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Old 04-03-2006, 12:29 PM   #1
MY99 2.5GT
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12 Legacy GT 13 Armada

Default Anyone Using A WRX ECU with an NA 2.5 Harness?

I saw a long while back someone had done a WRX motor swap into a 99 RS but kept the RS wiring harness for use with a WRX ECU. I remember reading that all they did was pull the pins on the RS connector and inserted them in a WRX connector. They had to add a few pins that weren't there to begin with for various sensors and such but it sounded pretty simple compared to pulling the entire harness loom and redoing it with a WRX one.

The questions I have are as follows:

1. What sensors/pins had to be added?

2. What RS sensors needed to be trashed in favor of WRX ones

If you have answers to any of the above question please post. Even better if youve done something like this let me know. I would really like to talk with you at length about what needed to be done.

I'm doing a Hybrid 2.2t block swap into my 99 Legacy GT w\ 2.5 DOHC heads and turbocharging. I can't go standalone because of emmissions. If I can run my setup from a WRX ecu with a reflash or piggy back I'd much rather do so then with the 99 NA ecu and piggy back.

Thanks
Brad
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Old 04-03-2006, 12:49 PM   #2
Matt Monson
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When we did Squeech's swap, we looked into this, and what he found was that the actual pin design itself was different on the RS and that they were not compatible. You could splice in all the WRX connectors, but you will still need to add all the turbo control, and the COP, and a few things for the OBD. Furthermore, the RS/LGT engine connectors are through the firewall and the WRX ones are through the fender. Personally, if you are using an Ej205 WRX ECU, I still think the easiest way is the complete merge. To do it with the harness in the car and dash still installed, you will need to do twice as many splices.

I am currently doing something similar with an Ej22T harness, and it's a pretty tedious conversion...
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Old 04-03-2006, 01:40 PM   #3
MY99 2.5GT
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So your suggesting buying a WRX ECU, Engine Side Harness and connector. Pull the stock harness and replace with WRX setup?

What was so tedious? Is it more then getting pinouts for both ecu's then cut and splice what is already there and adding what isn't?
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Old 04-03-2006, 01:53 PM   #4
BOY
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Its not an engine side harness from the EJ20, its the whole freakin thing and you have to separate out the engine side. Not hard, but very tedious.
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Old 04-03-2006, 02:31 PM   #5
jamesfacts
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Quote:
Originally Posted by MY99 2.5GT
So your suggesting buying a WRX ECU, Engine Side Harness and connector. Pull the stock harness and replace with WRX setup?

What was so tedious? Is it more then getting pinouts for both ecu's then cut and splice what is already there and adding what isn't?
You can't simply replace the harness because the WRX harness will not plug into the RS body functions like headlights, door plugs etc.

There are a number of good threads here explaining how to merge harnesses, and why its necessary.
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Old 04-03-2006, 03:16 PM   #6
Matt Monson
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Friday night I saw an '00 RS in pieces as an attempt was made to install a complete WRX harness (and dash, etc.) into it. What a freaking nightmare. I will never ever do that to a car. I don't get it. There is so much extra work just to get a WRX dash and gauges.

Realistically, one could patch a WRX harness into the RS bilkhead harness and route the WRX engine section across the firewall. But personally, I would never want to spend all that time sitting on the crossmember doing my soldering. Much easier to lay it out on a the workbench and sit down in a chair! There are many things in working on Subarus where extra steps make it easier (and easier) on the body than the shortcuts. Do it right, ONCE, is my motto...
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Old 04-03-2006, 04:09 PM   #7
MY99 2.5GT
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I have no problem sitting and soldering.

Correct me if I'm wrong but wouldn't all the soldering be done as the harness comes into the ECU under the passenger side carpet? My idea is more along the lines of making my own conversion harness. Pull the Legacy's current harness and cap it off. Cut each wire one by one and solder in a junction wire that will then be soldered into fully pinned WRX ECU Plug with open wire leads. Run lines for additional sensors and solder them into the WRX Plug leads where necessary. Doesn't seem like all that big of a deal as long as you can keep straight what wire goes where. I'm pretty sure this is what was done on the RS I'd seen a while back.

I guess mainly what I want to know is can anyone point me to a site or thread that shows pin by pin similarities and differences between Legacy/RS sensors/ECU Plugs and WRX sensors/ECU Plugs, what is already there and what will be added.

Just to clarify is the above what you guys mean by a full merge?

Brad

Last edited by MY99 2.5GT; 04-03-2006 at 04:23 PM.
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Old 04-03-2006, 04:18 PM   #8
MY99 2.5GT
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Matt - What conversion are you doing with the 2.2t?

Just thought I'd clarify beyond a doubt what I am trying to do.

By the way what is COP?

Last edited by MY99 2.5GT; 04-03-2006 at 04:24 PM.
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Old 04-03-2006, 07:30 PM   #9
Matt Monson
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Coil on Plug.

You still aren't following. Unless you completely strip the harness, which requires unwrapping all the tape and pulling out the wires you don't need, you will need to make 2, not one splice per wire. Splice 1 will be at the ECU for the connector. Splice 2 will be at the firewall, on the same wire, as you patch in the WRX harness to make it compatible with the WRX's engine connector. You need to replace connectors at both ends.

And you will still need to feed in and add all the previously mentioned connectors.

As for the Ej22T merge? #1, I will never do this again! I am doing it out of the car, but am still having to do the double splice thing. This was so that the car's owner could have it with his Legacy ECU in the kickpanel where the RS ECU goes. The '92-94 Legacy ECU lives under the dash by the trunk release latch. This double splicing crap is taking me forever. I was supposed to have delivered this merged harness a week ago and I am still not done. I haven't spoken to him today, but I am pretty sure the car's owner is miffed at this point. But there has just been so much extra BS that it's been ongoing. In addition to this double splice thing, I have been battling using an auto ECU into a manual car's chassis, AND there are OBD differences, even though they are both OBD-I, and the ground and power circuits are routed totally differently in the two cars. It's taking so much longer than any other swap I have ever worked on to make sure this is right, which it has got to be since the car owner is 500 miles away from me and I can't just pop over and trouble shoot once it's in the car. Ok, rant over...
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Old 04-03-2006, 08:06 PM   #10
bmxpunk
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you jinxed yourself when I came to your house matt. Damn I was thinking about doing this(have a line on some different heads) wiring for my impreza. wew will be in touch matt.
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