The performance of engine coolant control strategies on real driving emissions

Thermal management in internal combustion engines (ICEs) significantly influences fuel consumption and pollutant emissions, particularly during engine warm-up. In this study, an electric coolant pump was designed, optimized, prototyped, and installed on a small SUV equipped with a spark-ignition engine, replacing the original mechanically driven pump. A dedicated off-board experimental campaign enabled a full hydraulic characterization of all the branches of the cooling system, simulating also the opening and closing of the thermostat and finding a specific physically based correlation between the circulating flow rates with the pressure differences among each branch. Thanks to this knowledge, a cooling pump has been designed in an optimized way, prototyped and equipped with electrical actuation. The pump has been operated on the vehicle reproducing the flow circulation produced by the mechanical pump and, as main goal, the results deriving from a different cooling flow management. A series of Real Driving Emissions (RDE) tests on-road using different pump control strategies have been done. The complete path from preliminary laboratory testing, design, optimization, prototyping, installation on board, control strategy definition and real testing with emissions measurement has been performed, representing a very novelty in the vehicle panorama. Results demonstrate that smart coolant flow control via an electrical pump can accelerate engine and lubricant oil warm-up up to 150 s, resulting in lower tailpipe emissions referred to CO, NO, THC, CH₄, and PN, especially during the critical early phase of the driving cycle when the engine is cold. The reduction is significant with average figures in the range of 15–65%. Electrification of the coolant pump also leads to reduced parasitic losses and opens to opportunities for integration with hybrid powertrains. The study confirms the viability of thermal control as a transitional technology for enhancing ICE performance and environmental compatibility within the current vehicle fleet. The reference to a real driving is a novelty in the sector and it insures about the benefits obtained.