Cooling System Function

The concept of the cooling system in the E85 M54 ensures high coolant temperature in the crankcase which reduces the friction between cylinder walls and pistons, reducing fuel consumption. The increase of coolant temperature in the crankcase is achieved by flowing the coolant mainly through the cylinder head.

A low coolant temperature in the cylinder head has a positive effect on the entire torque characteristics of the engine: Low temperatures in the cylinder head lead to a high engine charge (air and fuel) and a rise in the anti-knock limit. In addition, a low coolant temperature in the cylinder head improves the durability of the components. This concept is referred to as the partial engine flow cooling concept (MTK).

The coolant is fed by the water pump via a cast-on feed duct to the rear end of the cylinder head and from there towards the front to the coolant outlet (radiator outlet if engine warmed up). The water jacket in the crankcase is connected to the flow in the cylinder head via bore holes in the crankcase and through the cylinder head gasket. This means that only a part volume of the coolant flows through the crankcase.

The MTK principle leads to a significant temperature increase in the crankcase with virtually unchanged temperature in the cylinder head.