Hartech fixes - interesting stuff - some questions
Discussion
Just been having a good read of baz hartech pt 4 & 5 guides. Very interesting.
I have a few questions I couldn't find specific answers to - apologies if I missed them....
How much for the low temp thermostat, fitted to a 'heathly car'? Is this mod considered equally valid for 996 and 997 engines, and do you expect it to mitigate fully against the weaknesses of the open deck design?
If you boroscope a car, and it shows no scoring at all - would it be safe to assume the ovality is ok and longevity could be greatly improved by the low temp thermostat mod alone? Or could there still be damage that will eventually worsen even with the mod. Is there any way of guaging this short of a full strip?
Are there any downsides to running the engine cooler than Porsche intended with the low temp thermostat? Does it affect economy and emissions adversely?
When did the 'single sprocket' crank and ims come into production? 997, or did late 996s have it? If so when, and how can you tell? Does the single sprocket crank design fully remove the previous ims weakness?
Edit .... This link answers some questions. Is this like the hartech fix?
http://www.lnengineering.com/ims.html
Your cylinder support mod to effectively create a closed deck is interesting. How long have these been running in engines you've modified? Do you think their potential effect on the cooling of the end of the cylinder is significant - might it create a differential cooling effect?
Nice work.
I have a few questions I couldn't find specific answers to - apologies if I missed them....
How much for the low temp thermostat, fitted to a 'heathly car'? Is this mod considered equally valid for 996 and 997 engines, and do you expect it to mitigate fully against the weaknesses of the open deck design?
If you boroscope a car, and it shows no scoring at all - would it be safe to assume the ovality is ok and longevity could be greatly improved by the low temp thermostat mod alone? Or could there still be damage that will eventually worsen even with the mod. Is there any way of guaging this short of a full strip?
Are there any downsides to running the engine cooler than Porsche intended with the low temp thermostat? Does it affect economy and emissions adversely?
When did the 'single sprocket' crank and ims come into production? 997, or did late 996s have it? If so when, and how can you tell? Does the single sprocket crank design fully remove the previous ims weakness?
Edit .... This link answers some questions. Is this like the hartech fix?
http://www.lnengineering.com/ims.html
Your cylinder support mod to effectively create a closed deck is interesting. How long have these been running in engines you've modified? Do you think their potential effect on the cooling of the end of the cylinder is significant - might it create a differential cooling effect?
Nice work.
Edited by ///ajd on Friday 26th August 22:59
Edited by ///ajd on Friday 26th August 23:00
Edited by ///ajd on Friday 26th August 23:37
graemel said:
Why bring it to a forum. Why not phone or better still go visit Baz and and ask him face to face ?. Most of us muppets on here including me have not got a clue. We just love our 911's
I assumed the answers might be of wider interest and would save hartech answering individually. Plus they are very similar, but not quite covered I don't think, in what baz has put on his site.It's good stuff - its explained in a rather long & thorough manner - but still understandable by non-technical readers I think.
I'm not here to wind people up - I'm thinking of buying a 02/03 996 C4S, but want to understand my options for inspection and preventative maintenance.
graemel said:
///ajd said:
I'm not here to wind people up.
That's fine. Just don't won't to read Baz getting into an ar*e kicking competition with one leg tied upI just want facts - and if that includes 'don't know' or 'depends' to some of my questions, then that's fair enough.
I've been tempted by how cheep leggy C4S have become - I've always liked them, and the more I read the more I think the 'issues' with these cars maybe becoming quite manageable - even out of opc warranty.
As I am not at work today (or for a few days) Can I add the answers to your original post below as follows?
Just been having a good read of baz hartech pt 4 & 5 guides. Very interesting.
I have a few questions I couldn't find specific answers to - apologies if I missed them....
How much for the low temp thermostat, fitted to a 'heathly car'? Is this mod considered equally valid for 996 and 997 engines, and do you expect it to mitigate fully against the weaknesses of the open deck design?
Please phone Grant on 0204 302809 for the latest prices - the thermostat on its own is £60.00 + Vat.
It will probably not solve the potential problem totally - because the cylinders will still go oval over time as various other wearing parts will increase temperatures etc. How good a mod it will prove to be - only time will tell for sure - it just help reduce the incidences and increase mileages before damage. It is not as important for a 996 3.4 as 3.6 and 3.8 engine sizes (and the Cayman S) and originally we did not think it neccessary for the early model - but now that mileages have increased we have seen a couple of scored 3.4's so now do recommend it and incorporate it if we are rebuilding the engine anyway.
If you boroscope a car, and it shows no scoring at all - would it be safe to assume the ovality is ok and longevity could be greatly improved by the low temp thermostat mod alone? Or could there still be damage that will eventually worsen even with the mod. Is there any way of guaging this short of a full strip?
You may see some lines that look like scoring but are just shadowing on the bore surface - you need to be familiar with looking at them with a camera (as it magnifies the impression and distorts the view) and then stripping and finding out the result to be confident of identifying the right scoring marks that are actually dug into the bore and therefore emanate from the piston. The ovality is not connected directly and will be a gradual process over time and mileage. Usually the "creep" problem of matrix based composites (i.e. Lokasil) is reduced if the temperature is lowered - but it is impossible to calculate by how much the test and reporting to find out would be to big a job even for the manufacturer - so sometimes you have to use your engineering background to judge the benefits.
Are there any downsides to running the engine cooler than Porsche intended with the low temp thermostat? Does it affect economy and emissions adversely?
I do not know of any downsides.
When did the 'single sprocket' crank and ims come into production? 997, or did late 996s have it? If so when, and how can you tell? Does the single sprocket crank design fully remove the previous ims weakness?
I presume you are referring to the Hivo chain change from the original roller chain drive between the crankshaft and the IMS. The hivo as drawn would look like a single sprocket but actually is more like a gear tooth profile than a sprocket (well is actually cut with a gear cutting profile). There is a strange mixture of internals that we cannot directly draw conclusions from - some early engines with later chain drives and some later ones with earlier drives - but either way the bearing is the same and just as vulnerable - in fact I prefer the earlier roller chain as it results in smoother transmission (IMHO).
Edit .... This link answers some questions. Is this like the hartech fix?
http://www.lnengineering.com/ims.html
I cannot now link over while in the middle of replying but we don't do things the same (although they are a similar organisation with similar engineering solutions and understanding). We do not regard the ceramic IMS bearing as necessary but our test about internal temperatures ares similar to theirs and they agree with out conclusions.
Your cylinder support mod to effectively create a closed deck is interesting. How long have these been running in engines you've modified? Do you think their potential effect on the cooling of the end of the cylinder is significant - might it create a differential cooling effect?
Remember also that the scoring or seizing occurs down the cylinder some way (nearer the bottom than the top) and from the lowest ring to the top of the piston is anyway manufacturer smaller (so doesn't touch the cylinder) so the very small area right at the top of the bore where it is fitted is not a critical area for heat transfer and oil temperatures and cylinder support.
I also think you are possibly missing the point that we also re-round the oval cylinders and then hold them in that position by using the retaining rings. This improves cylinder to piston ring sealing and increases heat transfer out from the piston through better contact with the cylinder. The ring fitted offers increased surface area to the coolant than the original surface it is fitted to - so should also improve heat dissipation/transfer (but I have no way of proving that except through area connected).
I don't remember exactly when we started fitting these rings and re-rounding cylinders but it must be over 6 years ago and no problems with it to date - only success.
Nice work.
Just been having a good read of baz hartech pt 4 & 5 guides. Very interesting.
I have a few questions I couldn't find specific answers to - apologies if I missed them....
How much for the low temp thermostat, fitted to a 'heathly car'? Is this mod considered equally valid for 996 and 997 engines, and do you expect it to mitigate fully against the weaknesses of the open deck design?
Please phone Grant on 0204 302809 for the latest prices - the thermostat on its own is £60.00 + Vat.
It will probably not solve the potential problem totally - because the cylinders will still go oval over time as various other wearing parts will increase temperatures etc. How good a mod it will prove to be - only time will tell for sure - it just help reduce the incidences and increase mileages before damage. It is not as important for a 996 3.4 as 3.6 and 3.8 engine sizes (and the Cayman S) and originally we did not think it neccessary for the early model - but now that mileages have increased we have seen a couple of scored 3.4's so now do recommend it and incorporate it if we are rebuilding the engine anyway.
If you boroscope a car, and it shows no scoring at all - would it be safe to assume the ovality is ok and longevity could be greatly improved by the low temp thermostat mod alone? Or could there still be damage that will eventually worsen even with the mod. Is there any way of guaging this short of a full strip?
You may see some lines that look like scoring but are just shadowing on the bore surface - you need to be familiar with looking at them with a camera (as it magnifies the impression and distorts the view) and then stripping and finding out the result to be confident of identifying the right scoring marks that are actually dug into the bore and therefore emanate from the piston. The ovality is not connected directly and will be a gradual process over time and mileage. Usually the "creep" problem of matrix based composites (i.e. Lokasil) is reduced if the temperature is lowered - but it is impossible to calculate by how much the test and reporting to find out would be to big a job even for the manufacturer - so sometimes you have to use your engineering background to judge the benefits.
Are there any downsides to running the engine cooler than Porsche intended with the low temp thermostat? Does it affect economy and emissions adversely?
I do not know of any downsides.
When did the 'single sprocket' crank and ims come into production? 997, or did late 996s have it? If so when, and how can you tell? Does the single sprocket crank design fully remove the previous ims weakness?
I presume you are referring to the Hivo chain change from the original roller chain drive between the crankshaft and the IMS. The hivo as drawn would look like a single sprocket but actually is more like a gear tooth profile than a sprocket (well is actually cut with a gear cutting profile). There is a strange mixture of internals that we cannot directly draw conclusions from - some early engines with later chain drives and some later ones with earlier drives - but either way the bearing is the same and just as vulnerable - in fact I prefer the earlier roller chain as it results in smoother transmission (IMHO).
Edit .... This link answers some questions. Is this like the hartech fix?
http://www.lnengineering.com/ims.html
I cannot now link over while in the middle of replying but we don't do things the same (although they are a similar organisation with similar engineering solutions and understanding). We do not regard the ceramic IMS bearing as necessary but our test about internal temperatures ares similar to theirs and they agree with out conclusions.
Your cylinder support mod to effectively create a closed deck is interesting. How long have these been running in engines you've modified? Do you think their potential effect on the cooling of the end of the cylinder is significant - might it create a differential cooling effect?
Remember also that the scoring or seizing occurs down the cylinder some way (nearer the bottom than the top) and from the lowest ring to the top of the piston is anyway manufacturer smaller (so doesn't touch the cylinder) so the very small area right at the top of the bore where it is fitted is not a critical area for heat transfer and oil temperatures and cylinder support.
I also think you are possibly missing the point that we also re-round the oval cylinders and then hold them in that position by using the retaining rings. This improves cylinder to piston ring sealing and increases heat transfer out from the piston through better contact with the cylinder. The ring fitted offers increased surface area to the coolant than the original surface it is fitted to - so should also improve heat dissipation/transfer (but I have no way of proving that except through area connected).
I don't remember exactly when we started fitting these rings and re-rounding cylinders but it must be over 6 years ago and no problems with it to date - only success.
Nice work.
hartech said:
You may see some lines that look like scoring but are just shadowing on the bore surface - you need to be familiar with looking at them with a camera (as it magnifies the impression and distorts the view)
Baz, do you think the pics on page 2 of this thread are scoring or just shadowing?http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Thanks for the replies baz,
On the thermostat cost of job question, no doubt the part is cheap, but I have no idea if labour is 5 mins (e.g. as for a idle control valve on a 3.2 carrera), or engine drop & partial strip at x+hours? Just wondered which it is.
My experience of creep is that is it highly temperature dependant - within certain tolerances it can be largely mitigated - hence there should be a point at which the 996/997 cylinders won't perceptably creep - it maybe that your thermostat mod actually achieves this, but hard to be sure without understanding the material. What is likely is that porshce thought they had got it right, so it may be that the engine design is only marginal in this respect (I.e. Your small change in effective coolant temp is enough to restore the desired creep margin).
I don't doubt that your cylinder support mod wil almost certainly improve the stiffness of the structure to the point that the ovality due to creep deformation is almost completely negated - in this respect I'm not, I don't think, missing the point. I wasn't aware they had been fitted for 6 years to customer cars - this is very significant as I'm sure they would have been back to you if they had had subsequent had issues. My question was more about secondary effects cooling and the difference that may arise between the top and lower parts of the piston travel within the cylinder - I assume the original design had full water exposure to 100% of the cylinder jacket where the piston moves - this is altered by your mod. It may be an irrelevant question.
What do you actually do to fix the ims issue? Is this explained in pt 4/5? I didn't notice if it was. I found the INengineering explanation & solution reasonable.
Cheers
On the thermostat cost of job question, no doubt the part is cheap, but I have no idea if labour is 5 mins (e.g. as for a idle control valve on a 3.2 carrera), or engine drop & partial strip at x+hours? Just wondered which it is.
My experience of creep is that is it highly temperature dependant - within certain tolerances it can be largely mitigated - hence there should be a point at which the 996/997 cylinders won't perceptably creep - it maybe that your thermostat mod actually achieves this, but hard to be sure without understanding the material. What is likely is that porshce thought they had got it right, so it may be that the engine design is only marginal in this respect (I.e. Your small change in effective coolant temp is enough to restore the desired creep margin).
I don't doubt that your cylinder support mod wil almost certainly improve the stiffness of the structure to the point that the ovality due to creep deformation is almost completely negated - in this respect I'm not, I don't think, missing the point. I wasn't aware they had been fitted for 6 years to customer cars - this is very significant as I'm sure they would have been back to you if they had had subsequent had issues. My question was more about secondary effects cooling and the difference that may arise between the top and lower parts of the piston travel within the cylinder - I assume the original design had full water exposure to 100% of the cylinder jacket where the piston moves - this is altered by your mod. It may be an irrelevant question.
What do you actually do to fix the ims issue? Is this explained in pt 4/5? I didn't notice if it was. I found the INengineering explanation & solution reasonable.
Cheers
I can comment on the downsides of running a lower temp thermostat - I am employed in an engine R&D consultancy working for the big car manufacturers.
Firstly hotter coolant temperatures are better for vehicle emissions - especially hydrocarbons - but I guess most Forum users won't be bothered about this.
Next there is a small improvement in fuel economy and reduced CO2 emissions due to bearings being slightly slacker, oil being slightly thinner - but the difference will be very small and not noticeable in the real world.
Finally and possibly more important to Forum members is the effect on oil dilution. This occurs when fuel leaks past the piston rings when the engine is first started. Also you get condensation of water lurking at the bottom of the sump. These pollutants can seriously degrade the function of the oil. An engine that does lots of cold starts and does not get properly hot will be very prone to this. Running a cooler stat will mean the pollutants take longer to be driven out of the sump oil. A 70 C stat should really only be used in engines that are going to get a darned good thrashing every time they are used
.
Firstly hotter coolant temperatures are better for vehicle emissions - especially hydrocarbons - but I guess most Forum users won't be bothered about this.
Next there is a small improvement in fuel economy and reduced CO2 emissions due to bearings being slightly slacker, oil being slightly thinner - but the difference will be very small and not noticeable in the real world.
Finally and possibly more important to Forum members is the effect on oil dilution. This occurs when fuel leaks past the piston rings when the engine is first started. Also you get condensation of water lurking at the bottom of the sump. These pollutants can seriously degrade the function of the oil. An engine that does lots of cold starts and does not get properly hot will be very prone to this. Running a cooler stat will mean the pollutants take longer to be driven out of the sump oil. A 70 C stat should really only be used in engines that are going to get a darned good thrashing every time they are used
.Edited by SilverstoneSid on Sunday 28th August 08:36
SilverstoneSid said:
I can comment on the downsides of running a lower temp thermostat - I am employed in an engine R&D consultancy working for the big car manufacturers.
Firstly hotter coolant temperatures are better for vehicle emissions - especially hydrocarbons - but I guess most Forum users won't be bothered about this.
Next there is a small improvement in fuel economy and reduced CO2 emissions due to bearings being slightly slacker, oil being slightly thinner - but the difference will be very small and not noticeable in the real world.
Finally and possibly more important to Forum members is the effect on oil dilution. This occurs when fuel leaks past the piston rings when the engine is first started. Also you get condensation of water lurking at the bottom of the sump. These pollutants can seriously degrade the function of the oil. An engine that does lots of cold starts and does not get properly hot will be very prone to this. Running a cooler stat will mean the pollutants take longer to be driven out of the sump oil. A 70 C stat should really only be used in engines that are going to get a darned good thrashing every time they are used.
Thanks SS - makes sense. Firstly hotter coolant temperatures are better for vehicle emissions - especially hydrocarbons - but I guess most Forum users won't be bothered about this.
Next there is a small improvement in fuel economy and reduced CO2 emissions due to bearings being slightly slacker, oil being slightly thinner - but the difference will be very small and not noticeable in the real world.
Finally and possibly more important to Forum members is the effect on oil dilution. This occurs when fuel leaks past the piston rings when the engine is first started. Also you get condensation of water lurking at the bottom of the sump. These pollutants can seriously degrade the function of the oil. An engine that does lots of cold starts and does not get properly hot will be very prone to this. Running a cooler stat will mean the pollutants take longer to be driven out of the sump oil. A 70 C stat should really only be used in engines that are going to get a darned good thrashing every time they are used
.Edited by SilverstoneSid on Sunday 28th August 08:36
Anyone know the answer to these questions below - plus the one about do "C4S have more effective cooling due to the Turbo bits/bumper" (do they really have the same rads as a turbo, or is it just the bumper?). Has Hartech seen relatively few C4Ss go pop is another way to look at it?
---
On the thermostat cost of job question, no doubt the part is cheap, but I have no idea if labour is 5 mins (e.g. as for a idle control valve on a 3.2 carrera), or engine drop & partial strip at x+hours? Just wondered which it is.
What do Hartech do to fix the ims issue (or is it commercially sensitive)? I found the INengineering explanation & solution reasonable.
It becomes increasingly hard to explain why so many questions make assumptions that are wrong and therefore become misleading. I don't know how many times I have explained that the cylinder block runs at a different temperature to the heads and the thermostat only operates at the resulting mixed together temperature. This is such a basic issue that is the root cause of the problems but can only be modified with a stripped engine.
This being the case the temperatures in the block with the lower temperature thermostat are about the same as almost every engine used to run on in the last 50 years - but with the standard thermostat are much higher. I think this totally negates comments about the polutants escaping past the rings etc. The thermostat we supply warms up slightly quicker than a standard one anyway and so the temperature the internal cylinder area reaches normal running temperatures as quickly as any normal engine would do. Frankly discussing this level of polutant transfer is so minimal anyway - it is just an unnecessary smoke screen to the fundamental problem - diverting attention from the true problem.
By measuring the creep to ovality of engines that have covered all mileages from about 15K to 150K it seems to us that the creep is at much the same rate and regular - following almost a straight line graph - and therefore will occur to all engines eventually and carry on during their life.
There is a difference in the rate of ovality creep between cylinders (as is common with composite constructions) and it has been a technical subject upon which accurate predictable guidelines have been slow to appear (due to this unpredictability) - it is not like metallic molecular alloys.
I have already explained that the area the support rings present to the coolant is actually higher than the original material AND that the top of the bore never seizes anyway and only ever a long way down - and that pistons are made smaller where the rings are and don't touch the cylinder wall anyway and that the rings don't reach the top of the piston anyway - so - not really sure how many times I need to repeat this simple fact that makes comments about the upper cylinder temperature a little irrelevant. However the support rings - by re-rounding the cylinders - increase the contact between the piston, rings and bore - where it does matter - which is extremely relevant.
Trying to find solutions to manufacturers problems are far more difficult than designing it right in the first place or re-designing the engine for a newer version while addressing these problems.
We do not claim that fitting a lower temperature thermostat is a permanent fix for all problems - for ever - only that it is inexpensive, and should increase lifespan.
None of our modification remove all weak areas of the engine because it was designed to just be capable of reliably providing the output planned and if you needed a more powerful example for track use they manufactured a more expansive engine with different internals. Unfortunately they got things (IMHO) too near the wire with new materials technology and risky design ideas that in some cases fail. We will be racing an example next season to try and find all the weak areas - in sequence and try and provide answers before they hit the general public. This will also prove our own existing solutions and hopefully enable the process of making these engines more reliable to keep up with them as they age.
Our IMS replaces the original bearing with one without seals (and therefore lubricated by the splash oil provided by the chain rotation) - a stronger spindle and nut (plus a lock nut) a fit checked by measurement. It is much the same as the LN solution except they use a more expensive but more fragile ceramic bearing that our tests have proven unnecessary. I don't think there is anything wrong with their solution and if you want to pay more for something that is similarly reliable - please do so - I have no problem with that.
Hope these replies help.
Baz
This being the case the temperatures in the block with the lower temperature thermostat are about the same as almost every engine used to run on in the last 50 years - but with the standard thermostat are much higher. I think this totally negates comments about the polutants escaping past the rings etc. The thermostat we supply warms up slightly quicker than a standard one anyway and so the temperature the internal cylinder area reaches normal running temperatures as quickly as any normal engine would do. Frankly discussing this level of polutant transfer is so minimal anyway - it is just an unnecessary smoke screen to the fundamental problem - diverting attention from the true problem.
By measuring the creep to ovality of engines that have covered all mileages from about 15K to 150K it seems to us that the creep is at much the same rate and regular - following almost a straight line graph - and therefore will occur to all engines eventually and carry on during their life.
There is a difference in the rate of ovality creep between cylinders (as is common with composite constructions) and it has been a technical subject upon which accurate predictable guidelines have been slow to appear (due to this unpredictability) - it is not like metallic molecular alloys.
I have already explained that the area the support rings present to the coolant is actually higher than the original material AND that the top of the bore never seizes anyway and only ever a long way down - and that pistons are made smaller where the rings are and don't touch the cylinder wall anyway and that the rings don't reach the top of the piston anyway - so - not really sure how many times I need to repeat this simple fact that makes comments about the upper cylinder temperature a little irrelevant. However the support rings - by re-rounding the cylinders - increase the contact between the piston, rings and bore - where it does matter - which is extremely relevant.
Trying to find solutions to manufacturers problems are far more difficult than designing it right in the first place or re-designing the engine for a newer version while addressing these problems.
We do not claim that fitting a lower temperature thermostat is a permanent fix for all problems - for ever - only that it is inexpensive, and should increase lifespan.
None of our modification remove all weak areas of the engine because it was designed to just be capable of reliably providing the output planned and if you needed a more powerful example for track use they manufactured a more expansive engine with different internals. Unfortunately they got things (IMHO) too near the wire with new materials technology and risky design ideas that in some cases fail. We will be racing an example next season to try and find all the weak areas - in sequence and try and provide answers before they hit the general public. This will also prove our own existing solutions and hopefully enable the process of making these engines more reliable to keep up with them as they age.
Our IMS replaces the original bearing with one without seals (and therefore lubricated by the splash oil provided by the chain rotation) - a stronger spindle and nut (plus a lock nut) a fit checked by measurement. It is much the same as the LN solution except they use a more expensive but more fragile ceramic bearing that our tests have proven unnecessary. I don't think there is anything wrong with their solution and if you want to pay more for something that is similarly reliable - please do so - I have no problem with that.
Hope these replies help.
Baz
Thanks for the clarification Baz - I see where you are coming from.
What's the approx cost of the thermostat mod only?
Any anecdotal evidence that the C4S is any less prone based on the no. of engine/cars you've had in (noting that the C4S is newer, probably slightly rarer than most 996s)? Or are these lining up outside your door at a reasonable rate?
I won't challenge your view that the creep would occur anyway even with your low temp thermostat mod - but it would be interesting to see to what extent it is reduced after your thermostat mod. It is possible it could be significantly reduced. It is however likely to be true that your ring support mods adds significant robustness to the design.
I recall a given material having creep properties at 200 deg C that would give a part a life measured in hours. The same material at 120 deg C had an expected life of 20,000 hours. The material was used for the skin of concorde - avoiding material creep problems is one of the design reasons concorde only went M2.0 - go any faster and the basic airframe would creep and have a very short service life. This is also the reason going faster than M2.0 is a very expensive business.
What's the approx cost of the thermostat mod only?
Any anecdotal evidence that the C4S is any less prone based on the no. of engine/cars you've had in (noting that the C4S is newer, probably slightly rarer than most 996s)? Or are these lining up outside your door at a reasonable rate?
I won't challenge your view that the creep would occur anyway even with your low temp thermostat mod - but it would be interesting to see to what extent it is reduced after your thermostat mod. It is possible it could be significantly reduced. It is however likely to be true that your ring support mods adds significant robustness to the design.
I recall a given material having creep properties at 200 deg C that would give a part a life measured in hours. The same material at 120 deg C had an expected life of 20,000 hours. The material was used for the skin of concorde - avoiding material creep problems is one of the design reasons concorde only went M2.0 - go any faster and the basic airframe would creep and have a very short service life. This is also the reason going faster than M2.0 is a very expensive business.
Edited by ///ajd on Tuesday 30th August 19:23
That's right ///ajd - I also ran two composite businesses in between my motorcycle racing engine period (one for aerospace engineering plc) and my present business and found out a lot about creep.
Unfortunately the exact construction of the Lokasil preform is not known in detail and I am sorry to say that if you read more about it - it becomes clear that the whole picture is not being revealed by the manufacturers - as there are clear anomalies that someone who has knowledge in that area - can detect (basically keeping some facts back).
However - as I reported before - the critical nature of temperature dissipation does show the potential for sudden rapid localised increases and bubbling (or boiling) locally would also explain this.
The whole problem of scored bores is multi-technical and is stretching across different technical disciplines and experience.
It is just luck that my own experience covers that area as well as general automotive engineering and design and has enabled me to connect together a lot of otherwise probably dis-associated facts and observations and come up with a common cause and partial remedy (if not stripped) and a pretty full one (if stripped and rebuilt).
However identifying the exact process with hard predictable figures would require resources well beyond our own and so we are left with our general opinion and gut feeling - that seems to have been proven a reliable system up until now.
Baz
Unfortunately the exact construction of the Lokasil preform is not known in detail and I am sorry to say that if you read more about it - it becomes clear that the whole picture is not being revealed by the manufacturers - as there are clear anomalies that someone who has knowledge in that area - can detect (basically keeping some facts back).
However - as I reported before - the critical nature of temperature dissipation does show the potential for sudden rapid localised increases and bubbling (or boiling) locally would also explain this.
The whole problem of scored bores is multi-technical and is stretching across different technical disciplines and experience.
It is just luck that my own experience covers that area as well as general automotive engineering and design and has enabled me to connect together a lot of otherwise probably dis-associated facts and observations and come up with a common cause and partial remedy (if not stripped) and a pretty full one (if stripped and rebuilt).
However identifying the exact process with hard predictable figures would require resources well beyond our own and so we are left with our general opinion and gut feeling - that seems to have been proven a reliable system up until now.
Baz
///ajd said:
Thanks for the clarification Baz - I see where you are coming from.
What's the approx cost of the thermostat mod only?
Any anecdotal evidence that the C4S is any less prone based on the no. of engine/cars you've had in (noting that the C4S is newer, probably slightly rarer than most 996s)? Or are these lining up outside your door at a reasonable rate?
I won't challenge your view that the creep would occur anyway even with your low temp thermostat mod - but it would be interesting to see to what extent it is reduced after your thermostat mod. It is possible it could be significantly reduced. It is however likely to be true that your ring support mods adds significant robustness to the design.
I recall a given material having creep properties at 200 deg C that would give a part a life measured in hours. The same material at 120 deg C had an expected life of 20,000 hours. The material was used for the skin of concorde - avoiding material creep problems is one of the design reasons concorde only went M2.0 - go any faster and the basic airframe would creep and have a very short service life. This is also the reason going faster than M2.0 is a very expensive business.
Found some more info here (US based)What's the approx cost of the thermostat mod only?
Any anecdotal evidence that the C4S is any less prone based on the no. of engine/cars you've had in (noting that the C4S is newer, probably slightly rarer than most 996s)? Or are these lining up outside your door at a reasonable rate?
I won't challenge your view that the creep would occur anyway even with your low temp thermostat mod - but it would be interesting to see to what extent it is reduced after your thermostat mod. It is possible it could be significantly reduced. It is however likely to be true that your ring support mods adds significant robustness to the design.
I recall a given material having creep properties at 200 deg C that would give a part a life measured in hours. The same material at 120 deg C had an expected life of 20,000 hours. The material was used for the skin of concorde - avoiding material creep problems is one of the design reasons concorde only went M2.0 - go any faster and the basic airframe would creep and have a very short service life. This is also the reason going faster than M2.0 is a very expensive business.
Edited by ///ajd on Tuesday 30th August 19:23
http://www.lnengineering.com/lowtemperaturethermos...
They offer a 160F Thermostat (71C). Its interesting that the new DFI engine appears to have a lower temp thermostat than previous engines according to them - though this could be for various reasons.
Its costs about £100, with fitting an a US OPC about £160 (calculated from US prices - not sure what this would cost in the UK).
I also found after re-reading Part 4 that the Hartech IMS fix for an as yet UNDAMAGED car is approx £800. Not sure if this is current.
I'm starting to think:
1. Buy C4S cheap - I'm talking leggy 70k miles 02/03 model on the edge of 9 year max OPC warranty period - but confirm no scoring of bores by boroscope or IMS damage by looking for particulates in oil (reliable method?) prior to purchase.
2. Upgrade IMS (£800) and change Thermostat (£260) on a healthy car - call it £1000.
3. Risk significantly reduced, but possibility of bore scoring not eliminated.
DRIVE ALOT
4. Inspect with boroscope every 6/12000 miles to monitor for scoring.
5. Strip and rebuild if necessary prior to complete liner failure - reducing cost of rebuild & then take the cylinder support mod.
There is a chance that step 5 could be deferred for many many miles - e.g. to 150k and beyond.
Is this a solution to owning a 996 out of warranty with minimal risk?
What are the flaws?
Edited by ///ajd on Wednesday 31st August 21:29
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