Porsche 911 GT3R 2010 Technical Manual page 16

3.5.2. Thermostat
The stock GT3 R is not equipped with a thermostat. As an option a
thermostat is available for cooler driving conditions (see parts catalog).
When competing under warmer conditions the car should be driven
without the thermostat in order to reduce the temperature level of the
cooling system.
with thermostat
return
supply
without thermostat
return
supply
The thermostat starts to open at 71 degrees celcius. It is fully opened at
85 degrees celcius.
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