A diesel engine multi-cylinder valvetrain model including a hydraulic engine braking system was developed. The model can be used for valvetrain dynamics analysis in both engine firing and braking conditions. Moreover, it can be used to investigate engine braking performance with conjugated analysis by combining the valvetrain model with an engine thermodynamic cycle simulation model. Dynamic valve lift profiles, which are important for accurate engine performance simulations, can be simulated with the model, including valve floating prediction for each cylinder during engine braking. The valvetrain model was used in the design of a diesel engine brake system and in the analysis of engine braking performance at the sea level and different high altitude and ambient temperature conditions. Valvetrain dynamics and the impact of EGR (exhaust gas recirculation) valve leakage or opening on engine braking performance were also evaluated.