Nathan, some more great info!
Does the felt pad or the silicon paste have any grit it?
I'm thinking like jewlers rouge.

I found the following PDF that has great information about Alusil Specific re-conditioning for this type of cylinder. It seems that this is a official MSI Motors/Kolbenschmidt document. The manufacturer says that they can be re-conditioned but Im sure tolerances still have to be within specs.

http://www.msi-motor-service.com/download/broschueren/alu_en.pdf

They mention that durring the felt process (final) that there is silicone polishing paste and no honing oil used.

William, with regards to our Goetze ring man, he suggests to go ahead and re-ring on the basis that in his 16 year history with the company, he can never recall any warranty issues on 911 rings (and our customers generally will try and find any excuse to claim for warranty work!) He said the phosphating will help assist initial seating, and the 911 Goetze ring is therefore suitable for all cylinder types. I mentioned in a previous post, the Goetze ring sells in excess of 5000 units per year (in European Aftermarket) with no warranty issues. Draw your own conclusions...

smestas,

That brochure is for retrofitting iron sleeves into aluminum blocks, not for honing alusil directly.


For anybody that cares,

Asusil, or any other hypereutectic alloy, is etched, not honed, at the factory. This is well documented. The reason it's etched is because the aluminum is easy to etch, and too soft to hone without galling on the microscopic level. By etching back the aluminum the silicon particles are exposed and they become the primary wear surface.

Hypereutectic alloys have been used for air cooled engine cylinders for 4 decades, including aircraft. For those of you with access to a university library, there are tons of references to the characteristics and performance of various types of silicon-aluminum alloy. I'd be happy to provide you with a few.

Rondinone,

Did you download or read the PDF link that I posted above? The whole document is Alusil specific from Kolbenschmidt. They even have specs in there for 944's and other PORSCHE models. The entire document is all Alusil specific.

I've deleted my previous post of page 8 of the document so not to confuse others by the images and actualy getting them to read the information.

Note the last honing operation, with the felt pad. It is exactly the same as using the silicone balls for the final hone. Both are considered plateau honing operations. Neither remove any real metal. THe honing operation I have been recommending is the same as the last step, even if the cylinder liners are not replaced. Again it places a new set of grooves to seat the new rings with, and removes any old extranious metal from the old rings.

The other honing operations are nothin SPECIAL. I have use the Sunnin hone as well as other hones for all the operations. You can even use a hand drill!!! (With suitable skills) I would not recommend the other steps to non skilled people, but the last step, the one with the grape style hone is a no brainer, no skill step. IF you can operate a drill you can do it, sucessfully.

For all the shops that do customers engines, try it, its only 80 bucks or so for the hones, use it on one of your race enignes first, if you do not beleive. You will very soon change your minds if you do. Have you ever fired up an engiine, and HEARD it break in withing 5 minutes??? Thats what these things do.

Nathan, thanks again for more info.
Simon, I noticed on page 8 of the document:

"The fourth and last machining phase is silicon lapping. In this process, the honing stones are replaced by felt pads. The cylinder bore and felt pads are coated with silicon polishing paste. Honing oil is not used. The felt pads and the silicon paste do not effect a measurable material removal. With this machining step, the silicon crystals in the cylinder block are exposed, which leads to a more durable and wear-resistant cylinder surface. An additional long lifetime can be expected from an aluminum cylinder block reconditioned in this way."

I'm not clear that this would be the same procedure our cylinders that have been in use. (I think the statement refers to the whole process which is the installation of new cylinder liners.

This partly answered my question. The paste is a type of polish.
Sunnen No. AN-30 KS Art. No. 50 009 859
Is this paste avalible?

It is not clear to me if the silicon crystals are impregnated just on the surface or thruout the casting. It does however state that it can be bored. So maybe the crystals are throughout the casting.

I also noticed that in the tables it lists at the bottom the Roughness RT.
The final polishing stone gets it to approx 0.6-0.8 my and the Silicon lapping actually makes it rougher (approx. 1-2 my)
What's a "my"?

All of this mounts more evidence that KS cylinders can and are reconditioned sucessfully.
Someone above (I can't see now while I am wirting this reply) asked for
a poll of who has done it sucessfully and who has failed re-ringing Alusil cylinders. So far I have only seen evidence to support it.

Yes I read it. I stumbled upon that document months ago while trying to decide what to do with my own engine. And it is about retrofitting alusil blocks. There's a picture of a guy sliding a liner into a block using dry ice to shrink the liner.

I'm not trying to be a jerk. I just don't want to see anybody foul up their engines by trying to do something that is universally recognized as risky. There's a conventional wisdom here that is being discarded.

I think we're trying to decide if it is 'conventional wisdom' or just standard practice that is justified for a professional builder, but overkill for the do-it-yourselfer.

The fact that not re-using alusil always works does not mean that re-using them will not work.

I just posted the question on the Contact Us link on the KS site.
Hopefully they will respond.

FWIW, I believe Rondinone. His description of aluminum etching instead of honing squares with my previous understanding. This exposes the silicon. Again, I knew this. Also, my cylinders and Doug's cylinders do not have hone marks, even in the skirt area where wear could not possibly have occurred. And finally, I believe that the thorough cleaning of my (in-spec) cylinders made my re-ring strategy successful, by re-exposing the etched surface. I continue to believe (and report to you) that my cylinder walls changed color and texture in JW's BFPW (large parts washer).

Fascinating discussion, though.

Alusils and re-etching chemicals
 

All,
I've red with much interest as one day I too wil have to deal with a broken head stud...knock on wood...it hasn't happened yet. Anyway, as far as etching is concerned. I used to use a motorcycle gas tank sealing product that cmae with an etching chemical. Applying this liquid to the inside of the tank (and ANY aluminum surface for that matter) instantly chnaged the color from a bright semi-polished look to a very dull, dark grey. Not only was the coclor changed, but as Superman pointed out after his parts were run the the BFPW, the surface seemed a bit...how would I put this...porus? Not a sllick, shiny surface, but a very high friction surface almost like comparing a super nice, fully waxed paint job to a flat finish paint. Do you suppose instead of taking the grape hone (which seems reasonable enough...with the intent of not causing the surface to gall), to the cylinder, the in-spec cylinder can be re-etched with the chemical to expose fresch silicon particles on the surface?
R/
Dustin

I completely believe that they can be reused, as evidenced by some people on this board. There's just no guarantee of success. But I also believe that attempting to hone alusil will lower your chances of success. This stuff was not designed to be honed.

The crystals are dispersed throughout the casting. Alusil is made by dissolving elemental silicon into molten aluminum. Like sugar in water, the silicon is more soluble at higher temperature. The silicon/aluminum melt is injected into the cast. As it cools, the solubility of the silicon decreases and tiny silicon crystals form. These crystals may make up 10-20% of the volume of the cast. The cast can be machined, but the final step to prepare the cylinder wall is an etching that eats back the aluminum and exposes silicon crystals, which become the wear surface. Think of it like a diamond tile saw. The exposed diamonds, which are visible, are the actual wear surface. The steel blade just hold the diamonds.

Believe it or not, alusil is actually more expensive to make because it's so difficult to machine. Even today engineers are trying to develop better tooling because conventional tooling doesn't last very long. Also, the rate at which the casts are cooled define the silicon particle size. So the casts have to be carefully cooled. We tend to think of alusil as a has-been material, but it's of great interest to the rest of the industrial world. It's still actively researched. I see a couple of papers a year on various silicon-aluminum alloys.

Personally, I've always suspected that alusil could be re-etched by the home mechanic. It's not difficult because there are commercial solutions (for semiconductor manufacturing) for etching aluminum at very controlled rates. I was going to try this on my own car if I ever needed to re-ring.

I should add that the cylinders should be really clean first. Otherwise the etch might not be consistent.

I bet Superman did unintentionally etch his cylinders. I'm not sure how, but I've been meaning to look into the formulations used in those parts washer solutions to see if anything makes sense. If I find anything I'll post it.

Rondinone et al,
Being new, I'm at a loss to understand why it seems like such a crap shoot to re-ring alusils? I mean, they had to have a fresh set of rings from the factory at some point, obviously. Is the gamble coming from the fact that the embedded material from the rings, blow by gasses, carbon and all the other nasty stuff an engine produces sufficiently "seals" the surface thereby making the success of a re-ring that much more difficult? As pointed out by some folks, a thorough cleaning and re-etching seems to increase the chances of a successful re-ring...dare I say in the realm of the original rings? Heck, I may pop off my barrels to find Nikasils (yea!) but still find this whole subject very intriguing. I really like the idea of a controlled etching (my motorcycle tank example seemed very extreme), and will probably give this a go if the P&C's are in spec. Really, for the cost of an in-spec, used set of Alusil P&C's, it seems like it's worth enough to experiment with them...

R/
Dustin

When I took my cylinders out they were very glazed and polished looking on the insides. After washing them myself with degreaser the insides became very dull/dry in finish much like what I imagine SUPERMANS were like. Im going to be running with them this way. Ive also contemplated giving them a few rubs with a scotch brite pad. What do you think?

Where are all the folks who have had a Alusil Re-Ring job go bad?

I don't know if I missed something or not, but what about nikasil plating the alusils back into spec and match hone them with a set of new pistons? I've done this for a few customers and have even repaired NLA 356 cylinders in this fashion.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

Charles,
I think what you may be missing is the cost factor. EBS quoted me around $1800 to do the procedure you mention (MUCh cheaper than new, and makes for a great alternative). If old, in-spec Alusils can be re-used for next to nothing, it makes for an even more attarctive alternative for dudes on budgets. Truthfully, I'd like to think I'd fork over the $$$ for either a new set of P&C's (or at least a set of replated P&C's), but I can't say I will have the same fortitude when it actually comes time to bust out the debit card...
R/
Dustin

Excellent thread!
Especially appreciate Rondinone's description of the Alusil structure.
Makes me think I'd like to volunteer one of my old Alusil jugs for a re-etching test. If they can be restored this way, I'd think it would be less expensive than having them plated with Nikasil.

I still think Jim (Superman) is right on the renovation of Alusil cylinders.
As he pointed out, John Walker used a powerful parts washer to clean the cyls. Note, he did *not* use any sort of hone, grape or otherwise.
In John We Trust.

Yup, when it comes to opening the wallet, with these engines you have to go wide wide open :-). If I'm not mistaken, my platers will re-do a set of alusils --> nikasil for under $1200 and they give a lifetime warranty on the work. I'm not sure if the price that EBS is quoting includes new pistons and rings, but if it did, that would explain the discrepency to my satisfaction. I have been using them for all my CNC billet aluminum cylinders for almost 3 years now and have not had one cylinder go bad to this day. There have been blems in the plating from time to time, but that's what my QC checks are for...

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance