Doing a swap! Questions about ECU and TCU from OBD1 to OBD2

[New92]

Hey guys, I have finally arrived at a long awaited dream. I acquired a 95 Ipreza LX Coupe and I have a EJ22t donor car from which I will be extracting the block, trans and any other bits I need to make the LX a turbo 5spd.

My goal is simple, a simple (lol) swap with mildly increased factory power based on existing mods. I think Im in pretty good shape. Both cars have the 2.2 installed, the LX however is OBD2 N/A Automatic. I am hoping to avail myself to your collective wisdom yet again and obtain feedback and suggestions concerning the choice of ECU and TCU as well as wiring in the Turbo.

Currently, Im looking at using the manifold off of the LX to move the SS block from OBD1 to OBD2. I need to keep the OBD2 for emissions. For the OBD2 turbo ECU and Transmission control I was considering sourcing controllers from a same year WRX GC8. I already have the supporting mods to handle the changes in input from the WRX ECU ie TMIC, Fuel Pump, MBC etc. I am wondering if there are any other recommendations? I currently have no plans to obtain beast like power or make a mad machine from this build. I simply want a dependable factory turbo with a very mild upgrade in power from basic mods. I would very much prefer to not tear the car down to the shell and remove and swap engine harnesses.

Your input is very much appreciated! - Ben

[wtdash]

Hi,
Look up BoostedSubie's Threads/posts on here. He did something similar, although he did swap in the SS harness.

Go spend some time over on RS25.com and see if you'd be happy w/just running wastegate boost (5-7 psi) w/either the stock EJ22 or the EJ22T. Lots of people just turbo the stock EJ22. It seems to be fine running a small amount of boost and can even run the stock injectors (but should look into a RRFPR).

You should have EGR on the '95 AT OBD2, too. You can run the complete EJ22T longblock w/the OBD2 IM - HERE's HOW....or you'll get a CEL.


OBD2 wasn't on the foreign WRX until maybe 2000 (obviously '02 for the USDM WRX)? The '93-'96 WRX/STi's EJ20G ECU was plug-in compatible w/the '91-'94 Legacy SS/TW, so it won't work w/your '95.

I did a '98 Forester Turbo project and there were no foreign turbo ECU's compatible w/my harness - WRX, Forester Turbo-S, or Legacy/Liberty (I used a Greddy Emanage piggy-back).

The TCU from a UK/Aussie 4EAT WRX 'might' work? I don't know, but I've read the TCU from the '90-'94 OBD1 Legacy will work w/the OBD2 '95-'98 Legacys, too...might be the same for the Impreza. But I wouldn't get too caught up on that....I would look into the 'Power Mode' TCU hack - HERE. It'll improve the shifting of your AT.


You'll likely need a new transmission if you can't keep your right-foot under control, but an Outback's transmission w/4.44 rear diff should be an upgrade option since it handles the extra hp/torque of the EJ25D.

You won't have a 'factory' turbo setup unless you do a harness swap, IMHO. But w/the info on the Web you should be able to build a nice daily driver.

GL and Have Fun,
TD

[Legacy777]

The whole OBD2 thing really complicates matters. Other's have been down that path and I'm just not sure they've been really satisfied with the results. I think Todd had some good advice, and hopefully others that have ventured down this path can also chime in.

[New92]

Hi,
Look up BoostedSubie's Threads/posts on here. He did something similar, although he did swap in the SS harness.

Ive looked over his threads when I first started considering this. His is one of the reasons I was scared off from swapping the harness. The other is that I can not pass emissions without the car remaining OBD2.

Go spend some time over on RS25.com and see if you'd be happy w/just running wastegate boost (5-7 psi) w/either the stock EJ22 or the EJ22T. Lots of people just turbo the stock EJ22. It seems to be fine running a small amount of boost and can even run the stock injectors (but should look into a RRFPR).

The car Im sourcing parts from I am very happy with. It was my DD at one time and Ive worked on it for years to build it up to a power level that I can live with (insert big grin). With the MBC i have it set at 10psi but that was on a completely open 3" TBE. Ill be installing a CAT and muffler so Im sure Ill bump it back up a pound or two as I had previously. I wont be using an FCD. I want to keep the block from the Legacy as its been my motor for 9 years. I know its history and maintenance and its closed deck. Im deff getting a FPR to better meter out the gas pressure Im getting from the Warlboro 255. Even with the full WRX exhaust I once had I was running a bit rich.

You should have EGR on the '95 AT OBD2, too. You can run the complete EJ22T longblock w/the OBD2 IM - HERE's HOW....or you'll get a CEL.

Thanks for the link. I found that as well and was much relieved to see the intake manifold would take care of the bulk of the conversion for me. I plan to upgrade the IM down the road as the stock LX IM flows less than the Legacy version I believe.

OBD2 wasn't on the foreign WRX until maybe 2000 (obviously '02 for the USDM WRX)? The '93-'96 WRX/STi's EJ20G ECU was plug-in compatible w/the '91-'94 Legacy SS/TW, so it won't work w/your '95.

Thats good to know. Ive been researching OBD for those model years but had not found a whole lot to definitively confirm if/when the turbo models changed over to 2. I used to know a guy locally who had a 2k model so Im still pinging other sources for some guidance.

I did a '98 Forester Turbo project and there were no foreign turbo ECU's compatible w/my harness - WRX, Forester Turbo-S, or Legacy/Liberty (I used a Greddy Emanage piggy-back).

Ive been reading up on piggy-backs for these cars. Theres a good bit of feedback on RS25 and most of it is not good. Did you source your settings online or set a base map and then slowly adjust? How long did it take you to dial it in? Were you happy with the end result? I ran a SAFC2 on my old project (99 Neon RT with 2.4 turbo swap) and that did a great job of cutting back on fuel saturation at idle as well as bumping up the rev range slightly. Ill search the posts for your write up on the Greddy unit but any feedback you have would be appreciated.

The TCU from a UK/Aussie 4EAT WRX 'might' work? I don't know, but I've read the TCU from the '90-'94 OBD1 Legacy will work w/the OBD2 '95-'98 Legacys, too...might be the same for the Impreza. But I wouldn't get too caught up on that....I would look into the 'Power Mode' TCU hack - HERE. It'll improve the shifting of your AT. You'll likely need a new transmission if you can't keep your right-foot under control, but an Outback's transmission w/4.44 rear diff should be an upgrade option since it handles the extra hp/torque of the EJ25D.

No worries there, I am not an automatic guy. I will be moving the 5spd from the Legacy into the Impreza. Im still researching to confirm what 5spd TCU will work. I may just grab one from the same model car. I found a pretty decent deal for $80 new.

I really appreciate the feedback and time you took to share. Ill keep digging and when set Ill open a build journal and this time provide better photos!

[New92]

The whole OBD2 thing really complicates matters. Other's have been down that path and I'm just not sure they've been really satisfied with the results. I think Todd had some good advice, and hopefully others that have ventured down this path can also chime in.

Thanks as always Josh. There is quite a bit of conflict about this very thing on RS25. As near as I can tell it comes down to cost. OBD1 is quite simply cheaper than the newer systems and easier to upgrade. As I have no plans to build this motor out anymore than I have, Im not overly concerned about sticking with OBD1 at this time. I will have a spare block to play with when I am done and am seriously considering my first engine taredown and rebuild. Id like to do the nasty fast beast of a build on the Legacy if I dont sell it when Im done. Id be interested in hearing others feedback as well. I certainly dont want to oversimplify the issues. In case Ive missed something critical, it would be great to hear about it now.

- Ben

[wtdash]

Did you source your settings online or set a base map and then slowly adjust? How long did it take you to dial it in? Were you happy with the end result?

Here's my '98 Forester Build. One of the main reasons I went w/the Greddy was due to getting a base tuning map from the guy who sold me the EMU - he ran it on his AMAZING '97 LGT swap (way b4 its current state of awesomeness). It started and ran my Forester (same ECU) and as long as I kept the boost <10 psi, it seemed OK, but in the end I couldn't get it tuned (took it to two turners) properly due to a broken piston, I believe....and I wasn't comfortable doing much w/the tuning.

. Im still researching to confirm what 5spd TCU will work. I may just grab one from the same model car. I found a pretty decent deal for $80 new.

I'm not sure what you're referring to there....I'm not aware of a TCU for the 5-speed? I know I didn't need one for my '90 5-speed swap, and I didn't come across anything when I was collecting parts for my '96 Impreza swap - bought my '93 SS instead.

EDIT (for posterity): The ECUs were the same for the 5-speed and Automatics for the '91-'94 SS/TW and 99% sure it's the same for the '90-'94 NA Legacy too - based on the Transmission ID pin @ B48.20 HERE, and also for each model year of the '95-'98 Subarus- just one of the pins on the ECU got a signal from the TCU to tell the ECU what trans was installed. The ECU's were different for the 5-speed vs. Automatic Subarus starting around '00, I believe.

OBD1 is quite simply cheaper than the newer systems and easier to upgrade.

My .02 on this - but not sure I'm understanding?? None of the USDM Subarus from '95-'02 have any directly related "turbo" cars from overseas that are plug-n-play in the ECU department. Although most of the parts will fit from a Legacy/Impreza/WRX/Forester, there's no easy options for just throwing the ECU in to run it properly.

There are multiple options that I'm aware of:
- Turbo the stock car 'as is' and hope it lasts....5psi seems to be a safe limit.
- Add EM to the existing ECU, such as a piggy-back - Greddy, SAFC, PP6, etc.
- Go Full Standalone - Megasquirt is a common option.
- Do a full harness swap:
--------- Newer - WRX and maintain OBD2 compatibility
---------- Older - Legacy SS/TW/WRX/STi and lose OBD2

GL,
Td

[New92]

Im looking over your build now. Thanks for explaining about how you arrived at your map.

"I'm not sure what you're referring to there....I'm not aware of a TCU for the 5-speed? I know I didn't need one for my '90 5-speed swap, and I didn't come across anything when I was collecting parts for my '96 Impreza swap - bought my '93 SS instead."

Yeah Im gonna blame that on fatigue and temporary insanity. I confused myself as well. Thanks for setting me straight and pointing out the obvious.

Ill read up some more on the piggy-back option and see what else I can find. I really do appreciate the input and advice.

- Ben

[Legacy777]

No worries there, I am not an automatic guy. I will be moving the 5spd from the Legacy into the Impreza. Im still researching to confirm what 5spd TCU will work. I may just grab one from the same model car. I found a pretty decent deal for $80 new.

The manual transmission cars do not have a TCU. You would pretty much follow the steps in my AWD & 5spd swap to remove the TCU and associated components to make the MT work.

[New92]

Yeah TD set me straight. I claimed temporary insanity. - ben