A method for controlling operation of a diesel engine having a plurality of cylinders, the engine including a first group of cylinders and a second group of cylinders, the method comprising of operating the first group of cylinders with a first intake and exhaust valve timing, the first group of cylinders inducting air and performing diesel compression ignition combustion of injected fuel; and operating the second group of cylinders with a second intake and exhaust valve timing, the second group of cylinders inducting air and performing diesel compression ignition combustion of injected fuel, wherein said second intake valve timing is retarded compared to said first intake valve timing or said second exhaust valve timing is advanced compared to said first exhaust valve timing.