Patent ID: 7181908

Claim:
Method for controlling a direct-injection gasoline engine during regeneration of a lean NOx trap disposed in an exhaust path of the engine, the regeneration characterized by a transition from stratified lean engine operation to homogeneous rich engine operation, the steps of the method comprising: (a) computing a feed-forward compensating torque, which consists of a single estimate for decreased engine torque during the regeneration of the lean NOx trap resulting from the transition from stratified lean engine operation to homogeneous rich engine operation; (b) determining a base desired torque to be provided by the engine; (c) increasing the based desired torque by the feed-feed forward compensating torque to obtain an adjusted desired torque; (d) controlling engine operation based upon the adjusted desired torque; and (e) repeating steps (b) through (d) during the regeneration of the lean NOx trap, thereby using the single estimate for the feed-forward compensating torque to compensate for decreased engine torque resulting from the homogeneous rich engine operation.