blend ratio immediately before the failure as an assumed blend ratio and compensates the stored value with the detection value of the knock sensor, whereby the engine control is executed based on the control blend ratio and the ignition timing acquired through the compensation.