WRX Engine Swap Advice

[ONeill]

Tl:dr - Can I swap an EJ205 from a V6 WRX into a V3 WRX STi without mods?

As older members may remember my V3 WRX STi (GC8D) appears pretty buttercup coloured and leaves a citrus aftertaste. Well the grapefruit, It's blown another engine.

 

I have acquired an EJ205 from a V6 WRX (GF8G) and am wondering if I can just bolt it in plug it up and bomb off into the sunset without any major issues or funny business required to get it going?

The EJ205 is only supposed to be a stop gap measure until I can get round to stripping down and rebuilding the EJ20K. It has taken me 2 years to get the new motor and now another 6 months to think about working on the car so this may take a while.

Any advice and suggestions would be greatly appreciated.

[Loren]

Without any changes? not even wiring changes? I doubt it.

[mitch8198]

kind of;

AFAIK the only external differences between Phase1 (ej20k) and Phase2 (ej205) the crank & cam trigger patterns and the intake manifold bolt pattern.

1. Take the toothed cambelt pulley's from the crank and top LH cam on your old EJ20k, this will fool the V3 ecu into thinking it's running the older engine.

2. Use as many sensors from the old manifold as possible on the new one. Unsure whether the throttle position sensor or idle control valve are cross-compatible due to the different throttle design on the newer engines. 

 

Could also just swap the shortblock (if you've spun a bearing), use all your old sensors and happy days.

 

 

[Loren]

Swapping the crank and left intake will get you part of the way... but what if the cam profiles are different? 

[mitch8198]

Yep cam profiles will be different and 205 probably has higher compression but it would run.

Definitely not perfect and would recommend not using the V3 STi 6S ecu because timing, boost and rpm limits would likely be too aggressive for the poor old wrx engine.

 

So the answer really depends on how dogey you want to be.

I used to race my wrx using a 97 forester ecu (normally a td04 & grey injectors) running a 93 RA engine, yellow injectors and a VF30 and it worked fine but that's a bit risky for most people 

Edited December 18, 2018 by mitch8198

[RaKid]

No - you can't

 

As @mitch8198 pointed out (and this the glaring elephant in the room) the manifold and heads and all of the sensors are completely different, not to mention the loom.

 

To make this work, simply strip down both engines to a short block and bolt your existing heads to the new short block (I'd recommend new HG's and machining of the heads while you're at it) then refit your manifold and you're good to go.