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Old 02-07-2011, 05:58 AM   #1
mtsuby
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Default 04 wrx to 04 sti

So i'm thinking about doing this swap pretty soon since my engine is getting a little tired. I've been doing a bunch of reading, but i haven't really found much on swaps within this year. I guess im just wondering how much of the wiring harness i'm going to need to replace since it's going to be the same year. The engine's wiring harness of course, and gauge cluster, but can i swap the ecu, and have the engines harness plug into the connector? or am i going to have to go full out on the wiring harness and do a full transplant? Any insight to doing this swap would be extreamly helpful.
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Old 02-08-2011, 12:52 AM   #2
mtsuby
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Anyone?
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Old 02-08-2011, 02:52 PM   #3
Zephyr
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The car will need to be rewired or you'll need to put the STi dash in. I have done a few of these for other people.
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Old 02-08-2011, 03:14 PM   #4
Team Scream
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Im on my 3rd swap.

What you need to do is get the manual for the WRX/STi for 2004.

The WRX was a 2.0 (non avcs) and the STi was a 2.5L (AVCS)
http://www.cars101.com/subaru/impreza/wrxsti2004.html

So the easiest way for you to swap is to build a 2.5L engine with non AVCS cams/heads and keep the engine drive by cable..

If you do that, nothing under the dash will need to be replaced, and you can use your WRX engine harness.
I would consider converting top feed TGV's for the engine if yours are side feed now as the injector selections are better.

On my 06 WRX to 06 STi swap, nothing had to be rewired except some minor stuff for the gauge cluster, but that is because both engines are 2.5L AVCS..

On my 06 Forester to 07 STi, I had to do a some merging but that was because I went from an auto tranny to the 6MT so I had to merge the harness for neutral safety, and reverse lights etc, and I had to add a pin to the ECU connector so that the ECU would then be recognized as a manual tranny ECU and I could then flash a manual tranny ROM to it..

I wish I knew more about the 04 but I just dont man, but thats why it pays to have the manuals BEFORE you ever turn a wrench.

Dont be intimidated by the prospect, it is a great project and will be extremely rewarding when you complete it..

The gauge cluster swap is well documented across years, so that is painless.

If you want to put a true STi engine in it, then a full bulkhead harness and ECU swap will be required as far as I can tell.

Last edited by Team Scream; 02-08-2011 at 03:25 PM.
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Old 02-08-2011, 09:20 PM   #5
mtsuby
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What service manual do you recommend? Chilton? Hayes?

Sounds simple enough to do. Who makes cams and heads for the 2.5's that are non AVCS?

With regards to a 6mt, is the wiring any different with that compared to a 5mt? and will i be running into any issues with lengths of the drive lines?

Will the gauge cluster from the sti plug in to the wrx wiring harness or are the connectors a little different?
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Old 02-12-2011, 05:28 PM   #6
Team Scream
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Quote:
Originally Posted by mtsuby View Post
What service manual do you recommend? Chilton? Hayes?
The factory Subaru manuals.
You can buy a subscription from Subaru, (I forget the link but a search will help). From there you have to download each module separately, it takes a lot of time, but well worth it. If you can find someone who already has it, perhaps you can talk them out of it.

Quote:
Originally Posted by mtsuby View Post
Sounds simple enough to do. Who makes cams and heads for the 2.5's that are non AVCS?
Kelford, Brian Crower, GSC

Quote:
Originally Posted by mtsuby View Post
With regards to a 6mt, is the wiring any different with that compared to a 5mt? and will i be running into any issues with lengths of the drive lines?
You can use the harness from your 5MT and it will connect with the harness in the engine compartment right at the bell housing for neutral safety and reverse lights, you may or may not have to splice the speed sensor connector wire, not sure on the 04.

You will need an STi driveshaft or an automatic driveshaft from most auto tranny Subaru's in the same range of years.

This is NOT true if you source a Forester (auto) driveshaft from an 06.
That much I know. The rear yoke bolt pattern is slightly off, but most other auto shafts work im told. I have always used the STi shaft because it is beefier.

Quote:
Originally Posted by mtsuby View Post
Will the gauge cluster from the sti plug in to the wrx wiring harness or are the connectors a little different?
The connectors are just slightly different preventing them from just plugging in, but it is an easy mod. You basically file down a tab and they plug right in.
You may have to swap a couple of wires in one of the connectors.
The cluster itself will fit perfectly and screw right into place with ease.
The bezel fits right back in and looks factory.

Do some searching and PM a few people with 04 STi's and see if they are willing to share their Service manuals privately.

Search for the STi cluster swap and you will find your year.
Here is one thread I know of:
http://forums.nasioc.com/forums/show...ht=sti+cluster
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Old 02-15-2011, 08:41 PM   #7
mtsuby
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great, thank you!
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Old 02-18-2011, 08:22 AM   #8
rjw5164
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Check out busted finger motorsports:
http://bustedfingermotorsports.com/f...91efc7fac8e2c6

They did a great job compiling some manuals and how-tos.

As for the swap itself, the easiest way to put an 04 ej257 into a WRX is to put all of your WRX sensors, wiring, intake mani, etc on top of the 257 long block. There's no need to worry about the cams. I don't know why people always bring that up. The 04 ej257 has the cam sensor pick ups on the back of the cam gears as well as the "half moon" mount on the head for the WRX cam sensor (mount just needs to be drilled/tapped). You'll want to upgrade your injectors and fuel pump as well. Get it tuned for the larger displacement and you'll be good to go.

Look up element tuning's guide on this type of swap. PM me if you have any questions.
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Old 02-25-2011, 03:14 PM   #9
bobglaub
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I have an 05 wagon, and my engine isn't just tired, she spun a bearing and she's starting to knock. I figure, since the engine has to come out anyway, may as well drop in a nice STI motor. My question is:

Can I drop in an EJ257 and bolt her right up to my existing 5mt tranny? What are the advantages to AVCS over non-AVCS? If I go with AVCS, I understand I have to replace all the wiring and ECU, does this mean i can no longer use my "impreza" cluster? I don't really like the look of the STI cluster, too much red. Plus I wanat my wagon to be a sleeper, i don't want people looking in and seeing an STI cluster, kinda takes the fun out of it.

If I use my 5mt, will it be able to handle the power/torque of the ej257? will the drive shaft work or should I replace that with the sti shaft?

Thanks.
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Old 02-25-2011, 03:20 PM   #10
Jspike
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If your going to spend all that money on a swap go with the 207 jdm motor with big port heads, it's a very easy swap and a better motor than the 257 pm me if you have more questions
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Old 02-25-2011, 03:24 PM   #11
Zephyr
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Quote:
Originally Posted by bobglaub View Post
Can I drop in an EJ257 and bolt her right up to my existing 5mt tranny?
Yes

Quote:
What are the advantages to AVCS over non-AVCS? If I go with AVCS, I understand I have to replace all the wiring and ECU, does this mean i can no longer use my "impreza" cluster?
It can be rewired to where you can retain your stock dash/cluster/HVAC.

Quote:
If I use my 5mt, will it be able to handle the power/torque of the ej257? will the drive shaft work or should I replace that with the sti shaft?
It will work fine so long as you don't drag launch the car regularly. Drive shaft does not need to be changed.

Shoot me a PM if you'd like more indepth knowledge.

Z
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Old 02-27-2011, 11:13 AM   #12
j_link
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ok are you going to use the 5speed from your car? If you are i just finished this exact swap.

All harness will need to be changed for a 04 STI harness, including ECU (05 will not work properly) This means gutting the car all the way down and doing all the harnesses.

Here are the problems you will experience. The gas pedal will need to be changed because STI is throttle by wire. This means making an adapter plate for bolting up of the new gas pedal. The harness for the transmission on the five speed is a four pin connector, and the STI is a 6 pin connector. You will need to find which wires connect the reverse switch, and the neutral switch o both ends of the connectors to splice them together. Next the headlights. Your high beams will be plug and play, but the low beams you will need to wire connectors, due to the fact the STI has HID. And the interior dash lights will not work. You will have to add a new ground for them as the STI controlled the lights through the instrument cluster, and the WRX did not. If you want your cruise control to work, I have been told you will need to change the clock spring and controls in the wheel of your WRX over to the STI. I have not done this yet, but I plan on it.

Now the last thing is the HVAC controls will need to be changed. This means swapping the blower box. The heater core distribution box, and the HVAC control, because the STI has electronic controls.

Doing the swap this way will gain a 100% working swap, with no check engine light, ABS will work, SRS will work. It sounds like alot of work, but just food for thought. My 04 WRX swap is the first Subaru I have ever touched. This swap took all of 4 day to complete in my garage. Once the wiring is done everything is plug and play.

I hope this helps.
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Old 02-27-2011, 11:19 AM   #13
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Quote:
Will the gauge cluster from the sti plug in to the wrx wiring harness or are the connectors a little different?
yes there is differences in the WRX and STI cluster harness. If you are using your WRX cluster, it will work fine, the only thing that won't is the illumination lights.
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Old 02-27-2011, 11:21 AM   #14
j_link
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check out www.y2kimports.com they helped me, with info to do my swap.
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Old 02-27-2011, 11:23 AM   #15
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