Cat Back Exhaust for Na Liberty (2.5i)

[Mark123]

Hi all,

First time posting, I'm need of some advice as I want to install a cat back exhaust on my NA 2.5i my04 liberty.

-My first question is, does anyone know of some good performance or exhaust shops in sydney or the illawarra region that I can go to get quotes.
-Should I go custom exhaust or a pre-fab x-force or something like that.
-Just for your info, my model has twin tips and I'd like to keep it in that same twin, single tip muffler style.
-I've read most people go for a hot-dog resonator to 2.25" type set up, is this a good choice?
-Also, I don't want to risk having the ECU think there is an engine problem because of the air flow etc, I'm assumming this is only a problem if the cat is replaced, am I right?

Overall I'm just after some wise words and advice from anyone who has the same car/has isntalled a cat back.

Cheers.

[Robbks]

I hear good things about Bankstown Exhaust



but seriously

I wouldn;t use anything bigger the 2" mufflers on the 2.5 and keep the stock piping diameter throughout.
there is not much to be gained in a cat-back exhaust on these things.
Replacing the CAT with a good quality 200CPI Metal Substrate CAT (Redback), keep the stock resonator it's straight trough pipe anyway
and some nice oval mufflers for the rear, in the standard dual or STi-style quad tips.

Have a look here for what i've proposed from out Site Vendors (Ultrex and TCP) on some NA-suitable mufflers
viewtopic.php?f=55&t=17245

[Mark123]

Thanks Robbks,

Seeing as though there seems to be a droning issue with these set ups not designed primarily for N/A's, should I go custom MS piping with a new hi flow cat and keeping the stock resonator to a couple of aftermarket sti mufflers? Or is that a bad idea haha I'm not really after performance, I just want that boxer rumble, I understand the limitations of these N/A engines and am happy to keep it as is.

Although if there are a few cheeky ways to get a few extra KW i'm all ears

[SH30RB]

Although if there are a few cheeky ways to get a few extra KW i'm all ears

i know you want that 'boxer' sound but the best way to squeeze a few KW might be some equal length headers and a tune, but the equal length headers will cancel out that typical boxer rumble. a tune would definitely help with driveability tho

[Mark123]

I've heard my ECU is old and cannot be tuned.. (04 model)

Or are you talking about a piggy back flash box or something?

In the case of the N/A's, which restricts the boxer rumble most lol? is it the resonator or the mufflers? If its the mufflers, I've half a mind to just replace them

[Robbks]

you won;t get a boxer rumble without putting on proper Un-equal length headers
or modifying WRX ones to fit. which takes a fair bit of work

here is an NA fozz with modified WRX turbo headers fitted to a modified exhaust

[Mark123]

That sounds pretty nice, so you're saying that the liberty exhaust and engine set up differs in such a way that it would actually sound completely different to an impreza?

I have a friend with an RS impreza, he has a bolt on. I don't know that much about it, but I'm fairly sure its just a muffler, with no mods to the cat/resonator/exhaust mainfold etc.

Are you guys saying that it is actually impossible to replicate this with a liberty through a bolt on set up?

[Robbks]

you CAN bolt on Aftermarket UEL Headers.
but without them you won;t get a proper boxer note.
You can't get the boxer note from the 1994> NA motors just by changing the cat-back system

the unique note comes from the timing of the exhaust gas pulses from two sides of the engine merging into a collector at the same time before being sent to the turbo.

The NA motors have a much more Equal length design which keeps the exhaust pulses properly separated and as such does not produce the same "beat"

[Mark123]

The NA motors have a much more Equal length design which keeps the exhaust pulses properly separated and as such does not produce the same "beat"

Right okay...So, if I understand this correctly, my friend that has the RS impreza should have the same exhaust note as a liberty with a bolt on muffler both being N/A's. I do like his car's exhaust note, as you said, it's not the "proper" boxer rumble but a similar one that I still enjoy

good to know that if I only end up going with the cheap option, I should still get an improvement and a similar boxer rumble...

I was just worried it was going to sound like an excel with a cannon haha

[Robbks]

what year RS Impreza?

[Mark123]

It's and 03 I believe, 2.5 litre.



Thats what it looks like...

[Mark123]

Thats better...sorry for the broken link

[west_minist]

Check and see if the ECU is Denso.

[gloryboy]

Check and see if the ECU is Denso.

Yes, because if you have a Hitachi you'll be screwed like I was

[turner_822]

Hey,

I just did a cat-back system on my my08 na (also added a high flow cat). It took me so long to decide and I spent ages getting advice but at the end of the day my choice was simple: you will not get much (if any) power, so paying several thousand for a nice sound is insanity (for a cheap-o like me anyway lol).

I went with a basic off-the-factory-line X-FORCE 2.25 inch cat back system and a high flow cat (see link below) Cost me $950 for the lot and $300 to fit (the bloke had to add a small piece to the cat). I can tell you right now: it does not drone badly in fact, sometimes on the highway you don't even know its there. When west_minist tuned my engine he said the 2.25 inch might be a bit restrictive like the stock but I didn't want my ears bleeding from a huge system, I just wanted a nice sound. The build quality is a little rough but it sounds great, especially now my engine is tuned and revs out to 6500-6800rpm before shift thanks Edward!!!!!

Ohh yeah make sure the ecu is DENSO. I have a denso and was also told it MIGHT throw an error code with the new high-flow cat but it didn't (thanks to Edward lol)

http://www.bestmufflers.com/bshop/produ ... a57fc3eac0

Hope it helped
Cheers