Alusil cylinder block DIY reconditioning

[ZimbutheMonkey]

Not sure if this information has made it on to this forum so I wanted to post it.

If you are doing a teardown on an Alusil block that has oil consumption issues, it looks as though you can recondition the block yourself for around $1000 ($150 in materials and $850 for rings).

Here's what you need:

https://www.goodson.com/search.php?m...keep_https=yes


By way of summary; Alusil blocks use a combination of Aluminium and Silicone which is suspended evenly throughout the entire casting assembly (i.e. it's NOT a cylinder liner)

The honing process removes a few microns worth of Aluminium, exposing the harder Silicone particles which create a porous and hard surface which retains an oil barrier for the piston rings to slide against.

So long as there is no significant scoring, you can use a drill at 150 RPM with the Sunnen felt pads and paste. You hone the bore for about 90 seconds until a dull, matte finish with a faint cross-hatch is obtained.

From what I can see, the paste contains silica, suspended in an elastopolymer. During the honing process, pressure against the cylinder wall should be kept to a minimum. This, combined with the silica being suspended in a medium which cushions the silica particles as they sweep against the honing surface is what makes the porosity uniform and the exposed silicone particles smooth enough as to not damage the rings during break-in.

Have a read through this thread, the latter 2/3 of the thread explains the process very well.

http://rennlist.com/forums/928-forum...dummies-2.html

Bottom line, if you have an oil consuming engine torn down for something like valvetrain servicing and want to take the extra step of disassembling the bottom end, it may be worth the time and effort to hone and re-ring the block. The materials to do it aren't overly expensive (vs a used block that may or may not work any better) and it appears to be quite straightforward to do a re-hone.

If I ever pull my engine for a valvetrain service, I think I'll give it a shot. I'll post up results if I ever get around to it (knock on wood, hopefully later, rather than sooner

Hope this helps

[aroderick56]

We have been honing the alusil blocks in the 944's , dont see why we can't on these blocks

[chain_slappins4]

but can you get oversize pistons that aren't a fortune on the 4.2?

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[aroderick56]

no, not enough material to bore for oversize pistons

[chain_slappins4]

so then honing isn't going to fix scored walls.. UNLESS the scoring is minor

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[chain_slappins4]

pretty silly to have a one time use block... can these blocks be sleeved?

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[aroderick56]

honing isn't for fixing cylinder wall scoring, so this will only work with cylinders without significant scoring. It will remove small marks but not much else

[aroderick56]

pretty silly to have a one time use block... can these blocks be sleeved?

Sent from the S4 with a Tap!!!

yes but its not cheap and not easy to do

[chain_slappins4]

so then getting a block with any type of compression loss due to scoring in hopes of fixing it is a waste of money

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[aroderick56]

all depends on what you consider a waste of money, i plan on sleeving my block in the future

[pwest15]

I believe it's possible to actually fix more than minor scoring by doing a nikasil coating treatment. I believe the coat the whole cylinder with nikasil, then hone everything away, a bit past oem tolerances just so all the scores are filled, and then they recoat and hone back to oem diameter. The nikasil which will hold up better than alusil as well and can possibly be an alternative to sleeving although I don't think you could push it quite as far. I know that a few shops were willing to perform this treatment on a BHF 4.2 block but their names have escaped me because I wasn't the individual who got in touch. I believe one is in Indiana and they charge something like $1200 but that's all I know haha

[aroderick56]

Just to add to pwest15, sleeving will be able to make more horsepower and be way more dependable

We do quite a bit of Porsche blocks for the road racing guys, both with nikasil and alusil but those guys are stock n/a just looking for a freshen

[chain_slappins4]

Just to add to pwest15, sleeving will be able to make more horsepower and be way more dependable

We do quite a bit of Porsche blocks for the road racing guys, both with nikasil and alusil but those guys are stock n/a just looking for a freshen

so then how much work is it to sleeve these BHF blocks? and how expensive?

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[jr1415us]

See this thread/ argument about the realities of sleeving the 4.2l motor: http://www.audizine.com/forum/showth...light=sleeving

[ZimbutheMonkey]

honing isn't for fixing cylinder wall scoring, so this will only work with cylinders without significant scoring. It will remove small marks but not much else

I can't say for certain how deep the scoring needs to be in order to render the block useless. However, it wouldn't surprise me if a good chunk of the oil consumption/compression loss that occurs in these engines is the result of a bunch of minor (even microscopic) scoring on the walls.

If this is the case, it may well be worth doing it, even if you can't remove all the scoring. If you can at least repair the bulk of the damaged sealing surface area, I;ll bet you could regain a good portion of lost compression and significantly mitigate future oil consumption.

The scoring/compression loss issues on our engines can't be that much different from the Porsche ones, and they seem to be getting good results with this treatment.

I mean, for the minimal cost of materials, why not give it a shot, it's a hell of a lot cheaper than rolling the dice on a used engine that may suffer from the exact same issue and as others have mentioned, sleeving these engines seems to be an expensive crap shoot at best (if it can even be reliably done at all).

[q_dubz]

Good info

[ZimbutheMonkey]

Good info

thanks

Maybe this has been discussed and I just missed it, but the impression I get is that people just seem to throw their hands up in the air and give up when it comes to oil consumption and compression loss.

It kinda surprises me that more people aren't doing this (or then again, maybe it shouldn't....) but it seems that re-honing has been a pretty common practice for some time in the Porsche community.

EDIT: there appears to be at least one thread on the subject on AZ http://www.audizine.com/forum/showth...-engine-honing

However, no one seems to have actually reported back on whether or not it succeeded.

As well, the ring sets aren't cheap by the looks of it (about $800).

Still, as long as there weren't a ton of deep gouges in all the cylinders, I'd sooner bet my $1000 on a rehone and re-ring vs a used block, even if there was some minor scoring left afterwards.

My thought is that even if you have a little residual scoring, having the proper porosity on the rest of the cylinder would likely allow for enough oil to be carried to regain you most of your compression.

[aroderick56]

i think alot of that has to do with people not having the experience or patience to figure it out. its very common with the porsche's, it could become more common with these engines. I think there is a huge disconnect because people are able to buy these cars inexpensively but dont/cant spend the money to pay repair bills.

[ZimbutheMonkey]

i think alot of that has to do with people not having the experience or patience to figure it out. its very common with the porsche's, it could become more common with these engines. I think there is a huge disconnect because people are able to buy these cars inexpensively but dont/cant spend the money to pay repair bills.

You make a good point, I guess I never viewed these cars as being cheap to buy.

That being said, there are a lot of people who have likely spent at least $2000-4000 to buy a used engine, and that's not chump change (at least in my books lol).

Also, since you seem to have some knowledge of the procedure, care to have a quick re-read of my post (I added an edit) and weigh in on the last part (re: the rehone restoring a good portion of the compression even if there was still some residual scoring afterwards?)

[q_dubz]

Yea I figured this out years ago before even owned the car. I've known plenty of Porsche owners over the years and have a few industry contacts who filled me in as well.

I'm not sure why there is this doomsday stigma about this engine. It's nothing special but people don't care to learn or at least conduct a little critical thinking on their own.

What follows is regurgitation of imperfect info from other sources that gets even more misconstrued over time.


Anyway, sleeving and nikulsil coating both with run about the same cost in the end..... Expensive lol.

[ZimbutheMonkey]

Yea I figured this out years ago before even owned the car. I've known plenty of Porsche owners over the years and have a few industry contacts who filled me in as well.

I'm not sure why there is this doomsday stigma about this engine. It's nothing special but people don't care to learn or at least conduct a little critical thinking on their own.

What follows is regurgitation of imperfect info from other sources that gets even more misconstrued over time.

well said.....

What really surprises me (given the value of their vehicles and engines) is that no one in the RS4 community has tried this. (then again, I guess your point above probably applies even more to that crowd lol).

Also, from what I've seen, Nikasil is also prone to damage if there is any hint of Sulfur in your fuel. Probably not a big issue in North America, but still, it's definitely a drawback of the procedure.

[SprintBlueWorld]

Let the experiment be made.

You could be a Hero to folks with this problem, and or a villan at the same time, to those who threw away their cars due to it. You have to consider though it's a lot of work just to be able to access the cylinders then button back up reinstall and test. Many wouldn't even try, and just part their car out. Many who do try have already made up their minds to throw money at it and not "scimp" out or risk the same or another sort of failure by trying to save money somewhere.

I still don't understand why no one has engineered metal guides for our cars. Are thry really that complex that a 3d printer couldn't replicate?

[emcaha]

I still don't understand why no one has engineered metal guides for our cars. Are thry really that complex that a 3d printer couldn't replicate?

It's not the complexity but the physical property requirements which would negate a 3D printer application. You'd also have to have a set of new guides to generate a solid model to use as the "master" for duplicating. There's been a few previous threads around the idea of making your own replacement guides and the application isn't very cost effective with such a small demand. This thought process is exaggerated with the idea of making your own plastic replacement guides.

The only real solution would be to get a set CnC'd but you're talking manufacturing on a one-off scale which again, isn't very cost effective. In general I think the same thought process as this thread's sleeving question would apply. With enough time and money anything is doable but is it a reasonable alternative.

[chain_slappins4]

It's not the complexity but the physical property requirements which would negate a 3D printer application. You'd also have to have a set of new guides to generate a solid model to use as the "master" for duplicating. There's been a few previous threads around the idea of making your own replacement guides and the application isn't very cost effective with such a small demand. This thought process is exaggerated with the idea of making your own plastic replacement guides.

The only real solution would be to get a set CnC'd but you're talking manufacturing on a one-off scale which again, isn't very cost effective. In general I think the same thought process as this thread's sleeving question would apply.

I was discussing with another member here about making all the guides out of steel or forged aluminum, even if just for myself. I think if I could get my hands on a clean set, blueprint it, then I could modify it, and essentially take that weak link out of the equation. the other members seems to think it would be dangerous given the fact that steel or aluminum does not give, but if it's designed correctly, or redesigned better, you don't need to worry about give.. just would need to do an analysis to see which material would be best suited to this application.

Sent from the S4 with a Tap!!!

[aroderick56]

You make a good point, I guess I never viewed these cars as being cheap to buy.

That being said, there are a lot of people who have likely spent at least $2000-4000 to buy a used engine, and that's not chump change (at least in my books lol).

Also, since you seem to have some knowledge of the procedure, care to have a quick re-read of my post (I added an edit) and weigh in on the last part (re: the rehone restoring a good portion of the compression even if there was still some residual scoring afterwards?)

Even if there was some scoring leftover, a fresh hone/pasting could provide better compression results. It is all very dependent on conditions

edit: I did discuss this with Dean about trying it on my block while it was all out. We decided, at least for myself, that it would be best to sleeve my spare block instead because of the ultimate power goal I want. More power and more durability

[aroderick56]

JHM timing kits already take out the weak links of the timing system, no need to try and engineer new guides.

[chain_slappins4]

JHM timing kits already take out the weak links of the timing system, no need to try and engineer new guides.

but the JHM timing kits still use plastic parts, correct? when you mix plastic with chains moving at what ever speed, and plus you have a metal cam that moves these plastic guides in and out, flexing the plastic back and forth how ever many cycles, nah.. I'd rather make them out of something a bit more durable then plastic.. it'll cost me nothing more then my time and material. I have the equipment to make it, already spent the money on education, and my family owns a machine shop.. besides, I love a good challenge...

Sent from the S4 with a Tap!!!

[Hooblah]

Is there no other coating that can be applied to the block other than alusil/nikasil? It's been almost 15 years since the first S4 was produced, surely there must be some new tech in that time? I remember nikasil going back to the 90s. In fact I've just googled it and wikipedia says nikasil was developed by Mahle in 1967. Near enough 50 years ago!

And what about coating the pistons and rings instead of the cylinders with coatings such as Nitron CA and Diamolith DLC?

Another approach could be oversize pistons. What's that likely to cost versus getting it recoated?

Here's an interesting article:
http://www.mmsonline.com/articles/au...n-applications

[chain_slappins4]

Is there no other coating that can be applied to the block other than alusil/nikasil? It's been almost 15 years since the first S4 was produced, surely there must be some new tech in that time? I remember nikasil going back to the 90s. In fact I've just googled it and wikipedia says nikasil was developed by Mahle in 1967. Near enough 50 years ago!

And what about coating the pistons and rings instead of the cylinders with coatings such as Nitron CA and Diamolith DLC?

Another approach could be oversize pistons. What's that likely to cost versus getting it recoated?

Here's an interesting article:
http://www.mmsonline.com/articles/au...n-applications

further up its been said that there really isn't enough material for a bore and oversize pistons, I thought that would be an option also.. but looks like that one is a no go

Sent from the S4 with a Tap!!!

[ZimbutheMonkey]

Is there no other coating that can be applied to the block other than alusil/nikasil? It's been almost 15 years since the first S4 was produced, surely there must be some new tech in that time? I remember nikasil going back to the 90s. In fact I've just googled it and wikipedia says nikasil was developed by Mahle in 1967. Near enough 50 years ago!

And what about coating the pistons and rings instead of the cylinders with coatings such as Nitron CA and Diamolith DLC?

Another approach could be oversize pistons. What's that likely to cost versus getting it recoated?

Here's an interesting article:
http://www.mmsonline.com/articles/au...n-applications

Technically, Alusil isn't a coating, the entire block casting is the same material throughout. After reading up on it and giving it some thought, I've actually realized that it's probably the best way of making an Aluminium block as it can technically be bored oversize and re-honed just like cast Iron.

Where the problem lies is that in order to shoehorn the block into the B6 frame, Audi made the space between the cylinder walls paper thin. If there was another 3-5 mm of material, you could just re-bore a severely scored block it, get it re-honed and put a set of oversized pistons in.

[Hooblah]

Hmm. Just how badly do the cylinders get scored? I can't see it being and deeper than 1mm, even 1mm is pushing it. And what exactly causes the scoring in the first place?

[emcaha]

I was discussing with another member here about making all the guides out of steel or forged aluminum, even if just for myself. I think if I could get my hands on a clean set, blueprint it, then I could modify it, and essentially take that weak link out of the equation. the other members seems to think it would be dangerous given the fact that steel or aluminum does not give, but if it's designed correctly, or redesigned better, you don't need to worry about give.. just would need to do an analysis to see which material would be best suited to this application.

"but the JHM timing kits still use plastic parts, correct? when you mix plastic with chains moving at what ever speed, and plus you have a metal cam that moves these plastic guides in and out, flexing the plastic back and forth how ever many cycles, nah.. I'd rather make them out of something a bit more durable then plastic.. it'll cost me nothing more then my time and material. I have the equipment to make it, already spent the money on education, and my family owns a machine shop.. besides, I love a good challenge...


Sent from the S4 with a Tap!!!

Yes, the JHM kit uses the OEM plastic components except the one updated RS4 metal guide. I agree if you have the means to do something like this easily then go for it. Have a machine shop at the place I work at as well and have built a few small pieces instead of buying before but nothing I deem as a critical component. A big factor in material selection is going to be the different hardnesses of interacting parts and what will inevitably become the "wear" item. Making the guides out of a harder material such as steel could transfer the wear to the chain itself which could becomes just as (if not more) detrimental. The same thought process would be applicable to the cams actuating the guides, more weight of guides or more required pressure from metal on metal could cause the cams themselves to fail.

Not knocking your thought process at all but it's definitely something to consider. Honestly, can't believe I'm even sounding like I'm defending the plastic guides but in the grand scheme of things if I had to choose a wear item out of the timing system, I think the guides are the proper choice (and I'd be willing to bet Audi had a similar thought process). It's inevitable that parts are going to wear, trying to figure out what the wear item will be or how to tailor it to the part you want to wear is the challenge.

I'd really like to see metal guides with possibly a plastic wear plate for the chains to ride on. Think there is a few components of the timing system which have this. That way if the wear plate was to fail/break you'd have the metal guide to fall back on and keep enough tension on the chain so you won't skip timing.

My .02 on the matter.

[q_dubz]

Let's be clear here. The guides will still wear. They are plastic covered. Otherwise it would be bad. They are NOT supposed to break.

[chain_slappins4]

Yes, the JHM kit uses the OEM plastic components except the one updated RS4 metal guide. I agree if you have the means to do something like this easily then go for it. Have a machine shop at the place I work at as well and have built a few small pieces instead of buying before but nothing I deem as a critical component. A big factor in material selection is going to be the different hardnesses of interacting parts and what will inevitably become the "wear" item. Making the guides out of a harder material such as steel could transfer the wear to the chain itself which could becomes just as (if not more) detrimental. The same thought process would be applicable to the cams actuating the guides, more weight of guides or more required pressure from metal on metal could cause the cams themselves to fail.

Not knocking your thought process at all but it's definitely something to consider. Honestly, can't believe I'm even sounding like I'm defending the plastic guides but in the grand scheme of things if I had to choose a wear item out of the timing system, I think the guides are the proper choice (and I'd be willing to bet Audi had a similar thought process). It's inevitable that parts are going to wear, trying to figure out what the wear item will be or how to tailor it to the part you want to wear is the challenge.

I'd really like to see metal guides with possibly a plastic wear plate for the chains to ride on. Think there is a few components of the timing system which have this. That way if the wear plate was to fail/break you'd have the metal guide to fall back on and keep enough tension on the chain so you won't skip timing.

My .02 on the matter.

that was another option I was looking at, but how to reliably fasten/attach the Delrin to the steel core... if they made these parts like this for the RS, is there maybe a way to modify it to fit the BHF blocks?

Sent from the S4 with a Tap!!!

[chain_slappins4]

Let's be clear here. The guides will still wear. They are plastic covered. Otherwise it would be bad. They are NOT supposed to break.

yes they will. anytime you have steel moving over plastic, the end result will be the softer material being worn away. on the issue of breaking... maybe a better idea would be to reinforce the plastic guides with steel or aluminum inserts around the known breaking points..

Sent from the S4 with a Tap!!!

[emcaha]

Let's be clear here. The guides will still wear. They are plastic covered. Otherwise it would be bad. They are NOT supposed to break.

100%. I am in no way defending or trying to justify the breaking of guides or the plastic guides themselves. And yes, the guides will still wear. It's a question of if other parts will begin to wear more with a change of materials.

Chain Sappin: You'd have to figure out some type of snap feature or something similar to not have to rely on screws, bolts, adhesive, etc. Ideally you'd overmold the plastic onto the guide and add some internal retention features but not very applicable in a one-off. The plastic on top of metal timing components I was referring to are in BHF engine already.

[q_dubz]

yes they will. anytime you have steel moving over plastic, the end result will be the softer material being worn away. on the issue of breaking... maybe a better idea would be to reinforce the plastic guides with steel or aluminum inserts around the known breaking points..

Sent from the S4 with a Tap!!!

that's exactly what the updated RS4 ones are...

[chain_slappins4]

that's exactly what the updated RS4 ones are...

only in the RS4 ones.. correct?

[q_dubz]

They swap over to s4

[chain_slappins4]

well shit.. then there is no need for any more talk on that subject

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