The compression would be obviously low on that car maybe even lower with the SC crank which is a shorter stroke. However there are other things that go into the mix.

Someone mentioned a problem with wrist pin size. The wrist pins are about 1mm larger. My guess is that the busging could be bored out that much. or bore out the rod end a little to accept the larger bushing.

Cylinder heights are about 1mm different. The dome shape and placement of the wrist pin also effect CR.
The coating seems to kill the deal anyway.
It was worth a shot!

There's a scale on the lower right of all those EM photos. It might say 10 um, that's 10 microns.

I'm really stoked about this rebuild. I will be sealing up the case this weekend, my cams are on their way back from EBS (330 grind), I've got my heads back from the valve rebuild, and now it looks like these cylinders are going to cooperate. I've still got some painting and transmission work to finish, so it's looking like another month before it's all back together. So it'll be that long before we know if this reconditioning worked.

Is anybody else here thinking about trying this AN-30 polish (besides anh911)?

Ok, i know this thead has gone on for what seems eternity with enough information on ausil to write a doctorit on it. I just got my parts back yesterday, including the cylinders. I gave my old boss a call, who runs the shop, to give me the smack down on everything that was done.
In his exact words, this is what he had to say about the cylinders. "We measured the cylinders, they were in spec. We sent them out to this place that does a "special" type of honing that they call lapping. The process involves a silicon paste that's slightly acidic. The reason for the acid is so that the paste will take a small layer of aluminum off and the silicon will replace it. Therefore the piston rings actually ride on a microscopic layer of silicon, which came from the paste, and never contact the aluminum. Put plenty of oil on the rings when you reinsert them into the barrels and break-in should be no problem."
I haven't read through the entire thread and all the theories that were posted on ausil cylinders and how they are "freshened up". But from scimming through, what he tells me seems along the lines of what some others here have mentioned. If anyone likes, i can take a close up picture of one of the inside walls and post it, they looks kind of different compared to when they left.

1fastredsc,
I think they got it partially right, in that silicon paste is used...AN-30 from Sunnen. It does not contain any acid, but it does remove the aluminum of the bore through mechanical action using a felt honing device to re-expose the silicon particles that are dispersed throughout the substrate. However, (Rondinone can correct me if I'm wrong) the paste does nothing more than lap the surface and does not deposit any silicon back into the aluminum substrate. They are also correct in saying that the rings actually ride on the peaks of exposed silicon particles, never actually contacting the aluminum. I think however, if the car has lots of miles, the rings finally machine the silicon particles even with the aluminum surface, and as a result, a severe pitting of the bore occurs.

Rondinone,
I have made arrangements to purchase a (relatively) low mileage set of alusil P&C's, whihc I am planning to polish with AN-30. I figure for a couple hundred bucks, if they last 50,000 miles it'll be worth it. If I get more then it's gravy but at least I'll have seen it with my own two eyes and will just have to pony up for a reconditioned set....

R/
Dustin

Rondinone, I think you will be very sucessfull with the rings sealing properly. Considering the method I used, I am confidant.
Maybe it's time to consolidate the into. Maybe Wayne can post an article in the tech section. He could possibly put together a kit.
How much of the AN-30 did you use anyway? What did it cost?

Konish, I bet they will last longer. anyway by that time someone might have resolved the overbore piston avalibility problem.

I used about 1/5 of a 1 pound can, and I could have used much less. The total cost was about $32.50 for the paste and a few bucks for the felt. As of this weekend all six cylinders are polished, and the new rings and pistons are installed back in the cylinders.

If this works on my car, and a few other people are willing to try it on their cars also, maybe we could consider a tech article. Although I'm also confident that this is going to work, I'm a bit hesitant to recommend this to anybody else until we've tried on some willing guinea pigs. I'll have mine up and running in a month or less.

Konish, yes the AN-30 is only mechanical. When I started out on this epoch I was thinking about using some sort of acid etch, or electrochemical etch, but then decided on the polish because of it's availability and some control problems associated with etching (not to mention that it's used on the cayenne). It's possible that some shop has developed their own procedure that works based on an acidic polish. It's interesting that we've now heard of two shops that can recondition these cylinders. It would be nice to have that sort of information available to the rest of the community, for those who don't have an adventurous spirit.

1fastredsc,

Please post those pictures you mentioned. I'd like to see if they look anything like mine. Thanks,

Rondinone,
Not a bad price on the paste, you mentioned a few bucks for the felt.
What did you use in the end? Did you happen to price sunnen's portable hone and their felt pads?
Who supplied it to you?
I like your idea about posting info about shops that will do this as well.

Rondinone,
I well remember when we were going down the road of etching, but the upside of allowing that "free thought" brought us to where we are today. I think too, Jack (aka Snowman) offered up some ideas about the grape hone that we have quasi-confirmed but was intially thought of a heresy by the circles of elders. I would conisder myself a willing guinea pig...can't wait to give it a try. Of course you're right in saying that 1fastredsc's shop may use a acidic paste for etching as well as the mechincal lapping action of the silicon. However, I am still a little suspicious of claims that the paste re-deposits silicon particles of any significance to the surface. Also, as you mentioned I would think that using acid in the silicon mix would result in the same control problems you mentioned about controlled etching. Having said all that, I will say that I have no idea what I'm talking about, but I am willing to learn. When I do get my cylinders, I'll have them spec'd and proceed from there....:-)

R/
Dustin

The felt was actually a turtlewax miracle towel from Advance that was cut, doubled over and wrapped around the stones of a cheap engine hone. Real felt would probably work better in hindsight, because the miracle felt tore up a bit too easily. I never looked into the portable hone, but if I ever do this again I'll probably think about it.

The paste can be ordered directly from Sunnen. Here are two numbers from the order sheet, but I can't remember which one I called.

314-781-2100
1800-325-3670

The part number is just AN-30.

I posted a patent earlier in this thread that detailed an etching procedure from Daimler Benz. It contained a pretty good technical discussion on the problems associated with etching, and that really sealed it for me. Being that I'm a chemist, and not an engineer, I was sort of enamored with coming up with a chemical approach. But there are just too many things that could go wrong, especially with a cylinder wall that might have lots of little invisible pits.

When I first removed my cylinders I thought that they looked pretty good. After cleaning them up I noticed that two had some pitting that wasn't visible before. Etching them would have been a disaster.

You guys must excuse the blurryness of the pictures, my digi cam doesn't compensate for the fact that i don't hold it still enough i guess. Anyhow, here are some photos, i'll give the cylinder a second shot this week before i put them on with the heads and close up the motor.
http://forums.pelicanparts.com/uploa...1075784769.jpg http://forums.pelicanparts.com/uploa...1075784794.jpg http://forums.pelicanparts.com/uploa...1075784824.jpg http://forums.pelicanparts.com/uploa...1075785153.jpg

1fastredsc,
Would you mind telling us where your cylinders were sent to have them cleaned up? They look great!

Also, does anybody remember the reply to this thread about a small shop in Canada that did another set of Alusils...there was also a mention of the old timer doing a bunch of vega work too...not that I own a vega...no, really....

R/
Dustin

Dustin,

PBH was the one who mentioned the "old timer" in Toronto, Canada. You can email him at: harper "at" fhwelding.com

His replies are on pages 12, 13.

Ok, there's one pic with a flash and one without. Extra credit if you can figure out what book that is under the cylinder. Anyhow, the shop i sent my cylinders to i believe sent them out to someone else to have this done. So i don't know who did the work, but the shop that took care of it for me was PowerTech Porsche in Rockaway, NJ. Just to repeat what's already been stated about this, the more permanent fix for this is to switch over to nikasil cylinders. This is more for the financially challenged looking for a temporary fix until funds permitt more costly upgrades.
http://forums.pelicanparts.com/uploa...1075834922.jpg http://forums.pelicanparts.com/uploa...1075834945.jpg

That's Wayne's rebuild book.

Please send the Kinesis wheels I won to................. :D

I thought the topic mostly dispels the belief that the Alusils cannot be reused with confidence, unlike reusing a Nikasil cylinder? :confused: The big slam against the Alusil was the "rings won't seat" issue. The refreshed cylinders pictured on a microscopic level here look to be ready to seat some rings and not be a temporary solution. As long as the P's & C's are in spec., switching to Nikasil P's & C's seems like a waste of alot of money. That is, unless you're increasing displacement or changing pistons for cam, valve clearance, or induction system (or all of the above) issues.

Looks *slightly* familiar...

I haven't read this entire thread, but I do have some opinions. You can reuse the Alusils, but do so at your own risk. Just about every expert rebuilder I spoke with does not like Alusils on rebuilds because they sometimes will not seat new rings. I guess if you're rebuilding your own engine, and you can afford the time to tear it down again if the rings don't seat, then fine. I have also heard that the Alusils may wear out very quickly after a rebuild - but I have also heard the contrary too.

It would seem that Nikasil is the only *sure* bet, which is why I recommended this approach in the book. While I'm sure that you could use Alusils in a rebuild, you may want to rethink that if you don't have time to swap them out later on...

-Wayne

Wayne:
Some have been waiting for your opinions here. When you get the time I invite you to read the entire thread. There really is alot of factual based knowledge in it. I especially treasure the info we recieved from the cylinder manufacturer (KS) and Sunnen. They have both developed a procedure and endorse it by providing the materials to do it. I think with the recommended procedure the longevity after rebuild is most likely extended and the risk of ring seating failure is signaficantly reduced.

What is great here is that enthusiast community has come together and found some viable options where before little information was known.

Many are rethinking the "Nikasil is a sure bet" because of the reported experience within the BMW community.

Then again if I were an expert rebuilder I would most likely recommend new parts every time as opposed to reconditioned parts. In that situation my reputation, and the consideration of warrantee claims would be on the line. (I think I've said that before.)

Again, a quest was made for anyone to report problems they had with rings seating following a ring-job on Alusils. After the few month's life of this thread we have only herd sucess stories and no failures.
(Many of the sucess stories were with very unconventional methods because of the lack of knowledge we have today.)

Please read all the information and circulate it among your engine experts and I would love to here their comments.
I have no place or intention of challenging anyone's wisdom and especially the knowledge you have consolidated into you book which I believe is a tresure as well.

For those of us that can't afford new P&C's and want to extend the life of their engine we have an option based on facts. Your endorsement and or comments would mean a lot.

The reason i stated this is because the shop that i sent my stuff to, although stands behind this procedure for ausils, still doesn't like them. The vibe i'm getting is that from their experience ausil is just flat out inferior for the performance minded to nikasil. That vibe might be because they are all racers in that shop, and that's all they think about. If ausil is every bit as good as nikasil, well than maybe i'm wrong. I do know that when i have the funds, some 98mm nikasil barrels with some 8:1 compression JE pistons will be in my sites (and a garrett turbo to go along with it :D). But until then, if i can get 60k miles out of these ausils, i'll be happy.

Understood 1fastredsc.

Thanks for the clarification.

Wayne,

It's about time you chimed in. Excellent rebuild book, by the way.

My only question is: how many expert engine builders have tried the Sunnen procedure for refinishing high silicon aluminum? My own wrench had never heard of it (he's owned a porsche shop for 20 years).