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Old 08-24-2014, 05:54 AM   #1
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Running cooler


It has been a bit hot here in Florida. Although I installed a lower temp thermostat it makes no difference in normal operating temperature when ambient temperature is high. I have read all the purported benefits of a low temperature thermostat. Having worked on cars for almost 50yrs. I do have some perspective on how cooling systems work. I am sure Porsche engineering designs consider an optimal operating temperature but not sure what that temperture is. Understanding cooler may be of some benefit I could not find on the forum a sound reasoning that low temperature thermostats are the solution. Once the thermostat is open it is actually the fans, radiators, rate of coolant flow, airflow and ambient temperature that affect operating temperature. If one wished to have an engine running cooler it would make more sense to me to install lower temperature fan thermostats.
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Old 08-24-2014, 07:15 AM   #2
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Originally Posted by opus69 View Post

It has been a bit hot here in Florida. Although I installed a lower temp thermostat it makes no difference in normal operating temperature when ambient temperature is high. I have read all the purported benefits of a low temperature thermostat. Having worked on cars for almost 50yrs. I do have some perspective on how cooling systems work. I am sure Porsche engineering designs consider an optimal operating temperature but not sure what that temperture is. Understanding cooler may be of some benefit I could not find on the forum a sound reasoning that low temperature thermostats are the solution. Once the thermostat is open it is actually the fans, radiators, rate of coolant flow, airflow and ambient temperature that affect operating temperature. If one wished to have an engine running cooler it would make more sense to me to install lower temperature fan thermostats.
You are overlooking the fact that the OEM stat actually forces the car to run at a higher minimum steady state temperature than the 160F stat does, which is why the same car running the lower temp stat will run cooler under steady state conditions than the OEM stat.

the OEM stat starts to open at 186F, but is not fully open until well beyond 200F, so that becomes the minimum temperature the car can cool down to. The 160F stat starts to open at 160F, and is fully open by the low to mid 170's, which become its steady state minimum temperature, giving you a nearly 25F gap between the two scenarios, which also includes oil temperatures as well.

Stuck in traffic on a hot day if a fully warmed up car, both cars will heat up, although the car with the 160 stat will take longer because it is starting from a lower temperature. Once moving again, air flow/fan action will cool both cars down again to the point where each thermostat begins throttling the coolant flow; the cars minimum steady state temperature; around 175F for the low temp stat, around 205-210F for the OEM stat.

As for Porsche engineering, they are more worried about the car's meeting stringent (read CA) cold start emissions requirements than how long your engine last once it is out of warranty. More interesting is the fact that all of Porsche's high horsepower cars (Turbo, GT2, GT3) run 160F stats from the factory................
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Last edited by JFP in PA; 08-24-2014 at 07:18 AM.
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Old 08-24-2014, 07:39 AM   #3
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I have not seen a lower operating steady state temperature based on the daily driving I am doing. Perhaps on the track or freeway where the volume of airflow would make the lower temperature thermostat beneficial. The point I was trying to raise was that perhaps for those of us who do the daily traffic grind a lower temperature fan thermostat would help to achieve an overall lower operating temperature not achieved by simply changing the thermostat. Just throwing it out there for discussion.
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Old 08-24-2014, 07:42 AM   #4
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I have not seen a lower operating steady state temperature based on the daily driving I am doing. Perhaps on the track or freeway where the volume of airflow would make the lower temperature thermostat beneficial. The point I was trying to raise was that perhaps for those of us who do the daily traffic grind a lower temperature fan thermostat would help to achieve an overall lower operating temperature not achieved by simply changing the thermostat. Just throwing it out there for discussion.
If you are using the dash gauge as a reference, I would not be surprised. The temp gauges in these cars are notoriously inaccurate and non linear. On cars with aftermarket gauges, it becomes a different story. And the fan actuating temps are controlled by code in the DME, and not very easy to alter.
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Old 08-24-2014, 01:32 PM   #5
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I have the low temp stat and in the summer, with the AC on, the fans are blowing at high speed all the time and the temp stays a little past the 8. With the AC off, the temp creeps up to the left side of the 0. So yes, the car will run cooler with the low temp stat.
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Old 08-24-2014, 06:27 PM   #6
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If I understand San Rensho correctly it is the fans being on with the AC which cool down the engine. The temp goes back up with fans not running. From what I have read low speed kicks in at 206 degrees and high speed at 215 degrees but the fans always come on with the AC and the temperature drops. If you wanted to have the engine consistently run cooler it would make sense to me to have the fans come on at a lower temperature. At these temperatures the thermostat would be open whether it is high or low temp.
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