This article will describe some of these systems, and the radiators used to cool them. Let’s begin with the most basic, the single jacket water circuit. Here, the cooling fluid is circulated through internal passages in the engine block to extract and carry away some of the heat produced by the combustion cycle. It is a single circuit because all cooling water is circulated by a single engine-mounted water pump. SCAC stands for “separate circuit after-cooled“. This technology circulates jacket water in the normal manner, but a separate water circuit is added to cool the engine’s intake air after it is pressurized by the turbocharger.