Cooling System: Description and Operation
Cooling System
Like in the previous model, the new 911 Turbo also features water cooling of the cylinders and cylinder heads based on the cross-flow principle with the water flowing from the hot to the cold side. This principle achieves a homogeneous temperature distribution with even loads on the components.
Despite the high cooling requirement, the engine of the new 911 Turbo makes do with just one oil-water heat exchanger, although this is larger than the one used in the 911 Carrera. The heat from the coolant is dissipated to the environment by means of two side radiator modules and one center radiator module in the front apron.
The water pump has been largely adopted from the current 911 Carrera engines and is attached as a separate module to the outside of the crankcase on cylinder bank side 1-3. To adapt to the improved engine performance and ensure adequate engine cooling, the new 911 Turbo features a water pump with increased volume flow. This is achieved by enlarging the water pump impeller.
As in the previous model, the bearing housings of the turbochargers in the new 911 Turbo are also cooled with water. This is done by a separate electrically operated water pump. The pump increases water throughput at low engine speeds to meet the cooling requirement. It also permits efficient cooling of the highly loaded turbochargers even when the engine is stopped after the vehicle has been driven with high power demands.
Sufficient supply of coolant to the turbochargers is possible only to a restricted extent at low engine speeds and therefore at low water pump speeds of the conventional water pump as well as with a stopped engine. This is particularly the case after heavy engine loading. As a result, coking of the lubricating oil in the bearing case and on the turbine shafts is only prevented to a limited extent. Here, the electrically operated additional pump supports coolant throughput and also ensures sufficient cooling of the turbocharger under these operating conditions.