[32vquattro]

.......have seen many sludged out Audi motors that lost the nicasil and mostly in V8's.....

That's very interesting info you offer up there considering Audi never ever used nicasil.

 

[Noisy Cricket]

FYI, mahle coats their pistons with a graphite coating that is suppose to eliminate the need for recoating. You simply use standard boring techniques and run their pistons as you would with iron bores.

The piston-cylinder problem is negligible, at least compared to the RINGS-cylinder problem.

Put it this way: around 1% of the world's energy useage is wasted on piston ring friction. Not petroleum useage, total energy including hydro, nuclear, etc.

Coated pistons are great because they allow the piston clearance to be minimized, so the rings stay square in the bore and therefore stay more sealed.

 

[pkw]

does audi just use a chrome ring for the alusil bores?

 

[Lord_Verminaard]

Barrel-shaped profile. Like Peter said, JE does supply correct rings for their pistons in the V8 blocks.

Brendan

 

[timmmy]

You do have to use a special honing process FYI, it is available but only 2 or 3 shops in the US that are setup to do it and really know how to do it and hace the correct eqpt.

I have done MASSES of research into this subject over the past few years and have vendors lined up for all parts of the process. If anyone needs it done get in touch.

H

 

[jhmotard]

Any idea of a ballpark cost to repair the Alusil?? A lot of people on AZ complain about oil consumption or scored cylinder walls and most get rid of the car or just replace the motor with a used one. It would be cool to have another option, if cheaper...

 

[scottmandu]

As far as repair of an Alusil bore, you have the option to sleeve or overbore, both are fairly expensive considering the cost to bore/hone a traditional block.

 

[timmmy]

You do have to use a special honing process FYI, it is available but only 2 or 3 shops in the US that are setup to do it and really know how to do it and hace the correct eqpt.

I have done MASSES of research into this subject over the past few years and have vendors lined up for all parts of the process. If anyone needs it done get in touch.

H

There are 2-3 companies in the US that are setup to do it properly, typical cost to hone an Alusil bore is $90-120/hole. The hard part is getting oversize rings that are designed for Alusil bores.

PM me if you need more info on this and other options.

Haydn

 

[Blue_Goose]

I think the common misconception is that Alusil is a coating. Nikasil is a coating. Alusil is a process creating the hypereutectic cylinder. Aluminum-silicon. So somewhat redundant. It is in the reading. Very good info here. I know now what to do. And if I am to build a forced induction S8 engine or recondition/overbore a 2.7T I have the info. It is definitely worth the cost when you consider what an R8, RS6, RS4 go for. Or for that matter the ever dwindling supply of 20V engines. With cars being parted merely for their engines in good no crusty condition its time to figure out an alternative.

 

[toml99]

I was always under the impression that if you bored an "Alusil" block(in my case 3.6pt), that it required some kind of proprietary process that as I recall was about $2800 in Germany in addition to any boring, which is why I don't recall any OEMV8Q american owners that have "bored" any blocks(step up if I missed you). I Know of at least 1 that reringed a motor years ago that had no wear on cylinders at the time, and that motor is still tight many years later(drove in it a few months ago, no smokey). Aside from ring failure/major neglect, I've always assumed that the Alusil block was way harder than the rings, and didn't usually have an issue. The 215K PT motor I"m gonna part here in the next week(hopefully), I"m planning on disassembling it totally(never done it), and have plans on making the block a coffee table......Can't wait to see what the bore's tell me. Car ate no oil when it was parked. Only an idiot would change his oil @10K....not sure why Audi/rest of them think it's ok even with syn.....it still get's dirty. Tom

 

[toml99]

Oh, by the way, if anyone on the west coast(near WA) want's a running 3.6, let me know soon....Ha. Tom

 

[kylel2838]

There is machine shop just outside of Richmond VA that has all of the proper equipment to do anything with Alusil. He used to work for Reynolds Corp who patented the original Alusil Technology that was originally used in the Vegas and is an awesome wealth of knowledge. He re honed the jugs on my 911 engine when I did a top end rebuild and did a beautiful job, and has done many 944 blocks through the years.

 

[Blue_Goose]

The Porsche guys seem to have been rebuilding these for years. Thanks for the heads up on the builder.

 

[123quattro]

FYI, mahle coats their pistons with a graphite coating that is suppose to eliminate the need for recoating. You simply use standard boring techniques and run their pistons as you would with iron bores.

The piston-cylinder problem is negligible, at least compared to the RINGS-cylinder problem.

Actually, getting aftermarket pistons to work in an Alusil bore is just as tough as finding rings. The pistons need a sacrificial skirt coating to wear in to the bore. Porsche used Alusil so there is lots of info floating around on this. Most stock pistons were coated with iron on the skirts. Aftermarket companies claim to have a skirt coating that works. No one with a Porsche 928 has had an aftermarket piston last longer than 10,000 miles.

The best option is to have the block bored like a normal block and then Nikasil dipped. It's about $1000 to dip a block. After that you can run normal rings/pistons so options are endless. There aren't issues with Nikasil anymore now that the sulphur has been removed from pump gas.

 

[Blue_Goose]

FYI, mahle coats their pistons with a graphite coating that is suppose to eliminate the need for recoating. You simply use standard boring techniques and run their pistons as you would with iron bores.

The piston-cylinder problem is negligible, at least compared to the RINGS-cylinder problem.

Actually, getting aftermarket pistons to work in an Alusil bore is just as tough as finding rings. The pistons need a sacrificial skirt coating to wear in to the bore. Porsche used Alusil so there is lots of info floating around on this. Most stock pistons were coated with iron on the skirts. Aftermarket companies claim to have a skirt coating that works. No one with a Porsche 928 has had an aftermarket piston last longer than 10,000 miles.

The best option is to have the block bored like a normal block and then Nikasil dipped. It's about $1000 to dip a block. After that you can run normal rings/pistons so options are endless. There aren't issues with Nikasil anymore now that the sulphur has been removed from pump gas.

From what I understand the Nikasil cylinder repair process is common enough. So maybe that is some information JE already has on hand as far as to why they carry pistons for the 4.2. The factory used an iron coating and barrel shaped ring faces are specified. It is reasonable to assume one could get a set of custom rings and have a set of pistons coated.

 

[123quattro]

The 928 guys have never found a supplier that can successfully coat pistons for use in Alusil bores. Companies sell them, but nothing has worked to date. That's why they either run two sets of 968 pistons, or go Nikasil and then run normal pistons/rings.

 

[Blue_Goose]

Well these guys bored over an Audi 2.7 which I thought was also in the Alusil category. They also used Mahle motorsport pistons to generate some large power numbers. This is a legit build.

http://www.redlinespeedworx.com/worx-wa ... -to-amaze/

 

[alxdgr8]

The 944 turbo (951) guys have 3 different piston choices for retaining the stock alusil bores, I'd imagine it's the same for the 928 guys. Mahle, JE, and Wossner all offer correctly coated pistons. Here's what Chris White from 944 Enhancement has to say (he's a big time 951 engine builder and builds LOTS of alusil bore engines along with MID and other steel sleeve blocks).

Ok time for some piston schooling…
There are several things to think about before you choose your piston de jour.

Frist - what alloy do you want? 2618 or 4032?
2618 - Thought by many to be 'stronger' alloy and a better choice for all out racing. Down side - Higher expansion ratio, faster wear and the alloy is slightly heavier than 4032. The 2618 alloy will start to deform under extremely high loads (caused by miss tuning)
4032 - Quieter on start up, better long term wear. The 4032 alloy will crack under extremely high loads (caused by miss tuning)
In truth either alloy will stand up to hard use in a 944 if the tuning is correct.
Stock pistons are very similar to the 4032 alloy. The original Mahle stroker pistons were 4032. Wossner use 4032 for almost all their pistons. JE will use either alloy but they prefer to use the 2618 on the high performance pistons.
I have used both and I have seen failures with both. They difference in strength in very small. If your engine goes into hard detonation while on boost at the track neither alloy will survive!
Second - piston manufacturer -
Mahle - makes the 'standard' stroker or 3.0 piston in batches every now and then. Seems to drive up the price and demand. They used to be the only alusil compatible pitons available and the price reflected that. I have not worked with them.
JE - big player in domestic racing pistons. They do make Porsche pistons to order but they (in my opinion) don't seem to want to cater to small production runs. Not big on custom engineering designs. Many of their forged blanks are made with chevy valve reliefs that are visible on the underside of the pistons - extra charge to have these machined off. They like to work in SAE measurements instead of metric. Most ring packs are SAE sized. The coatings they offer were not specifically developed for Alusil but they claim that they work. I have heard pro and con comments from people that have tried their alusil coating - I have not tired it.
Wossner - German piston manufacturer specializing in euro cars. I like working with Wossner because each and every order gets its own set of very detailed engineering drawings that I must approve before they manufacture the pistons. They will make virtually anything I ask. You can specify any finished diameter in .01mm steps - nice for making up replacement pistons - you don't have to go to the next 'standard' size. Wossner developed a coating expressly for Alusil blocks, it has been approved by BMW for their blocks (Porsche wont'' approve of anything!). I have one set of wossners that have over 100 track days - no measurable change in leakdown.

Customer Service -
To be truthful all the piston manufacturers can be a little unpredictable in delivery times. I do get annoyed with JE because they offer a 50% 'fast delivery' upcharge. This means that if I order a set of pistons and somebody pays the 50% for their pistons to be made first my order will be delayed. If I order pistons and I am told 6 weeks I expect to have them in 6 weeks - not 8 weeks because orders made after mine coughed up the 50% fee.
I have also had a several sets of JE's that were missed fabricated and even though it was their fault the replacement set were added to the back of the que - another 6 week wait.

I use almost all Wossners now because the engineers will work with me and I can get exactly what I want. I also like the ring packs they supply - lighter and a nicer finish that the standard stuff JE supplies.

 

[alxdgr8]

Well these guys bored over an Audi 2.7 which I thought was also in the Alusil category. They also used Mahle motorsport pistons to generate some large power numbers. This is a legit build.

http://www.redlinespeedworx.com/worx-wa ... -to-amaze/" onclick="window.open(this.href);return false;

2.7 is iron block.
IIRC, only the Audi V8's are alusil, pretty much everything else is iron.

 

[123quattro]

The 944 turbo (951) guys have 3 different piston choices for retaining the stock alusil bores, I'd imagine it's the same for the 928 guys. Mahle, JE, and Wossner all offer correctly coated pistons. Here's what Chris White from 944 Enhancement has to say (he's a big time 951 engine builder and builds LOTS of alusil bore engines along with MID and other steel sleeve blocks).

944 is half of a 928 engine. They both have the same oiling issues. Mahle and JE don't have anything that works. Wossner sounds possible, but I've never heard of anyone using them. Looks like about $200/piston assembly. That's pretty reasonable.

The only mention of these pistons on the 928 forum. No one has tried them. I don't doubt they work though.

http://forums.rennlist.com/rennforums/9 ... 8-a-3.html