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.