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Old 09-29-2007, 02:55 AM   #51
Scooby Specialist
Member#: 67608
Join Date: Aug 2004
Location: SoCal

They (V8 STi and USDM STi) are NOT forged. It can be clearly seen in the lack of pressure-deformation in the grain of the broken piston.

The grains will flow perpendicular to the surface in a broken forged piston and it's very easily visible.

I'm surprised this thread has survived argument so long with such good data pointing to the change to castings.
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Old 09-29-2007, 12:31 PM   #52
RIP 10/12/83 to 02/10/08
Scooby Specialist
Member#: 83254
Join Date: Mar 2005
Chapter/Region: NWIC
Location: Roy, Washington
98 2.5 RS
04 WRX


Originally Posted by Got Boost?
I will comment on this and would like to say that I have an 06 sti (USDM) and with 12-13k on a stock motor I had a failure. Broke a ring land on #2 piston and the dealer dismissed it 2 times. So I said f it, and went full stg 4. Guess what ... as soon as I got on the rollers, the problem reared its head. took the car to the dealer where it sits now. SOA is picking up part of the tab and I get stuck with the rest. If indeed they were forged, would I be in this same position? I can tell you that no they are not forged and have a brand new never been rotated set in my possesion.(ordered a new shortblock and picked it up to have some CP forged pistons installed) So this really pisses me off to hear/read about this. My car has been down for a while now,(long story with the dealer), and I am looking forward to being able to drive it again hopefully within the next couple days. The down side, I am out a bunch of cash and have to break in the motor again.
You have a bad tuner, no piston will survive detonation and that is what has been killing your pistons.
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