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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 883
Location: Bolton Lancashire


PostPosted: Mon Dec 26, 2011 6:56 pm    Post subject: Reply with quote

Sorry but all thermostats are open when a vehicle is in use (or the engine wouold boil over even with granny driving it) and I don;t see how granny driving has anything to do with either us trying to get an even lower temperature thermostat for racing (and therefore proves our understanding of what we need is right) and also shows that porsche appreciate the need to keep temperatures down when engines are worked hard as well. The wuestion is how much they are open as they controk coolant speed/flow and through that temperature.

I think we know enough to realise the engines are different (that is why I want to get on to see if I can fit it) but thank youf or pointing it out to others.

If the GT3 cup car relied totally on the thermostat being fully open all the time it was racing it would run at different temperatures depending on the ambient conditions and I doubt that would be a sensible way to go anyway - but need to test it and I will report back if I can get one and fit it.

one reason to use a low temperature thermostat in a race car is also to ensure it is flowing when you set off at the start and not experiencing a delay while the "system" cathces up.


Baz
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berni29
Watkins Glen


Joined: 24 Oct 2009
Posts: 2175
Location: Kent


PostPosted: Mon Dec 26, 2011 7:46 pm    Post subject: Reply with quote

Hi

I have followed a few threads on the problems with the 997, and wonder if an electric water pump that is not engine speed dependent might help?

All the best

Berni
_________________
993 C2 Tip 1994 187k miles. Black and Grey. M029 & Bilstein HD's, Elephant Racing RS bushes F&R, RS mounts, strengthened engine carrier, 100 cell cat inserts, HID's. Solid steering arms mod, top of the engine rebuilt, mapped by Wayne, suspension set up by Chris.
 
  
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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30194
Location: Hertfordshire and Hampshire


PostPosted: Mon Dec 26, 2011 9:39 pm    Post subject: Reply with quote

Just FYI, the road-going GT3 uses exactly the same thermostatic insert as the Carrera (996.106.125).

The use of a 55°C thermostat will simply mean the radiators (and ambient temp, air etc etc they are heat exchanging into) will start defining the thermal characteristics of the cooling above 55°C (and fully define above 69°C), rather than above 93°C (fully above 99°C) as they do for the standard tstat.

Unless the entire car is covered in radiators in a blizzard in Norway, the engine will still comfortably exceed 55°C water temp (higher for the oil).

The tstat operating regime always represents the lower limit of temperature (ie the car will effectively shut down coolant flow AT and BELOW this temp and maintain the block temp).
 
  
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Red993C4
Magny-Cours


Joined: 09 Dec 2010
Posts: 2723
Location: S. Wales


PostPosted: Mon Dec 26, 2011 10:59 pm    Post subject: Reply with quote

bazhart wrote:
Sorry but all thermostats are open when a vehicle is in use (or the engine wouold boil over even with granny driving it) and I don;t see how granny driving has anything to do with either us trying to get an even lower temperature thermostat for racing (and therefore proves our understanding of what we need is right) and also shows that porsche appreciate the need to keep temperatures down when engines are worked hard as well. The wuestion is how much they are open as they controk coolant speed/flow and through that temperature.

I think we know enough to realise the engines are different (that is why I want to get on to see if I can fit it) but thank youf or pointing it out to others.

If the GT3 cup car relied totally on the thermostat being fully open all the time it was racing it would run at different temperatures depending on the ambient conditions and I doubt that would be a sensible way to go anyway - but need to test it and I will report back if I can get one and fit it.

one reason to use a low temperature thermostat in a race car is also to ensure it is flowing when you set off at the start and not experiencing a delay while the "system" cathces up.

Baz


I highlighted the different operating conditions in road and racing cars because you seemed to be implying that the Cup's thermostat might also have been a better choice for 996/997 road cars.

"I must try and get one of those thermostats and see how to fit in in the race car 1st then a road car for test (we still have one of the test cars with temperature gauges fitted all over the engine).

However it also questions why such a high rated thermostat in the road cars?

............. - weird when it appears they already know what to do when they go racing!"


A Cup car has no problems getting up to temperature on track, but the famous granny might complain about poor heater and demister performance when driving to Walmart in a Minnesota winter if the car was fitted with a thermostat which opened below 60°C. And it's not just about emissions, as witnessed by the fact that cars were fitted with thermostats long before emission tests were introduced.
 
  
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Red993C4
Magny-Cours


Joined: 09 Dec 2010
Posts: 2723
Location: S. Wales


PostPosted: Mon Dec 26, 2011 10:59 pm    Post subject: Reply with quote

bazhart wrote:
Sorry but all thermostats are open when a vehicle is in use (or the engine wouold boil over even with granny driving it) and I don;t see how granny driving has anything to do with either us trying to get an even lower temperature thermostat for racing (and therefore proves our understanding of what we need is right) and also shows that porsche appreciate the need to keep temperatures down when engines are worked hard as well. The wuestion is how much they are open as they controk coolant speed/flow and through that temperature.

I think we know enough to realise the engines are different (that is why I want to get on to see if I can fit it) but thank youf or pointing it out to others.

If the GT3 cup car relied totally on the thermostat being fully open all the time it was racing it would run at different temperatures depending on the ambient conditions and I doubt that would be a sensible way to go anyway - but need to test it and I will report back if I can get one and fit it.

one reason to use a low temperature thermostat in a race car is also to ensure it is flowing when you set off at the start and not experiencing a delay while the "system" cathces up.

Baz


I highlighted the different operating conditions in road and racing cars because you seemed to be implying that the Cup's thermostat might also have been a better choice for 996/997 road cars.

"I must try and get one of those thermostats and see how to fit in in the race car 1st then a road car for test (we still have one of the test cars with temperature gauges fitted all over the engine).

However it also questions why such a high rated thermostat in the road cars?

............. - weird when it appears they already know what to do when they go racing!"


A Cup car has no problems getting up to temperature on track, but the famous granny might complain about poor heater and demister performance when driving to Walmart in a Minnesota winter if the car was fitted with a thermostat which opened below 60°C. And it's not just about emissions, as witnessed by the fact that cars were fitted with thermostats long before emission tests were introduced.
 
  
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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30194
Location: Hertfordshire and Hampshire


PostPosted: Mon Dec 26, 2011 11:20 pm    Post subject: Reply with quote

... I don't think Baz was suggesting there weren't thermostats before emissions tests, nor is he suggesting fitting no thermostat.

The question is why is the standard thermostat set so high (and it is lower on the later expensively engineered 997 DFI), the reason the high temp tstats are fitted to the 996 and 997 is they are a quick, cheap and guaranteed way to reduce headline arbitrary secondary emissions (like NOx etc) at the point of production, the downside is the long term health of the engine some years latter.

Can't disagree with the analogy of the dawdling granny in Minnesota, except for the fact perhaps she shouldn't drive a Porsche (or perhaps Porsche shouldn't have engineered a car for her, or under-engineered a car just to meet arbitrary emissions).
 
  
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Seve
Newbie


Joined: 18 May 2010
Posts: 22
Location: Düsseldorf


PostPosted: Tue Dec 27, 2011 6:49 am    Post subject: Reply with quote

I am sorry if my post seems trivial but you are still debating the 996.2 engine?
I ask, because I have read on this forum that the 996.1 has no over heating issues. If that's the case why did gt4 and other fit the hartech tstatt, is it to improve performance, fuel economy?

bye
 
  
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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30194
Location: Hertfordshire and Hampshire


PostPosted: Tue Dec 27, 2011 2:28 pm    Post subject: Reply with quote

Because (within reason), you can never be too cool Cool

Whist the 996.1 has a much lower propensity to bore scoring (due to torque, cylinder bore and piston stroke difference and less thermal energy than the 996.2s) it also has better intrinsic cooling to prevent bore scoring or head cooking thanks to a proportional flowed water jacket (hottest and last chambers/cylinders get the most coolant flow - eg cyls 3 and 6 get THREE TIMES the flow rate of cyls 1 and 4), it can still benefit from running cooler.

Specifically, GT4 has three radiators (ie plus the extra X51 centre radiator), using the old tstat means that centre rad (and indeed the original rads) have NO effect on cooling prior to 99°C (single sampling location water temp).

So if I want my car to run cooler, benefit from the extra rads in normal use (and indeed benefit from the extra rads in a temperature regime well away from borderline cooking my heads), I need to fit a low temp tstat.

Any extra fuel economy and power, is surely just a bonus to the healthier engine Thumb
 
  
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Seve
Newbie


Joined: 18 May 2010
Posts: 22
Location: Düsseldorf


PostPosted: Tue Dec 27, 2011 3:34 pm    Post subject: Reply with quote

Ok understand, thanks gt4 for the explination thumbsup
 
  
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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 883
Location: Bolton Lancashire


PostPosted: Tue Dec 27, 2011 4:47 pm    Post subject: Reply with quote

Also of course the Cup car rating means that on a very cool day - Porsche think it is OK to race an engine with relatively cool cylinders (which is what we explained in section 5 although several others disagreed wanting the cars to run hotter) and I stated the ideal temperatures for racing for maximum performance and it seems the cup cars run similar temperatures.

The whole point is that any engine producing more power than a similar engine of similar capacity will be experiencing more heat in the combustion chamber and therefore be running closer to the temperatures that can initiate detonation. The way this was protected in the past was to run the engine rich so that even in those areas inside the conbustion area where the distribution of fuel is a little weak - it does not reach the detonation point.

However this also leads to high emissions by modern standard and GT4 is absolutely spot on with his understanding and running higher cylinder /head temperatures is a way to reduce them again at the outlet side where they are measured (and more in keeping with the spirit of the reduction than bleeding air in to reduce the % but actually still sending the same weight of emissions into the atmosphere).

It just seems that in the bigger more powerful versions with the head gasket that makes the cylinders run even hotter - they are so near the limit for lubrication that some go past it.

Testing out a racing thermostat is a road car does not mean I propose the use of it - just that all test information by comparison is useful in trying to sort out this problem created elsewhere to the detriment of the reputation of the product and the bank balance of many owners.

Baz
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You can trust us to "CARE FOR YOUR PORSCHE"
www.hartech.org
 
  
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