My Subaru Engine Blew Up - What Should I Replace It With?

My Subaru Engine Blew Up - What Should I Replace It With?

Jul 11, '21

Above all else, when you are looking at an engine replacement of any kind, KNOW WHAT YOU HAVE FIRST.

If you are looking to upgrade your car with an engine swap (IE RS to WRX) this is not the post you are looking for, but lucky for you, we have posts that are - Best Engine Swap for Your Chassis and What To Know Before Swapping.

We get this question a lot and while we are happy to wire up any car, sometimes it's simpler and cheaper to find something compatible with your current ECU and harness. Subaru makes great engines but eventually with wear and tear (that or too much boost!), they fail like any other engine. In this post we discuss the easiest way to replace your engine and get your Subaru back on the road. We always recommend discussing this with your local engine builder because pulling something used out for something else used is not always the best option and many times it's not as expensive as you might think.


iWire's recommendation anytime it's a matter of basic replacement (not upgrading) is to keep the ECU and wiring the same and just replace the longblock. This isn't always as easy as it seems since not all EJs are created equal. 


To make sure this happens for a NA car, find a NA longblock from the same family to replace it. For turbo models, find a compatible turbo longblock of the same type. Once a compatible longblock is found, all that's left is to put the old harness and intake manifold on the new longblock. The reason we recommend this is because otherwise it will require a harness merge like when doing a RS to WRX swap aka an upgrade. Given the end result will be the same as the start point, there is no reason to spend the time and money to go through the process of a harness merge for any basic engine replacement.


What to look for in a replacement longblock?

Make sure that the new longblock has the same features as the old engine.

Features like:


Drive by Wire or Drive by Cable

2 wire camshaft position sensors or 3 wire camshaft position sensors - more about that here

ECU type -16 bit or 32 bit


EJ Series Engine Families


32 Bit ECU with Intake AVCS Models - All of the following turbo cars could use the same longblock interchangeably for repair because they are intake only AVCS, drive by wire models, and utilize 3 wire cam position sensors. We generally do not recommend using dual AVCS engines in single AVCS applications.


2004-2007 STi

2006-2014 WRX

2004+ Legacy GT

2004+ Forester XT

2004-2006 JDM Forester STi


Beware of the secondary air injection system. For models that have it, it would be wise to find a long block that also has it for smog purposes.


Engines without secondary air and are 32 bit platforms

2004-2006 STi

2004-2005 Forester XT

2005-2006 Legacy GT

2004-2006 Baja Turbo


32 Bit ECU with Intake and Exhaust AVCS Models


2008+ USDM STi

2008+ JDM STi (V10+)

JDM EJ20X and EJ20Y Models


16 Bit ECU - USDM WRX models can be interchanged easily with the JDM AVCS models by adding in the AVCS wiring


2002-2005 USDM WRX

2001-2006 JDM WRX

2001-2006 JDM STi


EJ205/7 differences


Non Turbo Applications

For non turbo engines it would be best to stick to an engine with similar features. For example a 2000 Impreza engine would not be good in a 95 chassis because phase 2 engines are not compatible with phase 1 wiring. Another scenario would be a 2007 NA engine in a 2005 RS would create an issue because the 2005 RS ECU is not able to control the AVLS on the 2007 engine.


EJ Platform

Phase 1 - 1998 and older

Phase 2 without AVLS - 1999-2005

Phase 2 with AVLS and 2 wire Camshaft position sensor

2006-2011 Impreza and Legacy

2006-2010 for Forester


FB Platform

2012+ non turbo Legacy, Impreza, and Crosstrek

2011+ non turbo Forester


Phase 1 to Phase 2 information


16 Bit to 32 Bit Swap - More detail about this can be found here

One common exception would be going from a 16 bit ECU to a 32 bit ECU (02 WRX chassis to 06 STi engine), but we would consider this more of a swap/upgrade because of the increased capabilities of the 32 bit ECUs. We do recommend this route for certain customers, but doing a similar 16 bit ECU swap from a JDM WRX or STi is going to be cheaper and simpler.

Tags: DIY, Engine Guide