mondtster

Did your engine not come with at least a partial wire harness you could salvage the connectors from? The Legacy EJ25 timing belt kit will work for the 20X/Y. In fact, most parts will interchange. But you want to be careful and use a resource to confirm parts interchange before just assuming things will work. The older JDM motors are far worse than these for finding the right stuff.

I can’t comment on the U20 heads but I can tell you that the Z20 and EJ20Y will not tolerate much timing with the fuel we have available in the US. I’ve wondered how much of that was related to the heads rather than compression ratio though. The EJ20X and 20Y are engines that were definitely designed more with fuel efficiency in mind than overall power output. This can be seen in the stock calibration files and also just by the choice of higher compression ratio.

Flash it back to stock while you’re trying to fix the other things. Record some data, get a baseline to figure out if the software is hurting you or not.

Make no assumptions. You really want to determine engine health and status before you start masking things with tuning. Among other things, can have air leaks that will not produce check engine lights. Did you happen to record any data prior to flashing the ECU? How were fuel trims then and how was DAM? I’d get your rattles fixed and make sure everything is ok but I’m guessing that isn’t going to be the absolute cure. My guess is that you have real knock and you’re going to want to address it.

PCV systems on turbo cars are always a compromise to satisfy emissions constraints. If emissions is not a concern I’d remove the whole system and vent to atmosphere. Your choice whether or not to run it through an oil separator. At a MINIMUM, you need to make sure the PCV valve will actually seal under boost. Otherwise you’re pressurizing the crankcase with boost pressure and making your problems worse. The turbo Subaru PCV system is one of the worst I’ve seen, but oh so typical of a production turbo car.

I'd love to know how, because far as I know the circuits aren't in the US ecu to do it. I'm thinking you're mistaken.

Is the car automatic or manual? The turbo used and the engine used (20x vs 20y) makes no difference. Edit: I’ll mention it again. The hardware in the ECU is the same for both the M/T and A/T applications. The difference is in the software. Interpret that as you see fit. There will be problems using A/T software in an M/T application though.

Part of the part number is the software that is in the ECU. All you need is the right hardware and you can put the software you want to run in it. I have a JDM ECU in a US car with Australian software. As I said before, these cars aren't terribly picky.

My first thought is that you have wiring or injector problems but you say you've checked those circuits. Assuming everything is actually good, you're back to the ECU. You say you had the immobilizer removed, how did you do that? I assume you had someone modify the ECU software? The software would be a common denominator and something I'd be looking at. I'm curious why you're putting this much time into using a stock ECU in a non-stock application? An aftermarket controller may be easier to work with. Last but not least, hello from a fellow instrumentation guy!

They're not that picky.

I thought the later Legacys were CANbus too, no?

The '06 style JDM and ADM ECUs are all in the same family and software can be swapped from one to another as you please. I'm actually running an ADM MT based ROM in a JDM AT ECU with no issues whatsoever. The newer cars may be different though. Starting out with the US STI ECU (the one with dual avcs) and ROM might be the easiest, if the pinouts match.

That's definitely the easiest way to do it, but if you wanted to you could do it via the diagram route too. They should have the pin locations on the individual schematics. When I did mine I sat down with the I/O pages as you suggest. If I were the OP I'd take the 2006 JDM I/O page and compare it to the 2009 US page. If it looks like stuff pretty much lines up I'd consider taking a risk and pinning the cam sensors and control circuits in the cavities that the 2006 diagram shows.

Don't waste your time with the JDM harness. It is set up for a RHD car and would be way more work than it is worth to mess with. Just use the US harness and add the necessary wires. That wire looks like it would work.

Shielded twisted pair is readily available. What I used was made by Belden, I don't remember the part number. Most of the wiring doesn't even need to be shielded for this swap. I used the US harness and made an overlay harness with the additional wiring necessary to run the exhaust cams. To get the proper terminals to connect to the ECU I bought a set of ECU harness connectors from a junkyard and removed the terminals I needed. Then I inserted them into the connectors on my good harness and soldered my overlay harness onto those new terminals.

The JDM ECUs do too have an immobilizer. I assure you it will not start unless the key codes in the ECU match the ones in the BIU. The VIN is not checked though...

Why spend money for a "harness" that is just a few wires? Make it yourself.

It will run on a US ECU ok. I ran one that way for a few thousand miles. The codes for whatever you eliminated during the swap will need to be dealt with but if you put all the US parts on it I wouldn't expect any codes to pop up when running the US ECU. There will be no control for the exhaust cams with this approach however.

If you look, it is easy to find the service manual for free. Long story short, to do this swap I would suggest sticking with the US wiring harness.

That was kind of my point. There's nothing wrong with a stock shortblock, but make sure the clearances are set for the kind of use the engine will see.

Which is why I've always questioned why people on this board seem to push buying a replacement shortblock from Subaru, rather than assembling an engine with tolerances more suited to a performance application in mind. I suspect that Subaru knows that their ring gaps are tight. People need to remember that these engines and cars were designed with a purpose in mind, and that was to be a passenger car, not some high performance machine. Things like emissions and oil consumption are far more important to them than reaching high marks for durability (although too low will cause a loss of customers). The area of the piston that breaks is where the high load bearing area is.

You can, I drove my car for a couple of weeks on the US ECU while I was working the details out on the JDM ECU. Have you looked into using an '08+ STI ECU? That might work in your application and give you dual AVCS.

If you have that old of a car I'd be inclined to use an aftermarket ECU. I personally wouldn't have went with a Legacy motor for this but to each their own.

Yes, I have.

I'm not going to do everything for you, the answers to the wiring needed are readily available via the diagrams in the factory service manuals. It should just require about 8 wires to be added. Two for each cam sensor and two for each valve. The dealership might be able to program the immobilizer for you, but I don't know. I pulled the key codes from the EEPROM in my US ECU and copied them to the EEPROM in my JDM ECU. Doing it this way will allow all your currently existing keys to work but I can't add a key without a trip to the dealership.