NOX CONTROL DURING ENGINE IDLE-STOP OPERATIONS

摘要

Methods and systems are provided for improving engine exhaust emissions while enabling exhaust catalyst regeneration following an engine lean event. Prior to a VDE event, or prior to an engine idle-stop, ammonia is produced and stored on an exhaust underbody SCR catalyst. Then, during the engine restart after the VDE mode or the idle-stop, the stored ammonia is used to treat exhaust NOx species while an upstream exhaust underbody three-way catalyst is regenerated.

主权项

1. An engine method, comprising:
during engine running, flowing exhaust through each of a first, second, and third close-coupled three-way catalyst to store exhaust ammonia on the first catalyst, the second catalyst located downstream of, and the third catalyst located upstream of, the first catalyst; selectively deactivating the engine during an idle-stop; and during an engine restart from idle-stop, adjusting regeneration of the third catalyst based on an ammonia content of the first catalyst.