Engine swap wiring question

[silver_s13]

Ok I am new to Subaru but have don tones of Nissan and Honda engine swaps.
Why do you guys feel the need to pull the dash and merge the harnesses rather than depinning and repinning the ECU connector? It accomplishes the exact same feat just with leaving the dash in place and. You can still do it one at a time and this way would likely require less work. Seems like it would easier to me but again, Subaru is new to me.

[meepers]

I have always wondered the same coming from the honda side of things. I think the turbo harnesses are setup completely different or maybe the connectors are different, but until I get into my swap I wont know for sure. I am going with the dash pull option since I am going with the complete sti swap including the new dash/console and custom door panels. The nice thing is I have done enough swaps and wiring that I have a ton of weather pack connectors, pins, and the correct crimpers. I loved the honda side of swapping, add 3 wires, lengthen a few, shorten a few, done.....

If it wasnt for subarus retarded cup holder that blocks the radio and ac controls and doesnt hold a modern sized cup, I wouldnt even swap the interior. As it is, I may just custom fab up a center console and get rid of the slide out cup holder completely. Good thing I can plastic weld!

[silver_s13]

I would imagine they would have to be similar pins unless Subaru just does everything differently than every other car maker. I mean there isn't that much controlled by the ECU for the body. Fuel pump and such. Seems the dash removal method may be a huge waste of time if the body harness section could just be repinned to match the new ECUs termination points.

[httrdd]

It is going to be a true pain in the ass this way and doubtful it would work. There are wires that triple off one crimp, there are connectors hidden inside dash,........... I would not see how it would be any easier since the ecu from the Svx (in my case) has differnt positioned pins and splits than the LGT ecu. No way this will working thinking about it now. Wouldnt everyone do it that way and not consider merging??

[silver_s13]

The fact remains that the majority of the ecu connections have little do with body harness functions so I still fail to see why it wouldnt work. I mean the dash connections are going to be the same. Speedo to speedo, tach to tach and so forth. I couldn't imagine anything other than ground splitting into more than one connection. As far as everyone doing it if it was easier, NO. We live in a forum where people cant give simple definitive answers. I could see merging if you were changing the dash but the tach signal is a tach signal and I see no reason for repinning not to work.We can go through the ECU pinout if needed to compare and figure out if it would. you have to double up connections for a RB20 swap in a S13 so why wouldnt you be able to on a Subaru?

[silver_s13]

To clarify, I am not talking EJ257 on a EJ25d ecu either.

[grayguy]

be a man, be a standalone haha

[StatGSR]

we never had to pull the dash on my legacy to wire up my eg33. merging was done in the passenger side foot well.

[httrdd]

Is that why you are having problems now? Lol. Before I did this swap I read other. Peoples build and found out that it would be more of a pia and you are almost guarenteed to miss something. Most pulled the harness with frustration after that and would neve so it again. Tomsvx said don't so it also.

[Huffer]

The fact remains that the majority of the ecu connections have little do with body harness functions so I still fail to see why it wouldnt work. I mean the dash connections are going to be the same. Speedo to speedo, tach to tach and so forth. I couldn't imagine anything other than ground splitting into more than one connection. As far as everyone doing it if it was easier, NO. We live in a forum where people cant give simple definitive answers. I could see merging if you were changing the dash but the tach signal is a tach signal and I see no reason for repinning not to work.We can go through the ECU pinout if needed to compare and figure out if it would. you have to double up connections for a RB20 swap in a S13 so why wouldnt you be able to on a Subaru?

I guess you might have to ask the question directly to those that have done the "full swap" - a lot of swaps you see these days are hybrid harnesses; essentially what you are suggesting. Merge the harnesses etc.

Pulling the full dash is usually done to "complete" the swap. Having the updated dash or full access to the entire body harness as well can sometimes be extremely useful in avoiding weird electrical bugs down the line.

And, as you say - you're new to Subaru's, so try not to shoot down the status quo (pulling the dash) when you don't have any direct experience with the Subaru harness. Your experience with Hondas and Nissans is invaluable I'm sure, but these are different cars for sure.

[StatGSR]

Is that why you are having problems now? Lol. Before I did this swap I read other. Peoples build and found out that it would be more of a pia and you are almost guarenteed to miss something. Most pulled the harness with frustration after that and would neve so it again. Tomsvx said don't so it also.


Lol probably, i need to steal chux sometime soon and trouble shoot it.

[silver_s13]

I am referring mostly to 4 cylinder turbo swaps. You H6 guys can chime in but I think it is just going to muddy the waters.

[httrdd]

Oh then in that case....Dont do it without pulling the dash. If you are talking WRX that is a more complex setup. I will post you a link to a guy doing a swap on RS25.com that has ironed out all the wiring for you and you tell me if you can do this without moving the dash. Let me look.

[chuckthefuk]

Huffer gave a very good summary of what to do..

The reason people pull the entire dash is because working in the passenger footwell is very annoying and problematic when you have only a few inches of wire to work with. Not to mention that sometimes certain signals take alternative routes to get to the main connector. Visually its "EASIER" to wire up. Is it necessary...? no. as long as you have both wiring schematics and can trace the wires back just by looking at the connectors and color codes.

Example: This member did a complete swap. Entire 04' Sti harness engine + body merged to all legacy accessories.

https://sl-i.net/FORUM/

To further elaborate.. as Huffer said your suggesting a Merge not a Complete swap. For a true complete swap certain enthusiasts remove the entire body harness first then purchase the engine harness + body harness from the the donor and transplant it directly to there "legacy".

I don't really see what all the commotion is about. Pulling the dash is an 1-2 hour job by yourself.

-Chuck