All 02-05 STi's had the semi closed deck block, forged rods, a good crank and forged pistons that will take some detonation. Run 25 PSI day in day out. High revving and Good for Motorsport. Tuff little bastard!!

06+ WRX/STi's have Hypereutectic pistons. Which are cast with increased silicon content that lessens their thermal expansion with heat. Will not tolerate detonation and big boost. Spot on tune needed if flogging this engine. Internal strengthening mods + forged pistons needed to really push this engine.

DCCD only in the 05-07 STi's.
A steering wheel angle Sensor input was added to the DCCD system in 06/07 model.

DCCD max split F to Rear
05 STi 35:65
06/07 STI 41:59

Differentials:
02-04 STi has Suretrac front + rear
05 STi has Helical front + Helical rear (odd ones had plated rear)
06/07 STi has Helical front + Plated rear

05 STI's onwards had strengthened hubs to cope with a wider track. Rims also increased in width from 7.5" to 8".

J

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