GTS Engine project
11-17-2009, 07:11 PM
#31
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11-17-2009, 08:14 PM
#32
Former Sponsor
It takes a whole bunch of ring damage and problems, to these engines, before they will smoke or have oil control issues. I've seen grooves cut 8mm wide and 2mm deep in cylinders that will not smoke...you'd have no idea that there was a problem, if the head was not off and you were not looking at a very bad cylinder.
Considering that the engines ran pretty well, without oil return holes drilled into the pistons, which pushed most of the oil into the combustion chamber, it is tough to imagine not being able to improve on that situation.
11-18-2009, 04:06 AM
#34
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Buy more and more of them until you either get enough long rings or run out of $$$.
11-18-2009, 02:06 PM
#35
Former Sponsor
Erkka:
I looked back at your post about the "excessive" ring gap on the new GTS rings. You state that you've found rings that have a gap .1mm to .2mm above the factory specifications.....only on the second ring?
That's a really little number....we vary our ring gap more than that, making the gap larger for the higher output engines....especially increasing the gap on the second ring.
Also note that the specification is for a "new" engine, which is going to have a more aggressive silicon bore surface than a used engine. A ring in a "new" bore is going to wear much more than a ring in a "used" bore, because of this fact, alone.
This is not going to ever cause anybody any problems....this is akin to "the sky is falling", the sky is falling", in my humble opinion. The amount of compression lost, past the second ring, with an increase of .1mm or .2mm of ring gap would never even be able to be measured, even with the most sensitive instramentation. And, if the ring is going into a used bore, the gap will probably end up less (in a 1000km) than the ring that went into a new bore.
Food for thought.
I looked back at your post about the "excessive" ring gap on the new GTS rings. You state that you've found rings that have a gap .1mm to .2mm above the factory specifications.....only on the second ring?
That's a really little number....we vary our ring gap more than that, making the gap larger for the higher output engines....especially increasing the gap on the second ring.
Also note that the specification is for a "new" engine, which is going to have a more aggressive silicon bore surface than a used engine. A ring in a "new" bore is going to wear much more than a ring in a "used" bore, because of this fact, alone.
This is not going to ever cause anybody any problems....this is akin to "the sky is falling", the sky is falling", in my humble opinion. The amount of compression lost, past the second ring, with an increase of .1mm or .2mm of ring gap would never even be able to be measured, even with the most sensitive instramentation. And, if the ring is going into a used bore, the gap will probably end up less (in a 1000km) than the ring that went into a new bore.
Food for thought.
11-18-2009, 02:23 PM
#36
Man of many SIGs
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Erkka:
I looked back at your post about the "excessive" ring gap on the new GTS rings. You state that you've found rings that have a gap .1mm to .2mm above the factory specifications.....only on the second ring?
That's a really little number....we vary our ring gap more than that, making the gap larger for the higher output engines....especially increasing the gap on the second ring.
Also note that the specification is for a "new" engine, which is going to have a more aggressive silicon bore surface than a used engine. A ring in a "new" bore is going to wear much more than a ring in a "used" bore, because of this fact, alone.
This is not going to ever cause anybody any problems....this is akin to "the sky is falling", the sky is falling", in my humble opinion. The amount of compression lost, past the second ring, with an increase of .1mm or .2mm of ring gap would never even be able to be measured, even with the most sensitive instramentation. And, if the ring is going into a used bore, the gap will probably end up less (in a 1000km) than the ring that went into a new bore.
Food for thought.
I looked back at your post about the "excessive" ring gap on the new GTS rings. You state that you've found rings that have a gap .1mm to .2mm above the factory specifications.....only on the second ring?
That's a really little number....we vary our ring gap more than that, making the gap larger for the higher output engines....especially increasing the gap on the second ring.
Also note that the specification is for a "new" engine, which is going to have a more aggressive silicon bore surface than a used engine. A ring in a "new" bore is going to wear much more than a ring in a "used" bore, because of this fact, alone.
This is not going to ever cause anybody any problems....this is akin to "the sky is falling", the sky is falling", in my humble opinion. The amount of compression lost, past the second ring, with an increase of .1mm or .2mm of ring gap would never even be able to be measured, even with the most sensitive instramentation. And, if the ring is going into a used bore, the gap will probably end up less (in a 1000km) than the ring that went into a new bore.
Food for thought.
I just want to thank you for your contributions to this forum and the 928 community in general. In case you haven't heard it lately, we really do appreciate you being involved and sharing.
11-18-2009, 03:24 PM
#37
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I know it sounds very small but specs are 0.25-0.40mm IIRR. I measured 0.60 in several cylinders. Both 1st and 2nd ring. Also these same cylinders had 50% leak down through pistons when I measured it before engine was started for first time. All of them have been lapped with correct stuff to renew Alusil surface. Fact that large leak is in same cylinders which had too large cap and leak happens downwards makes me think two are connected. I don't think this is random occurence. Maybe rings will settle and seal ok but I doubt it. Engine hasn't run enough long yet to say for sure.
11-18-2009, 04:36 PM
#38
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Ahhhh.....
928Int only have 3 of those oversize GTS pistons left....
Both me and a friend need more than 3 to fix our GTS engines.
I have a friend in Norway with the exact same problem.
Bummer.
They cost a fortune at Porsche.
What to do...?
And thank you so much for your inputs.
Very much appreciated.
928Int only have 3 of those oversize GTS pistons left....
Both me and a friend need more than 3 to fix our GTS engines.
I have a friend in Norway with the exact same problem.
Bummer.
They cost a fortune at Porsche.
What to do...?
And thank you so much for your inputs.
Very much appreciated.
11-18-2009, 04:50 PM
#39
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Is 0.5mm over size even enough to remove all problems from bores? If either engine has larger problems only cure for it is 968 or custom pistons. In any case it basically means all 8 pistons must be changed instead of just few which have problems.
11-18-2009, 05:56 PM
#40
With this problem with the Alusil bores, as I mentioned there is two other options that are worth investigating before steel bores go in. The Sume bore will work and they are in Switzerland which might not be too bad, road trip! I don't know the costs though.
The way I have my hopes set on is the chrome nitride, there is no reports of failure that I have heard off allow we all know some people keep this secret but it is increasing popular due to the friction gains after apply DLC. The last thing that is going to gall is DLC that I am quite sure off.
The one thing and I might ring the coater in the UK tonight is can a resin coating go on say one side of the piston, say the thrust side to try and quiten it as the dlc has no cushioning, F1 teams quite often run different coatings of the opposing sides of the pistons. So if people want me to make the call I will, otherwise I will wait till I am going to send all my stuff, such as valves cams liters, etc
Greg
The way I have my hopes set on is the chrome nitride, there is no reports of failure that I have heard off allow we all know some people keep this secret but it is increasing popular due to the friction gains after apply DLC. The last thing that is going to gall is DLC that I am quite sure off.
The one thing and I might ring the coater in the UK tonight is can a resin coating go on say one side of the piston, say the thrust side to try and quiten it as the dlc has no cushioning, F1 teams quite often run different coatings of the opposing sides of the pistons. So if people want me to make the call I will, otherwise I will wait till I am going to send all my stuff, such as valves cams liters, etc
Greg
11-19-2009, 05:51 AM
#41
Maybe a breakthrough, we'll see, the coater said that a DLC skirted piston is not for sale at present, they are under going evaluation at present. One reason he though would work was that DLC coated pins are common place in ally pistons these days and they never gall. At the moment no DLC.
However he did like the chrome nitride idea and that is available. They are going to get back to me with a price and are going to make contacts with people who know a lot about alusil as they have a contact.
I then discussed the PC-9 style coating over the chrome nitride and again received well. They are happy to help with the development, so if somebody wants to put their hand up please contact me and we can take it from there. It will be great to get a solution to this problem.
The chrome nitride btw is used to create a stabile layer for the DLC as such it strengthens/reinforces the surface, which to my mind is exactly what is needed to stop the galling mechanism of action from happening.
Greg
However he did like the chrome nitride idea and that is available. They are going to get back to me with a price and are going to make contacts with people who know a lot about alusil as they have a contact.
I then discussed the PC-9 style coating over the chrome nitride and again received well. They are happy to help with the development, so if somebody wants to put their hand up please contact me and we can take it from there. It will be great to get a solution to this problem.
The chrome nitride btw is used to create a stabile layer for the DLC as such it strengthens/reinforces the surface, which to my mind is exactly what is needed to stop the galling mechanism of action from happening.
Greg
11-19-2009, 09:50 AM
#42
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Greg, PM me with details. I'm looking for some 100mm pistons that I can use with alusil that will have a final comp. ratio of about 8.5:1 using S4 heads and a 951 wide fire ring gasket. What would the cost be on this? I have a solution already but it involves custom rods. If these pistons are cheaper than that I may be interested.
11-19-2009, 03:25 PM
#43
Well I am going to contact them for a price, I spoke with the engineer not the salesperson. Also I don't want lots of people ringing them, these guys are pros and do a lot of F1 and LeMans work as such customers spend a lot with them an they deal with mainly professionals, so I don't want them to get put off. I considered myself pretty lucky they are even talking to me and I figure I really need them and they don't need me.
For the US based guys why not try some local coaters that do DLC? Most coaters that do DLC will have chrome nitride and then you can get the PC-9 coating applied and it is all in the US. Much cheaper and more convenient I would have thought. I will get a price and if you still want to proceed we'll take it from there.
I described the PC-9 coating and while he said he didn't have any knowledge of it, he said "sounds like a type of moly spray" which may well be the case as it is sprayed on.
The guys in the europe want to see the pistons to see whether the Mahle coatings can be removed and how they are going to mount them, possible need to make jigs etc, so it is not so straight forward. I did say to the engine that the factory coatings were either chrome or iron. I also maybe the chrome is chrome nitride? He responded and said "yes it might be" So it will be nice if we have found Mahle's coating.
Greg
For the US based guys why not try some local coaters that do DLC? Most coaters that do DLC will have chrome nitride and then you can get the PC-9 coating applied and it is all in the US. Much cheaper and more convenient I would have thought. I will get a price and if you still want to proceed we'll take it from there.
I described the PC-9 coating and while he said he didn't have any knowledge of it, he said "sounds like a type of moly spray" which may well be the case as it is sprayed on.
The guys in the europe want to see the pistons to see whether the Mahle coatings can be removed and how they are going to mount them, possible need to make jigs etc, so it is not so straight forward. I did say to the engine that the factory coatings were either chrome or iron. I also maybe the chrome is chrome nitride? He responded and said "yes it might be" So it will be nice if we have found Mahle's coating.
Greg
11-19-2009, 09:04 PM
#44
Former Sponsor
Well I am going to contact them for a price, I spoke with the engineer not the salesperson. Also I don't want lots of people ringing them, these guys are pros and do a lot of F1 and LeMans work as such customers spend a lot with them an they deal with mainly professionals, so I don't want them to get put off. I considered myself pretty lucky they are even talking to me and I figure I really need them and they don't need me.
For the US based guys why not try some local coaters that do DLC? Most coaters that do DLC will have chrome nitride and then you can get the PC-9 coating applied and it is all in the US. Much cheaper and more convenient I would have thought. I will get a price and if you still want to proceed we'll take it from there.
I described the PC-9 coating and while he said he didn't have any knowledge of it, he said "sounds like a type of moly spray" which may well be the case as it is sprayed on.
The guys in the europe want to see the pistons to see whether the Mahle coatings can be removed and how they are going to mount them, possible need to make jigs etc, so it is not so straight forward. I did say to the engine that the factory coatings were either chrome or iron. I also maybe the chrome is chrome nitride? He responded and said "yes it might be" So it will be nice if we have found Mahle's coating.
Greg
For the US based guys why not try some local coaters that do DLC? Most coaters that do DLC will have chrome nitride and then you can get the PC-9 coating applied and it is all in the US. Much cheaper and more convenient I would have thought. I will get a price and if you still want to proceed we'll take it from there.
I described the PC-9 coating and while he said he didn't have any knowledge of it, he said "sounds like a type of moly spray" which may well be the case as it is sprayed on.
The guys in the europe want to see the pistons to see whether the Mahle coatings can be removed and how they are going to mount them, possible need to make jigs etc, so it is not so straight forward. I did say to the engine that the factory coatings were either chrome or iron. I also maybe the chrome is chrome nitride? He responded and said "yes it might be" So it will be nice if we have found Mahle's coating.
Greg
11-19-2009, 09:07 PM
#45
Former Sponsor
I know it sounds very small but specs are 0.25-0.40mm IIRR. I measured 0.60 in several cylinders. Both 1st and 2nd ring. Also these same cylinders had 50% leak down through pistons when I measured it before engine was started for first time. All of them have been lapped with correct stuff to renew Alusil surface. Fact that large leak is in same cylinders which had too large cap and leak happens downwards makes me think two are connected. I don't think this is random occurence. Maybe rings will settle and seal ok but I doubt it. Engine hasn't run enough long yet to say for sure.
That's a lot of leakdown. Tough to imagine all of that going past the ring gap, but you've got the example...