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Cylinder Scoring Information Source

Thanks GT4 - as I often explain - I am not a technical writer just an engineer trying to share knowledge and experience - but I am pretty sure your last post just confirmed what my section 5 says - although probably more eloquently - I certainly agreed with it - so I think we are on the same wavelength.

I have tried to get an even lower thermostat manufactured but so far need to buy several thousand - which I cannot justify - hence the re-balance of the internal flow to compensate.

Both our racing Boxsters - although manual - were selected by us because they were originally built with a third radiator - if that helps confirm our position in arduous circumstances as we expect next season.

Baz
 
See if you can source the 55°C Cup tstat from Porsche "for analysis".

I will ask Porsche Motorsport for details and prices.
 
Thanks GT4 - I didn't realise they used that rating in the Cup Cars (have not yet been involved with one) however I am delighted with the news because it totally vindicates what I wrote about the benefits of lower thermostat settings for reliability and performance and also the recent enquiry I made for a thermostat to open at somewhere between 55 and 62 degrees for our race cars (which resulted in the huge quantity I could not justify ordering).

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?

A further point I should have made in the section 5 is that as the thermostat controls coolant speed - and as the coolant is branched off through several internal galleries and slots etc - it follows that as the coolant speed changes - the proportions that flow in different parts will actually vary too. Usually this will handicap the smallest outlets (like the slots feeding the cylinders) and benefit the largest holes (like the ones feeding the head which they made larger for later engines) = when the going gets hotter - the cylinders will get even hotter - weird when it appears they already know what to do when they go racing!

Baz
 
Three reasons:

Emissions, emissions and emissions.

Everything else is foregone: power, fuel economy, reliability/longevity.
 
bazhart said:
Thanks GT4 - I didn't realise they used that rating in the Cup Cars (have not yet been involved with one) however I am delighted with the news because it totally vindicates what I wrote about the benefits of lower thermostat settings for reliability and performance and also the recent enquiry I made for a thermostat to open at somewhere between 55 and 62 degrees for our race cars (which resulted in the huge quantity I could not justify ordering).

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?

A further point I should have made in the section 5 is that as the thermostat controls coolant speed - and as the coolant is branched off through several internal galleries and slots etc - it follows that as the coolant speed changes - the proportions that flow in different parts will actually vary too. Usually this will handicap the smallest outlets (like the slots feeding the cylinders) and benefit the largest holes (like the ones feeding the head which they made larger for later engines) = when the going gets hotter - the cylinders will get even hotter - weird when it appears they already know what to do when they go racing!

Baz

Before you go jumping to wrong conclusions, keep in mind that:
a) the Cup cars use completely different engines with completely different coolant canal "architecture", and
b) a racing engine's thermostat is virtually only ever closed whilst the car is still in the pit lane and unrestricted flow is called for any time the car is on the track, whereas road cars have to provide for the eventuality of granny driving to the shops in winter weather in cold climates.
 
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
 
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
 
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).
 
bazhart said:
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.
 
bazhart said:
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.
 
... 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).
 
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:
 
Because (within reason), you can never be too cool 8)

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:
 
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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