Legacy GT EJ20X/Y Swap

Hey Guys I'm at it again! I purchased a 2005 Legacy GT sight unseen when I was in Afghanistan the price was way too good to pass up even if it was just for scrap metal. Anyway I knew the car had engine problems. Previous owner said it has been through a few turbos and consumes oil. So I figured it was consuming oil from the turbo and picked a used stock turbo. When I changed the turbo I removed the screen filters that are inside the oil feed banjo bolts on these cars (known to clog and kill the turbo) It always kind of stuttered and never really ran right. I drove it around for a while then it started to smoke and was constantly consuming oil (about 1 qrt every tank of gas) So I went about looking for a motor for it. Seems the stock EJ255 is getting to be expensive these days and hard to come by a good unit that isn't over $3,000. I did find a used EJ255 at a local used parts dealer. When I inspected that motor I found it had a broken piston. It did have a brand new turbo on it, like brand new. Being kind of upset that this motor was "tested" but obviously was not I decided to remove the new turbo and put my blown turbo that came on the Legacy on the broken motor. I then returned the motor for a full refund. They didn't look twice at it just chucked it in the scrap pile. I could not find any other EJ255s that were way out of my price point. So I started looking at other options, I kept seeing these EJ20X/Y on Ebay and they are priced right around $700-$1300. These motors have Dual AVCS paired with a Twinscroll turbo setup. Nitrated crank shafts, forged rods with cast pistons that have a forged cap? never heard of that before but they seem much better then the stock EJ255. After looking into what is needed to drop one of these motors into my Legacy I decided to drive out to a JDM engine importer in Philadelphia.

 

 

Needless to say they had plenty of engines for me to pick from.I was able to basically cherry pick what I needed from each engine. I made sure to grab an intercooler (these are different for the twinscroll setup) along with a stub of a downpipe (also different for the twinscroll) and pig tails for both engine harness plugs (chassis side) and off I went back to the garage.

 

 

*Don't mind the bimmer I'm slowly collecting parts for that thing* :roll:

 

First thing I did was remove the intake manifold from the JDM motor since it is setup for a right hand drive car the engine plugs are in the wrong location.

 

 

 

I then removed the harness from the intake manifold as I'll need to rob the wiring for the exhaust AVCS (05 Legacy only has intake AVCS)

 

 

 

And just like that I have what I need from the JDM harness and I'm ready to move on to removing the USDM engine from the car.

 

 

 

With the USDM and JDM engines on stands next to each other you can really see how clean the JDM engine is. I spent about 20 minutes picking this engine. So I removed the USDM intake manifold and removed it's wiring harness so I could merge in the exhaust AVCS.

 

 

I also replaced a few of the connectors on the USDM harness that were damages I scavenged these from the carcass of the JDM harness.

 

 

 

And this is where I'm at now. I have a completed left hand drive dual AVCS Legacy GT engine Harness. In total I added 9 wires (2 for the cam position sensor, 2 for the oil flow valve for each head plus a ground for shielding back to the engine grounds the shielding should keep ignition noise out of the mix.

 

Ok back at it for day 2 of the Legacy GT EJ20Y Swap. I left off day one having completed the engine wiring harness that will allow me to run the exhaust cam timing when paired with the JDM ECU. After looking over the two intake manifolds I realized they are exactly the same. The JDM manifold is way way cleaner then the stock one that was completely coated in oil and crud inside and out so I decided I would run the JDM manifold. I transfered over the things I need (mainly the stock USDM injectors as they are slightly larger) I also wish I deleted the TGV wiring from the harness but I didn't think about it until I got to this point and I didn't want to rip into the harness again as I really wanted to get the motor in and running. So I have a few plugs that are not used since I'm deleting the TGVs.

 

 

I also added some protection over the engine harness and cleaned it up a bit as I installed it to the JDM manifold.

 

 

I assembled the intake manifold and installed it on the JDM motor.

 

 

 

Here the motor is ready to be dropped in.

 

 

A quick clip I recorded with my cell phone of actuall dropping the motor in.

 

 

Once I got it in the car I was able to start it up just to make sure the motor is all good and I didn't miss anything major. After I fired it up I called it a night. I started friday evening around 5pm and finished cleaning up around 9pm. That closes out day 2 of the swap and the motor is in and running.

 

Here is a clip of the first start up.

 

 

Saturday starts day 3 of the engine swap and the final day for any major work on the car. I installed the radiator and moved onto my next major sticking point which is the downpipe. The JDM Legacy twin scroll turbo is different from the standard subaru turbo and even different from the more common twin scroll turbos that came on some STi models in non USDM markets. So finding a 3 inch downpipe has been impossible so far. To get the car back on the road I decided to take the downpipe stub I got with motor and merge it with the stock downpipe that came on the legacy. But first I had to run to the store and grab a small piece of pipe to connect to two downpipes. I recorded this clip it sounded so good with just the downpipe stub installed. Also the Check engine light is for the TGVs being deleted this is with absolutly no tuning work done.

 

 

Go easy on me here I used the cheapest flux core welder you can get and I had to account for the turbo sitting at a much different angle then the stock turbo. Also the front O2 sensor is located behind the turbo outlet in the downpipe on these setups So I had to account for that as well.

 

Here you can see exactly how different the turbo outlets are.

 

 

 

 

After installing the downpipe Melissa and I decided to take it for a 120 mile round trip to Atlantic city where I won $300 at the Roulette table and we saw Bob Saget at the Hardrock. The legacy ran great, I haven't dug into the ECU yet or ran the 8 wires I need from the engine plugs down to the ECU so when I get the JDM ECU I can run the exhaust AVCS but it runs surprisingly well with the exhaust cams static at full retard.

 

Edited March 1, 2020 by weenz0r

My JDM ECU showed up yesterday. I ordered an ECU from a 2004 Legacy hoping to avoid the immobilizer but after plugging the ECU in it turns out it does have an immobilizer chip so I have two courses of action I can attempt to talk Subaru dealer into programming my Keys into the JDM ECU chip or use some wizardry and clone my stock ECUs chip onto the JDM chip. I would much rather the dealer program my keys to the JDM ECU so hope fully I can make that happen. I would just move the chip from the stock ECU to the JDM ecu but I need to be able to switch back to the stock ECU for state inspection. So that is not an option. I was able to plug the ECU into the car and download the ECU image mostly to confirm it is what I need. Seems it has what I need exhaust cam AVCS control! :ugeek

 

I'm also thinking I can repin the TGV wiring from the engine plugs back to the ECU plugs to use for the exhaust AVCS so I shouldn't need to cut open the factory harness just move the pins around to the correct locations but I haven't looked to see if I'll have enough conductors yet I'll need 8 I'm thinking it should be no problem.

 

 

I am currently working on cloning my factory Immobilizer chip located on the ECU board. It contains the codes that match with my set of keys in order to start the car. I've got the hardware side built up and I'm running into a USB open failed error when trying to read the chip contents. I'll keep yall posted when I get this worked out and hopefully I'll be able to run the car on both the USDM and JDM ECUs soon!

 

 

 

I have done it! I successfully cloned my USDM immobilizer chip to the JDM ECU. I was having some major problems with some USB failures so as a last ditch attempt I decided to try the whole process on my other laptop and it worked! no errors I got two read files from each ECU to verify I was actually reading data and not just getting random characters in the hex file I then flashed the file I pulled off the USDM ECU onto the JDM Chip and ran out to test it!

 

 

Solid! Good work, thanks for taking the time to document. Too often on these forums people get the recommendation to spend 5k on an EJ255/257 YNANSB instead of this.

Thanks, I spent $700 on the EJ20Y and $135 on an ECU so way way cheaper than rebuilding the EJ255 and now I have quad avcs and I'm getting 23mpg mixed highway and around town so much better than the stock motor.

great job on the swap, looks like you know what your doing, other do not. Only problem I see is if you try to sell it. I saw many JDM swaps that I passed on and would not sell. Nice job man.

Solid! Good work, thanks for taking the time to document. Too often on these forums people get the recommendation to spend 5k on an EJ255/257 YNANSB instead of this.

 

5k, nawww man. I could have taken my car straight to the subie shop and had it back on the road in two weeks with a nice ej255 for 4k. I just decided to get a 257 and add tons of parts, lol for 5k it better be a turn key fresh motor and turbo.

5k, nawww man. I could have taken my car straight to the subie shop and had it back on the road in two weeks with a nice ej255 for 4k. I just decided to get a 257 and add tons of parts, lol for 5k it better be a turn key fresh motor and turbo.

 

This is the only "turn key fresh motor" I could find, and you have no idea what they replaced when they rebuilt it. And that doesn't include labor. $5k is awful ambitious for a rebuild.

 

 

https://www.jegs.com/i/ATK-Engines/059/712E/10002/-1

Nice work OP. I applaud you.

 

 

Amazing that the 2.0 liter engine ran just fine with the USDM ECU and no tuning. Were you monitoring/logging the ECU while driving to Atlantic city?

The y is a lovely motor and such a blast to drive with the twinscroll. Currently have a 20y with the JDM ECU and wiring harness installed. FYI, it has a higher redline than the USDM 255... something around 7500. Regarding the downpipe... I believe the 15+ twinscroll wrx downpipes will fit, but can't remember. Im trying to remember if mine was completely lost or we found it, but I wanna say the 15+ WRX has that funky mounting plate.

great job on the swap, looks like you know what your doing, other do not. Only problem I see is if you try to sell it. I saw many JDM swaps that I passed on and would not sell. Nice job man.

 

I paid $100 for the car knowing the motor was beat and paid $700 for the JDM motor. I now also have it running on either the JDM ECU or the USDM ECU so inspection is no problem I think if I ever sell it I'll come out on top even if I load another 100K miles on it.

 

As far as how it runs on the USDM ECU, It runs pretty well. Not perfect but good enough to drive around but I'm not out doing wide open throttle pulls with it or anything. I have been on a work related trip the past week so I haven't done anything with the Legacy all week. When I get home hopefully by Sunday I'm going to start swapping the factor TGV wiring over to the AVCS pin locations at the ECU end. Once I do that It will just be a matter of pinning the exhaust AVCS into the engine plugs in place of the TGV wires.

Edited March 6, 2020 by weenz0r

Nice work OP. I applaud you.

 

 

Amazing that the 2.0 liter engine ran just fine with the USDM ECU and no tuning. Were you monitoring/logging the ECU while driving to Atlantic city?

 

I did take a quick look on the Cobb on the way to AC and saw some Feed back knock correction under a bit of boost so I just kept it out of boost for the ride there and back. but I had a Cobb ots stage 2 map loaded so I'm sure it's alittle fat on timing ect.

I’m getting ready to start my swap this weekend and have a couple questions that I haven’t found answers to, but yours is the best write-up I’ve seen thus far. Did you just repin the AVCS wires back into the main orange plug on the USDM intake harness? How crowded or difficult was that part of the job?

You used the JDM ECU and the exhaust AVCS. I’m assuming that means you did not need to set the timing on the exhaust cams back a tooth, right? 
 

thank you!