ptuomov

Erkka --

I've got a set of 100mm low compression pistons with steel rings. They should run on dry cast iron liner or Nikasil in case you ship the block to Sweden for plating. They will not work on Alusil. The compression height is stock S4, and the the valve reliefs fit 968 valves. They weigh about 500g without rings and pins. Forged 4032 aluminum, mae by Pure Performance Motorsports. CR with S4 heads should be in the 8.3:1 neighborhood.

I'll sell those reasonably cheaply if you're interested. My finances have improved, and my plans for the "big" engine have expanded with it.

Tuomo

Vilhuer

Thanks for the offer. Friend will use Alusil block as he has '87 squirter block which has very good condition bores which had lapping done to them. If he were using dry steel liners like I plan to do...

Boomerang Baba

Hi,
So Erkka are you using alusil in your 2 engines and thus alusil coating for your new 103mm pistons?
What make are those 103mm pistons by the way?
Still wondering what to do.
I just read on 928Motorsports home page that they also make custom pistons.
Are they something to consider over and above the Ross Pistons?
They are called Arias...
Here is the link:

http://www.928motorsports.com/parts/...ed_pistons.php

Vilhuer

No, steel liners inserted into existing Alusil cylinder towers.

No idea yet as I'm just looking into what to get.

They are for steel liner or Nicasil coated cylinders. Will not work with Alusil like Ross claims their pistons do.

Boomerang Baba

Thx Erkka.
Thats very informational.
May I ask where and at what price you are having steel liners inserted?
You see I contacted a company in Oslo that wanted alot for that job...
Since you are having steel liners, cant you drill out all the alusil and have even bigger pistons..?
Cheers and thx again.
Michael

Fabio421

Woessner has a coating that they claim is compatible with Alusil. The 951 guys have been using them for a while ( see Chris White ) and they report no problems yet. I'm keeping my eyes open for proven alternatives. In the BMW world, Dinan has done alot of development with Alusil engine blocks in regards to over boring and stroking. I wonder if we could find out which manufacturer they are using for their pistons. I'll see if I can find out.

Fabio421

OK, I found it. Dinan buys their pistons from Mahle and Mahle makes them with the ferostan coating. See the video at 4:17 Is it possible to get a set of pistons from Mahle or will they only make them in very large batches? If they won't make a small batch, will they coat pistons that you send to them?

slate blue

Michael, I haven't got much time for a reply but the difference in the piston material determines the size of the bore. If you get it wrong you will have major/catastrophic problems, so you can't really say I'll use these aftermarket pistons. I would strongly recommend you use the oversize factory pistons and be happy with that otherwise you will get yourself in very deep.

Greg

Vilhuer

Few local machine shops have been fixing Alusil engines for years by inserting dry steel sleeve into one single cylinder and running original Porsche piston in it. Cost has been around $150 per cylinder. I might have to pay little more as I want little more complex setup than quick fixes these single cylinder sleeves have been.

Removing existing Alusil tower completely introduces whole new set of problems like how to seal botton end of steel tower against Alusil block. I don't want to go there and thus max bore size is limited to around 103mm.

As Greg says. If your engine has problems in single or just few cylinders have it/them bored to 100.50mm factory oversize and have lapping done to all other cylinders. Of course boring must be done correctly and new piston(s) cost $$$ but its still easier to fix under 0.25mm deep problems in bores using factory methods than build basically whole new short block using somewhat questionable aftermarket methods.

Vilhuer

Very interesting find. Seems Mahle uses coating only in skirt area when old Porsche pistons have it everywhere. Other modern coatings like one Wössner uses seem to also be skirts only. I have seen several Porsche pistons which have had problems higher up above rings. Not just below oil ring. Wonder how these new style skirt only setups work in that regard.

Boomerang Baba

Erkka, Fabio and Greg....
Thx for the input!
Very helpful.
Spending lots of mullah and driving around with a potential time bomb isnt cool....
So installing a couple of 100,5mm pistons makes alot of sense...
I wonder tho what the stroker pros in the US do...?
Nikasil cylinders and customs pistons..?
Perhaps they are afraid of chiming in and giving away their secrets...!))

FUSE69

Hi Michael!

Have you tried contacting these guy's for a quote on Nikasil?

http://www.blixtensracing.com/

They are in Huskvarna, Sweden.

If you already have, I'd be interested to know what they quoted you.

Boomerang Baba

Hei Fuse,
Vel min kompis er i samme situajson og her er hva han fant ut ifra Blixtenracing:
Har fått pris på nikasil beleggning 25.000 sek, rå pris da dette koster ca 8000 nok i usa.
Very expensive in other words...!
Almost 4000 US for Nikasil coating....!
Har du en S4 manuell..?
Fortell meg mer om din bil..!
Mvh. Michael

FUSE69

Hi Michael

Yep S4 Manual... It used to be yours!!! Though it looks a little different now...

Damn 25K for Nikasil!!! Cheaper to ship an engine from the US!

GregBBRD

I've had two engines with the Ross pistons in them. Both were junk before 100 miles....Unless they have changed things ...doubt this is an option.

I've had Mahle 968 pistons (US made Mahle...not only incorrect, but they won't do anything about it...companies that don't back up their products and their claims...well, they will go down the road of the rest of the companies that tried doing business like this....see ya...the US consumers will not put up with this) and they ruined the bores in less than 500 miles.

Pretty simple thing to figure out....you've got a GTS with 220,000km....that used stock, factory components. Why fight it? The stock parts work and they are still available! When you take it apart, measure the bores. If they are good and the pistons seem ok, drill the pistons and buy a set of stock rings. They will seal and work perfectly. If the bores are oversized, buy a set of factory replacement pistons and bore it to 100.5mm. Put it back together and forget it.

There are places to cut corners and save a few dollars, but this is not one of them. Use what works and is still available. Do your gambling somewhere else.

BTW....we use NIcasil and J&E/CP pistons in all our strokers. They seem to work great....however there aren't hundreds of them out there, and they don't have 220,000km's on them.