Re-ring Alusils?

[konish]

William,
The last sentence was the last of the web page, and I'm not sure if there was supposed to be anymore info, but I agree in that it is open-ended suggesting there was more to follow. However, elsewhere on the page, there was a link to the same page that Simon provided earlier, which I just assumed was the procedure to which the artilce refers.

R/
Dustin

[snowman]

I understand a lot about etching as I used to manufacure thin film mircrowave circuits, and design semiconductor ics that required even more precise etching and special processes. But what has been discribed so far is far from any kind of controlled process, and certainly no coupons have been mentioned, ie the first step in controlling this type of process.

What seems to fly over the heads of all these discussions is that the silicone ball type of hone is NOT what might be considered a conventional honing process in that it does things a little differen't, in very important ways than what honing stones do. Again I would refer you to the manufacturer for this information. I think you may find that the process with the Sunnin hone, using silicone paste may be exactly the same as using the siilcone balls, except that you only need a drill to use it, not a $30,000 Sunnin honing machine.

[konish]

Jack,
I read your answer to a previous questions about your actual experience using flex hones to recondition alusil cylinders, and it does sound like a reasonable process. I read as much as I could about the flex hone, and plateau honing over the past few days. Just out of curiosity, how many sets of Alusils cylinders for the 911 have you done this way, and were the results always the same...ie no smoke, good compression, etc. When was the last time you did this, and how many miles are on the last set (if info is available)? I'd really like to explore this option more, but I have to admit without more data, I remain a bit skeptical...but no more so than anything else we have discussed. Again it might be worth just running an experiment...worst case the P&C's have to be replaced, which is essentially square one anyway. Not trying to be a wise-ass, but if the thing works as well as you say, and it's as simple as running the hone in and out of the cylinder for a few passes, I wonder why the process isn't even being discussed as a possible alternative in any of the authoritative literature on rebuilding 911 engines? In every case, I've basically read that Alusils are disposable....? Again, take that last statement however you want, but it isn't meant as an attack or disrespect. Essentially, I think the real value of this thread is to reveal real data that PROVES Alusils can't be reconditioned reliably. For the most part, I rely on expert advice from guys who have great reps in this field, but as I seem to get their "word" second hand, its hard for me to draw any substantial conclusions on this matter.
R/
Dustin

[Rondinone]

OK snowman I'll take the bait. You probably posted the manufacturer's info before, but could you post it again along with some references to the hone's use? Also, are there any references that you are aware of for using this hone with the other alusil engines (vega, bmw)?

Believe me, I hope you are right. Buyign a specialized hone is far cheaper than buying new cylinders.

[snowman]

The following sites have very interesting info on cylinder honing. Free literature is offered that details how Flex hones work and why they are the way to go for final honing or reuse of cylinders that can be honed.

http://www.brushresearch.com/Index....chnicalBooklets
http://www.brushresearch.com/Index....e.FlexHoneTools

I have only a couple sets of Alusils. In addition I have done 7 or 8 other engines.
All with same result, rings seating within 5 minutes of startup, No to nil oil consuption, more power.

The auto tech professor who put me on to these has seen the results of several hundred engines, of all types, including many Alsuils. Always good, always worth doing. He has been using them since they came out, and typically tries every new innovation coming out of the woodwork.

I have read all the available literature, including the newsletters for full time engine rebuilders, and these things are the way to go. UNless you have a sunning hone and can use silicone paste, for just a few cents more, vs buying a $60 ball hone.

[anh911]

Sorry for jumping in here late but let me just make a couple of observations. First I'd like to say this is by far the best thread I've seen, exactly what makes the web such a cool thing...

On topic, it seems like the bad rap that Alusils got was earned in the early days well before it was understood (like it is now??? how to re-finish them, and Superman, well before the advent of the silicone flex-hones came out. I can imagine DIYers in the 60s and 70s using traditional honing equipment and cutting oil on them and having catastrophic results.

FYI I have found a doc that was scanned re this process for 944, 928 etc engines and will post or link once I finish downloading it. At first glance it also talks about using the c10 and finishing with the silicon and felts pads.

It seems to me all we need to do is find a source for the silicon paste, felt is easy...

[jgparker]

In the past, Alusils had a bad rap because they'd wear out of spec faster than Nikasils. The idea that they can not be re-ringed is a fairly new proposal by my memory. Both sets of Alusils I've had were far to worn to reuse anyway.

I agree, this is one of the best threads on this board in a long time. The best part it the discussion has focused on the facts, rather than degrading into personal attacks. Thanks everyone.

JP

[Porsche_monkey]

I have just had my alusils done by a local shop that says he has done hundreds of these on aircraft, Porsche, Mercedes, and Vegas.

They were 'honed' with a felt pad and an abrasive paste for about 30 seconds. They now look clean and shiny but close inspection shows a very light cross-hatch is present.

I don't think I can upload a hi-res picture here, but this what I they look like.

[konish]

PBH,
Wow, they sur elook good. Funny, I was just looking at aircraft engine rebuild sites about the very thing. Some of my friends in the squadron have private planes, and eventually they all have to submit to an overhaul. I would suspect that quite a few private aircraft use Alusil cylinders...most being made in the early to mid 70's, and I'm almost certain a percentage of them have been rebuilt by reconditioning the cylinders. Interesting post!

R/
Dustin

[Porsche_monkey]

I wouldn't pass the aircraft r&r test, I am at the low end of bore tolerance, but I don't expect to drive this car a lot, only the occassional weekend outing in the summer.

[konish]

Hmmm...seesm the BMW guys needed to swtich FROM Nikasil to Alusil in an attempt to stop the high sulphur content US fuels from destroying their Nikasil coatings. Here is the link:

http://www.koalamotorsport.com/tech/misc/v8shortblock.htm

R/
Dustin

[anh911]

PBH, could you ask the shop what paste they use ?? Thanks for the pic too, its a good example of what was said earlier about the difference between a traditional cross hatch on cast iron (non-porsche) cylinder walls and the correct finish on the alusil.

"Hmmm...seesm the BMW guys needed to swtich FROM Nikasil to Alusil in an attempt to stop the high sulphur content US fuels from destroying their Nikasil coatings. "

Does anyone know or have a guess as to why the BMW cylinders have this issue and the Porsche Niks don't? Is it the higher operating temps ??
(just curious)

[snowman]

Originally posted by anh911
[B]PBH, could you ask the shop what paste they use ?? Thanks for the pic too, its a good example of what was said earlier about the difference between a traditional cross hatch on cast iron (non-porsche) cylinder walls and the correct finish on the alusil..........

There should be NO difference between any cylinder of any material for the cross hatch pattern.

The angle of the cross hatch is important, though not especially critical. If the cross hatch pattern is not there it is a very very BIG problem as the rings will not be lubricated. Its these small grooves that hold the lubrication for the rings. With the correct ammount of grooves and approximate angle the grooves provide oil for the rings to float on.

If the grooves are worn out, ie gone, the cylinder walls and rings will wear rapidly. The grooves must ALWAYS be t here. A properly running engine will not have ring ridges, will have cross hatches, even at 100,000 plus miles (because the oil is lubricting and preventing wear).

[Bobboloo]

Hmmm...seesm the BMW guys needed to swtich FROM Nikasil to Alusil in an attempt to stop the high sulphur content US fuels from destroying their Nikasil coatings. Here is the link:

I read the link and found it interesting. Funny thing is all the Porsches where this problem hasn't shown up. Specially considering the high mileage SC's with Nickasils you see on this board that haven't exhibited this problem. Maybe BMW hasn't really discovered the root of the problem but have come up with an alternate fix.

[Doug Zielke]

Note the reference in the article to engine temperatures (changed EPROM and t-stat). Maybe it's a good thing to be air-cooled, with higher operating temps. Porsche has put plenty of Nikasil cyls. in engines, without any problems.

[Porsche_monkey]

[i]If the grooves are worn out, ie gone, the cylinder walls and rings will wear rapidly. The grooves must ALWAYS be t here. A properly running engine will not have ring ridges, will have cross hatches, even at 100,000 plus miles (because the oil is lubricting and preventing wear). [/B]

Sounds logical except that the high mileage alusils I have seen have no ring ridges and no cross hatches left. Does anyone have any evidence contradicting this?

My guess would be that the alusil surface can hold sufficient lubrication without a crosshatch.

[Rondinone]

Snowman, there is a difference between alusils and others. While your statement hold true for almost every other engine, alusils are not honed at the factory. There is no original cross hatch pattern. That doesn't mean that there aren't microscopic crevices to hold oil, however. The crevices are random interstices between silicon particles.

FWIW, here are some good references from the engineering journal "Wear" to articles concerning the wear properties of silicon-aluminum alloys similar to our alusils. Also see the IEEE journals and "Surface & Coatings technology". One of the interesting properties of alusil is that the ring material transfers to the cylinder wall during the initial break-in phase. This causes the cylinder wall to adopt a hardness similar to the ring, allowing for maximum durability. Knocking some of that material off could be part of the key to a successful reringing.

One of these days I'll post a list of references that I've found.

[snowman]

Interesting info. If the initial transfer of ring material to the cylinder walls is what keeps these things alive, then there should never be any cylinder wear, just piston ring wear and piston land wear. So unless something has gone wrong, one should be able to save these cylinders for several sets of rings. Or is there more stuff going on that allows cylinder wear as well?

In any case the removal of the original ring deposits would make a lot of sense. Having some cross hatch shouldn't hurt either. If silicone paste is used vs silicone flex hones, using the same grit, is there really any difference?

Anyone talked to a Porsche engineer yet?

[Rondinone]

You know snowman, there may be something to your honing ideas. Smestas posted this a few days ago:

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

I've read it before, and I always thought that they were referring to a cast iron liner that is fitted into an alusil block. Upon reading again, I see that they are fitting an alusil liner into an alusil block, to end up with something more like the lokasil. But then it's honed with the sunnen machine. My apologies to smestas!

Also, if you go to the Kolbenschmidt web site and read some of their literature, they emphasize that the new cayenne blocks are not etched, but that the silicon particles are "mechanically exposed". I suppose they did this because there is no way to etch only the cylinder (etching is done in a bath), and etching an entire engine block would have unintended consequences. But obviously honing can be done with the proper equipment. I know that somebody has contacted porsche to inquire about honing, but has anybody contacted KS? Or Sunnen?

It's also worth wondering this: Is the current alusil material the same as the older alusil material?

[anh911]

I sent KS an email yesterday about it and haven't heard back from them. I've also been trying to find out exactly what kind of silicone paste is ised and where to get it but nothing yet.