effectivement, les pistons ne sont pas les memes sur wrx et sti 2.5
sur sti c'est hypereutectiques, voici un copier-coller de la reponse de subaru america Hello Mr. XXXXXXX:
Thank you for your patience and for bringing this misinformation to our
attention. Here is the correct information on the pistons in all WRX STi
Sedans, from the 2004 through the 2006 models:
The pistons in all 2004 to 2006 STI vehicles are made from a lightweight
aluminum-alloy metal and manufactured using Hyperutetic, which is a high
pressure casting process. This process eliminates the micro defects in the
metal structure increasing the rigidity of the piston, especially at high
cylinder combustion temperatures. The process also stabilizes the expansion
rate of the piston improving the overall reliability.
Note: The pistons in all STI engines are not forged
The Press Release from 2004 was incorrect. Unfortunately, some of the
information from that Press Release, including the piston information, was
used again for the 2006 Press Release.
Subaru of America has corrected this information in its files and sincerely
apologizes for this situation. Again, we appreciate that you brought this
to our attention.
Sincerely,
John J. Mergen
Subaru of America, Inc.