What does that look like to you?
07-09-2013, 12:11 AM
#31
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Someone should make aluminum dry sleeves for these engines with Nikasil/Nicom plating. With interference fit they would probably be about as strong and about as heat conductive as the original cylinder tower. The big difference between plating the block vs. installing plated dry sleeves is that the plated dry sleeves can be shipped at a reasonable cost.
The Nicosil process leaves nickel behind....which is pretty damn hard stuff. The final honing process requires the use of a diamond hone...and they have to "crank" up the pressure on the hone very high, in order to get the proper finish.
This distorts any "thin wall" cylinders.
Charlie Spira was trying very hard to get Nicolsil liners for the 911 Cup and RSR engines....made from steel. Last I talked with him, he had given up trying to get this done....too much distortion.
A "dry wall" aluminum cylinder for a 928 with a 100mm bore would be pretty thin....and a 104mm bore would be really, really thin.
Not to mention that a dry cylinder distorts when it is installed and generally is sized and honed, when in place.
I think the only possible way to do this would be to machine away all of the cylinders and use wet sleeves.....but that severely reduces the strength of the existing brittle Alusil block....Porsche tried this with the 944GTR engines, with such poor results that they had to start over with another block made of aluminum without the silicon.
Billet blocks with replaceable wet Nicosil cylinders....that's the real solution....and essentially what a 944 GTR engine ended up having, in the end. Porsche did all the research and all the work on these engines....all it takes is money to go down the same path.
__________________
greg brown
714 879 9072
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
07-09-2013, 04:13 AM
#32
Rennlist Member
Thread Starter
Someone should make aluminum dry sleeves for these engines with Nikasil/Nicom plating. With interference fit they would probably be about as strong and about as heat conductive as the original cylinder tower. The big difference between plating the block vs. installing plated dry sleeves is that the plated dry sleeves can be shipped at a reasonable cost.
So JE said that the same etching process that is used with stock pistons should be used with their coated pistons?
So JE said that the same etching process that is used with stock pistons should be used with their coated pistons?
Turns out that this is not so simple....
The Nicosil process leaves nickel behind....which is pretty damn hard stuff. The final honing process requires the use of a diamond hone...and they have to "crank" up the pressure on the hone very high, in order to get the proper finish.
This distorts any "thin wall" cylinders.
Charlie Spira was trying very hard to get Nicolsil liners for the 911 Cup and RSR engines....made from steel. Last I talked with him, he had given up trying to get this done....too much distortion.
A "dry wall" aluminum cylinder for a 928 with a 100mm bore would be pretty thin....and a 104mm bore would be really, really thin.
Not to mention that a dry cylinder distorts when it is installed and generally is sized and honed, when in place.
I think the only possible way to do this would be to machine away all of the cylinders and use wet sleeves.....but that severely reduces the strength of the existing brittle Alusil block....Porsche tried this with the 944GTR engines, with such poor results that they had to start over with another block made of aluminum without the silicon.
Billet blocks with replaceable wet Nicosil cylinders....that's the real solution....and essentially what a 944 GTR engine ended up having, in the end. Porsche did all the research and all the work on these engines....all it takes is money to go down the same path.
The Nicosil process leaves nickel behind....which is pretty damn hard stuff. The final honing process requires the use of a diamond hone...and they have to "crank" up the pressure on the hone very high, in order to get the proper finish.
This distorts any "thin wall" cylinders.
Charlie Spira was trying very hard to get Nicolsil liners for the 911 Cup and RSR engines....made from steel. Last I talked with him, he had given up trying to get this done....too much distortion.
A "dry wall" aluminum cylinder for a 928 with a 100mm bore would be pretty thin....and a 104mm bore would be really, really thin.
Not to mention that a dry cylinder distorts when it is installed and generally is sized and honed, when in place.
I think the only possible way to do this would be to machine away all of the cylinders and use wet sleeves.....but that severely reduces the strength of the existing brittle Alusil block....Porsche tried this with the 944GTR engines, with such poor results that they had to start over with another block made of aluminum without the silicon.
Billet blocks with replaceable wet Nicosil cylinders....that's the real solution....and essentially what a 944 GTR engine ended up having, in the end. Porsche did all the research and all the work on these engines....all it takes is money to go down the same path.
Perhaps, I should have stuck to BMW M3s... Cheap and plentiful engines, with the S54 rightfully seen as one of the pinnacles of NA engine development...
07-09-2013, 07:08 AM
#35
Rennlist Member
Thread Starter
Care to add something useful or you are just chalking up posts?
I think it does - unless you have OEM pistons, I would not experiment with compatibility with Alusil.
I think it does - unless you have OEM pistons, I would not experiment with compatibility with Alusil.
07-09-2013, 07:22 AM
#36
Rennlist Member
A,
Saddened to read your post [and the implications] after all your hard work. It sure does sound as though it is a pull it all out and start all over again job. You would think that this type of issue had long been cracked- but maybe not by the sound of it.
TBF issues, engine breathing issues, GTS issues. MAF's, LH's etc etc- maybe Porsche knew what they were doing afterall when they pulled the plug on the 928! Still as that wise sage Dr Brown said, ultimately can only push up residuals as folks throw in the towel and send these things to the breakers or whatever- not that we are likely to profit out of it.
Maybe we can arrange to be buried in our 928's? Start a cult thingy?
I guess the next obvious question is whether you can shoe horn a E60 or maybe even a E39 motor into a 928 chassis? Doubtless cheaper if they would fit.
Maybe this is all a classic case of "so close but so far".
Regards
Fred
Saddened to read your post [and the implications] after all your hard work. It sure does sound as though it is a pull it all out and start all over again job. You would think that this type of issue had long been cracked- but maybe not by the sound of it.
TBF issues, engine breathing issues, GTS issues. MAF's, LH's etc etc- maybe Porsche knew what they were doing afterall when they pulled the plug on the 928! Still as that wise sage Dr Brown said, ultimately can only push up residuals as folks throw in the towel and send these things to the breakers or whatever- not that we are likely to profit out of it.
Maybe we can arrange to be buried in our 928's? Start a cult thingy?
I guess the next obvious question is whether you can shoe horn a E60 or maybe even a E39 motor into a 928 chassis? Doubtless cheaper if they would fit.
Maybe this is all a classic case of "so close but so far".
Regards
Fred
07-09-2013, 08:58 AM
#37
Nordschleife Master
Turns out that this is not so simple....
The Nicosil process leaves nickel behind....which is pretty damn hard stuff. The final honing process requires the use of a diamond hone...and they have to "crank" up the pressure on the hone very high, in order to get the proper finish. This distorts any "thin wall" cylinders. A "dry wall" aluminum cylinder for a 928 with a 100mm bore would be pretty thin....and a 104mm bore would be really, really thin.
Not to mention that a dry cylinder distorts when it is installed and generally is sized and honed, when in place.
The Nicosil process leaves nickel behind....which is pretty damn hard stuff. The final honing process requires the use of a diamond hone...and they have to "crank" up the pressure on the hone very high, in order to get the proper finish. This distorts any "thin wall" cylinders. A "dry wall" aluminum cylinder for a 928 with a 100mm bore would be pretty thin....and a 104mm bore would be really, really thin.
Not to mention that a dry cylinder distorts when it is installed and generally is sized and honed, when in place.
Here's what I was thinking about. Just daydreaming, not that I've ever done anything like this. What I was thinking about is a 100mm bore bored our to accept an aluminum sleeve. The sleeve thickness would be about the same as the factory's alusil repair sleeves. My imaginary steps are as follows:
1. Overbore the existing tower to a very close tolerance.
2. Build/use a fixture to compress the aluminum sleeve to simulate the interference fit and head compression.
3. Bore the sleeve in the fixture, Nikasil/Nicom plate it, and boron carbide (not diamond I think) hone it in the fixture
4. Heat the block and install the plated sleeve
What's going to make or break that idea is whether the fixture can accurately simulate the interference fit in the block. I have no idea if it would work. I wouldn't try it based on an internet post! ;-)
Obviously, sending in the whole block in the US is much simpler since we have two firms here that can Nikasil/Nicom plate V8 blocks.
I think the only possible way to do this would be to machine away all of the cylinders and use wet sleeves.....but that severely reduces the strength of the existing brittle Alusil block....Porsche tried this with the 944GTR engines, with such poor results that they had to start over with another block made of aluminum without the silicon.
07-10-2013, 04:14 AM
#38
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07-10-2013, 08:54 AM
#39
Rennlist Member
Thread Starter
Look, there are several vendors out there, who would happily sell you JE piston kit to repair Audi 4.2 V8 engines and would say the JE coating will work in an Alusil block. Moreover, there are reputable shops here in the UK, who stand-by their word that indeed JE pistons work in Alusil. It appears that the reputable shop that did the bore prep on mine, just did a **** job. I am not prepared to experiment one more time with my money. Well, I am, since fitting 8 dry sleeves into an aluminium block is not easy, but I think this is somewhat safer than experimenting again with alusil and aftermarket pistons...
Last edited by Cheburator; 07-10-2013 at 09:24 AM.
07-10-2013, 04:10 PM
#40
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Hallo.Here is the man with the ball bearing Whimpy.We have already built some engines with bore Alusil.Of course we also had damage.We have tried it with different piston.Wössner have no good results.They see the Pictures.Engine has run 6000 Miles.We therefore only use Nikasil coating.The company wich is offering in Germany.But the execution is in England.In Germany,there is a patent on the method.We only have good results.Regards uwe
07-11-2013, 07:12 AM
#43
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This is one more proof that no piston coating but the ferro-coating made by Mahle in Germany will work in alu-sil bores. Has anyone made direct contact with Mahle in Germany about custom made pistons with the right coating?
Ake
Ake
07-22-2013, 11:30 AM
#45
Rennlist Member
Thread Starter
The engine is still in the car. Will re-build my GT motor with fresh rings and will put on the fancy heads and ITBs on it to go racing this season. Meanwhile, the 5.5ltr block will be dry sleeved - have found a liner manufacturer which looks like a perfect fit...