Running 10C cooler in Sport than in Normal
10-26-2018, 06:35 PM
#1
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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)?
10-26-2018, 06:51 PM
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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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10-28-2018, 02:31 AM
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10-28-2018, 10:37 AM
#9
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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?)
10-29-2018, 05:41 AM
#10
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.
10-29-2018, 10:54 AM
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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.
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??
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...
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...
10-29-2018, 08:07 PM
#14
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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 
10-30-2018, 09:20 PM
#15
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