ENGINE WITH CYLINDER DEACTIVATION

摘要

A multi-cylinder spark ignition internal combustion engine is described having two groups of cylinders (10a, 10b). One group of cylinders may be selectively disabled by cutting off its fuel supply while continuing to receive air. The exhaust system includes an NOx trap (20) to store NOx gases while the exhaust gases contain excess air. During part load operation, the engine is run with one group of cylinders disabled most of the time during which NOx gases are stored in the NOx trap (20). In order to permit the trap (20) to be regenerated or purged periodically, both group are fired at the same time for short intervals to supply a stoichiometric or reducing mixture to the exhaust system.