Chris_in_the_UK
Estoril
- Joined
- 19 Mar 2014
- Messages
- 3,595
Any updates Phil?
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She''s in at Hartech getting the full £10k rebuild...
- Thread starter 911DG
- Start date
Chris_in_the_UK said:
Hi Chris, They have started rebuilding and have called me about a few ancillary engine items that should be considered as they are showing signs of wear etc lots of hoses , tandem pump (no surprise there lol) the high pressure pump had a fault code before they stripped it so I have agreed to those items plus a few more .So the car really should be good for another 10 years as its basically a new engine and with the rebuilt gearbox clutch flywheel and coolant pipes all changed this year ,plus the addition of the cargraphic 200 cell cats and headers to complete the cargraphic exhaust set up ,I hopefully will have a couple of years of low running costs and big grins. Its surprising how quickly after the initial shock of the cost of a rebuild you get your head around it and see all the benefits of a newly rebuilt engine etc.I guess helped by the fact that I had 4.5 years of very low running costs (mods aside) with my gen 1 and intention to stay with the car for at least another 3 or 4 years as my confidence in the marque is very high and do realise that the clutch/flywheel do wear and need replacing the coolant pipes also needed doing on the gen1 and is not unusual on a nearly 10 yr old car the engine was not a design fault and down to a cheap aftermarket part used by the previous owner leaving just the normally very reliable gearbox as being a little unusual a failure but certainly not unheard of . :thumb: :thumb:
bazhart
Barcelona
- Joined
- 20 May 2009
- Messages
- 1,343
On the basis that we just tell it how it is (and as professionally as we possibly can), we are now beginning to see a couple of patterns about these Gen 2 piston scoring incidents.
You may remember that ALUSIL was used on the 924S, 944 and 968 models but had to be used in conjunction with a hard iron coated pistons (Ferrostan) that then often lasted for over 250K and was about 0.013mm (or half a thou) thick .
To get away from the hard silicon particles being distributed all over the Alusil block (making it expensive to machine) Porsche introduced LOKASIL (short for Local Silicon) in which the hard silicon particles only existed near the cylinder sliding surface (making the rest of the cylinder block quicker and therefore cheaper to produce) and while they were built in conjunction with the same hard iron plated piston surface as before – they didn't suffer bore scoring (2.5 Boxster to 3.4 litre 996) – only 'D" chunking when the bores were increased in diameter and the wall thicknesses reduced.
Then we understand the process of plating hard iron was outlawed in Europe and replaced with softer plastic piston coatings (Ferroprint) that could not resist the occasional piece of silicon breaking free from the cylinder bore - digging into the piston surface and rubbing up and down the cylinder wall (breaking more particles lose) and eventually scoring bores.
Because with Alusil - the silicon emerges out of solution in Aluminium (when it is over 13% of the total mix) it is evenly distributed and securely bonded and although some lose particles do break free – they only do so after a long period of time and use (and then in small numbers and sizes). Alusil therefore provides a better sliding surface than Lokasil proved to be (in which uneven larger silicon distribution and less secure bonding allowed more silicon particles to come lose earlier) but makes a more expensive block to machine but a much stiffer and stronger one.
You may also have seen that we originally tested numerous different piston coatings (to try and find one good enough to last in Lokasil) and this included a new electroplated metallic coating by Mahle Motorsport (Ferrotec which we understand had stainless steel particles plated up to 2 microns thick – 0.02mm or 8 tenths of a thou thick) – that while much better than Plastic still didn't last as long as the original ferrous coated pistons did in Lokasil. Meanwhile some specialist piston manufacturers announced that the plastic coatings they use for Nikasil and ferrous liners would not work in Alusil or Lokasil.
Fortunately the more expensive electroplated Nikasil surface we have always use exhibits no such problem and can even run perfectly without any piston coating – so neither we (nor all the post early air cooled 911's, Gen 1 GT3 and turbos that also used Nikasil) experience bore scoring.
Faced with this problem Porsche returned to using Alusil in the new Gen 2 models but we think using the newer Ferrotec piston surface (we had already tested) that we thought might not be as hard as the original ferrous Ferrostan coating but might just be good enough to run reliably in the more long lasting Alusil blocks. Believing however that the less hard piston surface might still eventually wear off and cause a smaller bore scoring problem - and with time to develop a solution (and despite flack for daring to mention it) - we created typical Hartech Aerospace Alloy Nikasil Plated replacement liners for the Gen 2 engines (at our cost and risk) and embarked on a test program – just in case it became needed one day and meanwhile built a 4.0 litre version to fit in with our oversized engine replacement program.
The only bore scoring problem brought to our attention then was 5 engines where some cylinders in had suffered slightly from age related stress relieving and had shrunk inwards at the bottom of the cylinders (in the direction of piston thrust) reducing the piston clearance to almost zero and promoting full piston seizing on both sides. Obviously this was most likely to occur if the piston expanded quicker than the cylinder and therefore on cold days with spirited driving too soon after start-up. However we were concerned when stories of Gen 2 bore scoring started to emerge in Countries with warmer climates – wondering if there was a second failure mode to consider.
We have recently bought an engine (unfortunately no record of mileage or history) that had bore scoring and on inspecting of the as yet un-scored pistons, we found visually that the machining grooves usually in the surface (to retain oil) appeared to have worn off and become smooth while the colour had also changed in those areas and some typical scoring marks had emerged similar to Lokasil run pistons where silicon particles had grooved the surface (will try and post some photos soon).
On measuring these pistons the visually worn areas were about 0.05mm (or 2 thou) smaller than a standard piston (or 0.025mm or 1 thou thick radially) - the same thickness we understand the piston plating is – confirming the accepted view that Alusil requires a hard coated piston and showing that there is clearly a problem if the plating eventually wears off similar to the old Lokasil Gen 1 bore scoring (and extremely high mileage or highly tuned 944's and 968's).
I will try and take another picture and post soon to show this clearly revealing the machining lines that are worn off where the shiny area is and the torn area typical of Gen 1 Lokasil bore scoring.
Our conclusion from this is that there may be 2 failure modes (both rare) but that as time goes by and mileages increase – those engines that have been driven hard (and why not!) for most of their life (so that the piston loads are higher and piston surface wear rates accelerated) may eventually reach a mileage at which they wear away the new type of piston coating and score bores as before.
We don't know how many this may affect nor how high a mileage this engine has covered and assume that cars driven like the majority - will last a very long and perfectly acceptable time and be problem free. But as age ramps mileages up and some owners apply more aggressive driving styles we expect that it will eventually become a necessity to repair them for bore scoring in very small numbers.
Before all the hysterics about scare mongering etc please understand this is an information source and that we are just providing the evidence we have accumulated, our interpretation of it and in so doing – inviting more evidence to be posted from which we may all get a better understanding of the situation.
Baz
You may remember that ALUSIL was used on the 924S, 944 and 968 models but had to be used in conjunction with a hard iron coated pistons (Ferrostan) that then often lasted for over 250K and was about 0.013mm (or half a thou) thick .
To get away from the hard silicon particles being distributed all over the Alusil block (making it expensive to machine) Porsche introduced LOKASIL (short for Local Silicon) in which the hard silicon particles only existed near the cylinder sliding surface (making the rest of the cylinder block quicker and therefore cheaper to produce) and while they were built in conjunction with the same hard iron plated piston surface as before – they didn't suffer bore scoring (2.5 Boxster to 3.4 litre 996) – only 'D" chunking when the bores were increased in diameter and the wall thicknesses reduced.
Then we understand the process of plating hard iron was outlawed in Europe and replaced with softer plastic piston coatings (Ferroprint) that could not resist the occasional piece of silicon breaking free from the cylinder bore - digging into the piston surface and rubbing up and down the cylinder wall (breaking more particles lose) and eventually scoring bores.
Because with Alusil - the silicon emerges out of solution in Aluminium (when it is over 13% of the total mix) it is evenly distributed and securely bonded and although some lose particles do break free – they only do so after a long period of time and use (and then in small numbers and sizes). Alusil therefore provides a better sliding surface than Lokasil proved to be (in which uneven larger silicon distribution and less secure bonding allowed more silicon particles to come lose earlier) but makes a more expensive block to machine but a much stiffer and stronger one.
You may also have seen that we originally tested numerous different piston coatings (to try and find one good enough to last in Lokasil) and this included a new electroplated metallic coating by Mahle Motorsport (Ferrotec which we understand had stainless steel particles plated up to 2 microns thick – 0.02mm or 8 tenths of a thou thick) – that while much better than Plastic still didn't last as long as the original ferrous coated pistons did in Lokasil. Meanwhile some specialist piston manufacturers announced that the plastic coatings they use for Nikasil and ferrous liners would not work in Alusil or Lokasil.
Fortunately the more expensive electroplated Nikasil surface we have always use exhibits no such problem and can even run perfectly without any piston coating – so neither we (nor all the post early air cooled 911's, Gen 1 GT3 and turbos that also used Nikasil) experience bore scoring.
Faced with this problem Porsche returned to using Alusil in the new Gen 2 models but we think using the newer Ferrotec piston surface (we had already tested) that we thought might not be as hard as the original ferrous Ferrostan coating but might just be good enough to run reliably in the more long lasting Alusil blocks. Believing however that the less hard piston surface might still eventually wear off and cause a smaller bore scoring problem - and with time to develop a solution (and despite flack for daring to mention it) - we created typical Hartech Aerospace Alloy Nikasil Plated replacement liners for the Gen 2 engines (at our cost and risk) and embarked on a test program – just in case it became needed one day and meanwhile built a 4.0 litre version to fit in with our oversized engine replacement program.
The only bore scoring problem brought to our attention then was 5 engines where some cylinders in had suffered slightly from age related stress relieving and had shrunk inwards at the bottom of the cylinders (in the direction of piston thrust) reducing the piston clearance to almost zero and promoting full piston seizing on both sides. Obviously this was most likely to occur if the piston expanded quicker than the cylinder and therefore on cold days with spirited driving too soon after start-up. However we were concerned when stories of Gen 2 bore scoring started to emerge in Countries with warmer climates – wondering if there was a second failure mode to consider.
We have recently bought an engine (unfortunately no record of mileage or history) that had bore scoring and on inspecting of the as yet un-scored pistons, we found visually that the machining grooves usually in the surface (to retain oil) appeared to have worn off and become smooth while the colour had also changed in those areas and some typical scoring marks had emerged similar to Lokasil run pistons where silicon particles had grooved the surface (will try and post some photos soon).
On measuring these pistons the visually worn areas were about 0.05mm (or 2 thou) smaller than a standard piston (or 0.025mm or 1 thou thick radially) - the same thickness we understand the piston plating is – confirming the accepted view that Alusil requires a hard coated piston and showing that there is clearly a problem if the plating eventually wears off similar to the old Lokasil Gen 1 bore scoring (and extremely high mileage or highly tuned 944's and 968's).
I will try and take another picture and post soon to show this clearly revealing the machining lines that are worn off where the shiny area is and the torn area typical of Gen 1 Lokasil bore scoring.
Our conclusion from this is that there may be 2 failure modes (both rare) but that as time goes by and mileages increase – those engines that have been driven hard (and why not!) for most of their life (so that the piston loads are higher and piston surface wear rates accelerated) may eventually reach a mileage at which they wear away the new type of piston coating and score bores as before.
We don't know how many this may affect nor how high a mileage this engine has covered and assume that cars driven like the majority - will last a very long and perfectly acceptable time and be problem free. But as age ramps mileages up and some owners apply more aggressive driving styles we expect that it will eventually become a necessity to repair them for bore scoring in very small numbers.
Before all the hysterics about scare mongering etc please understand this is an information source and that we are just providing the evidence we have accumulated, our interpretation of it and in so doing – inviting more evidence to be posted from which we may all get a better understanding of the situation.
Baz
Porkaholic
Nurburgring
- Joined
- 11 Jan 2009
- Messages
- 452
Big thanks of relief to Mr Baz for clarifying in impressive detail but simple enough for people like me to understand :?:
I'll use this information to continue to drive my 997.2 with a degree of mechanical sympathy namely warming up, not racing a cold engine, annual oil and filter changes. And while it is still relatively low on mileage sleep at night
knowing that on law of averages bore scoring could well prove to be a non event but be aware that anything is possible, no guarantees. I got away with it for 60,000 plus miles on my 997.1 so I'm reasonably optimistic with my low miler 997.2. :thumb: whatever happens still cheaper than running an Aston or Lambo!
Now I've got a manual box on my 4S do I need to worry about this Phil?
I'll use this information to continue to drive my 997.2 with a degree of mechanical sympathy namely warming up, not racing a cold engine, annual oil and filter changes. And while it is still relatively low on mileage sleep at night
knowing that on law of averages bore scoring could well prove to be a non event but be aware that anything is possible, no guarantees. I got away with it for 60,000 plus miles on my 997.1 so I'm reasonably optimistic with my low miler 997.2. :thumb: whatever happens still cheaper than running an Aston or Lambo!
Now I've got a manual box on my 4S do I need to worry about this Phil?
medmick said:
And so did I mate for many years until James started out on his own doing mobile Porsche services and stuff. I have no reason to think its their fault or blame them, its just an in hindsight mistake for using unbranded cheap aftermarket parts from the Far East , eventually we will learn in the UK to buy things and buy them once, but to do that we need to stop buying Chinese goods.
bazhart
Barcelona
- Joined
- 20 May 2009
- Messages
- 1,343
Can I just add (without invoking another tiresome response about oils) that I know that the silicon particles remain well bedded in (with Alusil) until the oil basically washes back the aluminium substrate after which some gradually become lose.
IMHO using a thicker oil as the mileage increases helps create a slightly thicker space between the piston and the cylinder bore under load that in turn helps the silicon to escape before damaging the pistons.
Also we have not yet seen piston coating wear or bore scoring on the 3.6 only 3,8's.
Once a piston is properly scored it is difficult to measure or analyse the wear so it may be some time before we get a clearer picture of what's going on.
Baz
IMHO using a thicker oil as the mileage increases helps create a slightly thicker space between the piston and the cylinder bore under load that in turn helps the silicon to escape before damaging the pistons.
Also we have not yet seen piston coating wear or bore scoring on the 3.6 only 3,8's.
Once a piston is properly scored it is difficult to measure or analyse the wear so it may be some time before we get a clearer picture of what's going on.
Baz
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