Patent ID: 6205776
Filing Date: 2001-03-27
Classification: F02D,Y02T

Abstract:
An air-fuel ratio control system for a multi-cylinder internal combustion engine having a plurality of cylinders, comprising:an exhaust emission control catalyst disposed in an exhaust passage of the internal combustion engine;air-fuel ratio control means for individually controlling an air-fuel ratio in each of at least two of the internal combustion engine cylinders, wherein the air-fuel ratio control means controls the air-fuel ratio in at least one of the at least two cylinders to be different from the air-fuel ratio in at least one of the other cylinders of the internal combustion engine; andcatalyst temperature detection means for detecting a temperature of the exhaust emission control catalyst,wherein if the temperature of the exhaust emission control catalyst is lower than a first predetermined temperature, the air-fuel ratio control means reduces an upper limit of an air-fuel ratio for at least one of the at least two cylinders, in comparison with an upper limit of the air-fuel ratio for the at least one of the at least two cylinders used if the temperature of the exhaust emission control catalyst is equal to or higher than the first predetermined temperature.