EJ22 or EJ18 swap into EJ25D DOHC vehicle

[idosubaru]

Read and reread the section you have a question about - it's probably answered. If it's not answered - then it's something that doesn't matter like electronics, DOHC 2.5 verses SOHC 2.2, ECU, transmission, none of that matters. Don't make up questions on your keyboard, get in the garage and follow this:

This is for EJ22 swaps into an EJ25D vehicles. EJ25 = dual overhead cam engine found in:
1996-1999 Legacy and Outbacks
1998 Impreza RS and Forester

The following are plug and play, easy swaps into those vehicles listed above:
 

1. 1995 EJ22 with EGR
(all 95 automatics have EGR - impreza or legacy, doesn't matter)

 

or

2. 96-98 EJ22 with EGR and the EJ22 exhaust manifold.
(again legacy/impreza doesn't matter)

 

3. 1995-1998 EJ22 without EGR but with an EGR equipped EJ22 intake manifold. 

There's a simple vaccum hose rerouting to make it think it has EGR.  There's a thread in USMB for that. 
It requires sourcing a separate manifold and block and that hose rerouting so often not a good fit but in some cases it is.

Exhaust:
Usually get the exhaust manifold with the engine, but in general, any 96-01 single port EJ22 exhaust manifold will work.

 

1996 is single port exhaust (95 EJ22 and EJ25's are dual port), so that's why it is needed. Exhaust manifold bolts right in place and you have to unbolt it from the engine anyway to remove the engine, so it's no extra work really.

EGR:
Have to look to determine EGR for certain. Automatics usually have EGR - but not always in 1996-1998 so it's wise to check.

If you don't care about a check engine light (in states with no emissions and check engine light isn't included in inspection) - then you have other options as well:

Basically - any 1995 EJ22 or any 1996-1998 EJ22 with exhaust manifold will work, again legacy/impreza doesn't matter. More specifically:

3. 1995 EJ22 without EGR (manual transmissions don't have EGR in 1995

4. 1996-1998 without EGR and again get a single port EJ22 exhaust manifold.
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General notes:

swap the EJ25 flexplate onto the EJ22 engine.

some evap stuff is different in later years...easy to work around, search and someone put a link here if they find a good thread. just swapping/managing vacuum hoses, not a big deal.

automatic/manual does not matter. in 1995 automatics have EGR and manuals do not - so "auto/manual" is simply an indicator of EGR in 1995. but automatic/manual by itself is meaningless and doesn't matter.

Car runs perfectly fine, plug and play without EGR, but you'll get a check engine light which some states don't allow. In states where it doesn't matter - ignore the CEL and run it forever without issue.

 

 

EJ18's can also be swapped into an EJ25 easily:
1. remove the EJ18 intake manifold

2. install a knock sensor (the hole is already there and tapped, just unused)

3. install an EJ22 intake manifold - it bolts right up, identical bolt pattern/gaskets

At this point the engine is just like the EJ22's listed above electronically - plug and play.

Use any EJ18 1990-1996 - they are all dual port exhaust, same as EJ25D's.
I think they all also have EGR so you'll either:

 

A. want an EJ22 intake manifold with EGR
or
B. use an EJ22 intake mainfold without EGR and just block off the EGR hole in the head. Make a plate to cover it up or cut the EGR tube, crimp it, and weld it shut, or weld a small metal bead/ball into the EGR tube. This will give a check engine light though when installed in EGR engines, like EJ25D's.

I have never attempted swapping an EJ25 intake manifold wiring harness onto an EJ18 intake manifold, unsure if that's possible or no.

Again - use the EJ25 flexplate

 

 

[Gloyale]

I have never attempted swapping an EJ25 intake manifold wiring harness onto an EJ18 intake manifold, unsure if that's possible or no.

Again - use the EJ25 flexplate

Would be hack job. Ej18 uses it's own IAC. And TPS.

 

You could probably make it run by swapping throttle bodies and blockin iac ports. But wouldn't be perfect