A method for controlling operation of an internal combustion engine operating lean of stoichiometry is described. The engine is a multi-cylinder direct-injection engine operative in repetitive cycles each cycle including intake, compression, expansion, and exhaust strokes. The method includes adapting a plurality of fuel injectors to directly inject a first and a second mass of fuel into the cylinders during each cycle. Pressure sensing devices monitor in-cylinder pressure in the cylinders during ongoing operation. The first mass of fuel is injected into one of the cylinders. A cylinder pressure ratio is determined in the cylinder subsequent to injecting the first mass of fuel based upon the monitored pressure. The first mass of fuel injected is adjusted during a subsequent cycle based upon the cylinder pressure ratio.