Patent ID: 6604504
Filing Date: 2003-08-12
Classification: F01N,F02D

Abstract:
A method for transitioning an internal combustion engine between a first operating condition and a second operating condition, wherein the first and second operating conditions are characterized by combustion, in each of a plurality of engine cylinders, of a supplied air-fuel mixture having a first and second air-fuel ratio, respectively, and wherein one of the first and second air-fuel ratios is significantly lean of a stoichiometric air-fuel ratio and the other of the first and second air-fuel ratios is a stoichiometric air-fuel ratio, the method comprising:identifying at least two discrete sets of cylinders supplied with the air-fuel mixture at the first air-fuel ratio; sequentially stepping the air-fuel ratio of the air-fuel mixture supplied to each set of cylinders from the first air-fuel ratio to the second air-fuel ratio; and including retarding the timing of combustion ignition in one set of cylinders with respect to another set of cylinders until all sets of cylinders are operating at the second operating condition; and including decreasing a mass flow of air to all sets of cylinders simultaneous with advancing timing.