The Objective of the work is to upgrade existing series of multi cylinder DI turbocharged intercooled diesel engines to meet revised stringent Stage-II emission norms for diesel genset application. In this engine tuning activity, focus is given on optimization of engine without any major modification on engine design features.In recent years, the demand use and penetration of diesel operated generating sets for the power generation application has sharply rise in India. These sharp rises in the DG engines have made the high impact on pollutants emitted by these sets. Hence, concerned authorities have first enforced the limits on the pollutants emitted by these sets in the year 2004. Further these emission limits were tightened recently and reduced the emissions from diesel engines. Concerned authorities implemented the revised emission norms with effective from July 2014. The reduction in NOx+HC emission is around 62% for the engines having rated power above 75 kW. There is a reduction of around 33% in PM emission. The smoke limit mandatory at all the operating load conditions of the test cycle, which was only at rated load points in previous limits.This paper deals with the strategies applied and experimental work done to meet the revised Stage-II emission norms. The experimental investigations are carried out on series of turbocharged intercooled diesel genset engines. In the up gradation work, turbocharged and intercooled engines of different power ratings are optimized to meet the revised Stage-II emission norms. Various combustion related parameters like intake swirl, air fuel ratio, combustion bowl geometry, Injector nozzle configuration, hydraulic through flow, nozzle hole size, number of holes, injection pressure, start of injection, injection duration, high pressure pipe diameters along with Exhaust Gas Recirculation (EGR) are optimized and results are reported.