Alusil and Aluminum Pistons???

patkeefe · 03-26-2008, 05:10 PM

Hi:
Will aluminum pistons (garden variety Mahle RS 90mm) which have been coated with a dry film lubricant work in Alusil cylinders?
Anyone ever try this?
TIA
Pat

kenikh · 03-26-2008, 06:24 PM

Ping Charles Navarro.

Steve@Rennsport · 03-26-2008, 07:44 PM

Not for long,....

They need the iron-coating, just like what Kolbenschmidt did to make them last in that bore.

cnavarro · 03-27-2008, 05:46 AM

Yup, it's been tried. I had a poor soul with a mercedes whose mechanic tried that - lasted 1000 mi.

patkeefe · 03-27-2008, 06:14 AM

Thanks to all
I do not want to become relegated to "poor soul" category!

Charles, I suppose the KS factory coated the pistons with some sort of ferro-something coating, maybe a plasma, such that the cylinders bore the brunt of the wear, as opposed to the Nikasil/aluminum piston, which effectively sacrificed the piston?

I have coated skirts on these pistons, but they would need to have some sort of ferrous coating rather than the PC-18 (sic) I have. I suppose these would gall up pretty good, huh?

Thanks!
Pat

fumanchu · 03-27-2008, 08:37 AM

I had PC-9 on KS pistons in a 951 block. The iron coating was wearing off and I thought I would give it a try.....That car is a track beast to this day, and made 286 hp at the wheels on a chip and K26/8 turbo @15psi. I dont think alot of people have gone this route. Conventional wisdom and dollars keep it from happening.

When my 911 needs a build, I will going this route as I'm pretty sure the cylinders look like Alusil.

There are alot of coatings that mimic what the iron coating does. Actually, I was told the iron coating is old tech, and there are vast options today. Take this info with a grain of salt, as much of it is conjecture without empirical evidence. The only real facts I have is the application on a 951, and that car rips up British Columbia tracks. 911's may be different.

My question is how far can you bore an Alusil cylinder and be safe? Can a 95 mm be taken out to 98mm? Piston castings from JE could be used with a coating.... 3.2 liters on a budget? Who wants to be the guinea pig?
Shawn

cgarr · cgarr's Garage

Quote:

Originally Posted by Steve@Rennsport

Not for long,....

They need the iron-coating, just like what Kolbenschmidt did to make them last
in that bore.

Those would be the ones that are slightly magnetic?

patkeefe · 03-27-2008, 06:04 PM

Fumachu, that is interesting info.
I am going to further investigate the failure mechanism, metallurgically speaking, of aluminum in Alusil. I did read some sort of technical document from KS not long ago, which is what got me thinking about this.

cnavarro · 03-27-2008, 06:10 PM

There's no real need to be a guinea pig :-)

You can always bore and plate the cylinder, then run a run of the mill JE without worrying that you're going to have a failure, especially with the high cost a failure might incur from incidentals.

Regarding coating the pistons, google-ing "iron plated piston" comes up with lot of information, which can be supplemented by searching the SAE. I'm sure it could be done, but other than as an academic exercise, there really isn't any need to do so and cost savings would most certainly not be a consideration too.

Here's the bible on the topic:

http://www3.interscience.wiley.com/cgi-bin/summary/112658786/SUMMARY?CRETRY=1&SRETRY=0

patkeefe · 03-27-2008, 06:29 PM

Yup, at this point it is somewhat an academic exercise. I brought my Nikasil cylinders in today to get honed back to size. This exercise has been precipitated by bleeding from the wallet over a set of used pistons and cylinders from unmatched sets. Also, looking at the economics (please forgive this part), throwaway Alusils honed back to size using coated pistons would be relatively cheap. Provided it would work, of course. Also, this is for the track engine iterations, where I could look at it over a short duration and see how it would hold up.

Thanks for the link, Charles.
Pat

criv911 · 03-28-2008, 04:22 AM

I think the idea is that U.S. chrome wants about a $1000.00 to bore and plate a set of cylinders. Most of that is in the plating. When you add in a set of JE pistons your just about at the price of the JE/QSC combo that so many have used. I don't see a real savings there. IF you could just overbore [cheap] the cylinders and use a coated piston you might be able to do it for about half. I think I'm speaking for those of us that need a rebuild [valve guides] and can't bear all that work and leaving it stock. Maybe that's just me.

patkeefe · 04-03-2008, 06:06 PM

JE says they can coat pistons to work in Alusil cylinders.. I need further research.

Ray_G · Ray_G's Garage

I am kind of in the same boat, a set of alusils and LS pistons with no coating left on them. A ..001 coating would put the piston/cylinder clearance back to minimum specs. I did some searching today but did not find out much. was leaning toward the PC9 coating, but I don't really know.

cnavarro · 03:24 AM

Swain Tech's PC9 coating was never designed to be used as a substitute for the iron coating on the pistons with use with Alusil. I'm sure it will work for a while, but I'd say that time frame could be as short as 1,000 mi or as long as 15,000 mi as the coating does wear and is designed to do so. Either way, short of iron plating the piston in a process identical to what was originally used or a modern variant of it as used with modern lokasil engines would be advised.

Ray_G · Ray_G's Garage

Thanks Charles, I think I found a set of Nikasil cylinders anyway.