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A numerical study is conducted to investigate the effect of changing engine oil and automatic transmission fluid (ATF) temperatures on the fuel economy during warm-up period. The study also evaluates several fuel economy improving devices that reduce the warm-up period by utilizing recycled exhaust heat or an electric heater. A computer simulation model has been developed using a multi-domain 1-D commercial software and calibrated using test data from a passenger vehicle equipped with a 2.4 / 4-cylinder engine and a 6-speed automatic transmission. The model consists of sub-models for driver, vehicle, engine, automatic transmission, cooling system, engine oil circuit, ATF circuit, and electrical system. The model has demonstrated sufficient sensitivity to the changing engine oil and ATF temperatures during the cold start portion of the Federal Test Procedure (FTP) driving cycle that is used for the fuel economy evaluation.

A GT-suite commercial code was used to develop a fully integrated model of a light duty commercial vehicle with a V6 diesel engine, to study the use of a BorgWarner dual mode coolant pump (DMCP) in active thermal management of the vehicle. An Urban Dynamometer Driving Schedule (UDDS) was used to validate the simulation results with the experimental data. The conventional mechanical pump from the validated model was then replaced with the dual mode coolant pump. The control algorithm for the pump was based on controlling the coolant temperature with pump speed. Maximum electrical speed of the pump and the efficiency of the pump were used to determine whether the pump should run in mechanical or electrical mode. The model with the dual mode coolant pump was simulated for the UDDS cycle to demonstrate the effectiveness of control strategy.