996-997 wet-sump engine reliability: enter your stats here!
Discussion
Thanks for that JM1962 I suppose it is only fair for you to point out that my description was not 100% accurate although I don't think it adds anything to understanding the events or causes I was describing.
In my defence - unfortunately if I explained all the engine problems on here in the correct technical way without any background or analogies that enabled less well qualified people to follow the salient points - fewer people would benefit (and to be fair I have not noticed any other contributor covering anything like the technical issues I try to convey to the public to empower them to understand them if they need to or help them make informed choices to protect their interests). I try to find a balance between simplifying things and being correct so the majority benefit from being able to understand the issue - but this is always dangerous - as your posting demonstrates.
For your benefit (if I remember my schooling of 40 years ago correctly)
Coolant behaves like water and as such has different states from frozen to gas and in the middle steam. There are two types of steam - vapour and superheated steam (which is a gas).
Vapour is difficult to explain because it has lower density than liquid and hence increased volume. The problem is that increased volume of coolant (as steam bubbles) pushes coolant out of the expansion cap - so next time after it cools there is less coolant left inside and it doesn't neccessarily reach the same running pressure hence can boil/release steam bubbles/air bubbles whatever at a lower temperature than before and decrease the cooling potential at the source - the cylinder wall.
Fourty years ago we did not study atomic science much or molecular thoeory - but nowadays it is built into the education system from a very early age - a much better way of dealing with such issues.
If you understand this better than me I would be interested to learn exactly what steam vapour consists of. You are right it is not "air" bubbles because steam as a vapour is tiny droplets of water (or coolant) which I think must then be mixed in with with a gas (since the density reduces). But the gas will not be air because it has been formed from H2O - so is I suppose some form of a mixture of Oxygen and Hydrogen (whereas air is mainly Nitrogen - 78%).
It would be interesting to have this clarified but - in terms of helping readers understand the issues so they can decide for themseves what to do in the future to protect their interests or what questions to ask of their chosen repairer before commiting a rebuild or investigation somewhere that has limited options - I don't think whatever this gas is - makes any practical difference.
Baz.
In my defence - unfortunately if I explained all the engine problems on here in the correct technical way without any background or analogies that enabled less well qualified people to follow the salient points - fewer people would benefit (and to be fair I have not noticed any other contributor covering anything like the technical issues I try to convey to the public to empower them to understand them if they need to or help them make informed choices to protect their interests). I try to find a balance between simplifying things and being correct so the majority benefit from being able to understand the issue - but this is always dangerous - as your posting demonstrates.
For your benefit (if I remember my schooling of 40 years ago correctly)
Coolant behaves like water and as such has different states from frozen to gas and in the middle steam. There are two types of steam - vapour and superheated steam (which is a gas).
Vapour is difficult to explain because it has lower density than liquid and hence increased volume. The problem is that increased volume of coolant (as steam bubbles) pushes coolant out of the expansion cap - so next time after it cools there is less coolant left inside and it doesn't neccessarily reach the same running pressure hence can boil/release steam bubbles/air bubbles whatever at a lower temperature than before and decrease the cooling potential at the source - the cylinder wall.
Fourty years ago we did not study atomic science much or molecular thoeory - but nowadays it is built into the education system from a very early age - a much better way of dealing with such issues.
If you understand this better than me I would be interested to learn exactly what steam vapour consists of. You are right it is not "air" bubbles because steam as a vapour is tiny droplets of water (or coolant) which I think must then be mixed in with with a gas (since the density reduces). But the gas will not be air because it has been formed from H2O - so is I suppose some form of a mixture of Oxygen and Hydrogen (whereas air is mainly Nitrogen - 78%).
It would be interesting to have this clarified but - in terms of helping readers understand the issues so they can decide for themseves what to do in the future to protect their interests or what questions to ask of their chosen repairer before commiting a rebuild or investigation somewhere that has limited options - I don't think whatever this gas is - makes any practical difference.
Baz.
hartech said:
I would be interested to learn exactly what steam vapour consists of. You are right it is not "air" bubbles because steam as a vapour is tiny droplets of water (or coolant) which I think must then be mixed in with with a gas (since the density reduces). But the gas will not be air because it has been formed from H2O
Bubbles formed in boiling water will be pure H2O as a gas (also called steam).Just think about nitrogen as a gas, then think about liquid nitrogen - you've probably seen that as a liquid on TV. Nitrogen is usually found as a gas because its boiling point is -195.8 °C.
The only difference is that water is usually a liquid at our temperatures and has to be heated to 100C (a normal pressure) become a gas.
Baz
As I said, I was not trying to be picky, and I don't think it makes any difference to your findings. Steam (or air for that matter) surrounding the cylinders will not transfer the heat from the cylinders as effectively as water which is denser.
Water vapour formation is complicated but depends on the amount of kinetic energy contained within the water molecules being sufficient to allow evaporation at less than boiling point from the surface of a liquid. Steam and water vapour (which is water in gaseous form) is invisible, what you see coming out of the kettle is an aerosol of condensed water droplets within the invisible steam/vapour.
As I said, I was not trying to be picky, and I don't think it makes any difference to your findings. Steam (or air for that matter) surrounding the cylinders will not transfer the heat from the cylinders as effectively as water which is denser.
Water vapour formation is complicated but depends on the amount of kinetic energy contained within the water molecules being sufficient to allow evaporation at less than boiling point from the surface of a liquid. Steam and water vapour (which is water in gaseous form) is invisible, what you see coming out of the kettle is an aerosol of condensed water droplets within the invisible steam/vapour.
Edited by JM1962 on Monday 17th January 20:07
I know its off subject but ironically - the question of what the bubbles actually are is something I am struggling to discover any technical information about - but cannot get out of my head (I don't like mysteries).
Most information about water vapour refers to evaporation in air as the increase in Kenetic energy from heat excites some molecules enough to esacpe into the air - but nothing about trapped water in an enclosed space and bubbling instead.
Similarly all information describes vapour as water droplets in air (for which we must assume it is water or coolant - or both mixed - droplets in a gas). Only superheated steam is a pure gas (I seem to remember) so this wet steam phase is a bit of an oddity (which some reports suggest is still not fully understood by anyone - including all phases of water as ice, liquid ad gas).
If the droplets are still water (or coolant or breaks down iinto water and the coolant liquid) then the bubles can only be formed from the atoms in the molecular structure - oxygen and helium (plus anything in the coolant).
So is there a person out there who can explain this simply so I can put this confusing problem raised recently behind me - so I can clear my mind and concentrate back on the engine re-design and manufacture of parts, and preparation for the racing season that is all I should have going around my limited brain capacity at the moment.
Baz
Most information about water vapour refers to evaporation in air as the increase in Kenetic energy from heat excites some molecules enough to esacpe into the air - but nothing about trapped water in an enclosed space and bubbling instead.
Similarly all information describes vapour as water droplets in air (for which we must assume it is water or coolant - or both mixed - droplets in a gas). Only superheated steam is a pure gas (I seem to remember) so this wet steam phase is a bit of an oddity (which some reports suggest is still not fully understood by anyone - including all phases of water as ice, liquid ad gas).
If the droplets are still water (or coolant or breaks down iinto water and the coolant liquid) then the bubles can only be formed from the atoms in the molecular structure - oxygen and helium (plus anything in the coolant).
So is there a person out there who can explain this simply so I can put this confusing problem raised recently behind me - so I can clear my mind and concentrate back on the engine re-design and manufacture of parts, and preparation for the racing season that is all I should have going around my limited brain capacity at the moment.
Baz
Thanks Globs - but I think you will find that steam is only a pure gas when it is superheated and that the stage in between when it is a vapour is different.
Going back to the problem we face inside the engines - I think that due to the majority of the coolant going into the cylinder head (which is slower to react to combustion chamber temperature rises - so diluting any sudden temperature rises as the hotter block coolant is mixed back with it), relatively slow coolant speed in te block, the long distance between the engine and the radiators and the slow acting high temperature thermostat - bubbling occurs at the outer face of the cylinder wall before the coolant can return cooled enough to stop it - which has two adverse affects. (1) it reduces cooling (so pistons and oil surface temperatures rise as oil thickness reduces) (2) the increased volume created by the release of gas pushes volume out of the expansion tank and reduces subsequent coolant pressure inside the engine the next time it is run (until more bubbling and gas is released) so that this bubbling or boiling point is reached at lower temperatures.
Now I cannot see this "GAS" being water because it is not superheated and all the information I read state it is water droplets suspended in air (because they refer to an open vessel above which IS air that the water vapour droplets float into).
But there is no air down inside the engine (just as there is no air at the bottom of a saucepan when it is bubbling) - so those bubbles canot be water droplets but must be a gas or saturated gas of some sort and if water is made up of Hydrogen and Oxygen (the former of which is usually found as a gas because it has such low evaporation points) surely that gas is one or both or a mixture of the two in some other molecular or atomic relationship? Mind you this is not an area I have much knowledge of so I might easily be talking crap (and no clever "as usual" responses please!)
Baz
Going back to the problem we face inside the engines - I think that due to the majority of the coolant going into the cylinder head (which is slower to react to combustion chamber temperature rises - so diluting any sudden temperature rises as the hotter block coolant is mixed back with it), relatively slow coolant speed in te block, the long distance between the engine and the radiators and the slow acting high temperature thermostat - bubbling occurs at the outer face of the cylinder wall before the coolant can return cooled enough to stop it - which has two adverse affects. (1) it reduces cooling (so pistons and oil surface temperatures rise as oil thickness reduces) (2) the increased volume created by the release of gas pushes volume out of the expansion tank and reduces subsequent coolant pressure inside the engine the next time it is run (until more bubbling and gas is released) so that this bubbling or boiling point is reached at lower temperatures.
Now I cannot see this "GAS" being water because it is not superheated and all the information I read state it is water droplets suspended in air (because they refer to an open vessel above which IS air that the water vapour droplets float into).
But there is no air down inside the engine (just as there is no air at the bottom of a saucepan when it is bubbling) - so those bubbles canot be water droplets but must be a gas or saturated gas of some sort and if water is made up of Hydrogen and Oxygen (the former of which is usually found as a gas because it has such low evaporation points) surely that gas is one or both or a mixture of the two in some other molecular or atomic relationship? Mind you this is not an area I have much knowledge of so I might easily be talking crap (and no clever "as usual" responses please!)
Baz
hartech said:
Thanks Globs - but I think you will find that steam is only a pure gas when it is superheated and that the stage in between when it is a vapour is different.
The steam may well have some water vapour in it (i.e. clumps of H2O molecules) but it is steam, there is no air, no oxygen and no hydrogen in there - it's all H2O.Just the same as when you boil a saucepan - those bubbles rising up are H2O is gaseous form. H2O changes from a solid to a liquid at 0C and a liquid to a gas at 100C, at normal pressures. In the M96/M97 engine you have pressure so the temperature it boils at will be just above 100C..
The fact that it occupies a much greater volume is what increases the pressure and lifts the radiator or expansion tank cap.
As water is heated, sensible heat is added to raise the temperature to boiling point or saturation temperature. The saturation temperature for any given pressure can be found from steam tables. The term saturation temp means that the water/steam mixture is saturated with sensible heat. At atmospheric pressure this is 100*c. Next, all the heat that is put into the fluid does not raise the temperature but instead changes the state of the mixture from water to steam, this is known as latent heat, when all the water is turned to steam, if more heat is added the temperature will begin to increase and the steam becomes superheated. Tsat for 1bar is around 120*c, so if the radiator cap lifts at 1 bar that is the temp at which the water will boil. That's if it's pure water, which it isn't because it has antifreeze added which lowers the freezing point but also raises the boiling point a couple of degrees at 20% concentration.
As water is heated, sensible heat is added to raise the temperature to boiling point or saturation temperature. The saturation temperature for any given pressure can be found from steam tables. The term saturation temp means that the water/steam mixture is saturated with sensible heat. At atmospheric pressure this is 100*c. Next, all the heat that is put into the fluid does not raise the temperature but instead changes the state of the mixture from water to steam, this is known as latent heat, when all the water is turned to steam, if more heat is added the temperature will begin to increase and the steam becomes superheated. Tsat for 1bar is around 120*c, so if the radiator cap lifts at 1 bar that is the temp at which the water will boil. That's if it's pure water, which it isn't because it has antifreeze added which lowers the freezing point but also raises the boiling point a couple of degrees at 20% concentration.
Edited by JM1962 on Tuesday 18th January 19:03
Edited by JM1962 on Tuesday 18th January 19:04
Well that little deviation has been a useful diversion for me as I now realise that the droplets of water are mixed in with H2O as a gas (seems obvious I know but all the info states that water is only a true gas if it is not in contact with any water or water droplets - so I stupidly assumed that meant that unless it was superheated some other state for the bubbles existed) - probably got too much else on my mind - or just getting senile.
You are never too old to learn something interesting.
Baz
You are never too old to learn something interesting.
Baz
hartech said:
Well that little deviation has been a useful diversion for me
The problem of water boiling has ramifications beyond the Porsche cooling system, it's the reason that old brake fluid can give you braking failure if you lift off the pedal at the wrong time, and also the reason for the Chernobyl incident.I think it's safe to say that should I be in the market for a 987 one day I may prefer one with a pre-fixed Hartech engine in, apart from the IMS, RMS, wall cracking and big end wear the idea that the cylinders should be able to boil the water in any kind of non-fault usage is IMO horrifying!!
In fact I wonder if allowing the cylinders to be properly cooled would reduce cylinder cracking and ovality - it couldn't hurt could it?
I think you have a very good point there Globs because "CREEP" is a known problem with composite constructions and Lokasil is a composite and if it follows the usual rules will gradually creep in the direction of stress or load over a long period of time and quicker as the temperature increases (although I think the small difference in temperature would only make a small difference to the lifespan).
I think the problem we are fixing is difficult to test properly with our limited resources. For example we tested both water and the right coolant mix to find the temperature it started producing bubbles at. We did it in a saucepan with a temperature sensor in it and a light flame underneath and found they both started much below boiling point and around the thermostat setting - but then what we don't know is the actual temperature just at the surface of the pan bottom where the liquid is in contact with it (as just like boiling an egg - the temperature of the surface contact may well have been higher to create the bubbles. p.s. the mixed coolant bubbled slighlty sooner - but then our test controls are not ideal.
It was enough for us to suspect the cause and of course we also don't know what temperature is at the surface of the cylinder wall either - it could well be similar to boiling point just there as the oil is safe at those temperatures anyway.
As with all these technical problems - there is much we don't know and a lot we suspect, test and are satisfied with but finally you have to apply various observations and theories and see if practice and experience combined with logic all gell together to point in one direction.
In this case everything we do and test points to the engines running very much higher cylinder temperatures than we have seen before - proven OK in Boxsters and 3.4's but as they age - more borderline in the Cayman S 3.4, the 996 and 997 3.6 and the 3.8 - in which coincidently design changes would result in even higher cylinder coolant temperatures combining with definitely higher cylinder wall loadings (just look at the torque graphs to prove that).
But I think the problem is not so much the general steady running temperatures - but what happens when the there is a sudden change from moderate to very fast driving when the system is slow to respond to the increase in cylinder wall temperatures and they become temporarily excessive. Because these engines produce more torque at lower revs (when the water pump is rotating slower and delivering less coolant) that faster driving may well not include high revs but just using that beautiful fat torque these engines effortlessly produce.
We also tested a teflon coated frying pan and discovered that if very high temperatures are directed underneath the coating softens and the older the pan the sooner it does. If this is similar to what happens to the Molycote on the pistons, then that may explain why we find it has come off in patches and also why the problems seem to emerge after a period of time. Due to the very high porosity that makes it a superb lubricated cylinder surface - we also predict that Lokasil will have lower thermal conductivity than Alusil or Nikasil (but have no way of testing that) - but in every direction we look or consider the issue we find confirmation that cylinder wall temperatures could be the problem.
So far we have conducted many measurements and calculations for fluid flow rates for 7 different engine combinations, tests on different thermostat settings, coolant tests, and road tests in 4 different modes in two different cars - but still - although all the results supported our theories - it is a relatively small as a test program to prove anything concrete.
The fact of the matter is that there is a problem out there and we suspect that as the mileages increase - so will the presently rare incidences of engine failure and it would be wrong of us to simply rebuild engines the same as they came in as that obviously would result in failure again - for some - in time.
Instead we have thought out what we think is happening, tested our theories and made changes to the engines coolant flow rates and recently the thermostat basic setting. Along the way we found out that as temperatures rise the dashboard temperature guage reads lower than the actual coolant temperatures inside the engine and from elsewhere (well done that man) found out how to set the air con control unit to read a more acuurate figure (which confirmed our readings of actual inside engine temperatures).
Then we turned our attention to how to repair the scored bores ecconomically (preferrably without our usual 3.4 method of fitting replacement cylinder liners when the cylinders crack).
So we invested in slightly oversized pistons (currently in test for 4.6 and 3.8 engines) - to avoid the cost of liner replacement. If this works out OK - then as quanitites increase they will probably be slightly cheaper than the Porsche pistons anyway - so a doublt win/win situation.
We have also successfully tested re-hardened cranks with new wider shells, repaired oil pumps with new gears, re-round oval cylinders and stop them moving again, skim the uneven cylinder top faces and presently re-manufacture the Intermediate shaft (following a recent large price increase) providing three different specifications to suit all alternatives.
And all this (apart from the pistons) we manufacture or machine and modify - IN HOUSE!
Although this will reduce the number of failed engines we get to repair - we also have just stocked a large quantity of low temperature thermostats - to help prevent those whose engines are still OK from experiencing a failure in the future (although we are not retailing these yet unless we fit them so we can investigate the state of the cars first and monitor their progress - to make sure they don't already have scored bores or other contributory problems like leaking radiators, old water pumps or tired expansion tanks or caps).
Baz
I think the problem we are fixing is difficult to test properly with our limited resources. For example we tested both water and the right coolant mix to find the temperature it started producing bubbles at. We did it in a saucepan with a temperature sensor in it and a light flame underneath and found they both started much below boiling point and around the thermostat setting - but then what we don't know is the actual temperature just at the surface of the pan bottom where the liquid is in contact with it (as just like boiling an egg - the temperature of the surface contact may well have been higher to create the bubbles. p.s. the mixed coolant bubbled slighlty sooner - but then our test controls are not ideal.
It was enough for us to suspect the cause and of course we also don't know what temperature is at the surface of the cylinder wall either - it could well be similar to boiling point just there as the oil is safe at those temperatures anyway.
As with all these technical problems - there is much we don't know and a lot we suspect, test and are satisfied with but finally you have to apply various observations and theories and see if practice and experience combined with logic all gell together to point in one direction.
In this case everything we do and test points to the engines running very much higher cylinder temperatures than we have seen before - proven OK in Boxsters and 3.4's but as they age - more borderline in the Cayman S 3.4, the 996 and 997 3.6 and the 3.8 - in which coincidently design changes would result in even higher cylinder coolant temperatures combining with definitely higher cylinder wall loadings (just look at the torque graphs to prove that).
But I think the problem is not so much the general steady running temperatures - but what happens when the there is a sudden change from moderate to very fast driving when the system is slow to respond to the increase in cylinder wall temperatures and they become temporarily excessive. Because these engines produce more torque at lower revs (when the water pump is rotating slower and delivering less coolant) that faster driving may well not include high revs but just using that beautiful fat torque these engines effortlessly produce.
We also tested a teflon coated frying pan and discovered that if very high temperatures are directed underneath the coating softens and the older the pan the sooner it does. If this is similar to what happens to the Molycote on the pistons, then that may explain why we find it has come off in patches and also why the problems seem to emerge after a period of time. Due to the very high porosity that makes it a superb lubricated cylinder surface - we also predict that Lokasil will have lower thermal conductivity than Alusil or Nikasil (but have no way of testing that) - but in every direction we look or consider the issue we find confirmation that cylinder wall temperatures could be the problem.
So far we have conducted many measurements and calculations for fluid flow rates for 7 different engine combinations, tests on different thermostat settings, coolant tests, and road tests in 4 different modes in two different cars - but still - although all the results supported our theories - it is a relatively small as a test program to prove anything concrete.
The fact of the matter is that there is a problem out there and we suspect that as the mileages increase - so will the presently rare incidences of engine failure and it would be wrong of us to simply rebuild engines the same as they came in as that obviously would result in failure again - for some - in time.
Instead we have thought out what we think is happening, tested our theories and made changes to the engines coolant flow rates and recently the thermostat basic setting. Along the way we found out that as temperatures rise the dashboard temperature guage reads lower than the actual coolant temperatures inside the engine and from elsewhere (well done that man) found out how to set the air con control unit to read a more acuurate figure (which confirmed our readings of actual inside engine temperatures).
Then we turned our attention to how to repair the scored bores ecconomically (preferrably without our usual 3.4 method of fitting replacement cylinder liners when the cylinders crack).
So we invested in slightly oversized pistons (currently in test for 4.6 and 3.8 engines) - to avoid the cost of liner replacement. If this works out OK - then as quanitites increase they will probably be slightly cheaper than the Porsche pistons anyway - so a doublt win/win situation.
We have also successfully tested re-hardened cranks with new wider shells, repaired oil pumps with new gears, re-round oval cylinders and stop them moving again, skim the uneven cylinder top faces and presently re-manufacture the Intermediate shaft (following a recent large price increase) providing three different specifications to suit all alternatives.
And all this (apart from the pistons) we manufacture or machine and modify - IN HOUSE!
Although this will reduce the number of failed engines we get to repair - we also have just stocked a large quantity of low temperature thermostats - to help prevent those whose engines are still OK from experiencing a failure in the future (although we are not retailing these yet unless we fit them so we can investigate the state of the cars first and monitor their progress - to make sure they don't already have scored bores or other contributory problems like leaking radiators, old water pumps or tired expansion tanks or caps).
Baz
Globs said:
I think it's safe to say that should I be in the market for a 987 one day I may prefer one with a pre-fixed Hartech engine in, apart from the IMS, RMS, wall cracking and big end wear the idea that the cylinders should be able to boil the water in any kind of non-fault usage is IMO horrifying!!
Horrifying indeed. I have been looking at 996s and Cayman's but the thought of what might happen to the engine has made me realise that I can't afford one. I just couldn't budget an extra 8-10 grand for an engine repair/replacement. Looks like I'll be keeping my 968 a bit longer.Hi Baz
I have a Cayman S that I have owned from new, bought in launch week back in 05. It's done 66,000 miles now and gets quite regular track use as well.
Mike at Sports and Classic looks after the car and inspected the bores last week for me.
Would this be of any interest to you? I would like to try out the thermostat if at all possible. Don't mind being a bit of a guinnea pig for it.
Let me know if you need any more info.
Cheers
Jack
I have a Cayman S that I have owned from new, bought in launch week back in 05. It's done 66,000 miles now and gets quite regular track use as well.
Mike at Sports and Classic looks after the car and inspected the bores last week for me.
Would this be of any interest to you? I would like to try out the thermostat if at all possible. Don't mind being a bit of a guinnea pig for it.
Let me know if you need any more info.
Cheers
Jack
Hi Jack, sorry for the delay in replying and thank you for your kind offer.
The problem about these cylinder scoring is a massive issue and obviously not only is affecting quite a few 3.6's and 3.8 - but very rarely a 3.4 Cayman S as well. The numbers for the Cayman seem really low however and I am sure with someone like Mike looking after it you have little to worry about.
It has already cost us a small fortune to investigate the causes, manufacture casting patterns and jigs, manufacture cylinder liners, redesign IMS bearings, build test engines, design and make extended valves sumps and buy test cars, invest in new machinery, have special pistons manufacturerd and tested, support racing teams etc (incidently so far (touch wood and hoping not to be tempting providence) the new slightly oversized pistons - that will lower the rebuild costs - are testing out very well indeed). All this investment is justified by us because we believe that the numbers we will then rebuild over future years will recoup that investment and pay back a dividend eventually. The Cayman S oversized pistons are specified and drawn up but numbers do not yet justify a production batch.
The low temperature thermostat is a little different because when we rebuild engines we alter the coolant flow to cool the cylinders more (the lack of which we believe is the basic cause) so we don't really need to delve into this product to rebuild reliable engines for our customers (of which there are presently enough to work to full capacity and I can only see that increasing as they age).
When we both worked out (and we believe proved) the temperature issue and realised that a lower temperature thermostat could be fitted to undamaged cars and could possibly prevent them from doing the same we faced the question of whether we invest in a product we are unlikely to make any serious income out of that actually reduces the number of engines we would eventually rebuild or ignore it.
Fortunately (and in contrast to some manufacturers mercinary pursuit of income over reputation and customer support) it was never an issue for us and we are happy to make it available to protect owners from a financial dissaster - when we complete tests - however - having made that stand we do not want it to backfire on us because cars we have no control over may still fail for other reasons. So until we have tested them out fully we are only fitting them to cars we service and repair here - or are brought here for a thorough check over while we fit the thermostat - at least until we are more sure of the product and outcome.
Track use puts these cars through additional stress due partly because of the lack of oil supply to the sump when cornering and partly because you are hard on the throttle for longer than for street driving and the road (and therefore air) speed are lower in comparison to engine output - so radiator air speed is lower and typical track cars need at least a better sump arrangement (which we manufacture, tested last year and will be in production for this season) and a bigger oil cooler.
The Boxsters presently being raced may well not need a lower temperature thermostat because they have different piston design to the Cayman, and different temperature distribution around the cylinders and heads and the Cayman is not presently being raced in standard form.
I think therefore that it would be a bit of a diversion without our direct control if we fitted it to your car just now (will be OK sometime in the future when we have completed our tests).
This is not in any way to imply anything derogatory about Mike or you or your car - but is part of a painstaking process of testing under our own control that we have conducted on all our re-designs and products that has stood us in good stead for many years. I also don't want to suggest you transfer to our care as you are Mikes customer and we don't poach nor would want to. I do
hope you understand.
As long as you gradually increase the power delivery and revs to fully open the thermostat before full throttle use - I don't anticipate a problem which I do believe is more likely to occur in those cars that have rapid temperature rises that the rather slow cooling system cannot respond to quickly enough to prevent local short term overheating.
Hopefully our tests will be completed soon and the thermostats can be made generally available before the weather is good enough to conduct track tests.
When we are ready, Mike will be amongst the first to trial the thermostat under "Independents Porsche specialist trials" so you will be there amongst the first anyway.
Baz
The problem about these cylinder scoring is a massive issue and obviously not only is affecting quite a few 3.6's and 3.8 - but very rarely a 3.4 Cayman S as well. The numbers for the Cayman seem really low however and I am sure with someone like Mike looking after it you have little to worry about.
It has already cost us a small fortune to investigate the causes, manufacture casting patterns and jigs, manufacture cylinder liners, redesign IMS bearings, build test engines, design and make extended valves sumps and buy test cars, invest in new machinery, have special pistons manufacturerd and tested, support racing teams etc (incidently so far (touch wood and hoping not to be tempting providence) the new slightly oversized pistons - that will lower the rebuild costs - are testing out very well indeed). All this investment is justified by us because we believe that the numbers we will then rebuild over future years will recoup that investment and pay back a dividend eventually. The Cayman S oversized pistons are specified and drawn up but numbers do not yet justify a production batch.
The low temperature thermostat is a little different because when we rebuild engines we alter the coolant flow to cool the cylinders more (the lack of which we believe is the basic cause) so we don't really need to delve into this product to rebuild reliable engines for our customers (of which there are presently enough to work to full capacity and I can only see that increasing as they age).
When we both worked out (and we believe proved) the temperature issue and realised that a lower temperature thermostat could be fitted to undamaged cars and could possibly prevent them from doing the same we faced the question of whether we invest in a product we are unlikely to make any serious income out of that actually reduces the number of engines we would eventually rebuild or ignore it.
Fortunately (and in contrast to some manufacturers mercinary pursuit of income over reputation and customer support) it was never an issue for us and we are happy to make it available to protect owners from a financial dissaster - when we complete tests - however - having made that stand we do not want it to backfire on us because cars we have no control over may still fail for other reasons. So until we have tested them out fully we are only fitting them to cars we service and repair here - or are brought here for a thorough check over while we fit the thermostat - at least until we are more sure of the product and outcome.
Track use puts these cars through additional stress due partly because of the lack of oil supply to the sump when cornering and partly because you are hard on the throttle for longer than for street driving and the road (and therefore air) speed are lower in comparison to engine output - so radiator air speed is lower and typical track cars need at least a better sump arrangement (which we manufacture, tested last year and will be in production for this season) and a bigger oil cooler.
The Boxsters presently being raced may well not need a lower temperature thermostat because they have different piston design to the Cayman, and different temperature distribution around the cylinders and heads and the Cayman is not presently being raced in standard form.
I think therefore that it would be a bit of a diversion without our direct control if we fitted it to your car just now (will be OK sometime in the future when we have completed our tests).
This is not in any way to imply anything derogatory about Mike or you or your car - but is part of a painstaking process of testing under our own control that we have conducted on all our re-designs and products that has stood us in good stead for many years. I also don't want to suggest you transfer to our care as you are Mikes customer and we don't poach nor would want to. I do
hope you understand.
As long as you gradually increase the power delivery and revs to fully open the thermostat before full throttle use - I don't anticipate a problem which I do believe is more likely to occur in those cars that have rapid temperature rises that the rather slow cooling system cannot respond to quickly enough to prevent local short term overheating.
Hopefully our tests will be completed soon and the thermostats can be made generally available before the weather is good enough to conduct track tests.
When we are ready, Mike will be amongst the first to trial the thermostat under "Independents Porsche specialist trials" so you will be there amongst the first anyway.
Baz
By way of reafirming our approach - just this morning we have had a customer in to have the lower temperature thermostat fitted, but upon inspection we found that he already has scored cylinder bores.
If we had not done this check we would have found out about the scoring in the future and never have known if our thermostat had failed to stop it happening and furthermore could have been accused of the change causing it.
This would have also left us open to abusing our trust if another garage fitted the thermostat (knowing the scoring was already there) and later putting the blame on us for future problems.
Although we are convinced of the benefits - you can see why it is so important to conduct tests in the most controlled and reliable ways possible and we are just sorry that this means there will be a delay before it becomes generally available.
I am sure this is the right way to do things.
Baz
If we had not done this check we would have found out about the scoring in the future and never have known if our thermostat had failed to stop it happening and furthermore could have been accused of the change causing it.
This would have also left us open to abusing our trust if another garage fitted the thermostat (knowing the scoring was already there) and later putting the blame on us for future problems.
Although we are convinced of the benefits - you can see why it is so important to conduct tests in the most controlled and reliable ways possible and we are just sorry that this means there will be a delay before it becomes generally available.
I am sure this is the right way to do things.
Baz
Hi Baz,
Thanks for the reply.
What you describe is how I had imagined you would handle the situation.
I am more than happy to have you do a pre-inspection of the car prior to fitting it, and then give access to the car for regular check-ups.
I am obviously aware of all the other issues involved with tracking a Cayman and know of the various measures available to improve oil pick-up (mainly during long left-handers that have been patched by the deaper sump/Accusump/other oiling solutions) in the 3.4 as well as the ingestion and VOS issues that have been reported.
My car is standard in those terms, so I am not sure whether that would make it a better or worse candidate for testing. Can poor oil pickup and ingestion be a contributary factor in scored bores or is scored bores purely a result of over-heating from slow or poorly managed coolant? I suppose without that answer it is hard to tell whether the thermostat would help at all if there are other contributary issues that also need patching at the same time as the thermostat is fitted.
Jack
Thanks for the reply.
What you describe is how I had imagined you would handle the situation.
I am more than happy to have you do a pre-inspection of the car prior to fitting it, and then give access to the car for regular check-ups.
I am obviously aware of all the other issues involved with tracking a Cayman and know of the various measures available to improve oil pick-up (mainly during long left-handers that have been patched by the deaper sump/Accusump/other oiling solutions) in the 3.4 as well as the ingestion and VOS issues that have been reported.
My car is standard in those terms, so I am not sure whether that would make it a better or worse candidate for testing. Can poor oil pickup and ingestion be a contributary factor in scored bores or is scored bores purely a result of over-heating from slow or poorly managed coolant? I suppose without that answer it is hard to tell whether the thermostat would help at all if there are other contributary issues that also need patching at the same time as the thermostat is fitted.
Jack
Perhaps you could pop over for a chat about it all - rather than deal with it over the Internet then?
Again - today - another clue as to why we try to do things the right way. An enquiry from a Cayman owner whose car was seen to have scored bores in another dealer (linked with Porsche) and they wanted a huge amount of money to strip it down to see if they could then apply for a gesture from Porsche towards the cost of fixing it (and we already know that outcome).
This reafirms our advice to get any car suspected of problems here first because that would have ended up being unecconomic to bring to us after that payment and they - like us - already know only too well exactly what they will find inside (and if they really cannot they ought to be able to!).
If you pop over I can show you the sumps in production and explain why the others on the market actually don't do the job properly and we can cover several other issues and get you set up as soon as possible.
Baz
Again - today - another clue as to why we try to do things the right way. An enquiry from a Cayman owner whose car was seen to have scored bores in another dealer (linked with Porsche) and they wanted a huge amount of money to strip it down to see if they could then apply for a gesture from Porsche towards the cost of fixing it (and we already know that outcome).
This reafirms our advice to get any car suspected of problems here first because that would have ended up being unecconomic to bring to us after that payment and they - like us - already know only too well exactly what they will find inside (and if they really cannot they ought to be able to!).
If you pop over I can show you the sumps in production and explain why the others on the market actually don't do the job properly and we can cover several other issues and get you set up as soon as possible.
Baz
Gassing Station | 911/Carrera GT | Top of Page | What's New | My Stuff