Friend and I Building an 03 WRX STI Together. Any Recommendations?
 

Hey guys, hope you're all doing well and staying warm (cold as hell even here in Texas right now).

My friend is picking up an 03 STI shell with (what I'm assuming) is a functional 6sp transmission and drivetrain. So far our plans are to build up an EJ25 block/EJ20 head hybrid engine with aftermarket pistons to allow for valve clearances and lower compression for more boost, but I was wondering if anyone here is more familiar with Subarus or had any other input.

I know that some of the EJ engine series were prone to head gasket failures and oil starvation around the piston rings, but I don't really know what to do about that outside of using fresh new gaskets and making sure everything is sealed and seated properly. I'm also curious as to if the stock ECU can be tuned, or if it'll require a chip/aftermarket ECU, etc...

I'm still poking around on some NASIOC and some other Scoob forums, but I value the opinions of a lot of people here on S2KI so I was curious if anyone has experience with these platforms. Let me know what you guys think, or if there's any other recommendations on the build :) We're going to try to keep it relatively cheap, this car will mostly just be used for general hooning and shenanigans.

Why lower the compression on a motor with sufficiently low compression for boost already?

Here is what I would do:

Rotated mount turbo kit with Front mount intercooler - Opens many door for turbo options and removes heat soak.
Built block and motor with good fasteners and seals.
Meth injection.
Tuning.

Nothing else really needs to be touched.

On a stock motor, the rotate mount turbo kit will allow 400 AWHP. 450+ can be had with Meth injection on a stock block. A VERY good tune is needed to run these numbers. Ringland issues really only affected the 07/08+ models. Head gasket failures are more common on the N/A motor, not so much an issue with boosted motors. I had 160,000+ miles on a stock block 06 STi and no issues.

I'd say stay away or move on... :banghead:

Do you have personal experience that you would like to share? Or you knew a guy that had a friend that had an STi?

There wasn't an 03 STI, you sure you don't mean 04?

The stock ECU can be tuned and all that is required is a Tactrix cable.

Which used to be worth ~200 dollars and with some free software could datalog and tune yourself, it has full ECU control. You might have a tough time finding a tuner that will use the tactrix though.

I was informed it was an 03, but I'm contacting my friend now to confirm (we haven't actually picked the car up yet, everything I've heard has just been through him).

Excellent :) Thank you.

I'm sure we'll figure something out; I doubt we'll be going over ~350AWHP. May even try tuning it ourselves depending on how this all plays out.

There wasn't a 2003 STi in the states. If it is actually an STi, there is zero reason to do a hybrid engine. Hybrid engines are reserved for 2.0L WRX's that upgrade to the 2.5L block. If this is a WRX and you need to do a hybrid, you'd do yourself a favor sending the heads off to be machined out to mimic the 2.5L head, however, you'll still lack AVCS.

Close deck the block (Google Outfront closed deck) and use head studs and you shouldn't have any issues with head gaskets. They don't starve oil around the piston rings... Stock ECU can be tuned with a TacTrix cable and Open Source software (RomRaider and ECU Flash) or Cobb. The Cobb AccessPort with AccessTuner Race is a bit better than the Open Source route and offers features that aren't availale via Open Source (like real-time tuning). I have pretty much gone to using AccessPorts on all customer tunes. In either case, you shouldn't have a problem finding a tuner for either... Most will work with both.

Find out exactly what car it is first...



You better have a good understanding of Subaru's and their software or I guarantee BOOM!

The tactrix community has some excellent canned tunes. You have to look around. hit me up with a PM, I can send you my files that I have, ecu codes, etc.