A method is disclosed for controlling operation of an engine coupled to an exhaust treatment catalyst. Under predetermined conditions, the method operates an engine with a first group of cylinders combusting a lean air/fuel mixture and a second group of cylinders pumping air only (i.e., without fuel...http://www.google.fr/patents/US6925982?utm_source=gb-gplus-shareBrevet US6925982 - Overall scheduling of a lean burn engine system
