Influence the higher temperature of the cooling liquid on operational parameter of the piston combustion engine

The results of selected research of the results of the combustion engine cooling system which works with higher coolant temperatures are presented in this paper. The temperature of this liquid was increased to a higher level than the temperature of boiling water in normal conditions, by decreasing of heat transfer intensity. This presented system was designed for the four cylinder 4CT90 diesel engine with indirect fuel injection. Research was done on the engine dynamometer stand which was equipped with standard measure devices (for measuring: speed, torque, temperatures, and flow) and exhaust gas analyzers. By applying a pressure cooling system it was possible to maintain a stable, increased ca. 20 centigrade, coolant temperature for a standard engine cooling system at low overpressure 0.2 MPa. The results of increasing the cooler temperature were lower friction of unburned products during the combustion process (CO and HC) in the exhaust gas (up to 50%) at low torque and engine speed. This is the area where the catalytic reactor does not work because the exhaust gas temperature is too low. It was found that engine efficiency was increased up to 7% at maximum load and high engine speed. It is possible to achieve a temperature between 130 –140 centigrade for an overpressure of 0.3 MPa in the cooling system. It needs a special cooler, however, and leak proof pipes.