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Old 05-07-2007, 03:36 AM   #1
Scooby Newbie
Member#: 110414
Join Date: Mar 2006
Default supermoose 2 wire EJ20 swap FAQ

I AM POSTING THIS FOR SUPERMOOSE, I TAKE NO CREDIT FOR THIS FAQ, but some of the info here is very solid and revolutionary, so I thought I'd share it with you, He wrote this for rs25.

ok. here goes.

The biggest myth in swapping an ej20 in your car has been just romped on.

- wiring conversion is a 45 hour job
- i have to splice every single wire in the car to get it to even power things up, and ill probbaly fubaru it not ever be able to finish the project and end up selling the car in the end at a total disssapointing loss.

I'm new to subaru world and want a swap but the hell is this wiring conversion business. why does it cost a thousand dollars!!!. Well, the answer to the $1000 question is: its a thousand dollars because ECS's work is just that good. worth it.

In our case, we went a re-revolutionary style of swapping. MINIMALIST.

BUT, in our case we have proven that to go from taking apart the car to driving*, there are only 2 wires nessacary to fire up your JDM ej20.

The basics.

I'll briefly go into describing what goes into a conventional wire merge, describe the alternative and very H.I.N. RHD full JDM convesion (that i started), and now the newest uber Brisk method of swapping a JDM EJ20 while saving hella labor time to RHD swap, and making a LHD JDM WRX with only 2 wiring connections.

Full conventional wire merge:

USDM harness and JDM harness are stripped neeked, and individual sensors signals are ripped out of the JDM harness and inserted in the existing usdm car in their proper positions. remove 50 wires from each ecu and make them live in their proper places in the electrical system locomotive. alot of reading wiring diagrams, multimeter brilliance, and alot of cringy moments when you arnt totally sure if the JDM wire is a blue black, or a blb, or bwbl stripe+ pokadotted is supposed to be connected to the gyb wire on the usdm harness.

u mess up, you fry something. mabe a $2 sensor, maybe that uber rare version 6 STi-RA V-limited ecu. Cost you $450 and 3 weeks of time on rinkya to get another one too. Espically when you are the only guy around with a compatible JDM ecu (that you just fried) and its so rare that supermoose hasnt even touched one before. Thus, the $1K pricetag for a good vendor like ECS is well worth it. Professional build, merging, tested, proven true..... $1K well spent.

RHD JDM WRX full chassis conversion.

Shocking to everyone who had previously swapped, or was pondering swapping in north america, I had this retarded idea of making my LHD impreza L into a JDM WRX STi-RA V-limited by simply mirroring the firewall to fit in all mechanical pieces of the JDM RHD car and then bolting everything in. This took 2 weeks to build from start to competition, full removal of everything in the front half of the car, every single wire stripped out of the bulkhead and engine bay, complete 3/4 of braking system removal and re-plubing, re-installing and working the pedals, steering system, interior components- not in previous positions, but completely opposite. Things like flipping the trunk and flat fuel door lines, relocating the oh **** handles, hood latch and latch mechnism.... adds up to a very tedius and detail intensive endevor.

my car ran in 2 weeks and i drove it to work @ 7am that morning without working turn signal lights because i had finished filling the cooling system at 5am. fast forward 4 weeks later and i had a full interior with working windows - because i had to completly rewire them. RHD conversion is for the HIN crowd, or the very very very mechanically competent individuals who are BRAVE.

summary, rethink if you really want the life of RHD.

UBER brisK attak.

swApstar special. nobody else has presented it this way this way yet.

obtain entire wiring harness. ENTIRE WIRING HARNESS. not just the bulkhead bundle like you need for a wiring merge style conversion.

1. remove all LHD harnesses
2. clean out your dirty shell
3. remove plastic brackets on JDM harness surrounding: dash harness (4 thin long plugs), SMJ (2 big 10mm bolted square plugs)
4. fit in JDM body/chassis harness - fusebox arm to chassis connection /radiator arm, arm through lh side fender, through port by battery to engine.

reference to FSM wiring diagram to see routing of all the above. not that hard as shapes of plugs are unique, and plug bundles have all different numbers of arms.

once all the arms are in, then its time to tackle the rest of the interior. assuming your heaterbox and blower motor are removed to get to the LHD harness (the AC box can actually stay), you then
start making things go where they need to go.

-ECU arm lives in center console area (in place of old airbag computer thing and bracket
use open chassis holes left from previous harness to feed JDM RHD one into. connect MAF and ignitor chip arm to proper sensors, back engine 1 plug, side engine 2 plugs, all to their proper places. plug in full fusebox, install battery.
-Ignition bundle plugs have to go to the left side. To do so, remove enough tape so that the ignition bundle wires are free on their own (dont cut any wires), and then just route them over to plug into the ignition column/key hole side.
-Interior fusebox is on the right side in a JDM RHD car. Thankfully, the usa car benefits from leaving it there as it would be annoying to deal with around pedals.
- fuse box and main relay tree stay in that general area (rh side of bulkhead)
- plug in R1 plug to SMJ. The Grey plug off the super multiple junction (subaru turbo wiring format) has a 10mm bolt on its head. bolt it and the other SMJ plug in. make sure it goes on proper.
- Splice #1!!!!!
The R1 plug on the SMJ has ~ 26 wires. varying guages of thickness. in the thick ones, find a Black with red stripe. That is your fuel pump power wire.
-plug in everything, plug in all fuseboxes, everything (this is with dash out and minimal things installed- we just had hte steering column and x bar bolted in
-use test light. ground test light to cabin X bar and other end to the black with red strip wire from the R1 bundle. turn key in ignition- if you have everything hooked up right you'll have the light come on to signal power when you turn the key, and then turn off in about 3 seconds or so. that means your relay system is all working, etc.

-once test light verifys power, we are ready to figure out which wire we need to power to get the fuel pump to turn on

*you'll need to swap fuel pumps anyway (NA pump no go for turbo engine car) - and if you did, hopefully you remembered what colour the power wire is. trace the wire from the fuel pump plug itseif through the under chassis to seat plug, through the X over to F->R vein harness, and to the 3 plugs that should be a SMJ R1 plug body, but are not. after you've verified that wire, test if the fuel pump works with sending dirct 12v to that wire. if the pump turns on, then you have a ground to body fuel pump. if it dosnt, then find the ground on the NA chassis R1 equivilent 3 bundles, and ground it. (I didnt have to ground this, so this does not count as a splice for me). subaru is weird like that, some fuel pumps ground to holding mechanism, some to chassis.

-after you figure out which wire is which, make your splice (or 2 if you are unfortunate enough to have to ground the fuel pump too :P)
tape it up, etc. done.

-move on to splice #2 if the fuel pump audibily turns on when you turn the key ignition position to IGN on.


Locate the small connector that goes on the tab for the starter on your NA harness. Cut as long a piece of possible of tail for that connector plug (i.e. mouse with super long tail). shoudl be like 10" + or so at least. find the same thing on the JDM one and chop its head off. splice those to make a super long extention to let the JDM one x over from the right side instead. graft to avoid making 2 splices:P

*If you had to splice 2 at the last move, then you dont get to splice yet. you'll want to, but you used up the last splice by being unlucky

plug the tab in. if you've already used your 2 splices grab a screwdriver to get ready to short the starter to move.

turn the key and fire up your EJ20 swap. 2 wires baby.

**fire up and drive with 2 wires obviously is stating the obvious. to drive happily, you'll need brake lights, turn signals, windows working, etc. HVAC is a few more wires to intergrate, so is wiper system.
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Last edited by AaronB; 05-07-2007 at 10:32 AM.
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Old 05-07-2007, 09:59 AM   #2
Scooby Guru
Member#: 177
Join Date: Aug 1999
Chapter/Region: NWIC
Location: Austin, Texas, USA
The 93 W/EJ20K-sold
Subaru-less :(


not sure what i think about this post
first its NOT AT ALL SOLID just ask the people that have tried to finish the other wires ...

the other two ways are so much better its not even comparable

if i was a mod i would lock this thread
Jaxx is offline  
Old 05-07-2007, 10:00 AM   #3
Scooby Specialist
Member#: 66739
Join Date: Jul 2004
Chapter/Region: MWSOC
Location: Medina, Ohio
2002 WRX wagon


so a running EJ in 2 wires. but a driveable(legally) in 10?20? how many in all you think?


why would you want to hinder anyones swap? let it be, jared. this is good info for people who need the easy way sometimes. and in general good reading to recall personal swap memories. this will be good for people. why lock it? what does that accomplish.

personal vendettas aside, what is truly bad with it?

it makes it look easy like an SR swap(240sx) for the kiddies.

kheff46 is offline  
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