The air pollution and global warming has become a major problem to the society. To counter this worldwide emission norms have become more stringent in recent times and shall continue to get further stringent in the next decade. From OEMs perspective with increased complexity, it has become a necessity to use simulation methods along with model based systems approach to deal with system level complexities and reduce model development time and cost to deal with the various regulatory requirements and customer needs. The simulation models must have good correlation with the actual test results and at the same time should be less complex, fast, and integrable with other vehicle function modelling. As the vehicle fuel economy is declared in cold start condition, the fuel economy simulation model of vehicle in cold start condition is required.
The present paper describes a methodology to simulate the cold start fuel economy. The simulation methodology includes the engine heat balance equation, heat conduction through cylinder walls and heat convected by air. Based on the heat transferred and heat absorbed by the coolant, oil, block, the real time temperatures of engine oil, engine coolant and cylinder block are predicted. After the prediction of temperatures the engine friction as a function of oil and block temperature is predicted. The Idle speed is predicted as a function of coolant temperature and catalyst heating. The fuel consumption from hot start steady state condition will be corrected based the above (idle speed, engine friction) prediction. This methodology is used to simulate the cold start fuel economy.