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Old 08-21-2009, 10:35 AM   #1
Skapunker
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Default 08 wrx vs. sti engine

I searched but couldn't find anything and I need an answer fairly quickly. Does anyone know what the differences are between a wrx and an sti engine from a 2008 if any? I know of a long block for sale but I found out it's from just a wrx not an sti but since their both 2.5l's it doesn't seem like they would be different, mainly I want to make sure the internals are the same.

Also on that note since I'll be using it for a hybrid swap are there any differences in the 08 sti engine from previous sti's that would make a difference from a normal swap? I've been planning a sti hybrid swap into an RS for a while with an older sti engine and this 08 just popped up and it's a good deal.

Thanks in advance!
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Old 08-21-2009, 10:48 AM   #2
the suicidal eggroll
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Yes they're different, 08 STi has dual AVCS (intake and exhaust), 04-07 STi only has intake AVCS. The 08 WRX has AVCS also, but I don't know if it's intake or intake and exhaust. The heads are different between the WRX and STi, as are the pistons.
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Old 08-21-2009, 11:49 AM   #3
scramjett
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1) Dual AVCS on the STI and single AVCS on WRX
2) STI has slightly higher compression pistons but are of the same manufacturing type, i.e. hypercast
3) Composite versus metal intake manifold
4) I think the STI has an engine oil cooler whereas the WRX does not

Basically the 08 WRX has what is the pre-08 STI's engine except for the oil cooler.
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Old 08-21-2009, 12:20 PM   #4
Skapunker
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Default

Thanks for the replies!

So if the 08 wrx engine is basically an like the older sti engines then it sounds like just what I want.

The heads don't matter so much since I may not use them anyways, but do you know what the difference is eggroll?

It doesn't come with the intake manifold so I'm not worried about that either as long as an older sti intake manifold will fit on it no problem.

So it sounds like the main difference between the an older sti block and the 08 wrx block is that the 08 has higher compression pistons? Does anyone know what the compression is on an 08 wrx, I found it for the 08 sti earlier, but couldn't find what it is for a wrx.
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Old 08-21-2009, 12:44 PM   #5
the suicidal eggroll
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I believe the WRX heads are smaller, which would raise the compression up considerably, but it uses lower compression pistons to bring it back down.

AFAIK...
STi heads with STi pistons = 8.2:1
WRX heads with WRX pistons = 8.5:1
WRX heads with STi pistons = 8.7:1
STi heads with WRX pistons = 7.x:1 (don't know the exact number)
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Old 08-21-2009, 12:46 PM   #6
Skapunker
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Nice thanks
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Old 08-21-2009, 12:59 PM   #7
bhhamblin
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Both the WRX and STI have oil coolers
STI is lower compression
STI has differet cams
STI has dual AVCS on intake and exhaust
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