Method and apparatus of minimizing cylinder air/fuel ratio variation in multi-cylinder engine

PURPOSE: To provide an apparatus and a method for maintaining equal air flow among cylinders and independently controlling the air/fuel ratio of each individual cylinder in an internal combustion engine having a variable valve controller. CONSTITUTION: An air fuel controller 18 generates valve control signals for each individual cylinder by sampling with an exhaust gas oxygen sensor 16 and correlating the samples with corresponding combustion events. A valve lift for each variable lift valve is corrected to operate each cylinder at a desired airflow and air/fuel ratio. The valve lift of an intake valve can be varied in a camshaft type system incorporating a lost motion mechanism or similar device, or a system incorporating direct electrohydraulic or electromechanical valve actuation without a camshaft. The system and method can provide further flexibility in cylinder-to-cylinder air/fuel ratio control by combining it with a variable pulse width electronic fuel injector capability. COPYRIGHT: (C)1994,JPO