Bore Scoring Flat 6 Video Part #2
02-20-2019, 01:25 PM
#31
Racer
02-20-2019, 01:32 PM
#32
Three Wheelin'
I see your point, but in your example, in the medical field, we have better treatments, but still don't understand 100% the causation of many ailments. I'm in surgery all day every day... surgeons don't know why all these things happen. We have ideas. We know some things certainly do cause more problems then others. But it's also true that some people break all the rules and have no problems.
I believe we see the same in these engines.
Cw
I believe we see the same in these engines.
Cw
02-20-2019, 09:07 PM
#34
Burning Brakes
I am very grateful for all of the knowledge you share. The more I know, the easier it is to make informed decisions.
02-20-2019, 09:44 PM
#35
Rennlist Member
we are all intelligent enough (i hope) to know that there are often several ways to solve/address a problem without always knowing the very exact one specific cause of the problem given the many variables and without the immense time frame and focus on that one given issue. The main thing is that there are people such as Jake and Baz who know (and share) ways to solve them and offer intelligent and valid, dare i say, veritale hypothesis on the causes. Jake and Baz i know that if we locked you two in the same room with a number of several motors good and bad over a long period of time and accounting for all the variables across the pond that you would both ultimately come to the same conclusions - but obviously that is not real world and plus then who would then be be rebuilding our beloved cars/motors? Jake- don't be so sensitive and Baz, boy your english teacher must of loved you; especially like the term you you used "gladiatorial" in one of your posts -all good stuff keep it coming.
02-20-2019, 10:09 PM
#36
Rennlist Member
I for one really enjoy the technical explanations and am also annoyed by the trolls. I am appreciative to guys like Jake and Baz who have helped save Porsche from itself. These guys and others like them have dissected and diagnosed multiple issues with these engines where there is no manual to follow. Without the resources of a major manufacturer/corporation. Just independent shops, more or less self taught from the school of hard knocks. I knew and old guy who used to race Buicks' in the 60's. Buick had problems with the engines blowing up, and the engineers couldn't figure out what the problem was. They knew Jim used their engines and out of desperation gave him an unlimited supply of race engines to be their guinea pig and tester. He figured out what the Buick engineers couldn't, that the (I think) the coolant passages were undersized on one side of the block. Boy that old man knew everything about engines! When guys like that pass, the knowledge pool gets a little bit smaller.
I have tremendous respect for guys like Jake and Baz and others who solve problems without a manual. I work on and fix things myself without manuals where nothing makes any sense. Where only symptoms are present but never the cause. Where you have to play equal parts doctor, detective, and mechanic. I work in the commercial/industrial HVAC industry, I know all about engineering malpractice. Want to talk about York screw compressors and the design flaws they have. If you think a Porsche engine is expensive, price a 100 ton compressor! I understand mechanical things are never perfect and also involve trade offs with unforeseen consequences. I'm glad there's guys out there picking up the pieces and looking for what went wrong. Do they have a financial incentive? Absolutely! Thank God they do or we'd all be worse off. The manufactures incentive is to only get past the warranty period. Like Jake said in the video, the engines are built to pass emissions now.
I listen to explanations for issues from both Jake and Baz and I don't necessarily hear contradictions. I hear explanations that are completely plausible and possibly both correct simultaneously. I read these explanations and just nod and say to myself "sounds right to me". We would all be better off if we let these guys do what they do best, find and fix the problems the degreed engineers missed. Nothing would be better then to have these two collaborate and compare notes. If you have nothing better to do than badger and harass the guys helping the knowledge base perhaps this isn't the right forum for you. When guys like that leave in this small world, the knowledge pool gets quite a bit smaller.
I have tremendous respect for guys like Jake and Baz and others who solve problems without a manual. I work on and fix things myself without manuals where nothing makes any sense. Where only symptoms are present but never the cause. Where you have to play equal parts doctor, detective, and mechanic. I work in the commercial/industrial HVAC industry, I know all about engineering malpractice. Want to talk about York screw compressors and the design flaws they have. If you think a Porsche engine is expensive, price a 100 ton compressor! I understand mechanical things are never perfect and also involve trade offs with unforeseen consequences. I'm glad there's guys out there picking up the pieces and looking for what went wrong. Do they have a financial incentive? Absolutely! Thank God they do or we'd all be worse off. The manufactures incentive is to only get past the warranty period. Like Jake said in the video, the engines are built to pass emissions now.
I listen to explanations for issues from both Jake and Baz and I don't necessarily hear contradictions. I hear explanations that are completely plausible and possibly both correct simultaneously. I read these explanations and just nod and say to myself "sounds right to me". We would all be better off if we let these guys do what they do best, find and fix the problems the degreed engineers missed. Nothing would be better then to have these two collaborate and compare notes. If you have nothing better to do than badger and harass the guys helping the knowledge base perhaps this isn't the right forum for you. When guys like that leave in this small world, the knowledge pool gets quite a bit smaller.
02-20-2019, 10:52 PM
#37
So what to do?
Jake and Baz thanks for your time and effort on the videos and input. I agree with Jake and think it’s a combo of a couple of things that’s going on here. What I would like to know what to do about it?
What about making up a suggestion list and or recommendation per motor?
example 997.1 3.8l
Water pump every 50k with factory plastic or aftermarket metal turbine
3 year 30k coolant flushes
thermostat temp, stock or aftermarket ? Ever 50k
replace injectors every 60k with New factory Porsche or Bosch injectors.
oil service every 5k with factory filter (won’t get into oil brands now) 0w40 or 5w40?
liqui moly ceratec or any other additive?
engine flush to clean engine and ring pack?
BG44k or other injector cleaner? Im assuming 93 oct.
no long cold starts.
CCVV system every 50k
What about making up a suggestion list and or recommendation per motor?
example 997.1 3.8l
Water pump every 50k with factory plastic or aftermarket metal turbine
3 year 30k coolant flushes
thermostat temp, stock or aftermarket ? Ever 50k
replace injectors every 60k with New factory Porsche or Bosch injectors.
oil service every 5k with factory filter (won’t get into oil brands now) 0w40 or 5w40?
liqui moly ceratec or any other additive?
engine flush to clean engine and ring pack?
BG44k or other injector cleaner? Im assuming 93 oct.
no long cold starts.
CCVV system every 50k
02-21-2019, 05:14 PM
#38
Nordschleife Master
Panorama on this subject...
There's an extensive article on 997.1/M97 bore scoring on the February 2019 issue of PCA's Panorama - page 82 - along with an interview of LN's Charles Navarro.
02-23-2019, 12:13 AM
#40
Three Wheelin'
02-23-2019, 12:29 AM
#41
Former Vendor
Fooling the sensor makes the engine hard to start, and run poorly when it is cold. We often adjust this with ECU tunes for our engines.
I have done it with a potentiometer in line with the sensor.. Of course, this has complications.
02-23-2019, 01:06 AM
#42
Three Wheelin'
The proper was to do this is by adjusting fuel volume in the cold start, and just started fuel tables of the ECU.
Fooling the sensor makes the engine hard to start, and run poorly when it is cold. We often adjust this with ECU tunes for our engines.
I have done it with a potentiometer in line with the sensor.. Of course, this has complications.
Thanks, to the point, precise and advice well taken. This is what I'm looking for, It seems fooling the sensor has an adverse effect.
02-23-2019, 03:07 AM
#43
The information I sent privately to Jake includes video of "our 9A1 failures" I am sure he will result in him agreeing with our findings over here as they show the centre to bottom of the bore and piston seized both sides - not scoring). I also sent an analysis of Gen 2 and M96/7 piston profiles showing that the Gen 2 has less ovality and rod/stroke analysis of different models suggesting this is not a significant issue.
The difference in ovality of 9A1 pisotn is relevant and important because a piston has two webs running across it that are joined to the curved part of the piston at the edges whereas the centre (where the thrust loads that push against the cylinder wall and in turn push the rod down to rotate the crankshaft) is a curved piece of aluminium that is unsupported.
If a piston has too much ovality then if the piston gets too hot and expands too much (to cause a 2 sided seizure) it will usually be the centre of the piston faces that squeezes too hard against the cylinder wall and the seizure will be in the centre (which is most common).
Even if the cylinder stretches oval (as in M96/7 open deck cylinders) as long as the piston has enough ovality, it will have too much clearance to expand enough to seize both sides but the extra clearance will make it easier to squeeze out the oil film at lower rev high torque situations and rub the face on the thrust side against the cylinder wall, wearing out a soft coating and entrapping released silicon particles to damage the surface - one side only = bore scoring. Anyone that has used wheel plates (2 flat metal plates with oil between them you sit your wheels on when doing wheel alignment) will know that the loads are not enough to squeeze out all the oil and they freely move about as you adjust the geometry. However if you used too thin an oil or too heavy a car and left the weight on the plates long enough the oil would eventually all squeeze out and the plates would bind together) and this is similar to the oil film between piston and bore under thrust loads driving the car.
A common phenomenon in larger engines is like M96/7 scoring but they call it "scuffing" (because it is on the thrust side of the piston) and the people analysing those failures have worked out it occurs at low revs high torque scenarios - and this is because of the time factor the piston is trying to squeeze out the oil film between the piston and the cylinder wall. At 2000 rpm there is 3.5 times longer that the piston is squeezing the oil film thinner during one stroke than at 7000 rpm. If ever the metal of the piston face rubs against the cylinder wall under load without an oil film between them - it will quickly over heat and score, scuff or seize. this can partly explain why we have seen a higher proportion of M96/7 tiptronic engines score (over here) than manuals - because they normally accelerate from standstill in 2nd and with high torque compared to a manual in 1st (and hence another piece of our UK advice has been to select 1st in a tiptronic if you intend a fast take off).
The DLC coated pistons we tried in the M96/7 engines showed very interesting results. The surface that was beautifully shinny from new was still just as unmarked and shinny all over the thrust face on strip down except for thin score lines where a loose piece of silicon had broken free from the cylinder wall matrix and got entrapped between the piston face and the cylinder wall - so although the oil film was sufficient to keep the shinny DLC coating away from metal to metal contact at the cylinder wall - it was a small piece of silicon that still damaged the surfaces.
This helped us understand what was going on with the Lokasil engines and why the manufacturers stated that they needed a hard coated piston to survive (which incidentally they also supplied with the cylinder blocks). The change from cast to forged pistons coincided with the change from hard to soft piston coatings (and piston supplier) so although that could lead to a conclusion that it was the differences between cast and forged pistons that were significant - we thought it was the change from a hard iron coated piston to a soft plastic coating that was more relevant.
Similarly although too much petrol in the bore will dilute any oil there and make it less effective - it will (as confirmed by a boroscope) always settle in the bottom of the bore due to gravity in a horizontally apposed engine. This would make the underside of the pistons more likely to score if that was the cause - yet bank 2 (which almost all the scoring takes place) scores on the top where the thrust face is while bank 1 (that should suffer most if fuelling was significant) has the thrust face at the bottom (where is pools) yet rarely scores.
From this and the fact that the top of the cylinders are the hotter part of the cylinder (so oil films will be thinner) linked issues relating to the forces between the piston and Lokasil bore as the most significant issues influencing bore scoring and because Nikasil does not release loose silicon particles (and can run with any or no piston coating as a result), it solves the problem totally for us over here in the UK.
However the 9A1 Gen 2 engines are quite different. Because the pistons are less oval, bore clearances smaller and piston coating are harder than plastic and running in more solid Alusil that releases silicon particles at an insignificant rate (and they are smaller), so there are 2 causes that could lead to damage.
(1) This is what we have seen where both sides of the piston and bore are damaged in a seizure (not scoring one side). Because the piston in our scenarios is not hotter than it was designed to be (i.e. running OK) - but if the cylinder shrinks into it at the sides (due to ages stress relieving where the 2 sections of the casting at the bottom are pulling it inwards) it is also in line with the webs supporting the gudgeon pin bores (that prevent the piston skirt at the sides from flexing inwards) and so the pressure between the piston and bore at the sides is sufficient to squeeze out the oil film and result in a siezure (especially when too fast a warm up allows the piston to grow faster than the bore expands).
(2) This scenario is what could make scoring occur over in the USA where the bore is still round but something else has made the piston expand more than it was designed too do because it has become too hot. Because the piston has been designed with less ovality the sides "stick out" (for want of a better description) more than the centre in M96/7 pistons and as the sides are supported by the 2 webs where the gudgeon pin fits (like all pistons) - so if they got too hot the sides would expand more but resist being flexed inward under load and this could make the contact area that squeezes out the oil film until it is too thin or not there at all - be the sides of the pistons instead of the more familiar centres.
So whereas the M96/7 engines have more piston ovality and much bigger bore clearances (especially as they go oval through being unsupported), and are unlikely to experience a piston expanding too much so it is too big for the cylinder diameter and clearances (so unlikely to seize both sides) it could still score the thrust side because of loose silicon particles impinging on the soft plastic piston coating - a 9A1 Gen 2 engine could seize one side or both sides if the piston expanded too much.
I cannot see from the bore scoring video if the Gen 2 piston or bore were scored one side or seized both sides (the video I sent to Jake from our UK examples shows both sides). However IF the failures in the USA are one sided scores the tighter bore clearances combine with the shape of the pistons could cause that if the piston got too hot and therefore any contributing differences (like fuel, injectors, fuel pumps etc) could indeed cause the problem.
Even if the failures in the USA are double sided seizures anything that results in the piston getting hotter than intended could cause them.
It could be that in the UK a small number of engines have failed with scoring but were replaced under warranty in the main dealer network (and hence we have not seen that yet and have no experience of it) whereas the ones we have seen were older (and out of warranty) lasted longer, have had many more heat/cool cycles and were indeed caused by aged related stress relieving (as we first muted).
It could be that in he USA owners have brought failed engines to Jake earlier than the independent network got to see them in the UK.
So I am pleased to work out that for these reasons I can agree with the many posts that have suspected that we have both been right about our different experiences with and causes of 9A1 Gen 2 failures in our different Countries.
I can also now understand why there may be different influences in the USA and UK that affect the failures in M96/7 bore scoring incidents.
Over here although we change many things in the engines when we rebuild them - if we only ever changed the cylinder bore material to our Nikasil alloy cylinders (and adjust the coolant flow and LTT setting) it results in excellent reliability and so we cannot link any other significant issues with bore scoring other than the Lokasil material (since the plastic coated pistons that do not last in Lokasil do in Nikasil - cannot be faulted when running in Nikasil).
However although we are sure it is free silicon particles that damage the bores and scores them in Lokasil engines with plastic coated pistons, anything that reduces the effectiveness of the oil viscosity and lubricity would allow the pistons to run closer to the cylinder walls with thinner oil films and enable free particles to cause damage sooner. So if there is a problem with injectors as a result of fuel differences in the USA (that we don't experience over here), or more owners run with thin oils (as per the handbook) as they age and general clearances increase etc - that could again make us both right about the different contributory factors in our separate Countries.
How's that for a result?
Baz
The difference in ovality of 9A1 pisotn is relevant and important because a piston has two webs running across it that are joined to the curved part of the piston at the edges whereas the centre (where the thrust loads that push against the cylinder wall and in turn push the rod down to rotate the crankshaft) is a curved piece of aluminium that is unsupported.
If a piston has too much ovality then if the piston gets too hot and expands too much (to cause a 2 sided seizure) it will usually be the centre of the piston faces that squeezes too hard against the cylinder wall and the seizure will be in the centre (which is most common).
Even if the cylinder stretches oval (as in M96/7 open deck cylinders) as long as the piston has enough ovality, it will have too much clearance to expand enough to seize both sides but the extra clearance will make it easier to squeeze out the oil film at lower rev high torque situations and rub the face on the thrust side against the cylinder wall, wearing out a soft coating and entrapping released silicon particles to damage the surface - one side only = bore scoring. Anyone that has used wheel plates (2 flat metal plates with oil between them you sit your wheels on when doing wheel alignment) will know that the loads are not enough to squeeze out all the oil and they freely move about as you adjust the geometry. However if you used too thin an oil or too heavy a car and left the weight on the plates long enough the oil would eventually all squeeze out and the plates would bind together) and this is similar to the oil film between piston and bore under thrust loads driving the car.
A common phenomenon in larger engines is like M96/7 scoring but they call it "scuffing" (because it is on the thrust side of the piston) and the people analysing those failures have worked out it occurs at low revs high torque scenarios - and this is because of the time factor the piston is trying to squeeze out the oil film between the piston and the cylinder wall. At 2000 rpm there is 3.5 times longer that the piston is squeezing the oil film thinner during one stroke than at 7000 rpm. If ever the metal of the piston face rubs against the cylinder wall under load without an oil film between them - it will quickly over heat and score, scuff or seize. this can partly explain why we have seen a higher proportion of M96/7 tiptronic engines score (over here) than manuals - because they normally accelerate from standstill in 2nd and with high torque compared to a manual in 1st (and hence another piece of our UK advice has been to select 1st in a tiptronic if you intend a fast take off).
The DLC coated pistons we tried in the M96/7 engines showed very interesting results. The surface that was beautifully shinny from new was still just as unmarked and shinny all over the thrust face on strip down except for thin score lines where a loose piece of silicon had broken free from the cylinder wall matrix and got entrapped between the piston face and the cylinder wall - so although the oil film was sufficient to keep the shinny DLC coating away from metal to metal contact at the cylinder wall - it was a small piece of silicon that still damaged the surfaces.
This helped us understand what was going on with the Lokasil engines and why the manufacturers stated that they needed a hard coated piston to survive (which incidentally they also supplied with the cylinder blocks). The change from cast to forged pistons coincided with the change from hard to soft piston coatings (and piston supplier) so although that could lead to a conclusion that it was the differences between cast and forged pistons that were significant - we thought it was the change from a hard iron coated piston to a soft plastic coating that was more relevant.
Similarly although too much petrol in the bore will dilute any oil there and make it less effective - it will (as confirmed by a boroscope) always settle in the bottom of the bore due to gravity in a horizontally apposed engine. This would make the underside of the pistons more likely to score if that was the cause - yet bank 2 (which almost all the scoring takes place) scores on the top where the thrust face is while bank 1 (that should suffer most if fuelling was significant) has the thrust face at the bottom (where is pools) yet rarely scores.
From this and the fact that the top of the cylinders are the hotter part of the cylinder (so oil films will be thinner) linked issues relating to the forces between the piston and Lokasil bore as the most significant issues influencing bore scoring and because Nikasil does not release loose silicon particles (and can run with any or no piston coating as a result), it solves the problem totally for us over here in the UK.
However the 9A1 Gen 2 engines are quite different. Because the pistons are less oval, bore clearances smaller and piston coating are harder than plastic and running in more solid Alusil that releases silicon particles at an insignificant rate (and they are smaller), so there are 2 causes that could lead to damage.
(1) This is what we have seen where both sides of the piston and bore are damaged in a seizure (not scoring one side). Because the piston in our scenarios is not hotter than it was designed to be (i.e. running OK) - but if the cylinder shrinks into it at the sides (due to ages stress relieving where the 2 sections of the casting at the bottom are pulling it inwards) it is also in line with the webs supporting the gudgeon pin bores (that prevent the piston skirt at the sides from flexing inwards) and so the pressure between the piston and bore at the sides is sufficient to squeeze out the oil film and result in a siezure (especially when too fast a warm up allows the piston to grow faster than the bore expands).
(2) This scenario is what could make scoring occur over in the USA where the bore is still round but something else has made the piston expand more than it was designed too do because it has become too hot. Because the piston has been designed with less ovality the sides "stick out" (for want of a better description) more than the centre in M96/7 pistons and as the sides are supported by the 2 webs where the gudgeon pin fits (like all pistons) - so if they got too hot the sides would expand more but resist being flexed inward under load and this could make the contact area that squeezes out the oil film until it is too thin or not there at all - be the sides of the pistons instead of the more familiar centres.
So whereas the M96/7 engines have more piston ovality and much bigger bore clearances (especially as they go oval through being unsupported), and are unlikely to experience a piston expanding too much so it is too big for the cylinder diameter and clearances (so unlikely to seize both sides) it could still score the thrust side because of loose silicon particles impinging on the soft plastic piston coating - a 9A1 Gen 2 engine could seize one side or both sides if the piston expanded too much.
I cannot see from the bore scoring video if the Gen 2 piston or bore were scored one side or seized both sides (the video I sent to Jake from our UK examples shows both sides). However IF the failures in the USA are one sided scores the tighter bore clearances combine with the shape of the pistons could cause that if the piston got too hot and therefore any contributing differences (like fuel, injectors, fuel pumps etc) could indeed cause the problem.
Even if the failures in the USA are double sided seizures anything that results in the piston getting hotter than intended could cause them.
It could be that in the UK a small number of engines have failed with scoring but were replaced under warranty in the main dealer network (and hence we have not seen that yet and have no experience of it) whereas the ones we have seen were older (and out of warranty) lasted longer, have had many more heat/cool cycles and were indeed caused by aged related stress relieving (as we first muted).
It could be that in he USA owners have brought failed engines to Jake earlier than the independent network got to see them in the UK.
So I am pleased to work out that for these reasons I can agree with the many posts that have suspected that we have both been right about our different experiences with and causes of 9A1 Gen 2 failures in our different Countries.
I can also now understand why there may be different influences in the USA and UK that affect the failures in M96/7 bore scoring incidents.
Over here although we change many things in the engines when we rebuild them - if we only ever changed the cylinder bore material to our Nikasil alloy cylinders (and adjust the coolant flow and LTT setting) it results in excellent reliability and so we cannot link any other significant issues with bore scoring other than the Lokasil material (since the plastic coated pistons that do not last in Lokasil do in Nikasil - cannot be faulted when running in Nikasil).
However although we are sure it is free silicon particles that damage the bores and scores them in Lokasil engines with plastic coated pistons, anything that reduces the effectiveness of the oil viscosity and lubricity would allow the pistons to run closer to the cylinder walls with thinner oil films and enable free particles to cause damage sooner. So if there is a problem with injectors as a result of fuel differences in the USA (that we don't experience over here), or more owners run with thin oils (as per the handbook) as they age and general clearances increase etc - that could again make us both right about the different contributory factors in our separate Countries.
How's that for a result?
Baz
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997ajk (04-05-2021)
04-04-2021, 10:26 AM
#45
Nordschleife Master
Join Date: Mar 2003
Location: Destin, Nashville, In a 458 Challenge
Posts: 5,128
Received 903 Likes
on
532 Posts
Baz... Jake..... we understand how you can get concerned about negative posts.... but taking those too seriously is like watching Rachel Maddow/Sean Hannity and thinking the sky is falling and the earth will end today. Most of us here are not stupid and get it. I am learning a ton from all of you, and at a bare minimum, is great reading entertainment. Keep it coming!
OK, now I am going to offend some folks! I used to hang with Ferrari folks.... all they did was talk about the leather. I asked a sales rep at a Ferrari dealership what the fins on the back underside of one of their models did.... he said "Aero package!" ... I asked: "Yes, but does it relieve back pressure or produce down force?" He said " Umm... I don't know and walked away from me". My point here is that owning a Porsche has collateral experiences that I thoroughly enjoy and you guys are part of the fun and valuable education. Keep it coming!!
Peace
Bruce in Philly
OK, now I am going to offend some folks! I used to hang with Ferrari folks.... all they did was talk about the leather. I asked a sales rep at a Ferrari dealership what the fins on the back underside of one of their models did.... he said "Aero package!" ... I asked: "Yes, but does it relieve back pressure or produce down force?" He said " Umm... I don't know and walked away from me". My point here is that owning a Porsche has collateral experiences that I thoroughly enjoy and you guys are part of the fun and valuable education. Keep it coming!!
Peace
Bruce in Philly
Truly what I have noticed over the years is that the guys racing Porsches and owning cars like GT3 Cup Cars have Ferraris as their weekend cars for public roads.
It was actually guys at the track that really got me into Ferraris a little over 20 years ago when I refused to drive anything but Porsches and had 5 or 6 Porsches in the driveway.