997.2 Third Radiator
09-02-2010, 01:18 PM
#16
Poseur
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Porsche dumbed it down most likely because today's owners are **** excessive and don't understand what they're looking at other than higher is bad. When Porsche service centers started to get call after call about 'suspiciously high' coolant temps I suspect Porsche AG decided to 'pull the plug' on accurate reporting.
Years ago the oil temperature gauge (which was all we had) was spot on. Just be aware that your coolant temp is probably a lot closer to your oil temperature than you want to believe. There is no way your car is simply sitting at 175ºF during a hot summer drive. When my serpentine belt failed several months ago it took a bit but eventually (still driving) the lack of water pump movement caused my water temps to trigger the coolant gauge to kick up to about 245ºF. By then it's sort of useless. No damage was done, but the purpose of any analog gauge is to provide trending for the operator. If you can watch the trend of your coolant temperatures to climb but then go down when you have up shifted and are running at lower engine speeds then you can correlate engine speed with engine coolant temps. Without an accurate temperature gauge you are denied any insight into what is happening inside your engine--other than the oil temp gauge.
To get back to the original posting, I see no point in adding a third cooler if you don't really know what your coolant temperatures are today.
Years ago the oil temperature gauge (which was all we had) was spot on. Just be aware that your coolant temp is probably a lot closer to your oil temperature than you want to believe. There is no way your car is simply sitting at 175ºF during a hot summer drive. When my serpentine belt failed several months ago it took a bit but eventually (still driving) the lack of water pump movement caused my water temps to trigger the coolant gauge to kick up to about 245ºF. By then it's sort of useless. No damage was done, but the purpose of any analog gauge is to provide trending for the operator. If you can watch the trend of your coolant temperatures to climb but then go down when you have up shifted and are running at lower engine speeds then you can correlate engine speed with engine coolant temps. Without an accurate temperature gauge you are denied any insight into what is happening inside your engine--other than the oil temp gauge.
To get back to the original posting, I see no point in adding a third cooler if you don't really know what your coolant temperatures are today.
09-02-2010, 05:04 PM
#17
Drifting
Get an independent gauge and run the wires from the existing temperature sensors. Those are probably not dumbed down... its the display electronics that filter and smooth the sensor readings out.
That said, even on a 'hot' day, the air temperature is much less than the coolant temperature at operational temps, so the air is perfectly capable of cooling down the coolant via the radiators.
That said, even on a 'hot' day, the air temperature is much less than the coolant temperature at operational temps, so the air is perfectly capable of cooling down the coolant via the radiators.
09-02-2010, 07:57 PM
#18
Poseur
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I had thought about that as well but sometimes borrowing off existing wires may not be the wisest thing to do--as complex as these puppies are today electronically.
09-02-2010, 10:05 PM
#19
Rennlist Member
Porsche dumbed it down most likely because today's owners are **** excessive and don't understand what they're looking at other than higher is bad. When Porsche service centers started to get call after call about 'suspiciously high' coolant temps I suspect Porsche AG decided to 'pull the plug' on accurate reporting.
Years ago the oil temperature gauge (which was all we had) was spot on. Just be aware that your coolant temp is probably a lot closer to your oil temperature than you want to believe. There is no way your car is simply sitting at 175ºF during a hot summer drive. When my serpentine belt failed several months ago it took a bit but eventually (still driving) the lack of water pump movement caused my water temps to trigger the coolant gauge to kick up to about 245ºF. By then it's sort of useless.
Years ago the oil temperature gauge (which was all we had) was spot on. Just be aware that your coolant temp is probably a lot closer to your oil temperature than you want to believe. There is no way your car is simply sitting at 175ºF during a hot summer drive. When my serpentine belt failed several months ago it took a bit but eventually (still driving) the lack of water pump movement caused my water temps to trigger the coolant gauge to kick up to about 245ºF. By then it's sort of useless.
Maybe the newer Porsches are built better with a closed system that radiator/water pump work dynamically to keep the temp steady at 175, and measures it at a point where it's away from hotter oil (after cool down). I also remember a lot more water temp variation in older cars (non Porsche) but since late 90s all cars I've owned had steady water temp.
09-03-2010, 12:40 AM
#20
Poseur
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What I am stating is that the coolant gauge will rise to approx. 175ºF and then sit there, even if the actual temps climb to 200, 225ºF. If you get up to about 240-245ºF actual coolant temp the needle will quickly climb to just shy of the 250ºF mark to tell you it's really hot.
My complaint is that you will never get to see the analog needle slowly build up to 250--it will move quickly from the 175 mark to the 250 mark. Thus, its utility is substantially lessened.
We've had past discussions about what the true operating (coolant) temperature of the car is during normal operating conditions. The car does not run at 175ºF. It will be most likely around 192ºF. We just never see that.
My complaint is that you will never get to see the analog needle slowly build up to 250--it will move quickly from the 175 mark to the 250 mark. Thus, its utility is substantially lessened.
We've had past discussions about what the true operating (coolant) temperature of the car is during normal operating conditions. The car does not run at 175ºF. It will be most likely around 192ºF. We just never see that.
09-03-2010, 01:15 AM
#21
Rennlist Member
What I am stating is that the coolant gauge will rise to approx. 175ºF and then sit there, even if the actual temps climb to 200, 225ºF. If you get up to about 240-245ºF actual coolant temp the needle will quickly climb to just shy of the 250ºF mark to tell you it's really hot.
My complaint is that you will never get to see the analog needle slowly build up to 250--it will move quickly from the 175 mark to the 250 mark. Thus, its utility is substantially lessened.
We've had past discussions about what the true operating (coolant) temperature of the car is during normal operating conditions. The car does not run at 175ºF. It will be most likely around 192ºF. We just never see that.
My complaint is that you will never get to see the analog needle slowly build up to 250--it will move quickly from the 175 mark to the 250 mark. Thus, its utility is substantially lessened.
We've had past discussions about what the true operating (coolant) temperature of the car is during normal operating conditions. The car does not run at 175ºF. It will be most likely around 192ºF. We just never see that.
Here's the way cooling works from wikipedia:
When the engine is cold the thermostat is closed, with a small bypass flow so that the thermostat experiences changes to the coolant temperature as the engine warms up. Coolant is directed by the thermostat to the inlet of the circulating pump and is returned directly to the engine, bypassing the radiator. Directing water to circulate only through the engine allows the temperature to reach optimum operating temperature as quickly as possible whilst avoiding localised "hot spots". Once the coolant reaches the thermostat's activation temperature it opens, allowing water to flow through the radiator to prevent the temperature rising higher.
Once at optimum temperature, the thermostat controls the flow of coolant to the radiator so that the engine continues to operate at optimum temperature. Under peak load conditions, such as labouring slowly up a steep hill whilst heavily laden on a hot day, the thermostat will be approaching fully open because the engine will be producing near to maximum power while the velocity of air flow across the radiator is low.
Conversely, when cruising fast downhill on a motorway on a cold night on a light throttle, the thermostat will be nearly closed because the engine is producing little power, and the radiator is able to dissipate much more heat than then engine is producing. Allowing too much flow of coolant to the radiator would result in the engine being over cooled and operating at lower than optimum temperature. A side effect of this would be that the passenger compartment heater would not be able to put out enough heat to keep the passengers warm.
The thermostat is therefore constantly moving throughout its range, responding to changes in vehicle operating load, speed and external temperature, to keep the engine at its optimum operating temperature.
Once at optimum temperature, the thermostat controls the flow of coolant to the radiator so that the engine continues to operate at optimum temperature. Under peak load conditions, such as labouring slowly up a steep hill whilst heavily laden on a hot day, the thermostat will be approaching fully open because the engine will be producing near to maximum power while the velocity of air flow across the radiator is low.
Conversely, when cruising fast downhill on a motorway on a cold night on a light throttle, the thermostat will be nearly closed because the engine is producing little power, and the radiator is able to dissipate much more heat than then engine is producing. Allowing too much flow of coolant to the radiator would result in the engine being over cooled and operating at lower than optimum temperature. A side effect of this would be that the passenger compartment heater would not be able to put out enough heat to keep the passengers warm.
The thermostat is therefore constantly moving throughout its range, responding to changes in vehicle operating load, speed and external temperature, to keep the engine at its optimum operating temperature.
Just a theory...
09-06-2010, 12:53 PM
#24
Rennlist Member
I think it is interesting how some people don't trust the gauges. I must be naive and trusting, but I chalked it up to good engineering by Porsche. If I were designing the cooling system for a car, I would want to get up to optimum temperature quickly and then stay there. That's good process control. Unless I am mistaken, we have electric water pumps... Porsche would simply control the pumping rate (either proportional control or on/off) to control temperatures as desired. That's very easy to do and it makes sense from an operational standpoint, so I just don't see the reason to suspect our water temperature are somehow fake. Of course, the readings are buffered a bit so the gauge doesn't bounce around, but again that is normal (it might average over a period of a minute or so).
High oil temperatures seem to indicate the need for a larger oil cooler, but perhaps there is an oil-to-water heat exchanger, and if so then dropping the water temperatures would also reduce the oil temperature. I have no idea if such a heat exchanger exists in the 997.2, however.
It's also important to know where the temperatures are measured. I don't know, but I have opinions based on my observations. It seems that the oil temperature is measured at the oil cooler up front. I say this because it takes so long for the temperature to creep up. The oil in the engine gets hot faster, of course. As the oil near the engine heats up, more is pumped up to the oil cooler, and we see the temperature slowly rise. I could be wrong of course!
High oil temperatures seem to indicate the need for a larger oil cooler, but perhaps there is an oil-to-water heat exchanger, and if so then dropping the water temperatures would also reduce the oil temperature. I have no idea if such a heat exchanger exists in the 997.2, however.
It's also important to know where the temperatures are measured. I don't know, but I have opinions based on my observations. It seems that the oil temperature is measured at the oil cooler up front. I say this because it takes so long for the temperature to creep up. The oil in the engine gets hot faster, of course. As the oil near the engine heats up, more is pumped up to the oil cooler, and we see the temperature slowly rise. I could be wrong of course!
09-06-2010, 11:12 PM
#25
Three Wheelin'
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I think it is interesting how some people don't trust the gauges. I must be naive and trusting, but I chalked it up to good engineering by Porsche. If I were designing the cooling system for a car, I would want to get up to optimum temperature quickly and then stay there. That's good process control. Unless I am mistaken, we have electric water pumps... Porsche would simply control the pumping rate (either proportional control or on/off) to control temperatures as desired. That's very easy to do and it makes sense from an operational standpoint, so I just don't see the reason to suspect our water temperature are somehow fake. Of course, the readings are buffered a bit so the gauge doesn't bounce around, but again that is normal (it might average over a period of a minute or so).
High oil temperatures seem to indicate the need for a larger oil cooler, but perhaps there is an oil-to-water heat exchanger, and if so then dropping the water temperatures would also reduce the oil temperature. I have no idea if such a heat exchanger exists in the 997.2, however.
It's also important to know where the temperatures are measured. I don't know, but I have opinions based on my observations. It seems that the oil temperature is measured at the oil cooler up front. I say this because it takes so long for the temperature to creep up. The oil in the engine gets hot faster, of course. As the oil near the engine heats up, more is pumped up to the oil cooler, and we see the temperature slowly rise. I could be wrong of course!
High oil temperatures seem to indicate the need for a larger oil cooler, but perhaps there is an oil-to-water heat exchanger, and if so then dropping the water temperatures would also reduce the oil temperature. I have no idea if such a heat exchanger exists in the 997.2, however.
It's also important to know where the temperatures are measured. I don't know, but I have opinions based on my observations. It seems that the oil temperature is measured at the oil cooler up front. I say this because it takes so long for the temperature to creep up. The oil in the engine gets hot faster, of course. As the oil near the engine heats up, more is pumped up to the oil cooler, and we see the temperature slowly rise. I could be wrong of course!
the water is cooled by the front rads, the oil cooler is on top of the engine in the back. the oil cooler is cooled by air and water. i'm adding capacity to the energy the water can take from the oil cooler.
09-07-2010, 08:58 PM
#26
Rennlist Member
I stand corrected. Is the oil cooler shown here with the big red dot? (I added the red dot). This looks like an oil-to-water heat exchanger, and if that is how the oil is cooled, then lowering the coolant temperature would have a direct impact on the oil temperature.
09-07-2010, 09:27 PM
#27
Poseur
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What you have highlighted is the oil reservoir, on a 997 turbo engine. (A part of the dry-sump lubrication system). If you have a 997 you will not have that part.
Last edited by Edgy01; 09-07-2010 at 10:14 PM.
09-09-2010, 01:34 AM
#28
Three Wheelin'
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not sure why we're still talking about whether increasing the cooling with help reduce oil temps since it's rather obvious, but here's more documentation. i disagree that we need a quantitative water temperature to justify increasing the cooling to a car that's running hot.
09-09-2010, 04:49 AM
#30
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Here you go. Third Radiator DIY. Should not be much difference from the .1
https://rennlist.com/forums/997-foru...carrera-s.html
https://rennlist.com/forums/997-foru...carrera-s.html