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Old 11-13-2003, 12:39 PM   #2
Homicidal Maniac
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
2008 STI

Default Engine Swap Specifics:

Q: "To JDM or not to JDM?"
A: Here is a good discussion regarding the pitfalls of going JDM and USDM:

Q: "What does it really take to do a swap?"
A: You asked for it!,, and

Q: "I need some help identifying what JDM options are available."
A: Please take a look at this webpage:

Q: "Anything to look out for?"
A: The following thread gives you an example of things to check and watch out for:

Q: "How about a little insight on how to deal with emissions?
A: There are many threads with guesswork, but here is a little personal experience: and towards the end of this thread:
and finally some real world results:

Q: "Is there documentation for a USDM EJ20 swap?"
A: There are a few good threads about this:,,

Q: "I'm doing an EJ20 swap, which exhaust should I use?"
A: Until proven otherwise, the exhaust from a standard WRX from 1993-2004 has remained relatively unchanged. This means that if you are performing a swap from an Impreza chassis to an Impreza chassis, you can use any complete WRX exhaust. If you are swapping from an Impreza chassis to a Legacy chassis, then the exhaust must be lengthened to accomodate the longer chassis.

If you are doing a piece-meal exhaust, there are four types of downpipes available from any of the EJ20 equipped cars: the twin-turbo downpipe, a la GTB; the twin-scroll downpipe, a la STi Ver. VIII; the IHI flanged downpipe from a pre-MY01 JDM vehicle or post-MY01 non-JDM vehicle, a la USDM WRX or STi Ver. VI; or finally the IHI flanged downpipe from a post-MY01 JDM vehicle; a la STi Ver VII. The twin-turbo downpipe is only going to work in a RHD car, so this will almost never be used. The twin-scroll downpipe can only be used with an IHI twin-scroll turbo, so this will only be used with some STi Ver. VIII vehicles. The pre-MY01 JDM downpipe is the most common downpipe used with EJ20 vehicles. The post-MY01 JDM downpipe was introduced with the GG/GD chassis and is a few inches shorter than the pre-MY01 downpipe.

If you choose the pre-MY01, then you must mate it with a similar system. It can be mix-matched as long as it is not matched with a post-MY01 JDM system; this includes using cat-backs designed to work with the EJ25 engines. If you choose the post-MY01, then you must mate it with what is commonly referred to as a "JDM cat-back". The flange at the axle was rotated on the GG/GD chassis so the mid-pipe and the axle-back must be from the same chassis generation.

Q: "Is there documentation for an EJ25 swap?"
A: You can find some information in this thread:, this thread:, this thread:, and this thread:

Q: "Is there documentation for an EZ30 swap?"
A: Naturally, it is not all inclusive, but here is the work done by a fellow member: . His webpage detailing the swap is here:
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Last edited by Danny5; 04-03-2008 at 11:11 AM.
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