Looking at buying a 997... Is a Hartech repaired .1 as good
Discussion
I moved quick on it Mr Juice. Did the deal in January before the photos were uploaded on OPC used locator. At that point they hadn't inspected the car fully so after all the work and warranty can't imagine there was much profit in it. I'd have liked a Hartech car but at the time there weren't any for sale ant the 2yr warranty, although no watertight was a bonus. I can extend for one more year or put the money towards a Hartech rebuild which I expect to more than likely do at some point.
I hope you don't mind me correcting your misunderstanding Woolyjoe - because our Nikasil plated alloy liners do not score again.
This design and specification has been used by Porsche for their air cooled cylinders for years and for the 996/7 GT3 and turbo models with no scoring problems and we have manufactured and supplied thousands without any scoring.
The best commercially available bore finish is still currently Nikasil plating.
The Lokasil cylinders can score (usually promoted when small pieces of silicon become detached from the cylinder wall and get stuck between the piston and the cylinder bore as the piston moves up and down and pressure is applied to drive the car along).
That is why the scoring is always on the thrust side and not the other side.
The original pistons had a hard iron coating that resisted scoring when a particle of silicon escaped very well but the plastic coatings that replaced it do not last as long and eventually are penetrated.
Nikasil can run with any piston coating we have come across and even without any coating at all because the material is homogeneous and does not incorporate particles of silicon in an aluminium alloy matrix. If you machined the outer alloy away from a Nikasil plated cylinder you would end up with a thin tube of Nikasil whereas you could not machine anything away from either Likasil or Nikasil except retaining a mixture of aluminium alloy and particles of silicon.
Alusil (as used in 844/968 and Gen 2 models) is much better than Lokasil as it retains the silicon particles better and longer and if the do eventually escape they are smaller.
This is why the consideration for repairing an engine with damaged Lokasil cylinders takes into account the differences between fitting a short block or new engine with the very same Lokasil cylinders and piston coatings that have failed or replacing them with Nikasil plated cylinders - that are effectively "bullet proof".
Because Nikasil has a very shiny surface - if a camera is used to view inside the cylinders after they have run - the effect of the reflection often makes visual lines appear to look like scoring - but if they do they have no depth or detriment and are just visual (like polishing marks). Indeed it is only ever the case that scoring in Nikasil occurs if something else has gone wrong that would have damaged any type of cylinder anyway.
In fact Nikasil is so tough that even if some other failure (nothing to do with the cylinder) has dropped debris into the cylinder (like say a dropped valve or valve seat) and damaged the head and piston - the cylinders are sometimes still able to resit damage and are often re-useable.
So when the merits of different repairs are being considered - the reason that our Nikasil plated aerospace alloy cylinders are the best choice is because of their long term reliability, minimal wear, superb heat transfer capabilities and minimal expansion and contraction that matches that of the piston.
There are however different ways to design and fit even Nikasil plated alloy cylinders.
The cylinders in the engines in question are unrestrained round tubes at the top and bottom (only joined to the cylinder block via a central ring) and this makes the cylinder tubes less stable and prone to distortion and stretching oval (referred to as an "open deck design).
Some alternatives fit a new thinner tube (of various material choices) within the original tube (which has been machined out to accommodate it and is also now thinner) and after fitting the result is still unrestrained. Because 2 tubes fitted inside each other are weaker than one tube of the same overall inside and outside major and minor diameters - if they were already weak enough to distort oval before hand - it is no surprise that some solutions do so even more quickly.
Furthermore when trying to fit a thin cylinder into another thin tube - the interference fits often defeat the object. If the inner tube is too tight in simply pushes the outer tube out on fitting and visa versa - so it can be hard to impose enough tightness in the fit to create a stable outcome.
Some materials do not transfer heat as well as aluminium and have different expansion and contraction rates making them less suitable.
A "tube within a tube" solution also creates a heat transfer barrier where the 2 tubes touch.
We machine the original cylinder tube completely away and replace it so our cylinders are one piece and actually stronger than the original cylinder, ribbed externally to allow greater surface area to increase cooling, have no barrier for heat transfer (being "wet liners" directly in contact with the coolant) and are fitted at the top into a precision machined recess that converts the unstable original design (and that used as a replacement by several competitors) into the preferred "closed deck design" (as used in the replacement 9A1 Gen 2 engines).
We also improve the coolant flow into the cylinder block and supply our LTT with each job resulting in a very reliable solution that still costs less than a new engine.
I hope that clears up the situation.
Baz
This design and specification has been used by Porsche for their air cooled cylinders for years and for the 996/7 GT3 and turbo models with no scoring problems and we have manufactured and supplied thousands without any scoring.
The best commercially available bore finish is still currently Nikasil plating.
The Lokasil cylinders can score (usually promoted when small pieces of silicon become detached from the cylinder wall and get stuck between the piston and the cylinder bore as the piston moves up and down and pressure is applied to drive the car along).
That is why the scoring is always on the thrust side and not the other side.
The original pistons had a hard iron coating that resisted scoring when a particle of silicon escaped very well but the plastic coatings that replaced it do not last as long and eventually are penetrated.
Nikasil can run with any piston coating we have come across and even without any coating at all because the material is homogeneous and does not incorporate particles of silicon in an aluminium alloy matrix. If you machined the outer alloy away from a Nikasil plated cylinder you would end up with a thin tube of Nikasil whereas you could not machine anything away from either Likasil or Nikasil except retaining a mixture of aluminium alloy and particles of silicon.
Alusil (as used in 844/968 and Gen 2 models) is much better than Lokasil as it retains the silicon particles better and longer and if the do eventually escape they are smaller.
This is why the consideration for repairing an engine with damaged Lokasil cylinders takes into account the differences between fitting a short block or new engine with the very same Lokasil cylinders and piston coatings that have failed or replacing them with Nikasil plated cylinders - that are effectively "bullet proof".
Because Nikasil has a very shiny surface - if a camera is used to view inside the cylinders after they have run - the effect of the reflection often makes visual lines appear to look like scoring - but if they do they have no depth or detriment and are just visual (like polishing marks). Indeed it is only ever the case that scoring in Nikasil occurs if something else has gone wrong that would have damaged any type of cylinder anyway.
In fact Nikasil is so tough that even if some other failure (nothing to do with the cylinder) has dropped debris into the cylinder (like say a dropped valve or valve seat) and damaged the head and piston - the cylinders are sometimes still able to resit damage and are often re-useable.
So when the merits of different repairs are being considered - the reason that our Nikasil plated aerospace alloy cylinders are the best choice is because of their long term reliability, minimal wear, superb heat transfer capabilities and minimal expansion and contraction that matches that of the piston.
There are however different ways to design and fit even Nikasil plated alloy cylinders.
The cylinders in the engines in question are unrestrained round tubes at the top and bottom (only joined to the cylinder block via a central ring) and this makes the cylinder tubes less stable and prone to distortion and stretching oval (referred to as an "open deck design).
Some alternatives fit a new thinner tube (of various material choices) within the original tube (which has been machined out to accommodate it and is also now thinner) and after fitting the result is still unrestrained. Because 2 tubes fitted inside each other are weaker than one tube of the same overall inside and outside major and minor diameters - if they were already weak enough to distort oval before hand - it is no surprise that some solutions do so even more quickly.
Furthermore when trying to fit a thin cylinder into another thin tube - the interference fits often defeat the object. If the inner tube is too tight in simply pushes the outer tube out on fitting and visa versa - so it can be hard to impose enough tightness in the fit to create a stable outcome.
Some materials do not transfer heat as well as aluminium and have different expansion and contraction rates making them less suitable.
A "tube within a tube" solution also creates a heat transfer barrier where the 2 tubes touch.
We machine the original cylinder tube completely away and replace it so our cylinders are one piece and actually stronger than the original cylinder, ribbed externally to allow greater surface area to increase cooling, have no barrier for heat transfer (being "wet liners" directly in contact with the coolant) and are fitted at the top into a precision machined recess that converts the unstable original design (and that used as a replacement by several competitors) into the preferred "closed deck design" (as used in the replacement 9A1 Gen 2 engines).
We also improve the coolant flow into the cylinder block and supply our LTT with each job resulting in a very reliable solution that still costs less than a new engine.
I hope that clears up the situation.
Baz
referring to this I assume, i.e. replacement liners are not bulletproof, unclear whether he is including Nikasil replacements but that is what he is implying
woollyjoe said:
Also, isn't the 997.1 engine basically the same as a 996... and when you replace the liners, they can still score again. It isn't like you get rid of the issue?
That's not 100% congruent with what you've said though, is it?
You're clearly asserting that M96/97 engines, once rebuilt, are still subject to the same failure modes which occasioned the rebuild.
i.e. an M96 is rebuilt with Nikasil instead of Lokasil liners due to scoring, but that's just re-set the clock rather than resolving the issue.
You're clearly asserting that M96/97 engines, once rebuilt, are still subject to the same failure modes which occasioned the rebuild.
i.e. an M96 is rebuilt with Nikasil instead of Lokasil liners due to scoring, but that's just re-set the clock rather than resolving the issue.
Frankly - if you think my reply was too complicated and intended to bamboozle readers - you bring your own ability to understanding the issues fairly and your motivation in making such bold statements into such question that I think you should not be making sweeping statements about the quality and suitability of products that have proven exceptionally reliable in rebuilt engines that have similarly a great reputation.
Making brief response statements can be called into question because they do not explain why - but to criticise me for taking the time and making the effort to explain a complicated issue so you and others can make better judgements is extremely offensive.
When someone lays themselves open to scrutiny by broadening technical explanations - you will either find immediate responses from competitors who hold different views - or if it all goes silent - it is not because they are bamboozling anyone but because what they are saying is right, honest and true and as such you should draw your own conclusions about the quality of my replies and the intentions behind them.
Finally may I respectfully remind you that you are clearly not the authority that decides the content and length of replies to your uneducated statements and that there is nothing forcing you to read mine.
Baz
Making brief response statements can be called into question because they do not explain why - but to criticise me for taking the time and making the effort to explain a complicated issue so you and others can make better judgements is extremely offensive.
When someone lays themselves open to scrutiny by broadening technical explanations - you will either find immediate responses from competitors who hold different views - or if it all goes silent - it is not because they are bamboozling anyone but because what they are saying is right, honest and true and as such you should draw your own conclusions about the quality of my replies and the intentions behind them.
Finally may I respectfully remind you that you are clearly not the authority that decides the content and length of replies to your uneducated statements and that there is nothing forcing you to read mine.
Baz
Same old s
t isn't it. "Bore scoring", "IMS/RMS", all 911s will eventually die a terrible death and cost £20,000 to put right....It's all bks.
Just buy a 911 you can afford and drive the fker. I'm sure there are people out there that spend more time arguing on message boards about engine failures than they do driving the blasted machine.
t isn't it. "Bore scoring", "IMS/RMS", all 911s will eventually die a terrible death and cost £20,000 to put right....It's all bks.Just buy a 911 you can afford and drive the f
ker. I'm sure there are people out there that spend more time arguing on message boards about engine failures than they do driving the blasted machine.So as this thread appears to have some experienced professionals on it.............would the factory X51 upgrade on a 997.1 alleviate this problem, make it more likely or have no difference whatsoever?
My car is under Warranty for another 12 months - it would be nice to understand obvious symptoms and pre-emptive corrections before the worst happens.
Or is it just a case of drive it, enjoy it, and if it's going to have the problem, budget for it?
I hear so many mixed reports, hopefully this smaller thread will have the knowledge!
thanks in advance.
My car is under Warranty for another 12 months - it would be nice to understand obvious symptoms and pre-emptive corrections before the worst happens.
Or is it just a case of drive it, enjoy it, and if it's going to have the problem, budget for it?
I hear so many mixed reports, hopefully this smaller thread will have the knowledge!
thanks in advance.
I know that this reply will not be taken as really helpful because most people just want direct easy answers - however - the failures have a lot of influences and some can be issues that drivers can do something to minimise while others are just random and relate more to manufacturing variations.
The Lokasil does seem to have variable density, distribution of silicon particles and bonding strength (occasionally we find a bore where the oil had washed away sections all together for example).
The bores we measure (even from new) are not as round or parallel as we would like or that Alusil and Nikasil can be machined to. I think this may be due to the former manufacturing variables so that some parts are denser than others and the hones remove different amounts of material from different areas of the bores.
The plastic piston coating definitely varies. Some gradually wear through the coating, some have a piece fall off while others bubble and leave a piece on the surface but no longer stuck to the piston underneath (and we have pictures to prove all this).
The forces that press the piston against the part of the cylinder that scores do more damage at low revs and with high torque (and tiptronics set off normally in 2nd gear so tend to be used delivering more low speed torque).
I guess an X51 driver would be a manual car and usually revved higher - which is actually a good thing minimising the scoring (or more commonly referred to as scuffing elsewhere) but the difference in expected life would be minimal.
The type of oil and its viscosity creates a thicker or thinner barrier between the piston and the cylinder wall so different oils will provide more or less protection. The thicker the oil the less any loose silicon particles will impinge on the surfaces and the longer the piston coating will resist wear. A LTT will in most cases (except exceptionally hot days) lower cylinder temperatures and thus increase oil viscosity at the piston to cylinder interface.
A third radiator can make things worse unless it is fitted with a control mechanism so it only works when the main radiators can no longer cope.
When you put together the different owners driving styles that each car is likely to have in its lifetime, different oil change intervals and types used, and mix into that a random variation in Lokasil and piston coating variations in quality, thermostat setting and radiators connections etc - it is no surprise that the result is conflicting arguments and experiences and a varied feedback record of experiences.
On top of that all the cylinders gradually migrate oval and this increases the piston clearances and changes the face width of the piston that is pushing on the cylinder wall and the piston face temperatures (due to blow by) that thins whatever oil is in there.
So - you could be lucky and get huge mileage out of your car or you could be unlucky and it could already be mildly scored or about to score at virtually any mileage.
All this is bad news but at least there is a solution that is reliable long term and they are brilliant cars.
Sorry it is long but it is not my fault that it is a complex subject that I could easily write a book about. My responses are short compared to each subjects complexity and I try to use analogies where possible yo help non-engineers understand things better.
As I have often said you don't have to read. absorb or take note of any of it!
Baz
The Lokasil does seem to have variable density, distribution of silicon particles and bonding strength (occasionally we find a bore where the oil had washed away sections all together for example).
The bores we measure (even from new) are not as round or parallel as we would like or that Alusil and Nikasil can be machined to. I think this may be due to the former manufacturing variables so that some parts are denser than others and the hones remove different amounts of material from different areas of the bores.
The plastic piston coating definitely varies. Some gradually wear through the coating, some have a piece fall off while others bubble and leave a piece on the surface but no longer stuck to the piston underneath (and we have pictures to prove all this).
The forces that press the piston against the part of the cylinder that scores do more damage at low revs and with high torque (and tiptronics set off normally in 2nd gear so tend to be used delivering more low speed torque).
I guess an X51 driver would be a manual car and usually revved higher - which is actually a good thing minimising the scoring (or more commonly referred to as scuffing elsewhere) but the difference in expected life would be minimal.
The type of oil and its viscosity creates a thicker or thinner barrier between the piston and the cylinder wall so different oils will provide more or less protection. The thicker the oil the less any loose silicon particles will impinge on the surfaces and the longer the piston coating will resist wear. A LTT will in most cases (except exceptionally hot days) lower cylinder temperatures and thus increase oil viscosity at the piston to cylinder interface.
A third radiator can make things worse unless it is fitted with a control mechanism so it only works when the main radiators can no longer cope.
When you put together the different owners driving styles that each car is likely to have in its lifetime, different oil change intervals and types used, and mix into that a random variation in Lokasil and piston coating variations in quality, thermostat setting and radiators connections etc - it is no surprise that the result is conflicting arguments and experiences and a varied feedback record of experiences.
On top of that all the cylinders gradually migrate oval and this increases the piston clearances and changes the face width of the piston that is pushing on the cylinder wall and the piston face temperatures (due to blow by) that thins whatever oil is in there.
So - you could be lucky and get huge mileage out of your car or you could be unlucky and it could already be mildly scored or about to score at virtually any mileage.
All this is bad news but at least there is a solution that is reliable long term and they are brilliant cars.
Sorry it is long but it is not my fault that it is a complex subject that I could easily write a book about. My responses are short compared to each subjects complexity and I try to use analogies where possible yo help non-engineers understand things better.
As I have often said you don't have to read. absorb or take note of any of it!
Baz
thanks Baz
so - drive it harder and rev it harder - noted
The car is in Warranty - but I guess unless it fails within the Warranty period - nothing would be corrected and if it was, it would be back to original spec that fails..........
Do they all go eventually - or are all the comments about the small % that do.............?
so - drive it harder and rev it harder - noted
The car is in Warranty - but I guess unless it fails within the Warranty period - nothing would be corrected and if it was, it would be back to original spec that fails..........
Do they all go eventually - or are all the comments about the small % that do.............?
thanks - I agree on the oil usage - when they said that I was a bit surprised........but it's more like 1/2 per 1000k
So the thing doesn't hand grenade itself (assuming you keep the oil level correct)
I.e. - A pre-emptive fix isn't worth it.........just drive it until it happens and then spend the money with Hartech etc
So the thing doesn't hand grenade itself (assuming you keep the oil level correct)
I.e. - A pre-emptive fix isn't worth it.........just drive it until it happens and then spend the money with Hartech etc
RacerMDR said:
....just drive it until it happens and then spend the money with Hartech etc
I think many of them that on sale, just already on that specific age if one inspects/looks at it clearly. We have seen a few of stories here and 911uk that owners with only 60 minutes driving than catastrophic results.I, myself looked at these cars last year for a long time, and decided not to go ahead. In general, thanks to Porsche AG sloppy engineering, most cars that they produced between 2000-2008 is pretty eventful. One can easily look at, how many independent engine builders or mechanics made a living out of this in the last decade, not to mention big brands like hartech or Autofarm.
woollyjoe said:
carry on with your pitch.
It's probably easy to label hartech engineers here, to think that they have a conflict, but if you really read what they reflect on their research, it is quite impressive and informative -Not to mention free of charge here-. I guess we all know, what would be Porsche AG's response about any of these cars nearly terminal problems if you ask them? (Many would be clue-less in my humble experience and opinion) Edited by ooid on Tuesday 23 January 22:20
What’s the difference between the nikasil liners in a contemporary rebuilt Porsche engine and the nikasil liners which caused BMW so many problems in the 90s? IIRC the solution for BMWs was steel liners? But I also remember the problem was attributed to high sulphur low grade fuel. Has that problem gone away?
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