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Unless you rebuilding an engine with little to no budget you're going to upgrade to aluminum forged pistons. Besides being stronger than cast pistons, the lighter aluminum cuts parasitic power loss. That translates into more power at the wheels.
Recently Mahle showed us that there are distinct differences between their 4032 and 2618 alloys. The choice to use one over the other depends on your project. Are you building a street/strip machine or an all out racer? Choosing the wrong one can be devastating. To better understand, we'll let MAHLE explain.
4032 is a high-silicon, low-expansion alloy. Pistons made from this alloy can be installed with tighter piston to bore clearance, resulting in a tighter seal with less noise. 4032 is a more stable alloy, so it will retain characteristics such as ring groove integrity, for longer life cycle applications. Relative to 2618, 4032 is a less ductile alloy, making it less forgiving when used with boosted and/or nitrous applications.
The majority of Mahle forged PowerPak kits are made with 4032 alloy and require no additional piston-bore clearance. Mahle pistons are perfectly engineered to allow for the proper clearances assuming normal operation. For example, Mahle pistons for a small block engine will provide proper .0025"-.0030" clearances--right from the box.
2618 is a low-silicon, high-expansion alloy that is used for extreme-duty racing applications such as NASCAR, ALMS, etc. Due to its high-expansion characteristic, this alloy is engineered with additional piston to bore clearance. At the start of a cold engine, the pistons expanding process can be heard and is commonly referred to as the "piston slap". Once the engine warms up the noise subsides as the piston expands to its running clearance. 2618 is a more ductile alloy and grants higher tolerances with higher resistance to detonation. The forgiving characteristics allow for the most extreme conditions, but longevity is eventually negotiated after countless heat cycles.
Mahle pistons are designed for specific applications with the alloy that is best suited for that particular application.

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Piston Alloy Comparison
4032                                                           2618
High silicon                              No silicon
Low expansion                              High expansion
Tighter piston-to-wall clearance      More Piston-to-wall clearance  needed
Quiet Operation                              Noise when cold
Less ductile                                 More ductile
More stable & consistent          Higher resistance to detonation
Longer life cycle                              Shorter life cycles
Harder                                            Softer

Our pistons are manufactured from extruded high silicon, enhanced 4032 alloy (with additional Cu, Ni & Mg) that has low thermal expansion, excellent wear resistance and higher thermal conductivity. Our pistons with this alloy have withstood up to 42psi of turbo boost, with alcohol, without any problems

GTI писал(а):Себе поставил Supertech из 4032 - примерно на 100$ дешевле, чем МАНLE. Зазор 0,06мм.
тут можешь про них прочесть

Our pistons are manufactured from extruded high silicon, enhanced 4032 alloy (with additional Cu, Ni & Mg) that has low thermal expansion, excellent wear resistance and higher thermal conductivity. Our pistons with this alloy have withstood up to 42psi of turbo boost, with alcohol, without any problems

http://www.supertechperformance.com/products.html?id=9

42 psi - это 3 бара.
Думаю, что твои 1,5-1,7бара без спиртугана они выдержат.

Boroda писал(а):Ковка рулит
Стоковых поршней , в том числе и СТИшных народ уже не мало положил при увеличенной мощности и даже в процессе настройки , ну не держат они детон так как настоящая ковка и дело тут не только в сплаве но и в конструкции самого поршня .