Subaru Forester Owners Forum banner
1 - 18 of 18 Posts

·
Registered
2006 Forester XT Manual 5spd
Joined
·
33 Posts
Discussion Starter · #1 ·
Hi Guys,
I am very interested to know please, what sort of gains can be seen by purely adding a VF48 to the Forester XT and leaving all else stock?
Obviously the Ecu needs tuning after such an upgrade, but let's say a conservative at the least. Considering the 2006 XT is 169Kw from factory what sort of jump can be seen after slapping the bigger turbo on?

TIA

cheers:thumbsup:
 

·
Registered
2007 2.5XT Limited 4EAT
Joined
·
343 Posts
Unfortunately, it's not quite that easy...While you can slap a bigger turbo on there and get the car tuned, you will not get much more, if anything out of it without the supporting mods. Without more intake air, fuel, and exhaust you will just have a bigger turbo that takes longer to spool and produces no more power. The little TD04 under the hood isn't maxed out from the factory and it takes a larger exhaust to even get the most out of that turbo. Those pesky maths and physics.

If you are not prepared to throw all the money down to install the VF48 with the supporting bits right now, I would suggest starting with upgrading your exhaust and getting a tune to maximize the TD04. If you want to go bigger later you'll already have one of the pieces you need.

While you are pondering this bit of info...have a look at this:

https://www.subaruforester.org/vbulletin/f87/how-go-faster-than-sti-cheap-8337/

Might help you get a better idea of what you are getting into.
 

·
Registered
2006 Forester XT Manual 5spd
Joined
·
33 Posts
Discussion Starter · #3 · (Edited)
Thanks so much yes that makes sense, I have a decatted downpipe but need to Tune for it - I am almost wondering if a full catback system wont be better that just the decat?

how many KW can i gain with this "upgrading your exhaust and getting a tune to maximize the TD04"

roughly? Considering 169Kw is Stock
 

·
Registered
2007 2.5XT Limited 4EAT
Joined
·
343 Posts
I was told that it was necessary to upgrade the axle-back portion of the exhaust system as well as the downpipe to max out the TD04. I installed the cat back portion of a 2007 Impreza Sti and a catted COBB downpipe on my Forester when I had my car tuned...not sure what options you have in your part of the world...but you do not need a full 3"/76mm with the TD04. Also, the mid section of the stock Forester XT exhaust is the same as the STi so you don't necessarily need this portion if you were to go this route. You really only need the muffler section in your case is what I'm blathering on about.

As far as power gains from the exhaust and tune, it's hard to quantify since I did not have my car tuned on a dyno. I used a COBB Accessport and hired an E-tuner over them internets. But all the numbers you can find out there for this setup say you should gain 15-20Hp or 20-26Kw. Not sure if these numbers are idealistic or not but my butt dyno agrees with the estimates. The car is definitely faster than stock, not bigger turbo fast, but a considerable upgrade.
 

·
Registered
07 FXT
Joined
·
828 Posts
A stock STI has the same restrictive downpipe as the Foz, and in that configuration they are about 300 hp, maybe 240 at the wheel. The stock Forester intercooler is mostly worthless, so perhaps swap in an STI TMIC and turbo, and you should be around that 240 whp number, with a tune of course.
 

·
Registered
07 FXT
Joined
·
828 Posts
as for exhausts, the main restriction is the downpipe. I've run the stock midpipe and an STI muffler (slightly less restrictive that the stock XT) at about 350 whp, so you do NOT need to swap that out with a TD04. Unless you want it really loud.
 

·
Registered
2006 Forester XT Manual 5spd
Joined
·
33 Posts
Discussion Starter · #7 ·
I don't necessarily want it as loud as i do "rumbly" hehe, I would love that deep growl the Subies are famous for
 

·
Registered
2007 2.5XT Limited 4EAT
Joined
·
343 Posts
If you can get your hands on the muffler section from an 04-07 STi you will love it! It's got a nice rumble to it and it's definitely not loud, plus no droning at high speeds. As I mentioned, this is what I have on my car and I couldn't be happier. It's a far cry from the full 76mm catless turbo back that I had on my Impreza. That exhaust was crazy loud. I really don't know of any aftermarket systems that would be considered quiet or civilized. If you can't source the STi axle-back you could always talk to an exhaust shop and have them build you the rear section.
 

·
Registered
07 FXT
Joined
·
828 Posts
I don't necessarily want it as loud as i do "rumbly" hehe, I would love that deep growl the Subies are famous for
That rumble can turn to a nasty drone in our cars with the wrong exhaust selection. I prefer my current setup, an EL header and a 3" exhaust, the header tames the drone quite well, and sounds mean when you put the wood to it. But not so rumbly.
 

·
Registered
07 FXT
Joined
·
828 Posts
that STI axleback has a bad drone at 1.5-1.8k rpm inside the cabin. i usually have to downshift when cruising streets.
When in good working order, the STI mufflers I've experienced were almost as quiet as the stocker. The STI sounds noticeably deeper at cold start, but once under way is not appreciably louder. Until the packing blows out after many miles of hard use, then they sound awful. I suspect one problem is finding a decent used STI muffler, after 10 or more years of use there are no guarantees. If I was really set on a quiet setup and had the spare cash perhaps I'd buy a new one from Subaru if found for a reasonable price?
 

·
Registered
Joined
·
279 Posts
When in good working order, the STI mufflers I've experienced were almost as quiet as the stocker. The STI sounds noticeably deeper at cold start, but once under way is not appreciably louder. Until the packing blows out after many miles of hard use, then they sound awful. I suspect one problem is finding a decent used STI muffler, after 10 or more years of use there are no guarantees. If I was really set on a quiet setup and had the spare cash perhaps I'd buy a new one from Subaru if found for a reasonable price?
what does it mean when you say packing blows out?
 

·
Registered
2007 2.5XT Limited 4EAT
Joined
·
343 Posts
[what does it mean when you say packing blows out?]

The muffler is packed with fiberglass or other dampening media, this is what muffles the sound. After a long enough period of time the "packing" will break down and literally blow out the tailpipe leaving you with a hollow metal can for a muffler.
 

·
Registered
2006 Forester XT Manual 5spd
Joined
·
33 Posts
Discussion Starter · #16 ·
So I bit the bullet and got a decatted Stock downpipe, K&N Cone filter, BOV and a Tune on the Standard TD04. From around 121Wkw I am now on 142Wkw :grin2:
The car is so much more lively and responsive, much more fun to be had
I am only concerned about the occasional afterfire, is this expected after a tune?
 

·
Registered
2005 Forester XT Auto
Joined
·
1,069 Posts
So I bit the bullet and got a decatted Stock downpipe, K&N Cone filter, BOV and a Tune on the Standard TD04. From around 121Wkw I am now on 142Wkw <img src="http://www.subaruforester.org/vbulletin/images/SubaruForester_2014/smilies/tango_face_grin.png" border="0" alt="" title="Big Grin" class="inlineimg" />
The car is so much more lively and responsive, much more fun to be had
I am only concerned about the occasional afterfire, is this expected after a tune?
Congrats on the tune! On the afterfire, i don't have them on a custom stage 1 ball park tune, except I once had someone ask if my mazda 3 (2.5 NA) could be tuned specifically to make them lol. I'm not interested in finding out.
 

·
Registered
2006 Forester XT Manual 5spd
Joined
·
33 Posts
Discussion Starter · #18 ·
So after hours of research and pondering, I decided to remove my vent to atmosphere BOV, she is behaving herself now. Seems the aftermarket BOV creates a rich condition that im not entirely comfortable with
 
1 - 18 of 18 Posts
Top