997.1 Hartech BoreScore fix - longevity
Discussion
Afternoon all,
I know that bore scoring, hartech cylinder liners etc have been discussed almost to death but there is still a highly relevant angle that I haven't found much information on.
When a 997.1 with cylinder scoring has had cylinder liners installed by Hartech, is that problem then dealt with for the foreseeable future?
Are there any other issues to watch for once a hartech re-line has been done?
I've been impressed by the openess of Hartech on these forums so perhaps they will chip in.
Thanks in advance.
I know that bore scoring, hartech cylinder liners etc have been discussed almost to death but there is still a highly relevant angle that I haven't found much information on.
When a 997.1 with cylinder scoring has had cylinder liners installed by Hartech, is that problem then dealt with for the foreseeable future?
Are there any other issues to watch for once a hartech re-line has been done?
I've been impressed by the openess of Hartech on these forums so perhaps they will chip in.
Thanks in advance.
Nikasil alloy cylinders (like those we fit) will not score a bore under normal operating conditions. It would take something very unusual (like no coolant, a failed coolant pump or some other fuel or ignition issue) to create the conditions for a problem.
They could fail if something caused the pistons to run so hot that they no longer could fit inside the cylinder bore - when they would seize to both sides all round (and so would any other piston or cylinder combination under the same extreme circumstances). We know of one circumstance when this occurred and there as no coolant left in the engine but it was driven on until there was a failure.
Under normal running conditions there is nothing available that is more reliable and that that maintains the correct piston to cylinder clearances under all normal operating conditions - long term - than an alloy Nikasil cylinder tube.
This is why they are so reliable not only in our rebuilds but also in GT3's and Turbos.
The plating NIkasil forms a homogeneous tube bonded securely to the outer alloy and as a result silicon particles cannot become dislodged or fall off unless something very unusual has gone on.
Lokasil and Alusil are an alloy mixture in which there are separate silicon particles present - forming the hard surface. These are random and can become lose, are individually held in place by the alloy surrounding them and dislodge from the matrix when they rub between the gap between the piston and the cylinder bore.
This can be a particular problem as boring and honing inevitably leave some crystals more than half machined away so that they are not "dovetail" entrapped around their circumference by the alloy but are effectively tapered inwards allowing the drag from the piston rings to wobble them lose in time.
If the thrust pressure driving the car along is insufficient to entrap the lose particle in the gap formed by the oil film thickness then the particle may escape before damaging the piston or bore surface further - the reverse is true if the particle is too large for the gap when it will rub against the piston surface and could damage the piston coating or cylinder bore leading to the dislodging of more particles in a catastrophic event.
Things to avoid therefore are thin oil viscosity (either by choice or the local coolant temperatures), high running cylinder surface temperatures and very high torque loading at low revs.
Despite the reduced coolant proportion passing into the cylinder block in this model range (increased in Gen 2, GT3 and turbo engines), the original hard ferrous electroplate piston coating could resist this particle abrasion better than the later plastic coatings that unlike the ferrous coating - soften and reduce bonding strength with elevated temperatures.
Alusil created the silicon particles by mixing more of them with the alloy than the alloy can hold in a mixture forming a saturated matrix in which the excess silicon particles come out of solution and form crystals the size of which can be determined by the mixture and they are therefore well secured in the remaining alloy substrate.
Lokasil was formed by suspending and bonding the silicon in a porous preform that molten aluminium was forced through at very high pressure in the metal casting mould and we think does not hold the silicon particles in as even a distribution or as strong a bond - releasing more into the cylinder over time.
Two particle size ranges are referred to by the manufacturer with the later versions potentially having larger silicon particles.
Because there is no relevant particle degradation in Nikasil the pistons need no surface finish or can run with plastic coatings etc.
Because the degradation rate in Lokasil is higher it needs a harder and better bonded piston coating than current p lastic options to last as long as the harder ferrous piston coating.
Early Alusil cylinders (924S/944/968) with hard ferrous coated pistons lasted extremely long before any degradation could impinge on the piston (often only occurring when the head gasket had also degraded causing the rear cylinders to run hotter and therefore with hotter thinner oil that reduced the oil film thickness).
Because Alusil entraps the silicon particles better they should last longer than a similar plastic piston coating in Lokasil.
The pistons we have seen in use in the Gen 2 2009 onwards Alusil engines have been ferrous coating by what appears like a slightly softer version we also tested in Lokasil (still under road testing after two strip down checks) that does not seem quite as hard.
The more pressure the piston exerts on the cylinder wall the more damage can be done by lose particles. The 996/7 Turbo engines produce the greatest thrust pressure of the range but runs with alloy uncoated pistons perfectly well for huge mileages because of the suitability and superiority of Nikasil (and Porsche choice of Nikasil for that arduous application).
Although it is more expensive to produce a Nikasil Alloy cylinder tube - as a result of investment in expensive automated machinery - and high volumes - we have managed to supply our versions of similar quality to those Turbo and GT3 cylinders for a lower price - that includes machining out the original Lokasil and fitting the new cylinder.
Because some owners faced with a cylinder problem cannot afford to have the other Lokasil cylinders that have not yet failed replaced - some rebuilt engines will have a mixture of Nikasil and Lokasil cylinder bores. Most now take advantage of the discount we apply to having all three in bank 2 or all 6 replaced - to solve the problem long term.
I hope that answers your questions.
Baz
They could fail if something caused the pistons to run so hot that they no longer could fit inside the cylinder bore - when they would seize to both sides all round (and so would any other piston or cylinder combination under the same extreme circumstances). We know of one circumstance when this occurred and there as no coolant left in the engine but it was driven on until there was a failure.
Under normal running conditions there is nothing available that is more reliable and that that maintains the correct piston to cylinder clearances under all normal operating conditions - long term - than an alloy Nikasil cylinder tube.
This is why they are so reliable not only in our rebuilds but also in GT3's and Turbos.
The plating NIkasil forms a homogeneous tube bonded securely to the outer alloy and as a result silicon particles cannot become dislodged or fall off unless something very unusual has gone on.
Lokasil and Alusil are an alloy mixture in which there are separate silicon particles present - forming the hard surface. These are random and can become lose, are individually held in place by the alloy surrounding them and dislodge from the matrix when they rub between the gap between the piston and the cylinder bore.
This can be a particular problem as boring and honing inevitably leave some crystals more than half machined away so that they are not "dovetail" entrapped around their circumference by the alloy but are effectively tapered inwards allowing the drag from the piston rings to wobble them lose in time.
If the thrust pressure driving the car along is insufficient to entrap the lose particle in the gap formed by the oil film thickness then the particle may escape before damaging the piston or bore surface further - the reverse is true if the particle is too large for the gap when it will rub against the piston surface and could damage the piston coating or cylinder bore leading to the dislodging of more particles in a catastrophic event.
Things to avoid therefore are thin oil viscosity (either by choice or the local coolant temperatures), high running cylinder surface temperatures and very high torque loading at low revs.
Despite the reduced coolant proportion passing into the cylinder block in this model range (increased in Gen 2, GT3 and turbo engines), the original hard ferrous electroplate piston coating could resist this particle abrasion better than the later plastic coatings that unlike the ferrous coating - soften and reduce bonding strength with elevated temperatures.
Alusil created the silicon particles by mixing more of them with the alloy than the alloy can hold in a mixture forming a saturated matrix in which the excess silicon particles come out of solution and form crystals the size of which can be determined by the mixture and they are therefore well secured in the remaining alloy substrate.
Lokasil was formed by suspending and bonding the silicon in a porous preform that molten aluminium was forced through at very high pressure in the metal casting mould and we think does not hold the silicon particles in as even a distribution or as strong a bond - releasing more into the cylinder over time.
Two particle size ranges are referred to by the manufacturer with the later versions potentially having larger silicon particles.
Because there is no relevant particle degradation in Nikasil the pistons need no surface finish or can run with plastic coatings etc.
Because the degradation rate in Lokasil is higher it needs a harder and better bonded piston coating than current p lastic options to last as long as the harder ferrous piston coating.
Early Alusil cylinders (924S/944/968) with hard ferrous coated pistons lasted extremely long before any degradation could impinge on the piston (often only occurring when the head gasket had also degraded causing the rear cylinders to run hotter and therefore with hotter thinner oil that reduced the oil film thickness).
Because Alusil entraps the silicon particles better they should last longer than a similar plastic piston coating in Lokasil.
The pistons we have seen in use in the Gen 2 2009 onwards Alusil engines have been ferrous coating by what appears like a slightly softer version we also tested in Lokasil (still under road testing after two strip down checks) that does not seem quite as hard.
The more pressure the piston exerts on the cylinder wall the more damage can be done by lose particles. The 996/7 Turbo engines produce the greatest thrust pressure of the range but runs with alloy uncoated pistons perfectly well for huge mileages because of the suitability and superiority of Nikasil (and Porsche choice of Nikasil for that arduous application).
Although it is more expensive to produce a Nikasil Alloy cylinder tube - as a result of investment in expensive automated machinery - and high volumes - we have managed to supply our versions of similar quality to those Turbo and GT3 cylinders for a lower price - that includes machining out the original Lokasil and fitting the new cylinder.
Because some owners faced with a cylinder problem cannot afford to have the other Lokasil cylinders that have not yet failed replaced - some rebuilt engines will have a mixture of Nikasil and Lokasil cylinder bores. Most now take advantage of the discount we apply to having all three in bank 2 or all 6 replaced - to solve the problem long term.
I hope that answers your questions.
Baz
Many thanks Baz, good answer.
I will be buying in a few months and it's good to know where I stand if I decide to look for a 997 that's had the cylinders sorted.
I might even buy a reduced price 997 where the issue is known to be present (I have seen a couple of these) and get the fix sorted myself.
Cheers
I will be buying in a few months and it's good to know where I stand if I decide to look for a 997 that's had the cylinders sorted.
I might even buy a reduced price 997 where the issue is known to be present (I have seen a couple of these) and get the fix sorted myself.
Cheers
I think that buying with a known problem can be a great prospect (its what I would do) as the reduction in price more or less pays for the rebuild - you can add in any other upgrades and future proofing and not only enjoy a car running really well and with the comfort of excellent reliability and a warranty but much more saleable when you come to replace it (if ever).
On the difficulty with records we are limited in what we can divulge by the data protection act and customer confidentiality - but always provide written details of rebuilds and if they are not forthcoming that may explain the limit of the repairs.
If the seller had the rebuild done and provides us with his written permission (say and E-mail) then we are able to discuss the extent of a rebuild - reluctance to do so reveals obvious doubt!
Baz
On the difficulty with records we are limited in what we can divulge by the data protection act and customer confidentiality - but always provide written details of rebuilds and if they are not forthcoming that may explain the limit of the repairs.
If the seller had the rebuild done and provides us with his written permission (say and E-mail) then we are able to discuss the extent of a rebuild - reluctance to do so reveals obvious doubt!
Baz
While that is possible it is unlikely that a buyer looking through the registration document and old receipts cannot identify the previous owners. Furthermore anyone buying a car advertised with a rebuilt engine will want to see the invoice and find out what work was done.
All our invoice identify the owner at the time and the work done is their private information which they can choose to make public or not and so if we gave out the information we would not know if in doing that we have revealed information private to the owner at the time which the enquirer has already identified - apart from which it is not our place to discuss what work an owner (and our customer) had done to anyone phoning in - who might not even be a potential buyer - nor even for a car that is not actually for sale.
I repeat that if the person who paid for the work to be done by us allows our information to be revealed by giving their permission - we are only too delighted to do so but - if they don't - we will keep it private and advise the potential new owner that they should be suspicious if that permission is not being provided.
I cannot see anything wrong with that advice nor the position we take on our customers private information.
Baz
All our invoice identify the owner at the time and the work done is their private information which they can choose to make public or not and so if we gave out the information we would not know if in doing that we have revealed information private to the owner at the time which the enquirer has already identified - apart from which it is not our place to discuss what work an owner (and our customer) had done to anyone phoning in - who might not even be a potential buyer - nor even for a car that is not actually for sale.
I repeat that if the person who paid for the work to be done by us allows our information to be revealed by giving their permission - we are only too delighted to do so but - if they don't - we will keep it private and advise the potential new owner that they should be suspicious if that permission is not being provided.
I cannot see anything wrong with that advice nor the position we take on our customers private information.
Baz
Our video (available on our web site www.hartech.org) shows various issues connected with bore scoring including piston coating loss, our cylinders and much more.
Baz
Baz
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