A DFSS Approach to Design Cooling System of Small Passenger Car Having Rear Engine and Front Mounted Radiator

DFSS is a disciplined problem prevention approach which helps in achieving the most optimum design solution and provides improved and cost effective quality products. This paper presents the implementation of DFSS method to design a distinctive cooling system where engine is mounted in the rear and radiator is mounted in the front of the car.

In automobile design, a rear-engine design layout places the engine at the rear of the vehicle. This layout is mainly found in small, entry level cars and light commercial vehicles chosen for three reasons - packaging, traction, and ease of manufacturing. In conventional Passenger cars, a radiator is located close to the engine for simple packaging and efficient thermal management. This paper is about designing a distinctive cooling system of a car having rear mounted engine and front mounted radiator. This kind of arrangement requires lengthy coolant lines extended between the radiator and the engine throughout the length of the car, routed beneath the car. The U-shaped arrangement where radiator and engine are at higher coolant head and cooling lines are at very low coolant head becomes critical as air traps in the coolant system during coolant filling and de-aeration process. This restricts the coolant circulation during vehicle running-in and thus affect the life of critical components due to overheating. This paper also explains cooling system having external bypass instead of internal bypass to reduce overall cost and to provide simple and compact engine bypass circuit. The external bypass close to coolant pump offers a much lower resistance flow path as compared to the long radiator cooling lines increasing the risk of less coolant flows through the radiator as compared to bypass. These challenges were addressed using DFSS and DOE method. An optimum Design is finalized using DFSS approach and based on the analysis of the various tests carried out as per DOE. This design provide compact packaging of coolant system, ensure better thermal management and maintain good aesthetics of the automobile. The serviceability of the engine i.e. filling of the coolant and process of de-aeration is also simplified with the finalized design.