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Old 01-16-2014, 07:11 PM   #7
Scooby Newbie
Member#: 150125
Join Date: May 2007
Location: Denver, CO
2003 WRX wagon

Default 2003 WRX USDM engine blown, replace with JDM EJ205?

Bump! And adding my questions. I've read a lot of the JDM swap threads, and there is tons of contradicting information even when discussing this somewhat "like-for-like" replacement.

PROBLEM: I have Stock 2003 WRX USDM with a blown motor (no compression in #4) and several other lesser concerns. So I'm considering all options, but in this thread I hope folks can provide straightforward information on an engine replacement to an EJ205 JDM motor. I'm hoping there are folks out there that have completed the swap that can provide insight. I'll return the favor with a clean write up of my experience, once it is all done!

A Subaru tech will do most of the work. He has a bug eye himself but has not done a JDM swap yet.

1) It's a fairly straight forward bolt on replacement - (Sure it is )
2) Use USDM wiring harness and ECU
3) Use USDM cam pulley and sprocket (ensures USDM timing is maintained)
4) Use USDM intake manifold (for US emissions) and exhaust manifold.
5) Use USDM accessories (A/C comp, Alternator, P/S pump). Some JDM accessories "may" fit, but best to have your originals on hand.
6) Japanese and US octane levels are NOT different, so no gas difference concerns or tuning concerns.
7) Tune is a good idea, but not required
8) JDM and USDM compression ratios are both 8:1, so no issue (Some NASIOC/WRXtuner folks claim JDM is 9:1)
9) Good idea to replace gaskets/seals (OEM complete kit ~$200)


1) Are any of these assumptions misleading?

2) I'm not interested in AVCS b/c of the added complexity and possible issues, do I need a to ensure I have a non-AVCS EJ205 for simplest installation, or will an AVCS EJ205 be okay?

3)Are there any other major problems that we will come across?

4) Are there any other customization or USDM parts that I will need from my car?

5)Are there any defining characteristics on the JDM motor that will help ensure the simplest replacement. (non-AVCS, parts to make sure come with motor, etc)

Essentially, I'm looking for a clean-ish engine replacement experience with the end result being a reliable daily driver for 2-3 years (hopefully longer). I want to avoid getting bogged down with fabrications or hunting down hard to find (JDM) parts with no warning.

Thanks for any insight you can provide through your experience! Again, I'll post a clean/detailed write up once we are done with the project for folks that are looking to do the same in the future. I haven't been able to find one yet, and will all the aging EJ205 motors out there, this may become an increasingly relevant topic.

Eat, Sleep, Turbo!
2003 WRX mostly stock with Perrin uppipe, Mishimoto radiator
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Last edited by johnnieski; 01-16-2014 at 07:22 PM. Reason: incomplete info
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