Wow, there's so much misinformation in this thread, i don't know where to begin.
In terms of compression ratio, running a forged motor for turbo use with a stock compression ratio is more or less a waste of time. The first motor I built for my personal car (about 8 years ago) used stock compression pistons. Once I started making decent power, I would start running into issues with knock due to the CR. A year later, I rebuilt the motor with 8.5:1 pistons and ultimately made much more power with no knock.
If you're going to spend the coin to build your motor, why restrict yourself to low boost by having a high CR? It's simply counterintuitive. Learn from my mistake 8 years ago.
Moreover, there are no real drawbacks to running a slightly lower CR. You won't be able to feel a difference in off boost power, and you'll make more power under boost since you'll be able to run more boost an hotter timing. What's not to love?
As for 4032 vs 2618 Aluminum pistons (low silicon vs high silicon), the high silicon pistons actually have a lower rate of thermal expansion by about 15%. So to the poster that said that the high silicon pistons expand more, that's the opposite of the truth. The advantage of of high silicon 4032 is that you can run tighter piston to wall clearances and have less piston slap. The disadvantage is that the pistons aren't quite as strong as 2618. That said, CP, Arias, and Wiseco all use 2618 low silicon pistons.
It's true that Maxx Mazda melted some arias pistons. But it was not the fault of the piston...any piston would have melted in his case. He will be the first to tell you that he had his standalone set up wrong, the ignition timing was way off, and it caused the piston to melt. I don't care if your pistons are made by the hand of God, if they are aluminum, they will melt if your tuning setup is wrong.
Secondly, of the three brands mentioned, Wiseco has the most issues when it comes to structural integrity and production tolerances, piston noise, etc.
In the FS motor, I have experience with JE/SRP, CP, Wiseco, and ARIAS pistons. The only brands I would even bother with would be ARIAS and CP, as they are both great pistons.
Personally I prefer the ARIAS pistons since we actually have our own custom design for the pistons, and have perfected the piston over the years. One look at any of the work that I've done will show you what an anal bastard I am, and I've tweaked the hell out of the design of these pistons over the years. From the valve reliefs, to the ring package, to the wire locks, to the custom length wrist pins, as well as the largest oil squirter clearance available in any piston for the FS.
You'd be hard pressed to find anyone who has built more forged FS motors than myself, and we have a virtually flawless track record with our engines. I have been building FS engines since 2003 with outstanding results. We use the best quality stuff we can get our hands on. If ARIAS pistons (and Pauter rods) weren't outstanding, I wouldn't dare use them in my engines - I would simply start using the better product if one existed.
) and I needed something that could be sent to me directly and the Wisecos are usually on the shelf. Looking back I probably should've gone for some CP or JE ones, but not every shop will ship to Europe and the Wisecos was just the easist to get on a short notice.
