Automotive companies are using Model Based Development for developing complex control systems. Caterpillar uses Matlab model based development extensively for engine control. The controller is composed of individual functional level models from which autocode are generated and stitched together to create a flash file. Caterpillar uses a proprietary simulation tool called Dynasty to simulate machines and engines. Dynasty is not a Matlab based application; it is composed of libraries for engine and machine components. Using the Dynasty library components a plant model could be prepared for simulation purpose. Dynasty accepts the controller in the form of a Windows DLL file. Till date the generation of the DLL file from ECM autocode has been a complex manual process which was not robust. A new algorithm called Hierarchical Model Integration (HMI) provides an alternate process for integrating the control models in Simulink environment and generation of DLL files. Some new plant models are based on Simulink, even these need an integrated controller to run a closed loop simulation. HMI has helped establish a Virtual Product Development process which is robust and contributes to faster development of engine control systems.This paper discusses about the requirements to be met for a controller for co-simulation with a Dynasty plant or a Simulink plant, steps involved in integrating the control model, challenges faced, simulation results and improvement in development time.