Various embodiments relate to a method of operating an engine system with injectors having nozzle sac volume. The engine system may be a four-stroke, high power engine having a high-pressure common-rail injection system. A number of engine cylinders to fire is selected based on a fuel injection quantity per selected engine cylinder such that a nitrogen oxides (NOx) emission is less than a first predetermined threshold and a smoke value is less than a second predetermined threshold. The fuel injection quantity per cylinder may be higher than a nominal fuel injection quantity to improve fuel injector spray characteristics. The exhaust can be mixed with fresh air blowout from deactivated cylinders to further reduce smoke value. The engine system is operated with a firing pattern for the selected number of cylinders to fire.