Quote:
Originally Posted by old greg
With the same deck height as an FB20, an 80mm stroke would allow 134.3mm rods. At 8000rpm that means a mean piston speed of 4200 ft/min and peak piston acceleration of 3718 g, which ought to be fairly reliable (compare that to 4724 ft/min and 4344 g for a normal FB20).
Figure a forged bottom end (that's just how Subaru rolls), probably a semi-closed deck, with forged pistons in the STi and cast in the WRX.
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I found that a 82mm stroke would leave 4mm rod growth to 133.3mm to 82mm would be 1.62 (granted I didn't calculate CR reduction so it would be slightly higher). That would equal the same as 2ZZ and K20...
Perhaps a 2.0L with a 83-85mm stroke? Depending on what breathing characteristics they want it I can see 1.55-1.62. D4-S would also result in the ability for a higher CR; it wouldn't surprise me if we saw over 11.0:1 on cheapo gas.
I agree with the semi closed and the forged pistons (do Subaru run forged rods as well in the STI?).