Engine Question
 

Would a 06 WRX Turbo engine fit into an 04 STi?

Would any special modifications be required?

And if it would fit would there be any issues arising from using a WRX Turbo engine in an STi? (Just talking about daily driving, no racing of any sort)

Thanks.

(I'm a noob @ this stuff)

Physically it would fit in the engine compartment. Are you also swapping the ecu and transmission?

Negative. I take it that would be required for it to work...

I think probably just the ECU but I have no experience in that area.

Well shit.

I'm assuming dropping in a STi engine would be a piece of cake compared to trying to put the WRX engine in, right?

Know anyone who wants a WRX turbo engine with 36k on it? lol, back to square one...

I don't think an ECU is that expensive. Take a look on nasioc before you decide to scrap your project based on something I said.

The only thing different between an '06 WRX block and an '04 STi block are the heads. The STi has better flowing AVCS heads, the WRX does not. In fact, the short block (bottom end) even share the same part numbers IIRC. Of course the ancillary bits on the STi motor are a bit different with the WRX having a smaller turbo, smaller injectors, smaller intercooler... but none of that stuff is essentially different from the STi stuff.

You could probably even keep the '04 STi ECU if you are able to re-tune it for the smaller turbo/intercooler/injectors on the WRX motor. What's hard to do is use a WRX ECU to run an STi motor... there's no way to control the AVCS, but the other way around shouldn't be hard.

I'm afraid to ask why someone wants to put a WRX motor in an STi... did someone blow up their STi and need a cheap replacement?

An 06 has the same injectors as an sti so if he uses the sti turbo and intercooler it will probably be even easier than what you said, to get an easy tune.

'06 WRX's have side-feed '04 STi injectors?

I think Juice and Arrows are thinking too hard on this one.

If you have a broken STi, an the borkage is in the shortblock, then just put the WRX shortblock into the STi and call it good. If you have a problem in the STi head(s) then just get that fixed.

06 WRX's do have AVCS, but I believe the STi heads to flow better. And the pistons are different, and the WRX has a slightly higher compression ratio. There is a big thread with all the part numbers and parts compared side by side, but I am having trouble opening NASIOC right now.

Why would top feed or side feed matter to the ecu, I thought you were talking about size.

Top-feed and side-feed injectors even of the same size likely have very different latencies which would make a big difference requiring tuning of the ECU.

You are a revolving debate machine. You posted...

So when you said smaller you meant top feed?

You're right, pulling his sti engine and taking it apart and then taking apart his wrx engine and then rebuilding the sti engine with parts from the wrx engine would be way easier than just taking out the sti motor and putting the wrx motor in and getting it tuned.:rolleyes:

Yep.


I had a list of the broken components on the STi engine, but my mechanic has it. I need to get a copy of that.

Although I do know one or more piston rods is broken, oil pump is broken, dont know the state of the short block on the STi.

I'll get that list ASAP.

Thanks for the ideas guys.

What the hell is actually wrong with it anyway?

Okay, that answers that I guess.

If the problems are all in the shortblock, then yes, you should tear it down and put the WRX shortblock into the STi. That way, you still have an STi when you're done, not some weird hacked hybrid that will never quite work right without a custom tune.

I thought the injectors on the WRX were smaller *and* top feed vs. the side feed STi injectors. When you said they were the same, I though they might actually be literally the same, i.e. both side feed, which was news to me.

Either way, they'll need tuning to switch from one to the other.

Like Kevin said, the best way to fix an STi w/ a busted shortblock is to replace the shortblock and leave everything else alone.

'06+ WRX injectors are the same (or really, really close) to side-feed STi injectors. Since '04 STi engines use topfeeds, and are smaller than side feed STi injectors, they are not directly compatible with any WRX injectors. So Scott is right, you cannot plug-and-play between WRX and STi injectors unless both engines are '06+.

The only reasons not to simply plug the STi manifold/wiring/fueling on top of the WRX long block (to get around the fueling differences) are the differences in the head, which boil down to AVCS and cam profiles as I understand it. Downgrading an engine, or pieces of it, is just never a good idea.

:omg:

I don't think any STi <'07 has top feed injectors. There's a reason you can't swap STi block/heads under a WRX intake manifold. The WRX top feeds interfere with the AVCS solenoids unless you've got a Perrin fuel rail that will allow the front injectors to be clocked 90deg. That's why the STi all used side feed injectors up until the fuel rail re-design in '07 (IIRC).

I thought the '04s had the old "STi pink" injectors, but I haven't really kept up on the Lego details the last few years to be honest. I know the WRX got sidefeeds in '06 with the 2.5, but I could easily be wrong about when the STi got them.

Wait... so now we're back to the '06 WRX having exactly the same injectors as the '04 STi? :lol:

The STi never "got" side-feeds. It always had them, until recently when they switched to top-feeds. I didn't think any WRX's ever had side-feeds.

I think Scott and Kevin are thinking too hard on this one.

Arrows if you have a borked car, fix it.