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Old 09-04-2007, 08:52 PM   #1
DausWRX
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Default 2.5 or 2.0

so iv spent some time looking for a new engine for my stock 2002 wrx and im unsure where to go. Im looking for a 2.5 block but i wouldnt mind goin with a 2.0 but heard i would need to change out the ecu or something like that with the 2.5....can someone plz help thanks
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Old 09-04-2007, 08:56 PM   #2
MindzeyeWRX02
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You dont have to change out the ECU unless you wanted to run AVCS heads. You can put a 2.5 Shortblock in but you will need some type of Engine Management and a custom tune.

I am running a 2.5L STi short block with my 2.0L WRX head with a custom tune.

P.S. do a search on 2.5L Short block, Hybrid and other keywords that would tie into your search, there are a lot of posts about doing the hybrid swap on here.
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Old 09-04-2007, 11:19 PM   #3
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Def need a tune, but the factory ECU will run it fine, but I wouldn't get on it too hard until you get that tune, lest you run lean and go boom.
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Old 09-05-2007, 12:41 AM   #4
DausWRX
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Thanks, What exactly are AVCS heads? i hear that every where but i dont know what it means exactly and also if i buy a 2.5 block with AVCS heads will i need a pro tune or if a buy an COBB AP unit will that work jus as well?
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Old 09-05-2007, 02:27 AM   #5
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you will definetly need a protune and the cobb ap is a great investment. I just finished my sti short block swap into my wrx.
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Old 09-05-2007, 12:30 PM   #6
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Originally Posted by DausWRX View Post
Thanks, What exactly are AVCS heads? i hear that every where but i dont know what it means exactly and also if i buy a 2.5 block with AVCS heads will i need a pro tune or if a buy an COBB AP unit will that work jus as well?
hey nooB. search in this forum for "hybrid". there's 200 posts a week on hybrid questions.....this is exactly what you're doing.

AVCS is variably cam timing. Your 2.0l doesn't have it. the 2.5l's do. Your 2.0l processor doesn't have the capability to run AVCS......So if you want to go 'all out' and buy a longblock STi engine, you will also need the engine wiring harness and processor. (lots of $$$$).

Either way, you need EM whether you want EcuTek, Cobb, Utec, Hydra, etc, and you will want to get dyno tuned. Or else you risk the chance of breaking those weak little cast pistons in the 2.5l you just put in.
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Old 09-05-2007, 02:11 PM   #7
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hey nooB. search in this forum for "hybrid". there's 200 posts a week on hybrid questions.....this is exactly what you're doing.
LOL. Yeah the whole hybrid, avcs thing is talked to death and a search with some skimming through threads will get you a lot of info.

You can do the AVCS and run the Hydra EMS on your 2.0L ECU. But hydra is $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
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Old 09-05-2007, 04:04 PM   #8
Acostafan
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hey nooB. search in this forum for "hybrid". there's 200 posts a week on hybrid questions.....this is exactly what you're doing.

AVCS is variably cam timing. Your 2.0l doesn't have it. the 2.5l's do. Your 2.0l processor doesn't have the capability to run AVCS......So if you want to go 'all out' and buy a longblock STi engine, you will also need the engine wiring harness and processor. (lots of $$$$).

Either way, you need EM whether you want EcuTek, Cobb, Utec, Hydra, etc, and you will want to get dyno tuned. Or else you risk the chance of breaking those weak little cast pistons in the 2.5l you just put in.
Don't mislead the guy by telling him his pistons are crap. The pistons in the STI are hypercast, stronger than cast, but weaker than forged. They are more than adequate for a modest hybrid build(say up to 300whp).
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Old 09-06-2007, 01:02 AM   #9
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Don't mislead the guy by telling him his pistons are crap. The pistons in the STI are hypercast, stronger than cast, but weaker than forged. They are more than adequate for a modest hybrid build(say up to 300whp).

"hypercast" vs. cast.....You're picking your nose and still getting a booger.

they both are BRITTLE as ****. They may hold up, they may not. it depends on the tuning in the processor. If he runs the stock 2.0l one, we'll be reading a thread from him with the title of "why does my hybrid smoke, eat oil, and run rough???????????????????????????"
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Old 09-06-2007, 01:06 AM   #10
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I would say 2.5 %100 yes. No replacement for displacement man you will get so much more out of it!
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Old 09-06-2007, 09:48 AM   #11
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"hypercast" vs. cast.....You're picking your nose and still getting a booger.

they both are BRITTLE as ****. They may hold up, they may not. it depends on the tuning in the processor. If he runs the stock 2.0l one, we'll be reading a thread from him with the title of "why does my hybrid smoke, eat oil, and run rough???????????????????????????"
I assure you it runs quite well on the stock 2.0 ECU. HOWEVER, I would NOT run it for long. You will need a tune. I know plenty of guys belting out good numbers on your so-called boogers and have many miles on their engines.
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