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Premium Member
2004 FXTi
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Unfortunately, my old thread with exact pricing information was lost on the old forum, so I'll have to go from memory on some of the stuff.

First you need to select parts. Places to find these parts are on the classified section here, NASIOC, and ebay. Buyer beware, and try to get from reliable sources. The last thing you need is a VF39 turbo that only works as a paper weight.

Parts needed:

1. Larger turbo. The cheap option here is the IHI VF39. They are easy to find. They are stock on all USDM STI's. I got mine for $200. They are not perfect. They have problems with the housings cracking at a thin casting area. They are still a bit small for our 2.5L motors. Other options include VF34/VF30 or the VF22. They run $400 used. The VF 34 has a ball bearing cartridge and no cracking issues. The VF22 is slightly larger than all the other VF series, is ball bearing, but is of "older" technology. All these options will get you within 15 hp of each other.

With the VF 39 you need to port the wastegate or you will get a boost spike when running other mods, expecially in cold weather. Do not overport it. If you aren't comfortable with a dremel have somebody else do it. Here are some links:

http://www.pghsubarus.com/tech/porting/porting.aspx
porting a wastegate to get rid of boost creep, let's put this to bed. - NASIOC

If you want to spend more money and get a new turbo the options are many. I will not get into these options here. Just be aware that when you go larger than The VF turbos you will need larger injectors, a new fuel pump, and you might end up with a new transmission so be warned:censored: $$$$ouch. Oh, and I would buy an FP green, any 06-20G, or a rotated 30R. Read this thread:
Turbo FAQ: Read if you are thinking of upgrading! - NASIOC

2. Larger intercooler. Once again the stock USDM STI intercooler is the cheap way to go here. I paid $300 for mine with the y-pipe and all the fittings. You will also need the STI recirculation valve (BOV) and hose . You cannot reuse the one from the Forester. The recirc. valve won't bolt onto the STI intercooler and the Forester recirc. hose doesn't fit correctly on the STI BOV. Don't use an aftermarket BOV either. Please. The part number for the STI recirc hose is: 99071ac540.

With the STI intercooler you will get rubbing on your AC lines in two places at the firewall. You need to try to move them (an excercise in frustration) or put a thick rubber hose around them. I used the rubber insulation for a Volvo 240 gas line. See these threads about the rubbing AC line issue and the needed BPV hose:

Sti Intercooler - Page 2 - Subaru Forester Owners Forum

Installing STi Intercooler.... - Page 3 - Subaru Forester Owners Forum

There are many aftermarket intercooler out there that will work too. Some are great and inexpensive. Some have fitment problems. If you go that route, do your research.

3. Larger hood scoop. So you've got a larger intercooler but it would help to get more air to it right? At minimum, I suggest getting the JDM 2002-2003 hood scoop. $200 painted. The cheap imperfect solution to get sealing with a larger intercooler is to use tin snips, cut the two back corners of the forester ducting, bend them back and stretch the stock FXT rubber to fit. I got 90% coverage/sealing of my STI intercooler this way. This mod will not increase power on the dyno, but it will on the street.

The perfect solution comes from Subtle Solutions. It perfectly mates the JDM 2002-2003 STI hood scoop to the 2004-2007 STI intercooler. It just ain't cheap at $325. In fact it costs as much as the intercooler. He has done group buys on North American Subaru Impreza Owners Club
Subtle Solutions

4. Catless up-pipe. 2006 and later FXT's can ignore this. Your catless already. For 2004-2005 the cheap solution is a used 2004 or 2005 STI up pipe. I got mine for $50. Skip the aftermarket here folks. They are more likely to leak. The only thing you need to do is re-weld the heat shield on the STI up-pipe as it tends to crack and rattle, which is just annoying. Shouldn't cost more than $25. A buddy did mine for free. You will not use the EGT sensor that is in your up-pipe because of the cat. You will need to do the "resistor mod" which involves buying a 1/2 watt 2.2 kiloohm resistor at radioshack and inserting it into the EGT sensor harness then taping with electrical tape to avoid a Check Engine Light (CEL).

5. Downpipe. Used aftermarket. Lots of options here. Anything that works on a WRX/STI will work on our car. I chose a PDE catted which I got barely used for $350. If I was getting one new, I would get a Helix catted for $400. My only pitch is to get a downpipe with a cat. For 5 hp is it really worth spewing acrid black smoke into the air? Read the downpipe FAQ here:

Downpipe FAQ: Read if you are thinking of buying one! - NASIOC

6. Axle back exhaust. Here is one place you are probably best to get something new.
I ponied up the money for a Stromung 3" Forester specific axle back. $600. Other options are Cobb (made by stromung but with a resonated rear tip), Forced Air Technologies, and WBR. The WBR axelback is a smoking deal at $350 and would be what I would purchase. The axle back for the Forester is a bit longer with slightly different hanger locations than the WRX/STI. The advantages of the aftermarket FXT options is that they are quieter with larger mufflers for the FXT, and they are the correct length with correct hangers so they won't burn your rear bumper.

The cheapest route is to get a used stock STI axle back ($100) or used aftermarket WRX/STI axle back ($250), then have the hangers modified and rear tip extended. The disadvantage of the stock STI axle back is that it is only 2.5" and you will loose some HP. It is heavy. Also, even with modifications some people have burnt their rear bumpers. The advantage is that it is quiet. The used aftermarket WRX/STI axle backs will also need modification and might burn your rear bumper. They are also loud on the Forester because of our large rear cabin. If you don't like loud don't go this route.

Here are two threads on the stock STI exhaust with detailed information, pictures, and measurements:
http://www.subaruforester.org/vbulletin/f87/sti-exhaust-45897/
http://www.subaruforester.org/vbulletin/f87/05my-xt-07my-sti-ehxuast-28260/

7. ECU. If you have a 2004 FXT with 5MT then the cheapest route is to get a used 2004 STI ECU ($150). This will work fine but you will be restricted to just a bit above STI stock HP (about 250 awhp/tq). If you have a 2005 or later FXT you need to get a tune because the ECU swap will not work. The options are Cobb Accessport with Protune or ECUtek. I got an ECUtek flash with dyno tune for $800 at PDXtuning. If I had to do it over I would get a Cobb Accesport with a protune and then add a streettuner. This would allow you to run multiple maps with easy switching. It makes it easier to have a racegas map, methanol injection map, valet map, etc. With the ECUTEK, you would need to also have a UTEC for map switching. If you are getting a UTEC, you should already know more than the information in this thread. However, the general rumor is that the latest UTEC software is really sweet for those looking at advanced engine management options.

The Cobb Accesport with protune or ECUtek are set it and forget it tuning options. They are what you want for a daily driver.

8. Fuel. I got a used Denso fuel pump from Supra twin turbo ($110). I picked this pump because it is quiet and flows a ton of fuel. To install it you do have to bend the fuel pump bracket a bit, zip tie it and then crimp two wires. The other option is the Walbro pump which is a direct drop in. It is louder than stock, which might be annoying in our cars with the fuel tank inside the cabin.

You probably don't need the larger pump, but then again, maybe you do. At these power levels you are at least at the maximum that the stock FXT pump can handle. The stock FXT pump is identicle to the pump in the 2.0L WRX. The STI pumps are slightly larger. I'd get a larger aftermarket fuel pump just to be safe. Great page on fuel pumps:

Stealth 316 - Fuel Pump Upgrade Guide

You don't need larger injectors at the power levels of IHI VF turbos (well, except MAYBE the VF22). Anything larger and you NEED larger injectors.

So to sum up:
1. Used VF39 turbo ($200)
2. Used stock STI intercooler/BOV/recirc hose ($300)
3. New 2002-2003 JDM STI scoop and ducting ($275)
4. Used catless STI upipe ($50)
5. Used PDE catted downpipe ($350)
6. New Stromung 3" FXT axle back exhaust ($600)
7. ECUtek flash with custom dyno tune ($800)
8. Used Denso Fuel Pump ($110)

Total: $2685

Mustang dyno numbers (same dyno before and after):
Stock HP (see first picture for graph): 176 awhp/172 awtq
Modded HP (see second picture for graph): 267 awhp/302 awtq
Typical stock STI on this dyno: 235awhp/235 awtq

$/awhp: $29.50
$/awlbft: $20.65

Install time 3 hours with two very knowledgeable Subaru guys helping. Figure up to 8 hours.

With our the FXT having equal weight to an STI but better gearing 1/4 miles should be faster to an equally modded STI. I pull 1 car length ahead from 30-80mph on my friends 2006 STI. I pull the same 1 car lenth ahead from 30-80 on my friends 2005 M3 convertible and my mostly stock 1994 RX-7 twin turbo. My car has 52,000 miles on it and 25,000 miles on the mods. I have my original stock clutch. The car burns no oil. I'm happy.

Things I would do over:
1. I would get a revised 2005 or later STI ported and polished header and uppipe or equal length perrin headers. Likely this would give me extra hp, with a small drop in tq. Most similarly modded STI's do not make 300 awtq on this dyno.

2. I would get the Cobb Accessport with Protune and streettuner. This would allow easy map switching and it is worth much more on resale. Protune was not available when I did my car.

3. I will at some point get a larger 06-20G turbo and probably piggyback UTEC on my ECUtek. You get used to any amount of hp at some point.

Hope this is helpful,
Regards,
Justin Wade
2004 FXTi
 

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Registered
2007 Forester XT
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990 Posts
Nice sticky! hehe. I agree with everything, but a question on the aftermarket BOV. what about the PERRIN recirculating BOV part number PSP-INT-600

Edit: After doing my sti conversion, i used the STOCK 07 FXT BOV. on my sti intercooler. no problems at all.
 

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1988 BMW 535is
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776 Posts
nice writeup. I didn't know the VF39s had to be ported though. Hmm. I thought you just had to modify the restrictor pill.
 

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Premium Member
2004 FXTi
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763 Posts
Discussion Starter #4
Nice sticky! hehe. I agree with everything, but a question on the aftermarket BOV. what about the PERRIN recirculating BOV part number PSP-INT-600
I can't speak to this one specifically, but why go aftermarket when you can find used STI pieces that work perfectly practically for free?

Regards,
Justin Wade
2004 FXTi
 

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Premium Member
2004 FXTi
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763 Posts
Discussion Starter #5
nice writeup. I didn't know the VF39s had to be ported though. Hmm. I thought you just had to modify the restrictor pill.
The restrictor pill doesn't change the problem with creep which is a mechanical problem with airflow in the wastegate. The porting is only a small ridge on the corner of the wastegate "pipe." The restrictor pills don't really matter with a custom ECUtek or Protune. The tuner will take all this into account. And I used Perrin EBC on my setup FYI. Helpful, but not absolutely needed for boost control.

Regards,
Justin Wade
2004 FXTi
 

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Registered
2004 FXT
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403 Posts
Are all the mods in your list applicable to the 4EAT except for the STi ecu swap? I happen to be running a cobb AP
 

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Premium Member
2004 FXTi
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763 Posts
Discussion Starter #7
Are all the mods in your list applicable to the 4EAT except for the STi ecu swap? I happen to be running a cobb AP
Everything should work fine with the 4EAT. But just like with the 5MT your transmission might not last forever. At least one person with a VF22 killed a 4EAT.

Regards,
Justin Wade
2004 FXTi
 

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Premium Member
'09 STI
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4,128 Posts
Great write up and thorough too. I agree, it should be a sticky!

One point regarding the catted down pipe is that if and when you go to a bigger turbo this will also help with boost creep. Otherwise, an external wastegate is needed.

Is $600 a typo for the axleback?
 

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Premium Member
2004 FXTi
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763 Posts
Discussion Starter #9
Great write up and thorough too. I agree, it should be a sticky!

One point regarding the catted down pipe is that if and when you go to a bigger turbo this will also help with boost creep. Otherwise, an external wastegate is needed.

Is $600 a typo for the axleback?
Thanks.

And no $600 shipped is about right for the axleback. :icon_sad: Maybe it was closer to $500, but definitely not less.

Regards,
Justin Wade
2004 FXTi
 
G

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this is great my boy just got a 07 limited sti and one day i would like to walk on him...his face would be priceless
 

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2006 RX8
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423 Posts
Thanks.

And no $600 shipped is about right for the axleback. :icon_sad: Maybe it was closer to $500, but definitely not less.

Regards,
Justin Wade
2004 FXTi
Awesome compilation of information Justin! The Subaru WRX/STI impreza engines and parts have become the new small block chevy of this time frame. Lots and lots of parts and pieces available for a song. Sure makes modding a car like our FXT's a simple inexpensive process. Try doing the same with a BMW MCar, or an Audi S4.

As far as the axle-back pricing, most run in the $325-$400 range. Used you can definitely pick them up in the $250-300 range if you are selective and have the time. This includes Fat, Pro-drive, or how about the new WBR 3"? Catbacks typically in the $550-600 range is what I have seen.

Anyhow the bottom line is that cheaper is better, and as long as you have time to keep a close eye on the classifieds, particularly on Nasioc and Iwsti, you can find some smoking good deals. Make sure and ask very specific questions about the items you are buying though and ask for pics if possible.

Winter is coming as well, so prices will get better as folks sit on parts and no one is buying. People will be looking for money for the holidays. That may sound rutheless, but its simply taking advantage of the market when its at its best. Just a bit of strategic buying advice.

Thanks again Justin!

Jeff
 

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Premium Member
2004 FXT '05 6mt r180 Carbonetics 1.5w lsd
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1,094 Posts
Thanks for doing this Justin. Now we can only hope that people use the search feature for their upgrade questions.

Now that this is done, how about one thread on suspension mods :)
 

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Premium Member
2004 FXTi
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763 Posts
Discussion Starter #14
Thanks for doing this Justin. Now we can only hope that people use the search feature for their upgrade questions.

Now that this is done, how about one thread on suspension mods :)
The suspension sticky on how to out handle an STI for cheap is coming:icon_wink: And I'd make a how to out brake and STI for cheap, but well....you can't.

Hope people read this stuff. I might become slightly bitter like Unabomber on NASIOC:lol: Speaking of which, people should read all of Unabomers "manifestos" on NASIOC.

Regards,
Justin Wade
2004 FXTi
 

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Mexican Lorider
2004 FXT 5MT
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439 Posts
Nice write up!
A couple of things I'd like to add.

The Bosal UP is a STi UP and can be had for $150 new.

and the better news....

I'll soon be completing work on a VF3X map using Enginuity/ECUFlash for a free tuning solution.
 

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Administrator
2004 Forester XT Premium 4EAT
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29,449 Posts
The suspension sticky on how to out handle an STI for cheap is coming:icon_wink: And I'd make a how to out brake and STI for cheap, but well....you can't.

Hope people read this stuff. I might become slightly bitter like Unabomber on NASIOC:lol: Speaking of which, people should read all of Unabomers "manifestos" on NASIOC.

Regards,
Justin Wade
2004 FXTi
Thanks for taking the time to write this stuff up! We've needed our own "manifesto" for a while now, but it takes time and effort to compile all the information. The members here will thank you for taking the lead on this.
 

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513 Posts
This is exactly my plan. I'm trying to find a revised STi manifold as well.

I am at Stage 2 levels right now and it feels fairly good, but IU do need more and this should be perfect.
 

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398 Posts
Nice writeup! :biggrin:

One thing I'd like to say though... it is false to say to get a catted midpipe but a 3" muffler... you will actually lose more power from the Cat than the muffler... ;)
 
G

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You need to be congratulated for taking the time for the write up. Very benefical for all those newbies who are just discovering the Turbo world.

Permanent sticky warranted!!!
 
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