Abstract
This paper presents a new split cooling system that has been developed to satisfy society's increasingly more stringent demands for improved fuel economy and lower exhaust emissions. The new cooling system is incorporated in the VQ engine mounted in the Nissan Cedric/Gloria. It controls the volume of cooling water circulated to the cylinder block according to the cooling water temperature. This makes it possible to raise the cylinder bore temperature when the engine is cold or when the cooling water temperature is low, thereby reducing friction for improved fuel economy. It also enables the combustion gas in the piston crevices to warm up faster, which works to reduce the engine-out level of hydrocarbon (HC) emissions.