Cooling System
Cooling System
In addition to the significant weight reduction in all Cayenne models, mainly in the body and chassis, numerous detail features and the use of the state-of-the-art engine technology have contributed to reducing fuel consumption values. The thermal management system has made an important contribution to achieving these objectives.
More detailed information on thermal management can be found in the chapter describing the Cayenne S Hybrid engine, but only regarding the cooling system and the different warm-up phases. Information on activation of the electrically powered pumps and integral thermostats is described in the chapter "Engine control".
NOTE: Please read the work instructions in the Workshop Data before filling or bleeding the cooling system.
Thermal management
All Cayenne engines meet the high demands placed on a Porsche engine under all operating conditions and therefore also meet the special requirements that apply to warm countries. The Cayenne S Hybrid is designed to meet all performance requirements whether on-road, off-road or in traction mode. The cooling system ensures that the engine runs at a favorable operating temperature for optimum and permanent high performance. Further advantages are provided by the low fuel consumption and emission values, since all components reach the optimum operating temperature quickly. A new thermal management system is used for the engine, the Tiptronic S transmission and hybrid components (E-machine and power electronics) on the Cayenne S.
Warm-up strategy of the thermal management system on the Cayenne S Hybrid
Goal
- Rapid heating of friction-relevant fluids such as oils, implemented by way of static coolant, for example
- Heat management (focus on consumption and comfort, etc.)
- Decoupling of masses with sluggish thermal response in the system
- Enhanced heating comfort
Warming-up process
- Engine warm-up
- Heating of passenger compartment as required, transmission prevented from heating up
- Transmission heating
- Heat dissipated via main cooler
Other requirements
- Hybrid: Cooling requirements of the E-machine and power electronics are fulfilled at all times
The main areas of the thermal management system in the Cayenne S Hybrid are heat distribution between the combustion engine, transmission and passenger compartment (high-temperature cooling system). In addition to the high-temperature cooling system, a low-temperature cooling system is installed to cool the charge-air cooler and the hybrid power electronics.
The basic goal is to ensure that all components reach their optimum operating temperature as quickly as possible and to also meet the comfort demands of passengers by heating up the cabin quickly. At low temperatures and for cold engine starts in particular, it is important to manage the low amount of available heat in the best possible way. Efficient use of the available heat helps to save fuel, reduce CO2 emissions and comply with strict emission regulations.
High-temperature cooling system
The cooling system is part of the thermal management system and has two circuits which can be controlled depending on the coolant temperature via a thermostat. The thermostat permits automatic, demand-based suppression of the coolant flow when the engine is cold (cold start). As a result, the engine heats up more quickly and prevents friction more effectively, which presents the advantages mentioned previously. Depending on the increase in engine temperature, the coolant flow through the engine (small circuit) is then activated during warming up. After this, the large circuit is activated depending on the engine operating point and based on a map stored in the engine control. The thermostat control then regulates the coolant temperature depending on the load to ensure that the temperature conditions in the engine are adapted perfectly for the respective load point.
This thermal management system made it possible to reduce fuel consumption by accelerating the warm-up phase after a cold start. Furthermore, the Cayenne S Hybrid is also equipped with thermal management for the transmission, as already mentioned. Here also, the aim is to reach the optimum operating temperature as quickly as possible in order to minimize friction losses. For this purpose, the heat exchanger of the cooling system for the new 8-speed Tiptronic S is connected to the engine cooling system. If necessary, this allows the heat of the engine coolant, which is heated up more quickly, to be used to bring the transmission up to its operating temperature.
Function of thermal management:
When the case on the main water pump is closed, the water remains in the cylinder head and crankcase to heat the engine more quickly (stationary water). When the heating shut-off valve is opened and the auxiliary water pump is connected automatically, warm water is supplied to the heating system.
Effect of thermal management:
- Reduced cooling power during the engine operation phase
- This results in faster heating of the transmission and engine oil
- Less internal friction in the engine and transmission components
The result:
- Reduced fuel consumption
- Faster heating of the passenger compartment (with priority over engine oil heating)
- Increase in fuel economy of up to approx. 1.5 %
The cooling system is part of the thermal management system and has two circuits which can be regulated depending on the coolant temperature. An electric, map controlled thermostat that can be deactivated is used to regulate the circuits on the Cayenne S Hybrid. Depending on the increase in engine temperature, the coolant flow through the engine (small circuit) is then activated during the warming-up phase.
After this, the coolant radiator is activated (large circuit) depending on the engine operating point and based on a map stored in the engine control. The map control of the thermostat then regulates the coolant temperature between 201° F. (94° C.) and 221° F. (105° C.) depending on the load and therefore adapts the friction conditions in the engine perfectly to the respective load point.