real life wiring issues with newer ('00+) motors

[white_n_slow]

Everywhere I've read and heard, swapping a newer motor is a tremendous headache when it comes to actually getting the thing running.

What are the specific wiring issues that one would likely encounter? Which are the most problematic? Any personal experience/advice here on wiring from folks that have actually swapped in a newer motor?

If it helps, hypothetically, we're looking at '93 wagon 5mt N/A to late-model STi 6mt.

Feel free to be as general or specific as you want, I'm new to subarus.

[91White-T]

Its mostly the OBD II that causes a problem with newer engines into older cars. Plus on Subarus the engine harness is together with the main chassis harness, so you have both factors to contend with.

[Matt Monson]

This really is not as complicated as people make it out to be. The key to it is to use the manifold wiring harness from the original car on the new engine, assuming you are going to continue using the stock ECU. There will be certain OBD-II sensors that you will leave unconnected.

Dizzy and I are currently doing this with a 1.8l powered Impreza and putting an EJ25 w/EJ22 heads in there. We actually capped the IAC on the manifold since the 1.8's don't use one...

[white_n_slow]

well if thats the case, I'll make you help me when the time comes.

:edit: will a obd2 turbo motor run properly using only obd1 N/A sensors?

[americanyouth]

No, there will be numerous differences in the wiring between ODB-I and OBD-II cars.

[Matt Monson]

white,
my apologies for not reading your post to clearly. If you are looking to put an EJ257 into your '93, you will want to completely replace your main bulkhead wiring harness and use the Sti one. I was thinking of putting an NA EJ25 into your car. You will have to do a lot less work if you choose an older engine. A '94-96 WRX motor would be a pretty easy swap with minimal wiring and the ability to go the route I mentioned above. The only wiring would be the boost solenoid/pressure sensor/MAF stuff. And your whole swap would cost less than just the EJ257 engine itself.

'94-96WRX's came with a TD05 on them, and can easily put out more than 300chp in stock form...

[JasonGrahn]

:edit: will a obd2 turbo motor run properly using only obd1 N/A sensors?

Yes, it will RUN, but it won't run to the best of it's ability. This is as experienced with the 2.5L in my legacy running from the stock ECU.

[white_n_slow]

thanks for the input, fellas.

Whats the going rate for older wrx motors? My main reason for leaning in the usdm sti direction is the stoutness of the transmission.

[Matt Monson]

They're like lego I tell you. You can get an older WRX engine and still get a new tranny. Going rate on an old WRX swap is around $2000-2500.

I've got a '94 ECU, prepped wiring harness, MAF, and ignition system for sale. All you would need is a longblock and a front crossmember...

[white_n_slow]

thanks for the offer, but I'm not ready to start this project yet.. just researching up.

[Matt Monson]

no worries. Ask anyone that knows me. Parts just sit in my garage until someone lets me know they want them. I don't really actively try to sell anything, but just mention parts I have from time to time.

The ghetto garage is always open for business...

[white_n_slow]

Substitute Saab and Honda for Subaru, and thats my garage...