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Euro4 and EPA/02 emission regulations for the European and North American Heavy Duty truck market will require development of high efficiency, low pollution diesel engines. Informations received from main engine, truck manufacturers and literature surveys performed during the past two years shows that several technical solutions are being evaluated in order to reach the required emission levels. These technical solutions can be divided into 3 main groups: 1 Further optimization of fuel combustion including: increase of air to fuel ratio, further retardation of fuel injection timing. 2 Cooled EGR including: high recycled exhaust gas ratios, short EGR loop, compressed and aftercooled EGR. 3 Exhaust gas aftertreatment including: de-NOx catalysts, particle traps, particle afterburning. Different technical solutions will have different impacts on the heat rejection requirements and consequently on the layout and costs of the future cooling systems.

A simulation approach is developed to define the control strategies of a new ‘intelligent’ component of the engine cooling system: the variable speed fan system. The paper describes the way each component of the cooling loop is characterized by geometric data or test results to create a one dimensional network of the cooling circuit. Then, comparison with experimental confirms the relevance of the models and their limits. At last, several types of control strategies are evaluated on a simplified driving cycle. This study finally determines the necessary tests to obtain a correct model, able to adapt control strategies for any vehicle.