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Running 10C cooler in Sport than in Normal

 
Old 10-26-2018, 06:35 PM
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the_buch
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Default Running 10C cooler in Sport than in Normal

I'm wondering why this is and if true why wouldn't I always choose Sport mode to get this benefit from an engine protection viewpoint (though probably give up a bit of mileage)?
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Old 10-26-2018, 06:51 PM
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worf928
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Normal. And yes, the higher temp is for emissions/efficiency. And yes, no reason not to run in Sport mode most of the time.
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Old 10-26-2018, 07:12 PM
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Found this to be true too, I always drive in sport mode
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Old 10-26-2018, 08:16 PM
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Jean
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Is this intake temperature or are we talking about water temp?
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Old 10-26-2018, 08:53 PM
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Oil temperature, so an accurate difference (as you know the water temperature gauge is fake news).
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Old 10-26-2018, 09:37 PM
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I didn't know this!!!
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Old 10-27-2018, 08:54 PM
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FWIW, this is the same thing that occurs on my Spyder as well, so it's not just for the TT/TTS.
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Old 10-28-2018, 02:31 AM
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Originally Posted by guab View Post
FWIW, this is the same thing that occurs on my Spyder as well, so it's not just for the TT/TTS.
It's pretty much all the modern Porsches. 991, 991TT, 981, 95B (Macan)...
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Old 10-28-2018, 10:37 AM
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So what changes to accomplish this, and while I can see the higher temperature being better for fuel mileage, which is better for long-term engine wear? (Perhaps the higher if there’s less friction thus explaining the mileage gain?)
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Old 10-29-2018, 05:41 AM
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Originally Posted by the_buch View Post
So what changes to accomplish this, and while I can see the higher temperature being better for fuel mileage, which is better for long-term engine wear? (Perhaps the higher if there’s less friction thus explaining the mileage gain?)
If I recall reading this correctly, there are louvers that close off some of the airflow to the front radiators in Normal mode to reduce drag, and that reduced airflow increases the oil temperature. So it's not really the increased temperature that gets better mileage - it's reduced drag. I remember this specifically from my C4S - not sure that the Turbo does this though.
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Old 10-29-2018, 10:54 AM
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Originally Posted by JR956678 View Post
If I recall reading this correctly, there are louvers that close off some of the airflow to the front radiators in Normal mode to reduce drag, and that reduced airflow increases the oil temperature. So it's not really the increased temperature that gets better mileage - it's reduced drag. I remember this specifically from my C4S - not sure that the Turbo does this though.
Weird - you'd think Porsche would want to reduce drag in the sportier modes? Plus, how much difference could that bit of drag make at average speeds more typical of running in Normal?

I'm still trying to figure out whether the higher operating temperatures might result in reduced friction to deliver higher fuel mileage and therefore less wear and tear, or if the higher temps result in a combustion efficiency though possibly greater heat-related stress??
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Old 10-29-2018, 11:54 AM
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yes, anytime i go to sport/sport+ oil temp comes down about 10d, ‘14 C2S
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Old 10-29-2018, 07:56 PM
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AFAIK, the higher efficiency / lower emissions is a hotter base temperature combustion effect not a mechanical effect.

The mechanism... 991s (any flavor) don’t have active louvers that block airflow. 992s are reported to have louvers. The ‘87-‘90 928s have louvers too.

The waterpump in the 9A1 motor is belt driven. I spent some time today looking for references materials and didn’t find anything to jog my memory on the mechanism for the 9A1 and 9A2 motors. Could be a ECU-controlled valve for water or oil...


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Old 10-29-2018, 08:07 PM
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Thanks all. For those interested, I found an older thread on the 991 board with some speculations: https://rennlist.com/forums/991/1081...port-mode.html ... I'll try not to duplicate effort
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Old 10-30-2018, 09:20 PM
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Originally Posted by the_buch View Post
So what changes to accomplish this, and while I can see the higher temperature being better for fuel mileage, which is better for long-term engine wear? (Perhaps the higher if there’s less friction thus explaining the mileage gain?)
Well, knowing how effective an oil fan override switch is on an aircooled car, my guess would be the engine management would simply change the fan on temperature when you select sport mode.
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