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-   -   Running 10C cooler in Sport than in Normal (https://rennlist.com/forums/991-turbo/1107813-running-10c-cooler-in-sport-than-in-normal.html)

the_buch 10-26-2018 06:35 PM

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)?

worf928 10-26-2018 06:51 PM

Normal. And yes, the higher temp is for emissions/efficiency. And yes, no reason not to run in Sport mode most of the time.

hcvone 10-26-2018 07:12 PM

Found this to be true too, I always drive in sport mode

Jean 10-26-2018 08:16 PM

Is this intake temperature or are we talking about water temp?

the_buch 10-26-2018 08:53 PM

Oil temperature, so an accurate difference (as you know the water temperature gauge is fake news).

neil.schneider 10-26-2018 09:37 PM

I didn't know this!!!

guab 10-27-2018 08:54 PM

FWIW, this is the same thing that occurs on my Spyder as well, so it's not just for the TT/TTS.

worf928 10-28-2018 02:31 AM


Originally Posted by guab (Post 15391573)
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)...

the_buch 10-28-2018 10:37 AM

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?)

JR956678 10-29-2018 05:41 AM


Originally Posted by the_buch (Post 15392331)
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.

the_buch 10-29-2018 10:54 AM


Originally Posted by JR956678 (Post 15394195)
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??

Pmorritt 10-29-2018 11:54 AM

yes, anytime i go to sport/sport+ oil temp comes down about 10d, ‘14 C2S

worf928 10-29-2018 07:56 PM

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...



the_buch 10-29-2018 08:07 PM

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 :)

JB 911 10-30-2018 09:20 PM


Originally Posted by the_buch (Post 15392331)
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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