thermostat temperature
11-02-2004, 04:59 PM
#1
Track Day
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thermostat temperature
I've got a european 928s which has a high temp thermostat. What's the temp suitable for US operation and do i have to change fan switch. any ideas..... 
11-02-2004, 07:56 PM
#3
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The ONLY thing the temperature range of your thermostat does is determine the time it takes for your car to reach operating temperature. The thermostat in your 928 is not ususally completely opened or completely closed, but constantly regulates the temperature of the coolant along with other feedback loops. Stay with the 83 degree thermostat.
11-02-2004, 08:42 PM
#4
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Hi,
so well put Ernest. It also maintains the temp in the most desirable temperature band of course and this is just another reason to keep the S4's flaps fully operational too
Regards
Doug
so well put Ernest. It also maintains the temp in the most desirable temperature band of course and this is just another reason to keep the S4's flaps fully operational too
Regards
Doug
11-03-2004, 11:42 AM
#5
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Both Ernest and Doug are very correct. Stay with the 83. Anything cooler and your car will take longer to warm up and most likely will still reach the high temp it was running before the change.
11-03-2004, 11:52 AM
#6
928 Collector
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Here we go again 
... I dissent. I have tested the 75-deg thermostat over the past almost 5 years in all of my several 928's and I love it. Why? Because it keeps temp down and keeps the car from overheating in traffic. Why is this? Because the electric fan comes on (on earlier cars) and the fans come on much earlier, keeping the temp so low that it has a long way to go before overheating. Stress the car a bit. Run it hard, then idle through traffic with a stock thermostat and it will overheat. Or at least get helluva hot.
Is bloody hot necessarily bad for your car? No. Is lower temp bad? No. Does bloody hot cook everything under the hood? Oh yes. Does the thermostat do nothing but extend the time your car takes to fully warm up? Sure -- if by "reaching operating temperature" you mean getting bloody hot. My cars never get bloody hot. Ever. So I';ve been running at under operating temperature for 5 years on 5 928's. I never see the top white mark, but they do ... so I guess my 928's will NEVER reach "operating temperature" ...
... I dissent. I have tested the 75-deg thermostat over the past almost 5 years in all of my several 928's and I love it. Why? Because it keeps temp down and keeps the car from overheating in traffic. Why is this? Because the electric fan comes on (on earlier cars) and the fans come on much earlier, keeping the temp so low that it has a long way to go before overheating. Stress the car a bit. Run it hard, then idle through traffic with a stock thermostat and it will overheat. Or at least get helluva hot.Is bloody hot necessarily bad for your car? No. Is lower temp bad? No. Does bloody hot cook everything under the hood? Oh yes. Does the thermostat do nothing but extend the time your car takes to fully warm up? Sure -- if by "reaching operating temperature" you mean getting bloody hot. My cars never get bloody hot. Ever. So I';ve been running at under operating temperature for 5 years on 5 928's. I never see the top white mark, but they do ... so I guess my 928's will NEVER reach "operating temperature" ...
11-03-2004, 12:15 PM
#7
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Originally Posted by heinrich
Here we go again ... I dissent. I have tested the 75-deg thermostat over the past almost 5 years in all of my several 928's and I love it. Why? Because it keeps temp down and keeps the car from overheating in traffic. Why is this? Because the electric fan comes on (on earlier cars) and the fans come on much earlier, keeping the temp so low that it has a long way to go before overheating. Stress the car a bit. Run it hard, then idle through traffic with a stock thermostat and it will overheat. Or at least get helluva hot.
Is bloody hot necessarily bad for your car? No. Is lower temp bad? No. Does bloody hot cook everything under the hood? Oh yes. Does the thermostat do nothing but extend the time your car takes to fully warm up? Sure -- if by "reaching operating temperature" you mean getting bloody hot. My cars never get bloody hot. Ever. So I';ve been running at under operating temperature for 5 years on 5 928's. I never see the top white mark, but they do ... so I guess my 928's will NEVER reach "operating temperature" ...
... I dissent. I have tested the 75-deg thermostat over the past almost 5 years in all of my several 928's and I love it. Why? Because it keeps temp down and keeps the car from overheating in traffic. Why is this? Because the electric fan comes on (on earlier cars) and the fans come on much earlier, keeping the temp so low that it has a long way to go before overheating. Stress the car a bit. Run it hard, then idle through traffic with a stock thermostat and it will overheat. Or at least get helluva hot.Is bloody hot necessarily bad for your car? No. Is lower temp bad? No. Does bloody hot cook everything under the hood? Oh yes. Does the thermostat do nothing but extend the time your car takes to fully warm up? Sure -- if by "reaching operating temperature" you mean getting bloody hot. My cars never get bloody hot. Ever. So I';ve been running at under operating temperature for 5 years on 5 928's. I never see the top white mark, but they do ... so I guess my 928's will NEVER reach "operating temperature" ...
I respectfully disagree with just about all of your theories.
Does your car "overheat" at 83c? Of course not. Does the temperature that the thermostat opens have anything to do with when the fan comes on? Of course not.
Once the thermostat is open, be it at 75c or 83c, it no longer has any effect on the engine temperature. Period. From that point on, it's all a game of heat generated vs. heat dissipated. 'Dissipated' is a function of heat transfer at the block, and heat transfer at the radiator, plus the transport in the coolant. The only thing that the thermostat can influence is the transport, and a wide-open thermostat, be it at 75c or 83c, looks the same to the coolant.
Reaching "operating temperature" is important for a number of reasons. It helps het the oil up to temperature so it lubricates better, and more importantly it helps the oil shed moisture that accumulates as a byproduct of combustion. Engine manangement on most cars reads the coolant temperature and adjusts the mixture a little rich, kinda like driving around all day with the choke partially pulled out, if it detects a colder engine. It's OK though, since the cat cleans up all that spare CO once it warms up.
I have no doubt that your car will run cooler with the 75c thermostat. I've experimented with one in my car, and it did run cooler almost all the time. Exceptions would be on hot days when dissipation was less, at which time the thermostat was full-open as described above, and the heat balance was again the dependent factor. Of course, these are the times when you might want that extra transfer capacity. But once the thermostat is open, it can't any of that. So the hot-day coolant temp won't change a lick with the different thermostat.
Sorry!
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11-03-2004, 12:28 PM
#8
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In my case at least, the "heating up in traffic" problem was solved by upgrading the electric fan. I have the 83 degree t-stat. The original electric fan was a little anemic, IMHO. Well, more than a little. 
YMMV.
YMMV.
11-03-2004, 12:35 PM
#9
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When the thermostat opens has everything to do with everything. If the thermostat holds hot water back until the engine is at 83deg, then the engine starts slowing down in its heating process at 83 degrees. With the 75deg unit, it starts at 75deg. The radiator does not come into play before that moment, at all. Once hot water mixes with the massive amount of cold water in the radiator, it then immediately lowers the engine's temperature. This happens with both units. In traffic, after a while the radiator warms up to engine temp, and the fan switch turns the fans on at its rated threshhold, in my case my unit is a 75deg one. This immediately begins to once again cool the radiator coolant and all engine coolant circulated through it, to 75 degrees (in your case, 83).
So .... my engine runs cooler than yours. Period.
You are welcome to call my statements "theories" but when I look at the coolant gauge on my cars, I see in black and white, a needle that sits one entire hop lower than yours.
As to overheating: if everything works right, your car should never overheat with either unit, but I have tested this "theory" personally. When the 83 degree thermostat is installed, the car starts cooling much later than the 75 degree unit does. So, it takes longer to get to the point that the car is "too hot" for me than for you. I find 83 degree units are constantly going UP and DOWN ... UP and DOWN ... UP and DOWN in temp, but the 75deg unit stays much more constant at the first white line or near it, even on-track and even in heavy city driving. Why? Because while your car is wrapped in a cosy 83deg blanky, mine has all its cooling components working hard to keep it cooler.
Whatever works for you Bob, I have no particular desire to evangelise the lower-temp thermostat. If running with your temp gauge at one hop higher constantly works for you, I'm going to be your biggest supporter.
So .... my engine runs cooler than yours. Period.
You are welcome to call my statements "theories" but when I look at the coolant gauge on my cars, I see in black and white, a needle that sits one entire hop lower than yours.
As to overheating: if everything works right, your car should never overheat with either unit, but I have tested this "theory" personally. When the 83 degree thermostat is installed, the car starts cooling much later than the 75 degree unit does. So, it takes longer to get to the point that the car is "too hot" for me than for you. I find 83 degree units are constantly going UP and DOWN ... UP and DOWN ... UP and DOWN in temp, but the 75deg unit stays much more constant at the first white line or near it, even on-track and even in heavy city driving. Why? Because while your car is wrapped in a cosy 83deg blanky, mine has all its cooling components working hard to keep it cooler.
Whatever works for you Bob, I have no particular desire to evangelise the lower-temp thermostat. If running with your temp gauge at one hop higher constantly works for you, I'm going to be your biggest supporter.
11-03-2004, 12:59 PM
#10
928 Collector
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Originally Posted by SharkSkin
In my case at least, the "heating up in traffic" problem was solved by upgrading the electric fan. I have the 83 degree t-stat. The original electric fan was a little anemic, IMHO. Well, more than a little.
YMMV.
YMMV.
11-03-2004, 03:24 PM
#11
Rennlist Member
While I haven't actually overheated... not to the point of boiling the coolant anyway... I did make some observations that led me to be concerned about the possibility. If your problem is solved, that's all that matters. My problem is solved, and that's what matters to me. If people don't like your solution -- or mine -- they don't have to implement them. Unless/until some "Department of Homeland Thermostats" is created, we have choices and every right to make them.
11-03-2004, 04:11 PM
#13
Three Wheelin'
Without going into great details, in the course of lowering the nom. operating temp on a 1989 S4 auto when the outside temps are in the 90+deg range.
I have:
1. Tested both T-stats. Found no measurable difference.
2. Tested and exchanged fan control units (Model spec). Found no measurable difference.
3. Tested different coolant mixture ratios. This did make a slight difference.
4. Drilled three-six 3/16 holes (Three is opt.) in the T-stat to improve flow. Found to make a slight difference.
5. Installed a remote fuse block to replace the two factory fuse holders. Found to make a notable difference.
6. Removed front flaps and motor. Found to make a very slight difference.
7. Replaced Factory Rad. with a DEVEK Rad.
All mods done have made a positive difference but more R&D is needed.
Things still on the to-do list.
1. Replace the fan controllers with ones from a GTS.
2. Add a small fan in front of the AC condenser.
I have:
1. Tested both T-stats. Found no measurable difference.
2. Tested and exchanged fan control units (Model spec). Found no measurable difference.
3. Tested different coolant mixture ratios. This did make a slight difference.
4. Drilled three-six 3/16 holes (Three is opt.) in the T-stat to improve flow. Found to make a slight difference.
5. Installed a remote fuse block to replace the two factory fuse holders. Found to make a notable difference.
6. Removed front flaps and motor. Found to make a very slight difference.
7. Replaced Factory Rad. with a DEVEK Rad.
All mods done have made a positive difference but more R&D is needed.
Things still on the to-do list.
1. Replace the fan controllers with ones from a GTS.
2. Add a small fan in front of the AC condenser.
Last edited by T_MaX; 11-05-2004 at 02:26 AM.
11-03-2004, 08:05 PM
#14
Burning Brakes
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Hello
Thank goodness everybody can have an opinion and theories - we all have these and they make Rennlist a great place because of it
Some people here will judge these as such too!
The 928's integrated cooling system cannot be compared to an average car as it is substantially unique - a thorough understanding is VERY helpful and not always easy for new owners
FACTS are ALWAYS important to note (all temps shown +/-2C) ;
1 - the OEM coolant thermostat OPENS at 83C and is FULLY OPEN at 98C
2 - the oil thermostat OPENS at 87C and is likely to be FULLY OPEN at about 92C
3 - all aluminium engines SHED HEAT rapidly via air flow around it - not only via the coolant
4 - many engine management sensors are triggered and operate via the engine's "core" temperature and the cooling system's "management" as Porsche's Engineers intended
The following DATA from my ‘89 S4 which has been acquired over two years using an IR reader (backed up by similar data from others) may interest you (each reading was taken after at least 30 minutes and/or at least 30-50kms running);
5 - the core operating temperature is around 88-94C
(my Z3 2.8 operates at 88-92C)
(my heavy trucks average 87C with a warning at 100C and engine shutdown at 106C)
6 - the flaps remain at only 30% open up to an ambient of at least 34C (the fan speed will vary of course)
7 - the oil temp is usually around 88-92C
(my Z3 2.8 operates at about 98-100C)
(my heavy trucks average 103C with a warning at 115C and engine shut down at 121C)
See NOTE below
8 - the S4's "overheat" warning system is first activated at 118C and finally again at 120C. This is an accurate indicator that operating around 90-110C is quite normal and as Porsche intended!
Some OBSERVATIONS from oil and cooling system monitoring over two years in ambient temperatures ranging from -5C(air chill about -15C) to above 42C may be of interest:
9 - Most 928 owners do not understand how the integrated cooling system works. Many will never quite comprehend the coolant's flow characteristics. Some Service Providers don't know either. For normal use some Service Providers recommend lower crack point thermostats, lower triggered fan sensors, removing the S4's flaps ("...they don't do anything....") or even high viscosity oils! Many of these things MAY be totally counterproductive. The engine NEEDS to quickly get to 83C and then to the design operating temperature about the 88-94C range
(Racing use requirements MAY be somewhat different of course)
10 - If all of the 928's cooling system's integrated components are in "average" to "above average" condition the cooling system will function well to keep the engine operating as the Porsche engineers intended (88-94C)
11 - The "living" temperature gauge is NOT an accurate depiction of the engine's core temperature. At best it is an indicator that reads about 5C below the engine's "core" temperature or somewhere above that. I have seen the gauge on one S4 read nearly 100C when the core temperature was about 92C
12 - Some owners unfamiliar with a 928 will think it is overheating because of the gauge or what is a high under hood temperature. This should be checked to confirm what the engine's core temperature really is before spending a lot of money. Most "over heating" reports are usually wrong unless of course you have a true fault such as coolant loss, faulty thermostat, coolant pump and or sensors and etc
13 - Many 928 owners discount the very good operating characteristics of the (correctly working) viscous fan in earlier cars. These fans can and do the job very well indeed
14 - Raising about 16 litres of oil and coolant (about 8 litres of coolant is behind the thermostat) quickly to operating temperature is a real task. The other 8 litres of coolant may never reach the thermostat's opening point at all during many trips! And it may not even open the flaps or trigger the fans which of course require 79C measured at the coolest (almost) part of the radiator!
See NOTE below
15 - In very cold conditions the 928's engine WILL struggle to reach operating temperature (88-94C) and then maintain it! One reason of course is the engine's all alloy construction!
NOTE: ENGINE OILS - the Anti Wear (AW) components in the oil's additive package including the Viscosity Improver (VI) (especially in mineral oils) is activated by temperature and the sooner the oil temperature is above 80C the better. An oil's IDEAL operating temperature range is roughly about 85C-110C and the 928 engine is VERY EASY on its engine oil if it is of the correct quality rating A3/B3 and viscosity (typically 5w-40) for the temperature the vehicle is used in
If anybody would like a summary of the 120 temperature test results I have (high, low, average, median) please contact me privately
Again - everybody to their own appraisal, theory and opinion and no offence intended with the information provided here. I hope it helps some new owners understand their car a little better
Regards
Doug
Thank goodness everybody can have an opinion and theories - we all have these and they make Rennlist a great place because of it
Some people here will judge these as such too!
The 928's integrated cooling system cannot be compared to an average car as it is substantially unique - a thorough understanding is VERY helpful and not always easy for new owners
FACTS are ALWAYS important to note (all temps shown +/-2C) ;
1 - the OEM coolant thermostat OPENS at 83C and is FULLY OPEN at 98C
2 - the oil thermostat OPENS at 87C and is likely to be FULLY OPEN at about 92C
3 - all aluminium engines SHED HEAT rapidly via air flow around it - not only via the coolant
4 - many engine management sensors are triggered and operate via the engine's "core" temperature and the cooling system's "management" as Porsche's Engineers intended
The following DATA from my ‘89 S4 which has been acquired over two years using an IR reader (backed up by similar data from others) may interest you (each reading was taken after at least 30 minutes and/or at least 30-50kms running);
5 - the core operating temperature is around 88-94C
(my Z3 2.8 operates at 88-92C)
(my heavy trucks average 87C with a warning at 100C and engine shutdown at 106C)
6 - the flaps remain at only 30% open up to an ambient of at least 34C (the fan speed will vary of course)
7 - the oil temp is usually around 88-92C
(my Z3 2.8 operates at about 98-100C)
(my heavy trucks average 103C with a warning at 115C and engine shut down at 121C)
See NOTE below
8 - the S4's "overheat" warning system is first activated at 118C and finally again at 120C. This is an accurate indicator that operating around 90-110C is quite normal and as Porsche intended!
Some OBSERVATIONS from oil and cooling system monitoring over two years in ambient temperatures ranging from -5C(air chill about -15C) to above 42C may be of interest:
9 - Most 928 owners do not understand how the integrated cooling system works. Many will never quite comprehend the coolant's flow characteristics. Some Service Providers don't know either. For normal use some Service Providers recommend lower crack point thermostats, lower triggered fan sensors, removing the S4's flaps ("...they don't do anything....") or even high viscosity oils! Many of these things MAY be totally counterproductive. The engine NEEDS to quickly get to 83C and then to the design operating temperature about the 88-94C range
(Racing use requirements MAY be somewhat different of course)
10 - If all of the 928's cooling system's integrated components are in "average" to "above average" condition the cooling system will function well to keep the engine operating as the Porsche engineers intended (88-94C)
11 - The "living" temperature gauge is NOT an accurate depiction of the engine's core temperature. At best it is an indicator that reads about 5C below the engine's "core" temperature or somewhere above that. I have seen the gauge on one S4 read nearly 100C when the core temperature was about 92C
12 - Some owners unfamiliar with a 928 will think it is overheating because of the gauge or what is a high under hood temperature. This should be checked to confirm what the engine's core temperature really is before spending a lot of money. Most "over heating" reports are usually wrong unless of course you have a true fault such as coolant loss, faulty thermostat, coolant pump and or sensors and etc
13 - Many 928 owners discount the very good operating characteristics of the (correctly working) viscous fan in earlier cars. These fans can and do the job very well indeed
14 - Raising about 16 litres of oil and coolant (about 8 litres of coolant is behind the thermostat) quickly to operating temperature is a real task. The other 8 litres of coolant may never reach the thermostat's opening point at all during many trips! And it may not even open the flaps or trigger the fans which of course require 79C measured at the coolest (almost) part of the radiator!
See NOTE below
15 - In very cold conditions the 928's engine WILL struggle to reach operating temperature (88-94C) and then maintain it! One reason of course is the engine's all alloy construction!
NOTE: ENGINE OILS - the Anti Wear (AW) components in the oil's additive package including the Viscosity Improver (VI) (especially in mineral oils) is activated by temperature and the sooner the oil temperature is above 80C the better. An oil's IDEAL operating temperature range is roughly about 85C-110C and the 928 engine is VERY EASY on its engine oil if it is of the correct quality rating A3/B3 and viscosity (typically 5w-40) for the temperature the vehicle is used in
If anybody would like a summary of the 120 temperature test results I have (high, low, average, median) please contact me privately
Again - everybody to their own appraisal, theory and opinion and no offence intended with the information provided here. I hope it helps some new owners understand their car a little better
Regards
Doug
11-04-2004, 12:57 AM
#15
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Uh, what Doug said.
esp. the part about viscous fans... they control the engine compartment and coolant temperature very well.
T_MaX,
You will find that a stock pusher fan from the 78-79 moves an incredible amount of air. It draws 30 amps, though, and requires a robust electrical feed circuit. Upon deletion of my stock fans after installation of the supercharger, the early fan was just what the doctor ordered. Be sure to gasket between radiators to insure laminar flow.
esp. the part about viscous fans... they control the engine compartment and coolant temperature very well.
T_MaX,
You will find that a stock pusher fan from the 78-79 moves an incredible amount of air. It draws 30 amps, though, and requires a robust electrical feed circuit. Upon deletion of my stock fans after installation of the supercharger, the early fan was just what the doctor ordered. Be sure to gasket between radiators to insure laminar flow.