Bore Scoring Flat 6 Video Part #2
02-18-2019, 12:34 PM
#1
Three Wheelin'
Thread Starter
Bore Scoring Flat 6 Video Part #2
02-18-2019, 01:04 PM
#2
Former Vendor
02-18-2019, 04:35 PM
#4
02-18-2019, 04:47 PM
#5
RL Community Team
Rennlist Member
Rennlist Member
Very interesting... thanx!
Jake and Baz have seen different failure modes for the 9A1...... UK sees seizures and sees narrowed block/sleeves, USA sees the clanking, oil burning bore damage. Why the difference?
Peace
Bruce in Philly
Jake and Baz have seen different failure modes for the 9A1...... UK sees seizures and sees narrowed block/sleeves, USA sees the clanking, oil burning bore damage. Why the difference?
Peace
Bruce in Philly
02-18-2019, 06:05 PM
#7
Thanks for posting. Very informative! I am a little confused on the injector piece Jake was talking about. I understood about bad injectors but he lost me when he talked about starting the car when its warm. Was he saying its better for the car to cool down before you restart? For example, say the car is at operating temp and the driver on a manual has a habit of stalling the car a lot which leaves fuel in the cylinders. The driver then starts it again and goes on down the road. But this driver does this a lot...was Jake saying this could be one piece of the equation?
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02-18-2019, 08:34 PM
#8
Thanks for posting. Very informative! I am a little confused on the injector piece Jake was talking about. I understood about bad injectors but he lost me when he talked about starting the car when its warm. Was he saying its better for the car to cool down before you restart? For example, say the car is at operating temp and the driver on a manual has a habit of stalling the car a lot which leaves fuel in the cylinders. The driver then starts it again and goes on down the road. But this driver does this a lot...was Jake saying this could be one piece of the equation?
02-18-2019, 08:41 PM
#9
Originally Posted by Wayne Smith
I believe the intent was to explain a way to see that your injectors may be failing (leaking), and if they are failing this could lead to leaked fuel sitting in your cylinders that could then cause damage since it would negate lubrication.
Short story, don't let the car sit and idle for 10 min. It allows the car to idle too rich for too long. It's not good for the engine.
Cw
02-19-2019, 10:07 AM
#11
Bruce, this is a difficult situation for me because I respect everything that Jake does and think the time he has spent making these videos is a credit to him. He no doubt rebuilds great engines and his contribution to general knowledge is exceptional and I really don’t want to take issue with him when we are both doing a great job in our own Countries for our own customers.
I understood that this started to discuss 9A1 Gen 2 engines but the content of video 2 seems to be entirely M96/7 Gen 1 engines and the prognosis is quite different.
Video 2 contains information that is generally right and correct and if you are rebuilding an engine then changing as many parts for new ones (as you can persuade the customer to fit) will not make the engine any worse and could make a future failure less likely - so is always beneficial if the customer can afford it.
Just discussing the 996/7 Gen 1 engines - there may indeed also be a different perception of what to do when rebuilding an engine (or indeed financial resources) between typical customers in the USA and GB with American customer possibly able to afford a different approach to UK ones or benefit from different techniques to convey the issues. it may also be the case that general knowledge of engine based issues is different in our 2 Countries?
We have also been slow at using the modern medium of film to explain what we originally wrote and posted on our web site buyers guide stage 4 about these engines at the start of the millennium (although it is still a very long read on our internet site and identifies causes and contributory factors that are still right today). Our only up to date efforts have been the 2 videos on our web site.
However although I cannot disagree that there are factory design and manufacturing variables, that Lokasil was a failed experiment, that fuels influence performance, that the rod stroke ratio is 3% off perfection in the larger engines, that temperatures influence reliability, that fuel injectors might be faulty and that environmental factors can influence it all - the odd thing is that because we have designed what I still think is the best possible solution (by machining out the whole original cylinder and replacing it with a whole aerospace alloy Nikasil plated aluminium cylinder with ribbed exterior) and by making small adjustments to the coolant flow while we machine the crankcases - we have rebuilt hundreds of engines and fitted thousands of liners without any other changes and achieved 100% outcomes for tens of thousand of miles and obtained a fantastic reputation as a result.
I say this is odd because we have placed the failures of bore scoring soundly at the foot of the performance of Lokasil and the change to plastic coated pistons.
Nikasil will run perfectly with coated or uncoated pistons and so I reach a difficult position to compare what we have experienced in the UK and what seems to be the case over there in the USA.
When we rebuild engines we do of course change bearings, rings etc. We may re-use good used or new or re-coated pistons, we fit our Nikasil plated cylinders but we make no changes to most of the issues raised in the video but obtain superb reliability and no problems.
Apart from the usual bearings and gaskets the only thing we have really changed from the original specification is the Lokasil bore material and the stiffening support resulting from removing all the original cylinder material and closing the deck at the top with a precision machined and fitted top hat shoulder on the new cylinder.
If just doing this renders the engines exceptionally reliable thereafter (even winning racing events) I can only conclude that despite all the other issues mentioned in the video being valid criticisms of the engine design and general idealistic changes during a rebuild - that it was the Lokasil material, the open deck design and the plastic piston coating (being unsuitable for Lokasil) that causes bore scoring, because when we fit our cylinders (and stabilise the support) while using everything else original – they work perfectly well afterwards once again.
Now the 9A1 Gen 2 engine is different because it is a superb general design and much better than it's predecessors. Although Alusil also requires a hard piston coating (and despite the fact that the Gen 2 piston coating does not appear quite as hard as the original Alusil hard iron coating that was banned in Europe) the piston profile changes that increased the support area seem to have rendered the engines extremely reliable.
I can only comment on the ones we have had here for repair. The ones that have what others call “bore scoring” (which occurs on one side of a piston and if in Lokasil usually because the hard silicon content has flowed off the surface and impinged on the piston to scrub up and down the cylinder bore causing scores on one side only) the Gen 2 engines we have here have all seized on both sides of the piston and at the lower level in the cylinder than usual.
All these crankcases have cylinders that have shrunk inwards where the thick section is at the bottom of the cylinder that holds the main bearings. This is not present in Gen 1 engines because the crankshaft is fitted in a cassette and the bottom of the cylinders are open deck. When they shrink it is also where the piston is manufactured more oval but not in the centre (where you would expect it) and the clearances have reduced to fractions of what they should be. In each case the part of the seized bore we can measure shows shrinkage and the adjacent un-seized cylinder shows half that shrinkage while the furthest away shows no shrinkage.
It may only be 5 engines so far but they are all the same (and look remarkably similar to the ones in the photos in this post). It therefore seems reasonable to conclude that this caused the seizures during warm up when the piston expanded quicker than the cylinder and cold seized. As age related stress relieving is a well known phenomenon in alloy castings (especially with large section changes) and because the large main bearing carrying area would inevitably cool slower in the centre than the cylinders, it is not unreasonable to imagine a cast in stress trying to pull the section towards the centre and if it did so it would distort the bottom of the cylinders exactly as we have measured. this would take many heat cool cycles to materialise and therefore would only afflict older cars and those used more regularly. However I cannot claim that this is the cause and all I can do is apply what I see and measure with what I know and this explanation fits everything. As an experienced engineer I find the evidence compelling but I might very well be proven wrong as more evidence emerges.
That Jake and I might differ in our interpretation of causes is not unusual among engineers and does not necessarily mean only one of us can be right. It should not really be left to such small businesses to try and solve problems caused by a huge and profitable manufacturer that impact on owners expecting better from the reputation of their purchases and we need to try and stick together and not fall out with each other. As far as I can determine you have a good source of engine repair specialists over there with Jake and LN and we are similarly doing a good job over here and it would be a much happier situation if we happened to agree on this issue. I hope that in the fullness of time we will find more common ground but in the meantime – regardless of the differences in our present interpretation of the causes – we seem to be providing what our customers need and long may it continue.
Other Gen 2 repairs we have been involved in that have not seized did not exhibit that shrinkage so there may be other causes with this model and we do not yet have enough evidence to be sure.
Just for the record - I do not recommend leaving a car ticking over from cold - you should drive off as soon as you start it but not using full revs or throttle - but gradually driving it at higher revs and throttle opening as the temperatures increase.
Baz
I understood that this started to discuss 9A1 Gen 2 engines but the content of video 2 seems to be entirely M96/7 Gen 1 engines and the prognosis is quite different.
Video 2 contains information that is generally right and correct and if you are rebuilding an engine then changing as many parts for new ones (as you can persuade the customer to fit) will not make the engine any worse and could make a future failure less likely - so is always beneficial if the customer can afford it.
Just discussing the 996/7 Gen 1 engines - there may indeed also be a different perception of what to do when rebuilding an engine (or indeed financial resources) between typical customers in the USA and GB with American customer possibly able to afford a different approach to UK ones or benefit from different techniques to convey the issues. it may also be the case that general knowledge of engine based issues is different in our 2 Countries?
We have also been slow at using the modern medium of film to explain what we originally wrote and posted on our web site buyers guide stage 4 about these engines at the start of the millennium (although it is still a very long read on our internet site and identifies causes and contributory factors that are still right today). Our only up to date efforts have been the 2 videos on our web site.
However although I cannot disagree that there are factory design and manufacturing variables, that Lokasil was a failed experiment, that fuels influence performance, that the rod stroke ratio is 3% off perfection in the larger engines, that temperatures influence reliability, that fuel injectors might be faulty and that environmental factors can influence it all - the odd thing is that because we have designed what I still think is the best possible solution (by machining out the whole original cylinder and replacing it with a whole aerospace alloy Nikasil plated aluminium cylinder with ribbed exterior) and by making small adjustments to the coolant flow while we machine the crankcases - we have rebuilt hundreds of engines and fitted thousands of liners without any other changes and achieved 100% outcomes for tens of thousand of miles and obtained a fantastic reputation as a result.
I say this is odd because we have placed the failures of bore scoring soundly at the foot of the performance of Lokasil and the change to plastic coated pistons.
Nikasil will run perfectly with coated or uncoated pistons and so I reach a difficult position to compare what we have experienced in the UK and what seems to be the case over there in the USA.
When we rebuild engines we do of course change bearings, rings etc. We may re-use good used or new or re-coated pistons, we fit our Nikasil plated cylinders but we make no changes to most of the issues raised in the video but obtain superb reliability and no problems.
Apart from the usual bearings and gaskets the only thing we have really changed from the original specification is the Lokasil bore material and the stiffening support resulting from removing all the original cylinder material and closing the deck at the top with a precision machined and fitted top hat shoulder on the new cylinder.
If just doing this renders the engines exceptionally reliable thereafter (even winning racing events) I can only conclude that despite all the other issues mentioned in the video being valid criticisms of the engine design and general idealistic changes during a rebuild - that it was the Lokasil material, the open deck design and the plastic piston coating (being unsuitable for Lokasil) that causes bore scoring, because when we fit our cylinders (and stabilise the support) while using everything else original – they work perfectly well afterwards once again.
Now the 9A1 Gen 2 engine is different because it is a superb general design and much better than it's predecessors. Although Alusil also requires a hard piston coating (and despite the fact that the Gen 2 piston coating does not appear quite as hard as the original Alusil hard iron coating that was banned in Europe) the piston profile changes that increased the support area seem to have rendered the engines extremely reliable.
I can only comment on the ones we have had here for repair. The ones that have what others call “bore scoring” (which occurs on one side of a piston and if in Lokasil usually because the hard silicon content has flowed off the surface and impinged on the piston to scrub up and down the cylinder bore causing scores on one side only) the Gen 2 engines we have here have all seized on both sides of the piston and at the lower level in the cylinder than usual.
All these crankcases have cylinders that have shrunk inwards where the thick section is at the bottom of the cylinder that holds the main bearings. This is not present in Gen 1 engines because the crankshaft is fitted in a cassette and the bottom of the cylinders are open deck. When they shrink it is also where the piston is manufactured more oval but not in the centre (where you would expect it) and the clearances have reduced to fractions of what they should be. In each case the part of the seized bore we can measure shows shrinkage and the adjacent un-seized cylinder shows half that shrinkage while the furthest away shows no shrinkage.
It may only be 5 engines so far but they are all the same (and look remarkably similar to the ones in the photos in this post). It therefore seems reasonable to conclude that this caused the seizures during warm up when the piston expanded quicker than the cylinder and cold seized. As age related stress relieving is a well known phenomenon in alloy castings (especially with large section changes) and because the large main bearing carrying area would inevitably cool slower in the centre than the cylinders, it is not unreasonable to imagine a cast in stress trying to pull the section towards the centre and if it did so it would distort the bottom of the cylinders exactly as we have measured. this would take many heat cool cycles to materialise and therefore would only afflict older cars and those used more regularly. However I cannot claim that this is the cause and all I can do is apply what I see and measure with what I know and this explanation fits everything. As an experienced engineer I find the evidence compelling but I might very well be proven wrong as more evidence emerges.
That Jake and I might differ in our interpretation of causes is not unusual among engineers and does not necessarily mean only one of us can be right. It should not really be left to such small businesses to try and solve problems caused by a huge and profitable manufacturer that impact on owners expecting better from the reputation of their purchases and we need to try and stick together and not fall out with each other. As far as I can determine you have a good source of engine repair specialists over there with Jake and LN and we are similarly doing a good job over here and it would be a much happier situation if we happened to agree on this issue. I hope that in the fullness of time we will find more common ground but in the meantime – regardless of the differences in our present interpretation of the causes – we seem to be providing what our customers need and long may it continue.
Other Gen 2 repairs we have been involved in that have not seized did not exhibit that shrinkage so there may be other causes with this model and we do not yet have enough evidence to be sure.
Just for the record - I do not recommend leaving a car ticking over from cold - you should drive off as soon as you start it but not using full revs or throttle - but gradually driving it at higher revs and throttle opening as the temperatures increase.
Baz
02-19-2019, 02:45 PM
#12
Former Vendor
Just for the record - I do not recommend leaving a car ticking over from cold - you should drive off as soon as you start it but not using full revs or throttle - but gradually driving it at higher revs and throttle opening as the temperatures increase.
That said, we don’t completely agree, nor do we disagree. l would like to see some pics of the 5 engines you’ve seen as well. Our operating environments and fuels vary greatly, so l’d like to see what constants we have between the two sides of the Atlantic- even more than what the variables are.
I have learned more from the engines we have built electively that have not seen a failure, than the engines we have seen with failures. The ability to pull apart engines that were factory new a decade ago, with as little as 11 miles on them were huge in understanding these engines. Running these same engines in pro classes after blueprining them also showed a lot of things we’d have never seen otherwise. We are doing those same things wth the newest of engines now, and in a decade what we are learning now will matter.
As far as using videos to convey information:
l chose to fight this for a decade. l only decided to shoot these videos after analytics proved that people would only stay on a webpage for an average of 3-5 minutes without scrolling away. A 30 minute read was not sinking in. It was a waste of my time.
The modern human will sit on Youtube all day long to learn, and they will watch videos over and over again. What l have learned is the use of 13 letter terms, and the most technically impressive words also isn’t understood. Writing like that may have made me feel better about what l had written, but the reader was lost in it. They didn’t understand anything beyond layman’s terms in today’s world. Most don’t know a piston from a lifter.
The videos allow me to be me. They allow me to explain this stuff in the simplest of terms, and show the pieces, and the wear first hand. People then grasp the topic, and seem to fully understand it. l have learned that the key isn’t trying to enamour the viewer with what l know, or the terms l use. The key so far has been “less is more”.
These videos take a ton of time, and resources, but nothing has truly hit the spot with these topics like the video series have. Having a dedicated facility where l can shoot these, and offer our hands- on training is the only way l can make this happen. l have actually enjoyed the videos, which is something that l never expected would happen.
Of course, now that its successful, l am sure that others will spin off from it. Thats what happens.
02-19-2019, 03:25 PM
#13
Three Wheelin'
What can I say ? Admittedly these are all aged engines and I've seen comments that Porsche is out of the loop due to warranty expiration. It would be nice if Porsche steps onto the plate to at least address the cause of this. We've seen all possible reasons of the bore scoring and nothing definitive on the cause. Every subsequent postings add to the list of the reasons and a disclaimer that there is no one cause. If I were to visit my doctor for a problem and a diagnostic with 20 different reasons and advisable treatment, then we are no better than 150 years ago when the ICE engine was first invented by Nikolaus Otto in 1876. Porsche has been on this game with the flat 6 for ages and I'm sure they can't be clueless of why this is happening. Or perhaps it is too isolated of a case for them to even bother.
02-19-2019, 04:54 PM
#14
Team Owner
Just got the email with the three videos. Very well done and thanks for the effort. Look forward to the third one in the 996/97 series when it comes out.
02-19-2019, 06:00 PM
#15
Originally Posted by HenryPcar
What can I say ? Admittedly these are all aged engines and I've seen comments that Porsche is out of the loop due to warranty expiration. It would be nice if Porsche steps onto the plate to at least address the cause of this. We've seen all possible reasons of the bore scoring and nothing definitive on the cause. Every subsequent postings add to the list of the reasons and a disclaimer that there is no one cause. If I were to visit my doctor for a problem and a diagnostic with 20 different reasons and advisable treatment, then we are no better than 150 years ago when the ICE engine was first invented by Nikolaus Otto in 1876. Porsche has been on this game with the flat 6 for ages and I'm sure they can't be clueless of why this is happening. Or perhaps it is too isolated of a case for them to even bother.
I believe we see the same in these engines.
Cw
