Quote:
Originally Posted by sperry
I guess I missed the memo that "all" STis have crap pistons and tunes. 'Cause I certainly don't remember that being the case with the '04/'05 cars. Sure, they've gotten progressively worse with the lean tunes and cheaper pistons. But the 1st US STis were pretty stout.
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My 04 STI pinged audibly on 91 octane when it was new and stock. I think there was a factory reflash for this. I see stock STI's with IAM <1 and lots of knock learning sometimes (when I hook up to check them). I really think the stock tune is meant for 93 octane.
The newer STI tunes stay in closed loop (targeting 14+:1) too long for emissions reasons, and this leads to knock, even moreso with an aftermarket downpipe and no tune.