Diesel engines have a worldwide spread and acceptance. However, they are also a major source of NOx and particulate matter emissions, and these emissions can pose significant health concerns. Exhaust gas re-circulation (EGR) is a widely used method in diesel engines for controlling NOx production. While EGR rates can be varied to ensure engine performance and reduce NOx emissions, EGR also influences the ignition delay, reduces the peak combustion temperature and increases particulate emissions. Moreover, the injection timing directly affects NOx and particulate emissions under these broad and highly variable set of conditions. An effective CFD-based design tool for diesel engines must include robust and accurate predictive capabilities for combustion and pollutant formation for variable injection timing and EGR rates. The objective of the present study is to evaluate CFD modeling of diesel engine combustion and emissions for various combinations of EGR rates and injection timings. Of primary importance to this paper detailed chemistry combustion model and multi-component spray models were used. Model sensitivities were analyzed to provide insight about the prediction accuracy. The engine operating conditions are varied with EGR levels between 10% and 49% and different injection timing in a validated CFD setup. Numerical predictions of cylinder pressure trace, heat release rate, ignition delay, NOx and particulate emissions were compared with a large set of experimental results. From these comparisons conclusions were drawn regarding predictive capabilities for varying injection timing and EGR rates.