Fuel injection control in supercharged engine

Claim 1

A fuel injection control system in a supercharged engine, which comprises, in combination: an intake system for the supply of suction air to at least one combustion chamber of the engine and including an air cleaner; an exhaust system for the discharge of exhaust gases from the combustion chamber; a first air flow sensor means disposed in the intake system downstream of the air cleaner for detecting the flow of the suction air entering the intake system through the air cleaner; a supercharger disposed in the intake system downstream of the first air flow sensor means for providing the combustion chamber with a supercharged air; a secondary air supply passage extending from a portion of the intake system downstream of the supercharger to the exhaust system for supplying a portion of the supercharged air to the exhaust system; a second air flow sensor means disposed in the secondary air supply passage for detecting the flow of the air towards the exhaust system; a fuel control means operable in response to respective outputs from the first and second sensor means to detect the total flow of the suction air and the flow of secondary air flowing through the supply passage and to control the quantity of fuel to be injected, which fuel quantity corresponds to the difference between the total flow of the suction air and the flow of the secondary air; an abnormality signal detecting means for detecting the generation by the second sensor means of a signal of a value deviating from a predetermined range of values; a reducing means for controlling the flow of the secondary air so as to decrease it in the event that the detecting means detects the occurrence of an abnormality; and a control modifying means for, in the event of the abnormality, modifying the fuel control means so as to control the quantity of fuel to be injected solely in dependence on the output from the first sensor means.