Alright kids, after some looking and dumb luck I'm going with a plumbed external wastegate on my 04 WRX. Heretofore I was discouraged by the loudness of an atmo dumped EWG (there's a time and place for that, but I'd like to choose said times and places), and the cost of custom plumbing a dump. Then I found a setup for sale for pretty cheap, went in and nabbed that like something quick.

Motor is 2.0L to review, just in case. EWG is TiAL, 38mm, dump tube as said is plumbed into the downpipe. It's quite the Frankenexhaust, featuring a TiTek bellmouth welded to a cat and that into what I am told is meant for a Turbo XS muffler (extra long or something), but it looks and feels sound.

I'm less sure about the up pipe (which came as part of the whole setup), which looks like it was fabbed from the ground up, as the pipe diameter is pretty tiny, and there's some real rough edges near the V-band flange. I could grind and smooth them down, but as said the bore size is pretty mini next to the soot lines where the edge of the gaskets were. Might just get a GS/Turbo XS one.

I read there is much benefit to having a small turbine ("hot side") with an EWG, and I'm looking for good setups for my motor and driving style.

Car is 95% DD, I might track it a few times, like to kick it around on the weekends or when and where the streets are emplty. In lieu of daily driving, I'd like more torque off boost and/or faster spool with more top end - TBE, right header and a tune (required for the EWG anyhoo) will address some of this of course.

At present with the stock TD04, I start spooling around 3K, full at 4K. Moving spool start to 2, 2.5K, and/or holding boost to redline (or darn close) would be pretty sweet.

To narrow things down, I have a TD04 with cracked wheels I picked up to practice PnP on, so unless anyone sugguests otherwise, using that otherwise ok housing sounds like a good starting point, esp. after getting it ported and polished. That said, others housings bought standalone aren't too expensive.

I was eyeing a VF43 with a cracked wasteagte up for sale on the forum here, just trying to see if it would mate with the TD04 turbine housing. If so, I could tear the faulty hot side and slap the lil one on there, and vroom vrrom zoom zoom. Other turbos with simmilar ailements, bought for cheap, might fill the bill too? Again fitment is the ish, and I'm still figuring out which figures need to match, or if I can get away with porting the turbine wheel well a mil or so (smells like a bad idea, but dunno for sure).

General thoughts and theory on the matter are welcome and encourged.

 

Ok ill try to start some discussion. First off, you miiight be asking for too much here.. well, depending on the combos of your "and/or"s. Quicker spool coupled with holding boost to redline dont usually go together. Im not saying its not possible, but we would need to determine why a smaller hot side causes boost to fall off up top. Sticking with the td04 housing sounds like the most viable option, the only way I can think to get it to spool better would be to- Pnp the stock exhaust manifold and stock UP (keeping as small of diameter in that piping as possible for increases air velocity), and by going e85 (more exhaust gasses).

Now, how to get your td04 hotside turbo to hold boost to redline.. BACKTRACK-- I was doing some reading on the spool and boost characteristics of a .63 turbine housing vs .82 housing on a gt3076r. Both housings for externally gated. I read multiple accounts of how the .63 housing couldnt hold boost up top as well as the .82 did, although boost came on sooner. The conclusion was that the smaller turbine couldnt flow enough air to keep the turbo spooled fast enough to provide ample boost in high RPMs, regardless of the fact that the system was externally gated... it all came down to how much air could flow through the turbine housing. The only way I could see you being able to hold boost better with the td04 would be to port the **** out of the housing and put in the largest exhaust wheel that will fit. I dont have any experience with swapping a diff cold side onto the td04 but it seems like if you could mate that vf43 cold side with it, you would be golden. You might need to find a used 16g cold side if the IHI center housing has a diff side compressor connection. I did a quick search and could only find a diagram for the td04...

 

@superusdm - First, thanks for getting this started. I've some more research and diagrams along the way to further things, and I'll get on that later today.

It's kinda weird how unreadily available specs are clearly and confirmable available on these things, though then again the whole hybrid turbo thing doesn't seem extensively perused.

I also got the TD04 turbine off last night. Only took some PB Blaster. Maybe some naval jelly, maybe sitting for a few weeks. Maybe a hammer. Maybe. This kinda has me worried about de-housing another (functional) turbo, so might source that out to a shop.

Stay tuned...

 

Hence the 'or' of the and/or haha. I know this is a game of compromises, just looking to see where and how they can be made, and how best in favor of my goals. Let's lean on quick spool in this case.

"Backpressure" is the explaination I hear, and is the same reason a big housing is slow to get started.

Doing an aftermarket header/up pipe/down pipe, and am going E85 when I get it tuned.

Like I said, the whole set had an up pipe with it, with quite the tiny bore. I want to gather some more opinions about it before I put it on, but if I do I'll be smoothing down the ins and outs. The step I am worried about, as I am about what amounts to a bulb of a cavity between the top of the pipe and the bottom/entrance of the turbine. The header to up pipe connection I'm also concerned about, it will be a fairly shallow angled funnel.

Lemme get this down now, and I'm gonna poke around some more for specs to see if they'll mate up. Rather not get a replacement wheel and have to get it balanced, for if going that route I'd do a lot more number crunching to see what's a truly "ideal" setup, but that might be more time and effort than I'm willing (or able really - I'm an armchair enginner most of the time) to pull off.

Pics of parts to follow too.

 

Bottom of up pipe. Note the gasket and soot lines.










Jaggy jaggy.




Yeah, gonna grind that...




The full setup. Fits outside the car, dunno about in it yet.

 

Please elaborate. A smaller housing would have greater backpressure, therefore more exhaust gasses would be bypassed through the EWG rather than passing through the turbine, resulting in the turbine not spinning fast enough to provide full boost in higher RPMs. Are we on the same page with this one?

Holy hell thats one ugly UP. I brain farted on that one, obviously you're not going to be using the stock UP. Is that flange rotated the correct way to mate up to the stock manifold? If so, you should consider Pnp the stock manifold rather than going aftermarket header. An aftermarket header will cause your turbo to spool slower. IF you can use your stock manifold, then all you need to worry about is the UP to turbine connection. Is there any way you can completely smooth out the inside of that UP?

As you pointed out, this may be more work than its worth/you want to do. I'd bet you could get full boost at 3200rpm holding all the way to redline with a td05/big16g (pnp manifold/smoothed UP/tmic).

...

Just did some more research. Looks like the 16g/vf compressor housings are all made to work with a td05 and up chra. Did find http://www.ebay.com/itm/TD04H-TD04HL-15G-MHI-Turbo-Compressor-Housing-Wheel-/271172593909?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f232568f5&vxp=mtr though.