The "Problem" the experts have is that they are changing someone bokoo big bucks to rebuild their engine for them. If you were the big bucks rebuilder "expert" would you
a. experiment and use something that might not work, give you a bad name, and make the customer unhappy?

b. Use the best materials and methods known to man to give your customer the best possible service and never have a comeback?

If you are not quite the stellar "expert" but want to maximize the bucks your shop makes, then you ALWAYS use brand new cylinders...etc Never give the customer a break even when possible. Are YOU going to re use these cylinders?

If you are selling parts, are YOU going to go out of your way to tell the customer to re use his old parts? (and NO Wayne is not the object of this comment, as it is a generality, and generalitys never apply to everyone).

The whole point is that it is not in the general best interests of the "EXPERTS" to even look into the question possed by this thread, consequently why should we be suprized to learn that they are not up to snuff on the subject. If you have read this carefully you will realize this is not a slam against "experts". Its only what rational people who are concerned about their business and reputation would do under the circumstances. IE ignore a risky, unknown, process with little likely hood of return.

This is the kind of thing the avid amateurs must pursue, but using true expertize.

I beg to differ snowman, the "experts" are there to make money, yes. But that doesn't mean reusing the old parts won't make them money. I'm sure that if the "experts" where more in tuned in our methods of avoiding $$$$$ charges they'd indulge. For example, this sunnen product must still be boughten from somewhere. If i were an "expert", i'd test the procedure then advertise it myself. Why? Because from the little i know, most shops make the most money from labor, not profit off of parts. And the procedure of lapping your cylinders from the way i understand it is mostly labor. Or someone like wayne can sell a felt tool to lap the cylinder, along with this AN-30 product you gentlemen speak of. Make sense.

I just edited out my own response as not relavent to this thread. its gone. I changed the last sentance and left it in.
suffice it to say I disagree with 1fastredsc.

I am especially suspicious about the talk about silicone deposition and etching. I frankly do not beleive it, my opinion. The information produced so far on this thread is probably much more accurate, and usefull.

Well, as it turns out I HAVE re-ringed my Alusils ;) The used Nikasils I purchased were well out of spec, & so I returned them for a refund. Given the information which has come out in this post, and putting my faith in the my Goetze colleague, I've rebuild my motor with new Goetze rings and just a quick wipe clean of the bores ie no special treatment. It will be a few weeks before the car's running but I'll keep you updated as to how it goes.
Fingers crossed!!

Nathan,
Just goes to show you just can't trust those junk Nikasil cylinders...everyone knows that they are basically a one-time use part anyway. ;-)
Wow, that was liberating...

R/
Dustin

This has been an incredible thread!! Sorry for my confusion but I wanted to ask for clarification what the concensus is:

1. The Nicasil cylinder is harder than the piston, and if it's still round you can put in new iron-coated aluminum pistons (sized individually to match) and Goetze phosphate-iron rings?

2. After honing with AN-30 and felt, the honing compound is left in the cylinder because it fills in the pits? A low speed is beter than high because it allows the felt to dig the aluminum between the silicone particles better?

3. Stone honing(even fine grit with oil) is too rough on the Nicasil surface because it creates undesired deep crosshatching? What about for overboring .30(or whatever the standard is) at a higher speed in a pressure wash solution so it cuts the top of the surface better, followed by fine finishing? Still a non-no?

4. Break in new engine using heavy loads so the outer ring material wears into the walls and creates a quasi-mist of iron coating similar to that of the rings/pistons? These are both relatively soft and hold oil and flex slightly to create a low drag surface after break-in?

Nice work gentlemen. I'm sure there more to come.

John,
I think you are confusing Nikasil coated cylinders and the Alusil cylinders that have been the subject of this entire thread. Nikasil cylinders do not require iron coated pistons...aluminum pistons are used. Also, the purpose of the iron coating on the pistons of Alusil cylinders is to prevent galling between the the cylinder and piston. Stone honing is possible with Alusil cylinders provided they are done by the method outlined by Sunnen and finished with AN-30.
AN-30 does NOT deposit anything on the surface of the cyls...it is simlply a lapping paste that cleans up the folded, distorted metal left behind by either the rings or by the honing process to re-expose the silicon particles within the aluminum substrate of the cyl. After the process the reminaing AN-30 compound is removed via parts washer, or simply wiped out. Basically, at a microscopic level, the silicon particles are left proud of the aluminum substrate of the cylinder...essentially forming islands of silicon particles. The piston (rings, actually) never actually touch the aluminum material of the cyl becasue they ride on the peaks of the silicon islands (see the profile graphs on earlier pages). Obviously, the rings will eventually wear the peaks down flat, and the contact between cyl and piston will cause pitting of the aluminum. Hopefully, if oversized pistons are sourced with the proper coating, the cyls could be overbored leaving a surface (after the proper procedure) similar if not exactly like the factory surface.
Again, the problem with overboring Alusil cyls at this time is that there aren't oversized pistons available with iron coating...but some Pelicans are looking into that as well. With any luck a manufacturer will realize that most folks rebuilding SC's and Carreras using Alusils would jump at the opportunity to reuse their old cyls and buy new, over-sized, higher-compression pistons...simply by taking an exisitng product (ie aluminum piston) and coating it with the ferro-coat and tin.
I'm not sure what you mean by the last statement, but ideally the silicon particles would stay exposed forever and not get clogged by the ring material. From what I understand, the randonly dispersed silicon crystals exposed on the cyl wall provide and ideal surface for oil to accumulate in the "wells" between the silicon peaks....like an ocean surrounding a thousand little islands. When the area between the peaks begins to accumulate ring material and piston material, I would think that the wear at this pint would rise dramatically....near the end of the cylinders life expectancy...say 200,000 miles :-)

R/
Dustin

Nathan,

300 posts and the best you can do is a quick wipe?

Just kidding. How many miles were on your cylinders?


John,

I'll answer #2, because that's the only one I know anything about. I'm also going to yammer on in summary of what we've learned.

There isn't yet a real consensus about anything, but what we have done here is to dig up a bunch of info about alusils. Some of the most important information includes:

1. Alusils are a high-silicon aluminum eutectic. The silicon particles are formed in the casting process, as the aluminum-silicon mixture cools and the silicon solubility in the aluminum decreases. The silicon particles precipitate in the aluminum just like rock candy does in cooling water. The silicon is not put there afterwards like it is with nikasil (spit). Hence, the silicon particles are present everywhere in the cylinder casting. The silicon particles were originally exposed by etching back the aluminum after machining the bore. The exposed silicon particles provide a wear surface for the rings. There is no direct aluminum-ring contact, or at least there shouldn't be.

2. KS still produces alusil blocks for the Cayenne, and some mercedes and bmw engines. Rather than chemically etching the aluminum back as before, they now use a procedure developed by sunnen. A very helpful KS engineer seems to think that the cylinders can be reconditioned pretty easily. So did a certain phone rep at Sunnen.

3. Sunnen also markets it's procedure and all the parts necessary to carry it out. Others have posted both the procedure instructions and the relevant catalog page numbers in this thread. The most important part of the procedure is the use of AN-30. Although there is silicon in the AN-30, it's there only as an abrasive, because it matches the hardness of the silicon in the alusil. It's like drilling hardened steel with a hardened steel bit. You won't get very far. But you can drill aluminum with a hardened bit.

4. Some reckless types on this board have tried to recreate the sunnen procedure at home using a cheap spring-loaded engine hone wrapped in felt, plus AN-30. According to some measurements posted earlier, it seems that about 8 minutes of polishing at 100 rpm was adequate. The sunnen procedure calls for 2 minutes, but that's with much beefier equipment. A good indicator for the home job seemed to be the shiny area around bdc. When it started to take on a bit of texture, the rest of the cylinder was ready. It feels like a real fine chalkboard, btw. You can even screetch your fingernails.

5. Some electron micrographs were posted earlier in an attempt to understand how alusil behaves. Those were taken of a very worn cylinder (220k), so there was alot of pitting. Although the polishing compound could be left behind in pits, that's not the intention. Highly pitted cylinders would be poor candidates for a rering anyway. (on edit: Jerry StGermaine's contribution of a used cylinder was very important to this endeavor. It provided practice plus information, which resulted in the confidence to try out the AN-30 on my own cylinders).

My cylinders were slightly pitted in #2 and #5. One interesting note was that the pits were not clearly visible when the cylinders were first removed. After polishing they were obvious. One might ask if the polishing caused the pitting. Maybe, but unlikely. I think they were filled with oil when first removed. When they were oiled for assembly the pits became less obvious.

I just finished the longblock today. Hopefully we'll be starting it up in a few weeks or so.

If you listen to cartalk on npr, some guy called in this week and asked about #4, i.e. break in easily like the factory says or run it hard to seat the rings. Click and Clack said follow the factory procedure. With alusil, there is a compacted debris layer that forms, but I don't really know enough about it to say anything intelligent. I'll probably follow the original factory break in, because I believe that I have recreated the factory cylinder finish. We'll see, won't we?

Great re-cap guys.
It's getting hard to add anything useful except wish Nathan, Rondinone and other's well on their rebuilds. Keep us posted!
Next continue urging Anh911 on his quest for oversized coated pistons.
Any news?
I'm not usually in to this but what about a name for this quest?
Th Myth-buster theme has run it's course. I would say case closed.
We got SCWDP but that's another story and leaves out the Carrerra guys.
I also am intrested in keeping the thread alive as we seem to be in intermission until something new comes up. (Lobby music is playing in my head.)

BTW 3600 miles on my Scotch Brite job today and getting smoother and stronger! It's supposed top be a balmy 45 in D.C. Today!

Rondinone, my cyls have done approx 79k. See my earlier post regarding surface finish. I had mine checked and were within spec for a new cylinder, hence the "quick wipe". I figure if it works, we'll all be laughing, if not, I'll just have to blag another set of Goetze rings from work and start again!!

My bet is that you will be fine!
Good luck!

Bump. Sorry about the typo with the two cylinder materials, plus an idea.
When washing out the AN-30, use a baking soda/basic oil-based wash so it neutralizes(for a day or two) the acid residue in the pits. Is rust neutral Ph?

I think AN-30 is neutral, ie not acidic and therefore dosen't require anything but plenty of washing with hot water with a little Tide laundry detergent, original formula, mixed in, a good stiff bristle brush and a very good rinse. (note don't forget to wipe down the cylinder with a fine coat of oil after cleaning to prevent rust). Can this be confirmed with the Material Safety Data Sheet?

It is a bit hard to get good photos of the surface, but I have two shots that seem ok.

My cylinders were done witht the Sunnen method on a Sunnen machine (by the old-timer who used to do Vega's, the car not the city).

Can someone post higher res pictures? Mine are way too big...

I sent them to Jeremy but he has not replied....

Yes, Jack, AN-30 is not acidic. It's made up of oil, sodium stearate (emulsifier) and the silicon. I cleaned my cylinders by wiping them with mineral spirits, then acetone, then a good hosing with brake cleaner.

Rust is a mix of iron oxides and iron hydroxides, depending on the conditions under which it forms. pH is a measure of proton concentration in solution. It's calculated as -log(proton concentration), so low values indicate higher proton concentration. Acids are solutions of high proton concentration, or low pH. Although rust can be dissolved by low pH, and is more quickly formed at high pH, it's not considered acidic or basic. Laundry detergents, bleach, and most cleaners tend to be higher pH, while naval jelly and soap scum remover are lower pH.

Thank You.

Rondinone et al,
Quick question. I just bought a set of Alusils (P's and C's) which are reported to have 108k miles on them. The bores look fairly fresh...not anything like the pitted experimental cyl that Rondinone sacrificed at the Alusil altar. However, I have noticed lateral scratches on every cyl (save one) that are not only shiny in appearance compared to the rest of the cyl, but are easily detectable with my fingernail. For some reason I just don't remember this type of scratching on other cars I have rebuilt, but to be fair, they were water cooled VW's, and I don't think I scrutinized them very hard. The scratches are consistent with the movement of the rings (along the paralell plane of the piston travel) and are perfectly paralell to each other around the circumference of the bore. One is particulalry bad...the scratch runs the entire length of the cyl for the entire piston path...almost looks like a perfect manfacturing seam. I would assume that some of this is normal (since it occured on every cyl to different degrees), but if prepped with the Sunnen method, should the scratches cause that much of a problem for ring seating? I'm not overly concerned becasue they were really purchased for two reasons: experimentation and to act as a stop gap measure until I can REALLY build the motor I want...say when I retire :-) Are scratches more indicative of a motor that let go a bearing (or some other nasty piece) and the resultant material getting trapped under the rings to cuase them. I was a little dismayed when the box they arrived in was from Motor Meister...but the cyls were in a Mahle box (lol)...dude I bought them from built his motor with FRESH Mahle P&C's, that must have been painful on the old back pocket. At any rate, I'd like to hear any and all thought on this matter if y'all would be so kind...Jack, Rondinone, PBH WIlliam Miller...calling all believers...

R/
Dustin

I think that if you can feel it with your fingernail it needs to go. Either with local polishing eg scotch-brite (short term fix) or Sunnen method (long term fix?).

Mine had scratches in some of them. One was pretty long and deep, like you stated I could feel it with my fingernail. My guess was that at some point a piece of dirt (something hard) caused this. You have to be very careful (Clean) while the inside of the cylinder is exposed to the elements. I think that's part of the reason why Wayne recommends not even taking the pistons out.

Cylinder #4 had no noticable dammage from the broken ring. My guess is because the ring material is softer than the silicon. The broken ring was worn like a mushroom shape on the edge that meets the cylinder.

I wonder if some of the smaller scratches could be from silicon particles
comming loose from the cylinder wall. They are probably too small to see.

Anyway most or the scratches were gone after scotch brite hone. Only the one being notable.

For me this was a budget rebuild to extend the life of the engine.
Luckily the expensive parts were in spec. So, the bottom end is fresh as well as the heads. (New valves, guides, springs.) I ported out the intake side of the heads to match the larger Euro intake runners.)
My P&C's were in spec except for the one noted scratch.

So I am good to go for a while I hope. 10,20,---50K I don't know.
Hopefully anh911 finds someone to supply the oversized coated pistions before I need to do it again.
I plan to do a leakdown, and valve adjust the next time I change the oil. Within a month or two. I will report my results. I don't have a good comparison in terms of performance because the fuel injection was bastardized from the time I bought the car. I finally found a rebuilt Euro fuel distributer that solved 99% of the problems. I think the last 1% is will be resolved when I have some time to spend on dialing in the CIS.

Off Topic Rant:
This may be true for most K-basic CIS but as the car warms up there is a period of time where the cold running compensation components (Auxilliary Air Valve & Control Pressure regulatior) have warmed up to their normal warm running positions and the engine has not reached it's normal operating tempatures. This creates a lean condition until the engine temp catches up. This is only causing a rough idle for 5-10 minutes. (Longer on colder days and shorter on wamer days.) Anyway I need to run it a little rich to compensate.

I bought a new control pressure regulator and the system pressure and the control pressure are dead on the high end of the specifications.
My guess is that when the Fuel distributer was flowed it was done at a slightly higher control pressure. I may need to raise mine up a bit but I hate to open up an new part. Off idle it is always on the rich side probably a little too rich.
I am currently tuning with an analog A/F meter.

Sorry to divert, but we have some pretty good problem solvers here. I'll start another thread if anyone wants to follow.



It's plenty rich on initial warm up.

My cylinders had light scratching also, although I don't believe that any scratches were really that deep. After reconditioning I don't recall any scratches being left behind, but they may have been masked by the added texture.

Check your ring lands. The bad cylinder may have suffered from a broken ring.

Barring a problem with the ring lands, I probably wouldn't worry about it. Can you post a picture?