I have a conversion question pertaining to a 2004 WRX. A fellow co-worker’s son has a 2004 WRX in excellent condition with the following problems:

-Blown motor from a self attempt at tuning a UTEC.
-Possible no warranty coverage since the car has been modified.

My conversion question is this. If I can get this car for cheap from the owner, (i.e. vehicle value minus the cost of motor repair) why not put a full 2004 STI swap in the 2004 WRX. From doing research in the conversions forum I know that there is DCCD and AVCS on the STI along with DBW that I will have to contend with if I swap a salvaged STI into this WRX. I would think the 2004 wiring harness would be similar but I know they are not the same. Would it be easier to pull the entire harness from the STI and put it into the WRX or would it be easier to splice the different pieces of the STI harness into the existing WRX harness. I wasn’t able to find a direct statement that would put my mind at ease on what the best path would be for this conversion. Looking for any information you guys might have on the wiring differences and possible issues I might experience from doing this swap. If you guys know of any posts I missed, please feel free to cut and paste a link so I can read up. Thanks in advance for your help.

How "blown" is the motor? I cracked two ring lands in my 2.5 and just finished a rebuild with nice forged pistons for well under $1000 in parts with some extra goodies. That was with no machine work needed. If his 2.0 is scored then I know there is a place in Asheville that'll bore it out perfectly, and then you get to use .020 over pistons (insert grunting here). I'd do a few more things like crank work and replacing rods if you have to get into that kind of machine work. Still under $2k with that labor probably.

All questions that are kinda hard to decipher until the motor is out.

If the motor is worse than machineable, a nice block from Cobb or similar, and bolt your parts to it. If the heads are damaged, another chance to order a little more power. (more grunting)

Keeping the stock tranny, which in the 04 isn't (supposedly) as weak as the 02-early 03 WRXs, I'd just drop in an ACT or Spec clutch and Pressure plate. Resurface the stock flywheel and bolt it all back up.

That way you have a better than stock motor. A decent tranny setup. And you haven't replaced any electronics.

STi swap. Feasible, sure, but you'll still have the cast pistons. I'd get the wiring harness entirely if possible, simply for the plugs at the ECU end. There aren't that many extra wires, but deciphering pins on the ECU and all the random ghost-issues that splices can develop over time... the whole harness is definitely a bonus.

His UTEC won't work on an STi ECU either. So that's another $600 down the tubes if you want EM. Unless you really really want that DCCD, which I personally never use, I don't think the hassle would be worth it.

[gratuitous plug] If you don't do this sort of stuff yourself, I do. I have that car memorized and I don't charge anything like subaru's rates. And I actually have fun doing it, unlike the 9-to-5ers at most dealerships.[end plug]

If/When I do a swap I may have to drive to NC to take advantage :P

If you want a 04 STi, buy it. There are about a million differences between the WRX and STi wiring harness, subframes, etc, and a full STi drivetrain w/ interior, brakes etc will cost you more than the WRX easily.