Does any one know an alternative for the stock pistons in the 3sgte gen 3
Good info in this post. I'll add that 2618 piston engine life is really affected by cold starts/light usage. It takes a solid 10-15 mins to get pistons up to a normal operating temp window, and that's where the engine wear (rings/pistons/bores etc.) will mainly happen when PTW clearance is high. A 2618 piston engine driven on the street will still have a lower life than a cast or 4032 piston engined all things being equal, just because on the street you're going to have a bigger PTW on a 2618 piston vs. 4032/cast piston (it'll close up as you get the pistons really hot on track), but if you're sitting there doing a ton of cold starts and driving your car around town, you can definitely see yourself having all the symptoms of worn rings/bores in as little as 30-40k mi.Look up discussions on 4032 vs 2618 Aluminum for forged pistons. Long story short:
2618: Is low Silicon alloy, has a higher ductility than 4032 so it doesn't crack as easily (read: detonation less likely to damage them). But that has the draw back of making the piston expand more with heat, which means you have to run larger PTW clearances. Couple disadvantages to that: piston slap is a potential issue, and it allows the piston to rotate on the pin (piston rock). If you look at the piston rings and notice how they have flat sides with square edges, they're supposed to sit flat and square in the bore. Piston rock slowly wears the edges down and rounds the ring out, the ring lands also lose their shape slowly. It'll be significantly worn around 50-60k mi typically. Most 4032 makers recommend 0.030-0.035" PTW. Engine builders are nervous about having an engine lock up from too little clearance and will almost always want to go closer to 0.040", which is a lot.
4032: Is a high Silicon alloy, it is harder than 2618. It will crack more easily, but it expands less than 2618 so you can run PTW clearances about as tight as OEM. Your rings stay squarer in the bore and will last about as long as stock. They're ideal for street driven cars (99% of builds) but are less tolerant to operator error... Poor tuning and detonation namely.
Aftermarket cast: Just had a motor with a set of these I'm rebuilding. They seem like they duplicate the casting of the OEM piston, and are supposedly all sourced from Nippon pistons whom made the OE pistons, but who knows for sure. They seem OK but still made to be as cheap as possible. I've seen them for $30-40/piston.
Mahle is the only manufacturer that makes 4032 pistons for the 3SGTE (86.5mm ONLY) anymore, I just got a set. Their recommended PTW is 0.0016-0.0024". The coating on the pistons seems to be a bit under 0.001" thick so the "real" PTW is generally going to be a hair under 0.003", very close to stock.