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Almost nothing is more critical in the 991 prior to going on track is Coolant temp. The 991 thermostat slams open and closed. Closed under high RPMS like on track warm up can build a pressure wave in the coolant system and can easily blow off coolant lines. Full opening of the thermostat is 72 degree C. Desired operating temp on track is 75-80 C. This sometimes is tough. Porsche 991 cooling system is remarkable. As such, in many cases with temps even hitting 70 Fahrenheit outside you may need to tape the center radiator shut. It is such a known element that Porsche technical manual tells you how to tape the side radiators after the front is closed off to further increase operating temps. So it is important to have car going to grid essentially at operating temp. Then reviewing data during day to see if tape needs to go on or off. Here is a graph as a car was coming up to speed on an outlap. You can see pressure build as he is on gas and not up to temp and when hit 65 C and high rpm a hose blew off.
BTW Gaffers tape works best. Sticks great, and leaves no glue residue when you remove.
Going to grid with gaffer's tape over radiators. Check. Following pace car with gaffer's tape? I can barely blink during a race, let alone look down at coolant temps. Dang it!!!
Thats why you need to go through data after each run and build a chart for how much tape vs temp you need. Also you have to take into account temp changes during the day. There is some work involved to get it right.
Thats why you need to go through data after each run and build a chart for how much tape vs temp you need. Also you have to take into account temp changes during the day. There is some work involved to get it right.
Wow, are those temps for the cup only, or all 991s? The 996 thermostat doesn’t even start to open until 86C, and the high speed fans don’t even kick on full max until 107C.
Wow, are those temps for the cup only, or all 991s? The 996 thermostat doesn’t even start to open until 86C, and the high speed fans don’t even kick on full max until 107C.
I experienced "Chasing" temps during my first time in the car where ambient temp was in the 30's. Had to tape all access points to minimize air flow to get engine temps up. Amazing what a little tape can do.
01-21-2018, 04:25 PM
991 Cup Cooling Temp
