Abstract In Conventional internal combustion engine cooling system, the coolant pump is belt-driven by the engine crankshaft. The direct coupling between engine and cooling pump results in an excessive low of cooling luid at part-load conditions and waste of energy in running the pump at engine cold start, which affects the engine eficiency and, as a consequence, the global fuel consumption. A study has been conducted on a Maruti 800cc MPFI engine cooling system in order to ind a way to reduce common overheating problems at idle conditions and intermediate engine speeds with restricted airlow. The study involves testing of an engine radiator in a wind tunnel (calorimeter) to simulate the actual driving conditions. The coolant low rate, pressure, and temperature characteristics were monitored at different positions in the cooling system while engine speed and load was varied. Engine performance test were carried out for different radiator ram air speeds. The results show that by adjusting the low rates according to certain variables, the overall effectiveness of the cooling system can be increased and hence overheating problems can be minimized. A solution is proposed for improving the cooling system by employing an epicyclic gear train to vary the speeds thereby to vary the coolant low rates in accordance to the coolant temperature. Introduction The coolant system is an integral part of an engine to control its temperature, thermal stress and deformation. As the highest thermal load of an engine occurs at the highest engine load (i.e., wide open throttle, WOT) and at the highest speed, the cooling system has to be designed so that the maximum temperature, thermal stress and deformation under this condition are well controlled. At a lower engine speed and WOT, the thermal load is lower. But, suficient cooling is still needed to suppress engine knocking and reduce charge heating for higher volumetric eficiency in SI engines. At light engine loads or during idling, both the thermal load and knocking are no longer a problem. Instead, HC emissions [1] and friction/heat-transfer losses become major concerns. The cooling system should allow the engine temperature to stay high to reduce HC emissions and friction/ heat-transfer losses. During engine cold-start and warm-up, the low temperatures of the combustion chamber surface and the catalyst result in increased HC emissions, which are a major problem in engine exhaust emission control. An engine in this case needs to be thermally isolated rather than be cooled. Conventional engine cooling systems cannot completely satisfy all the requirements. Coolant temperature, coolant low rate, coolant properties and coolant system pressure are four parameters in an engine coolant system which directly affects the heat transfer rate. Among the four parameters, the coolant properties are most dificult to control in an operating engine. Coolant-system pressure might be controllable. But, increasing the heat transfer rate by reducing the system pressure at WOT to promote nucleate boiling may be jeopardized by ilm boiling. In addition, pump erosion at low pressure may also become a problem. Therefore, pressure control is not discussed here. Coolant temperature and coolant low rate, hence, are the only parameters to be considered. Kenny et al. [2] proposed an electric thermostat to replace the mechanical thermostat. The electric thermostat can control the cooling temperature to achieve high coolant temperature at low engine loads and low coolant temperature at high engine loads. To control both the coolant temperature and the coolant low rate, Couëtouse et al. [3] proposed a cooling system using an electric pump and an automatic water valve. There is no doubt that the electric thermostat and the electrically-driven pump can improve the control over the cooling system. But, there are some issues about the applications of such systems in production engines. First, because many new components are needed, such as sensors, micro- controllers, actuators, and electrical motors, the cost of such cooling systems may be high. Second, there is an energy loss penalty by such cooling systems. Power transmission from the engine crank shaft to the coolant pump is more eficient by mechanical connection than through an alternator and an electrical motor. The electric thermostat, actuators and other new components also consume some energy. Therefore, the beneit from lower friction and heat-transfer losses at light engine loads due to the use of the electrical pump may be offset, or overridden, by the energy loss penalty. Cooling System Optimisation of a Multi - Point Fuel Injection Engine 2016-28-0085 Published 02/01/2016 M A Vadivelu, C Ramesh Kumar, and C D Naiju Vit University CITATION: Vadivelu, M., Kumar, C., and Naiju, C., "Cooling System Optimisation of a Multi - Point Fuel Injection Engine," SAE Technical Paper 2016-28-0085, 2016, doi:10.4271/2016-28-0085. Copyright © 2016 SAE International Downloaded from SAE International by C D Naiju, Thursday, January 14, 2016