997.2 3.8 Engine Failure
02-17-2019, 09:52 PM
#466
Three Wheelin'
A lot of motor oil now carry the new API rating of SN-PLUS which is recommended for DI engines. Just about all major brands has changed their detergent formulas due to engine manufacturers' recommendation.
02-18-2019, 12:09 AM
#467
02-18-2019, 12:45 AM
#468
Three Wheelin'
Do a google and they all mentioned that they are changing over and the labelling might not reflect that until their production on bottling catches up with the new labels. However, the ingredients (detergent) are already within the new spec on the shelves in the stores although some minus the rating label.
02-19-2019, 02:05 AM
#470
Advanced
(2) Nikasil is not like Alusil or Lokasil both of which require a hard coating on the piston to survive long term.
Alusil can get away with a less hard coating than Lokasil but still needs one because although the silicon particles are smaller and better distributed they still come loose and can impinge on the piston coating. When this happens, because the base matrix is still aluminium the damage usually results in a deep score or leads to lots of deep scores when the parts dig deep into the aluminium surface.
Nikasil forms a complete thin skin strongly bonded to the aluminium and a smooth but oleophilic surface that does not need any piston coating to survive (although a plastic coating can make lifespan even better).
Baz
Alusil can get away with a less hard coating than Lokasil but still needs one because although the silicon particles are smaller and better distributed they still come loose and can impinge on the piston coating. When this happens, because the base matrix is still aluminium the damage usually results in a deep score or leads to lots of deep scores when the parts dig deep into the aluminium surface.
Nikasil forms a complete thin skin strongly bonded to the aluminium and a smooth but oleophilic surface that does not need any piston coating to survive (although a plastic coating can make lifespan even better).
Baz
"The nickel solution can then be electroplated onto the aluminium cylinder bore. The piston rings will then rub off the exposed nickel, leaving a very hard layer of silicon carbide to protect the aluminium piston from direct contact with the aluminium cylinder. "
If the "piston rings can rub off the exposed nickel" then your newly Nickel plated sleeve in the old block more or less resulting very similar to the original Alusil block. As the result silicon can still come loose, albeit less. Would you think BOTH methods should have coating on the piston?
02-19-2019, 05:48 AM
#471
Hi rmstar, I think you may have misunderstood that explanation.
Alusil is made by molten aluminium in which there is more than 13% silicon. Aluminium can absorb silicon until its saturation point after which nodules of silicon grow together to create a very evenly mixed distribution of hard nodules solidly locked into the matrix.
On machining the bore you end up with aluminium with silicon and by exposing the surface (after honing) you end up with lots of small peaks of silicon and at a microscopically lower level aluminium.
Because of the hard silicon pistons must have a hard coating to avoid being scratched by those peaks while the "valleys" hold oil. The 924S, 944 and 968 models were made of this and generally lasted for over 200K without cylinder problems.
It is a good process but the rest of the casting also has that silicon making it hard and expensive to machine (although the hard areas supporting main bearing shells are a bonus). It is usually gravity or low pressure cast with sand cores.
Lokasil was made by creating a pre-formed tube in which larger silicon particles were suspended in a porous matrix and fitted into the metal casting mould. The molten aluminium was then cast under huge pressures so that it permeated the pre-form, burning off the components holding the silicon particles in suspension and allowing the aluminium to flow around the particles and set them in place.
In our experience it leads to some uneven distribution (we have found areas where oil sloshing around has eroded the aluminium and silicon away completely for over 1mm deep and other areas where on boring or honing it is clear some areas are more silicon rich than others. The advantage is the rest of the block is easy to machine. The disadvantage is that to use metal moulds (to withstand the casting pressures) the cylinders ended up not being supported at the top or bottom (allowing them to flex and crack in early models). The silicon particles seem less well bonded into the aluminium matrix than Alusil.
Many years ago in our discussions with the manufacturers they confirmed that Lokasil will only work with a hard iron coated piston. We understand this is to withstand the wear caused by silicon particles that get exposed or break free and rub up and down the bores before being washed away.
All early engines from the 2.5 Boxster up to most 3.4 996's had hard iron coated pistons and didn't score bores. The larger engines after the 3.2 Boxster S had thinner cylinder walls (in fact the 3.4 was the same casting as the 3.2 but bored out an extra 3mm). This made the 3.4 weaker and the pressures from the piston loads gradually stretched the cylinders oval until they cracked.
The last 3.4 996's. 34 Cayman S's, 3.6'3 and 3.8's had larger silicon particles to make the cylinders stiffer and to slow down the creep to ovality and cracking. However - unfortunately they also had to change the piston coating to a plastic coating that was less hard and the combination of larger less well bonded particles breaking free and a softer piston coating allowed the silicon to impinge on the aluminium piston face and rub the silicon particles into it and against the cylinder wall and in the process knocked out more silicon particles to join in the damage and result in cylinder and piston scoring.
Nikasil provides a Nickel matrix embedded with silicon. On honing the surface is smooth and has to be honed to an exact pattern and depth (Ra typically 0.2 to 0.3) On running some Nickel is at a microscopically lower level than the silicon peaks but it is still all there and for a depth of around 0.1mm. The plated surface is therefore a well bonded sleeve of Nickel and silicon in which the surface only has been honed (creating oil retention areas) and the silicon is microscopically exposed. But underneath and still bonded to it is layers of Nickel and silicon forming a hard substrate.
Because Nikasil is such a brilliant material you don't need any piston coating and it hardly ever wears out. It is also oleophilic (retains oil at the surface). Most air cooled 911's had a Nikasil bore, as did 996/7 GT3's and Turbo's - none suffering bore scoring.
So despite concerns often raised by others attributing bore scoring to a variety of issues (which are issues - including variability in design and quality, fuels, road/stroke ratios, piston off-set, piston coatings, fuel injectors and the environment) and despite there being some temperature issues - we have rebuilt hundreds of engines by replacing the bore with a wet aerospace aluminium, ribbed, closed deck Nikasil plated liner - that have run perfectly reliably for tens of thousands of miles (as recent example being one that failed at 50K but has since covered over 100K more after our rebuild) and perfect racing reliability in the UK for the last few years winning the major Porsche championships.
So - WHAT DOES THIS TELL US? If we can replace the Lokasil bore with our Nikasil plated closed deck liners and they are perfectly reliable despite not changing any of the issues others may raise as causes - surely it means to anyone able to link cause and effect - that the cause of scoring is the Lokasil bore process. If it were any of the other issues then failures would surely still occur? Furthermore if our solution has over more than a decade replaced thousands of these liners/cylinders with perfect reliability - how can anything else be the principle cause of bore scoring than the bore surface we have replaced?
Gen 2 9A1 engines are a different subject and a different cause/problem (and the 2 should not be confused or combined in understanding bore scoring). For the most part it looks like gen 2 problems are seizures on both sides of the pistons and not scoring on one side - but can also be repaired by the same type of replacement Nikasil cylinder.
Baz
Alusil is made by molten aluminium in which there is more than 13% silicon. Aluminium can absorb silicon until its saturation point after which nodules of silicon grow together to create a very evenly mixed distribution of hard nodules solidly locked into the matrix.
On machining the bore you end up with aluminium with silicon and by exposing the surface (after honing) you end up with lots of small peaks of silicon and at a microscopically lower level aluminium.
Because of the hard silicon pistons must have a hard coating to avoid being scratched by those peaks while the "valleys" hold oil. The 924S, 944 and 968 models were made of this and generally lasted for over 200K without cylinder problems.
It is a good process but the rest of the casting also has that silicon making it hard and expensive to machine (although the hard areas supporting main bearing shells are a bonus). It is usually gravity or low pressure cast with sand cores.
Lokasil was made by creating a pre-formed tube in which larger silicon particles were suspended in a porous matrix and fitted into the metal casting mould. The molten aluminium was then cast under huge pressures so that it permeated the pre-form, burning off the components holding the silicon particles in suspension and allowing the aluminium to flow around the particles and set them in place.
In our experience it leads to some uneven distribution (we have found areas where oil sloshing around has eroded the aluminium and silicon away completely for over 1mm deep and other areas where on boring or honing it is clear some areas are more silicon rich than others. The advantage is the rest of the block is easy to machine. The disadvantage is that to use metal moulds (to withstand the casting pressures) the cylinders ended up not being supported at the top or bottom (allowing them to flex and crack in early models). The silicon particles seem less well bonded into the aluminium matrix than Alusil.
Many years ago in our discussions with the manufacturers they confirmed that Lokasil will only work with a hard iron coated piston. We understand this is to withstand the wear caused by silicon particles that get exposed or break free and rub up and down the bores before being washed away.
All early engines from the 2.5 Boxster up to most 3.4 996's had hard iron coated pistons and didn't score bores. The larger engines after the 3.2 Boxster S had thinner cylinder walls (in fact the 3.4 was the same casting as the 3.2 but bored out an extra 3mm). This made the 3.4 weaker and the pressures from the piston loads gradually stretched the cylinders oval until they cracked.
The last 3.4 996's. 34 Cayman S's, 3.6'3 and 3.8's had larger silicon particles to make the cylinders stiffer and to slow down the creep to ovality and cracking. However - unfortunately they also had to change the piston coating to a plastic coating that was less hard and the combination of larger less well bonded particles breaking free and a softer piston coating allowed the silicon to impinge on the aluminium piston face and rub the silicon particles into it and against the cylinder wall and in the process knocked out more silicon particles to join in the damage and result in cylinder and piston scoring.
Nikasil provides a Nickel matrix embedded with silicon. On honing the surface is smooth and has to be honed to an exact pattern and depth (Ra typically 0.2 to 0.3) On running some Nickel is at a microscopically lower level than the silicon peaks but it is still all there and for a depth of around 0.1mm. The plated surface is therefore a well bonded sleeve of Nickel and silicon in which the surface only has been honed (creating oil retention areas) and the silicon is microscopically exposed. But underneath and still bonded to it is layers of Nickel and silicon forming a hard substrate.
Because Nikasil is such a brilliant material you don't need any piston coating and it hardly ever wears out. It is also oleophilic (retains oil at the surface). Most air cooled 911's had a Nikasil bore, as did 996/7 GT3's and Turbo's - none suffering bore scoring.
So despite concerns often raised by others attributing bore scoring to a variety of issues (which are issues - including variability in design and quality, fuels, road/stroke ratios, piston off-set, piston coatings, fuel injectors and the environment) and despite there being some temperature issues - we have rebuilt hundreds of engines by replacing the bore with a wet aerospace aluminium, ribbed, closed deck Nikasil plated liner - that have run perfectly reliably for tens of thousands of miles (as recent example being one that failed at 50K but has since covered over 100K more after our rebuild) and perfect racing reliability in the UK for the last few years winning the major Porsche championships.
So - WHAT DOES THIS TELL US? If we can replace the Lokasil bore with our Nikasil plated closed deck liners and they are perfectly reliable despite not changing any of the issues others may raise as causes - surely it means to anyone able to link cause and effect - that the cause of scoring is the Lokasil bore process. If it were any of the other issues then failures would surely still occur? Furthermore if our solution has over more than a decade replaced thousands of these liners/cylinders with perfect reliability - how can anything else be the principle cause of bore scoring than the bore surface we have replaced?
Gen 2 9A1 engines are a different subject and a different cause/problem (and the 2 should not be confused or combined in understanding bore scoring). For the most part it looks like gen 2 problems are seizures on both sides of the pistons and not scoring on one side - but can also be repaired by the same type of replacement Nikasil cylinder.
Baz
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Wayne Smith (11-22-2023)
02-19-2019, 10:41 AM
#472
RL Community Team
Rennlist Member
Rennlist Member
Thanx Baz..... but it appears the 9A1 failures you are seeing in the UK... seizures... are different than here in the US which are classic scoring and clacking. No?
Edit: sorry Baz... I didn't see your post on this here: https://rennlist.com/forums/997-foru...l#post15649143
Peace
Bruce in Philly
Edit: sorry Baz... I didn't see your post on this here: https://rennlist.com/forums/997-foru...l#post15649143
Peace
Bruce in Philly
02-19-2019, 11:26 AM
#473
That's OK Bruce and I have sent a more detailed reply to the video 2 post. The pictures of the Gen 2 scoring look very like our seizing over here and at the same position in the bore etc so it would be interesting to know the outcome of measuring the remains of the bores and adjacent ores accurately.
Baz
Baz
02-19-2019, 08:47 PM
#474
So I should be using DI40 with my 997.2 at 10 years old and 28,000 miles. I’m taking mine in for service and not sure if my guy has this oil. Owned since new and in So California. I’d rather do the correct thing than not but have been using Mobil 1 since new.
02-19-2019, 11:11 PM
#475
Advanced
Hello Baz,
I read your riveting argument on Nikasil liners vs steel liners for Porsche on another forum, very well written. You also amazed me with your in depth and precise technical explanation of this 9A1 that I feel you should be in technical college lecture room. I learned a lot from the last few days. Thanks again for taking your time to answer.
All the Best.
Frances
I read your riveting argument on Nikasil liners vs steel liners for Porsche on another forum, very well written. You also amazed me with your in depth and precise technical explanation of this 9A1 that I feel you should be in technical college lecture room. I learned a lot from the last few days. Thanks again for taking your time to answer.
All the Best.
Frances
02-20-2019, 10:45 AM
#476
rmstar thanks for the vote of confidence but I do think that Jake is a natural (and he seems to really enjoy it) so I think he has that all tied up and is very good at his presentation and I seem to get too busy immersed in technical stuff (which I prefer) to find the time to make such excellent video's.
It took us years to work out all the contributing factors that cause problems with these designs of engines since 1998 and to design, manufacture and test solutions before bringing them to the market. I keep thinking that a new model will be OK and then something else crops up that needs my attention (while I am trying to semi-retire).
We were lucky that I used to make alloy Nikasil cylinders for racing 2 strokes all of 45 years ago - so I already understood a lot about it when the first engines cracked the cylinders. They didn't score bores because the pistons had a very hard iron coating that resisted the silicon particle wear.
Because something had to replace the broken "D" chunked piece we developed thicker alloy Nikasil cylinders and they worked perfectly. When we noticed that only about 10% of the coolant was flowing through the cylinder block fitted temperature sensors into the cylinder block and found that there was a temperature rise that accounted for the scoring on bank 2 so modified the flow and fitted a lower temp thermostat.
When the later engines started to score bores we had some oversized pistons made intending to bore and hone out the original scored area but it only exposed the problems with Lokasil so instead we fitted a version of the same successful cylinders we had already made and used for "D" chunking and they have been very reliable.
Of course we do many other things and make racing accessories etc but the basic repair for the bore scoring has been well proven for many years and still goes from strength to strength.
Jake may well be right that the public nowadays need video portrayal of technical matters to have enough patience to follow it through and although I am used to writing I guess we should think about how to do the same following his excellent lead. I am not sure who we could get to do the narrative though as I am getting so old I would probably scare most people! (LOL)
I fear however that it might throw up differences that result in disagreements all over again - I hope not anyway.
Baz
It took us years to work out all the contributing factors that cause problems with these designs of engines since 1998 and to design, manufacture and test solutions before bringing them to the market. I keep thinking that a new model will be OK and then something else crops up that needs my attention (while I am trying to semi-retire).
We were lucky that I used to make alloy Nikasil cylinders for racing 2 strokes all of 45 years ago - so I already understood a lot about it when the first engines cracked the cylinders. They didn't score bores because the pistons had a very hard iron coating that resisted the silicon particle wear.
Because something had to replace the broken "D" chunked piece we developed thicker alloy Nikasil cylinders and they worked perfectly. When we noticed that only about 10% of the coolant was flowing through the cylinder block fitted temperature sensors into the cylinder block and found that there was a temperature rise that accounted for the scoring on bank 2 so modified the flow and fitted a lower temp thermostat.
When the later engines started to score bores we had some oversized pistons made intending to bore and hone out the original scored area but it only exposed the problems with Lokasil so instead we fitted a version of the same successful cylinders we had already made and used for "D" chunking and they have been very reliable.
Of course we do many other things and make racing accessories etc but the basic repair for the bore scoring has been well proven for many years and still goes from strength to strength.
Jake may well be right that the public nowadays need video portrayal of technical matters to have enough patience to follow it through and although I am used to writing I guess we should think about how to do the same following his excellent lead. I am not sure who we could get to do the narrative though as I am getting so old I would probably scare most people! (LOL)
I fear however that it might throw up differences that result in disagreements all over again - I hope not anyway.
Baz
02-20-2019, 02:59 PM
#477
I think the summary for the 997.2 is that oil doesn't really matter regarding scoring. Either going to happen or not. Letting engine warm up before driving aggressive maybe helps to allow for equal metal expansion but if it's a block/cylinder anomaly from manufacturing like Baz explained then won't matter. Regarding LSPI resulting in rod bearing wear then yes DI40 probably helpful.
02-20-2019, 10:00 PM
#479
Rennlist Member
Lokasil bores-yes except GTx and Turbo
Forged pistons
Modern Fuels-yes
Rod to stroke ratio
Pistons rocking in the bore
Piston offset
Emissions standards-yes and I would think even more strict for .2 generation
Injectors- .2 has direct injection so are these more reliable or have they just not had enough time to fail yet?
Maybe these are topics for future videos so I apologize if I'm jumping the gun. Thanks again and keep them coming.
02-20-2019, 10:22 PM
#480
Advanced
and I seem to get too busy immersed in technical stuff (which I prefer)
to find the time to make such excellent video's.
Jake may well be right that the public nowadays need video portrayal of technical matters to have enough patience to follow it through and although I am used to writing I guess we should think about how to do the same following his excellent lead. I am not sure who we could get to do the narrative though as I am getting so old I would probably scare most people! (LOL) Baz
This is also feed back for Jake's video. It's already very good for general audience but I think you could kick it up a notch.
Try to include a White/Black board and/or some animation on top of your real sample. As you can see in the Engineering Explained guy`s comment section, people love it.
For anyone who still have kids going school, just ask them about Khan Academy and they can tell you why.
https://www.khanacademy.org/
Ps. We had huge disagreement of White vs Black board choices when I was in a committee to design lecture room for our university. Mathematician/Physicist/Chemist (Black board) vs Comp Science/Biologist/Art (White board). However, both sides agreed that we need one or other!
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Lanre Soetan (07-13-2019)