Analysis of the effect of cold start on fuel economy of gasoline automatic transmission vehicle

FTP75 driving cycle is used in many countries for evaluation of vehicle fuel economy. FTP75 has 3 phases, where the Phase 1 and the Phase 3 have a same velocity profile, but the Phase1, which is known as cold start phase, shows lower fuel efficiency than the Phase 3. In order to analyze the difference of fuel economy between Phase 1 and Phase 3, vehicle tests are performed. The test results show that the differences of fuel economy is ranging from 3.9% to 18.5%. The factors of the difference of fuel economy for gasoline automatic transmission vehicles are analyzed in this research. The key factors affecting the difference of fuel economy are engine friction loss, torque converter loss and accessory loss. The quantitative analysis of these factors is performed.