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Forum Member
2004 FXT
Joined
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955 Posts
Discussion Starter #1
Is there a HP limit on the 2.5 STi CBE?

What kind of HP difference should I be looking at with...

4EAT (b&m supercooler installed), VF43, STi TMIC?

I currently have a 3" GReddy Ti-C exhaust, but am looking for something more "sleeper/stock"-ish. I doubt it'd get more than 260hp, so, being it'll probably be that, if not lower... would the STi CBE be ok?

I hope that made sense... These New Castles are tasty.

:woohoo:
 

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Premium Member
2017 VW Golf SportWagen 5MT
Joined
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10,887 Posts
STi catback will work fine for 260whp, come drive my car if you want. That said, I'm going to be trying a 3" just because.

Nah, it's all about Guinness. Although, a New Castle would be my second choice.

Stan
 

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Registered
05 FXT
Joined
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1,540 Posts
^ I'm in the same boat. I'm still on the stock FXT mid section and I think it's the current bottle neck my setup.

And I also agree, the Guinness I had last night are better than New Castles.
 

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Premium Member
2007 Forester XT 4EAT-VTD
Joined
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2,145 Posts
I think if you were to use a straight-through midpipe with no resonator and a straight-through axle-back (the STi is not), there would be minimal difference with a VFxx turbo.

As you know, I went with the MadDad 3-inch Whisper CB that uses a straight-through axle-back and non-resonated midpipe and have been very pleased with it. BTW, the Maddad uses a resonated tip and slightly longer muffler than the WRX/STi version, but is 3-inch all the way through and not objectionably loud. In fact, I am always amazed at how quiet it for such a set-up, which has to do with the packing used in the muffler and the resonated tip.

I believe if there's any difference 3" vs. 2.5" it would be most noticeable in pre-boost throttle response. I did notice a big difference in throttle response when I went from the stock exhaust with STi axle-back to the MadDad 3-inch Whisper when I did the turbo swap. The much larger Perrin TMIC also made a difference when I installed that last month, so right now my FXT feels very responsive. I'm hoping I may see additional improvement next week when I install the new turbo inlet and afterMAF hose.

IMO, pre-boost throttle response makes a huge difference in daily driving. Between the exhaust (including the PnP GS EMs), the huge Perrin TMIC, and the throttle mapping that keeps me out of boost for the first 50% of throttle, the FXT is a real treat to drive. Of course, going into boost is lots of fun too, but the car feels very strong even when I do not - which is how I drive it the vast majority of the time.

Sorry for the long response - I hope this helps.
 

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Premium Member
2017 VW Golf SportWagen 5MT
Joined
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10,887 Posts
I have 51K on my car, I've changed a few things on it but I never ran it without a resonator in the midpipe -- ran OEM FXT pipe, now OEM STi. I'll be swapping it out for a full 3" next week -- if there is a difference to be felt, you bet I will feel it. I just hope those around me can live with the added noise. I'll report back.

Stan
 

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Registered
2005 Forester XT SOLD
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145 Posts
I have a similar VF48 mod package with a Cobb catted downpipe and full STi back. I had a dyno tune last week and was getting 250ish HP on a mustang dyno on 91. The tuner felt my limitation was the sti exhaust. That is fine for me because I dont want a loud car at all. I would consider the Maddad if I could hear it in person. I only have a non-stock sounding deep idle that goes away as soon as the RPMs come up.

Also if you grind off the hanger from the back of the stock FXT muffler it fits the STi muffler almost perfectly and welds right up. Lots of folks seem to run without that one but I doubt Subaru puts it there for fun.
 

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Registered
2004 Subaru FXT MT
Joined
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1,853 Posts
Post turbo, bigger is always better for performance. No exhaust would be perfect. :biggrin:

So really, the significant factor in your decision making is noise/sound. I personally like having a wide open 3" with just a muffler. I don't think its too loud. But its personal preference. I know many on this board that would disagree with me.
 

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The Sub kit guy
2005 Forester X & XT VF39
Joined
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13,100 Posts
I'm one of the people that like my car to be quiet, so with my VF39 I have a Cobb catted DP and a STi catback. I still put down 280/312 @17psi and 293/[email protected] and 312/366 @21 psi with race gas. Those numbers would be higher with a full 3" setup, but I'm will to trade 15hp or so for a quiet car.

I've tried a full 3" setup just to see if I'd like it, and boost does seem to kick in a bit sooner and it drove a little smoother overall. If I lived in a less hilly area or was single without kids I'd have a 3" maddad whisper setup on my car.
 
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