3" Catback discussion

[Garrison]

Hi, :smt006

I'm building an exhaust system for my 3" downpipe, and I'm debating between two different types of resonators. I'm going to have the "muffler shop special" made for me after I decide and that'll be the end of it.

I'm going for muted aggression here. I know the boxer rumble isn't inherently loud and obnoxious, but I've heard systems that were oddly similar to a v8 truck running open headers in terms of loud. I can't stand that. I'm running a 2.5"-->3" obx twin-loop muffler, which I enjoy and I think I'll keep. With that in mind which of these two is going to work for my needs better?

Magnaflow
http://cgi.ebay.com/ebaymotors/_W0QQcmd ... MEWAXQ3aIT (http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_trksidZp3984Q2em1423Q2el2649QQitemZ390338296771QQsspagenameZSTRKQ3aMEWAXQ3aIT)

VMS Racing
http://cgi.ebay.com/ebaymotors/_W0QQcmd ... MEWAXQ3aIT (http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_trksidZp3984Q2em1423Q2el2649QQitemZ360389108740QQsspagenameZSTRKQ3aMEWAXQ3aIT)

System will probably include something like this as well:
http://cgi.ebay.com/ebaymotors/3-Cataly ... 2eb77d0cc1 (http://cgi.ebay.com/ebaymotors/3-Catalytic-Converter-High-Flow-Stainless-Steel-/200646921409?pt=Motors_Car_Truck_Parts_Accessories&hash=item2eb77d0cc1)


Opinions? Experience? ... Bueller?

[anothernord]

That seems awful cheap for a high-flow cat. You'll probably need 2 of them if you hope to pass.

[StatGSR]

don't see much point running a 3" exhaust into a 2.5 inch muffler...

[Garrison]

That seems awful cheap for a high-flow cat. You'll probably need 2 of them if you hope to pass.
Actually, all 3 o2 ports will be in front of the catalytic convertor. I'm going to use the o2 spacer bung trick.




don't see much point running a 3" exhaust into a 2.5 inch muffler...
Why is that?

[Baddog]

I once read "your exhaust only flows as well as its smallest point"

[Garrison]

So you're saying build a 2.5" instead, or ditch the 2.5" muffler in favor of the full monty?

[Garrison]

There is also this option:
http://cgi.ebay.com/ebaymotors/JDM-02-0 ... 2567189c40 (http://cgi.ebay.com/ebaymotors/JDM-02-07-SUBARU-IMPREZA-WRX-STI-3-CATBACK-EXHAUST-/160643456064?pt=Motors_Car_Truck_Parts_Accessories&hash=item2567189c40)

[StatGSR]

There is also this option:
http://cgi.ebay.com/ebaymotors/JDM-02-0 ... 2567189c40 (http://cgi.ebay.com/ebaymotors/JDM-02-07-SUBARU-IMPREZA-WRX-STI-3-CATBACK-EXHAUST-/160643456064?pt=Motors_Car_Truck_Parts_Accessories&hash=item2567189c40)


It wont bolt up to a legacy (needs to be extended), but is a very popular choice for many people i know (with both imprezas and legacys)

but yes, a 3" cat back isn't a 3" cat back if it has a 2.5" muffler. if you really want the benefits of 3" piping you need to ditch the muffler.

[Garrison]

There is also this option:
http://cgi.ebay.com/ebaymotors/JDM-02-0 ... 2567189c40 (http://cgi.ebay.com/ebaymotors/JDM-02-07-SUBARU-IMPREZA-WRX-STI-3-CATBACK-EXHAUST-/160643456064?pt=Motors_Car_Truck_Parts_Accessories&hash=item2567189c40)


It wont bolt up to a legacy (needs to be extended), but is a very popular choice for many people i know (with both imprezas and legacys)

but yes, a 3" cat back isn't a 3" cat back if it has a 2.5" muffler. if you really want the benefits of 3" piping you need to ditch the muffler.
Understood. Can I get a catalytic convertor to help fill in the gap?

EDIT: Actually, you probably need to see my setup. The more I think about it, the more I think it would fit. I have a looong DP.

[prodriver1]

is your car turbo? if not 3" is way too big.

[StatGSR]

The cat would still be before where the "cat back" exhaust starts, so no, not really, in general you would have to extend the mid pipe, maybe you can get away with extending in front of that exhaust when you weld in the cat, but obviously i cant guarantee that

[httrdd]

Yea I would say 3" is too big for the 2.5l. It sounds great, but you are loosing a lot on low end. Ask me how I know. Running the 3" on my H6 swap is great and will prob go bigger for the s/cd build. 3" on a n/a 4 cyclinder is loosing more than it is gaining. I would not go higher than 2.5".

[Garrison]

I am currently non-turbo'd and running 2.25" "muffler shop special" with UEL headers to 2.5 muffler. Stock cats :-(

I'm going to be installing this (oddly similar to what it will look like on the car). *note the o2 bung locations*:
https://sl-i.net/FORUM/images/imported/2011/09/IMAG0069-1.jpg
https://sl-i.net/FORUM/images/imported/2011/09/IMAG0070-1.jpg

As you can see, I'm very excited :grin:

Wastegate will need to be extended slightly due to my having changed the angle of the up-pipe flange and down-pipe mouth:
http://i1003.photobucket.com/albums/af158/Garrisonbowers/IMAG0068.jpg

So, this is the exhaust I'm talking about in the above posts.

[httrdd]

Ooooo I see! Thats going to be fun. In that case dont run anything under 3" :D

[prodriver1]

word... the bigger the better on turbos.

[Garrison]

Guess it's ebay then.

Any info/help on which o2 ports to use? I would use the last bung but the wastegate is introduced into the pipe before-hand.
Is the back of the turbo too hot?

[Garrison]

I need some more help before I pull the trigger on a catback. Why will the wrx not fit? The downpipe seems to be the same length. Is length the only issue?

This looks like it will fit, but I can't see a resonator welded anywhere on it.
http://cgi.ebay.com/ebaymotors/96-00-SU ... 43a94d2c8c (http://cgi.ebay.com/ebaymotors/96-00-SUBARU-Impreza-2-5RS-3-Catback-Exhaus-EJ25D-GM6-/290603216012?pt=Motors_Car_Truck_Parts_Accessories&hash=item43a94d2c8c)

[StatGSR]

The wrx exhaust and all impreza exhausts for that mater are too short because the legacy is a physically longer car.

[Garrison]

Will it bolt up and can it be extended later. I.e. will it work until a shop can extend it?

Or hell, I guess I could just go back to the idea of the muffler shop special then. Just buy the cat and muffler that I want.

[prodriver1]

Will it bolt up and can it be extended later. I.e. will it work until a shop can extend it?

Or hell, I guess I could just go back to the idea of the muffler shop special then. Just buy the cat and muffler that I want.
yes you can have the tipe of the wrx muffler extended, the covers come off and then you weld.

[Garrison]

Cool, pulled the trigger on a wrx catback from cj-garage (us company) for dirty cheap.

voila:
https://sl-i.net/FORUM/images/imported/2011/09/sti0207catback-1.jpg

[Huffer]

Yep, go 3" all the way back. You'll flow better and get better spool up. The exhaust shop will have to extend the midpipe, not the muffler tip so much. :)

[Garrison]

According to wikipedia, the difference in the wheel bases of the two cars is ~ 10" (legacy 95-99MY is 186", WRX 2002-2006MY is 176"). That's not too awful, and if I'm feeling green, plenty of space to add a cat or 2.

[nikolaus.conrad]

I am currently non-turbo'd and running 2.25" "muffler shop special" with UEL headers to 2.5 muffler. Stock cats :-(

I'm going to be installing this (oddly similar to what it will look like on the car). *note the o2 bung locations*:
https://sl-i.net/FORUM/images/imported/2011/09/IMAG0069-1.jpg
https://sl-i.net/FORUM/images/imported/2011/09/IMAG0070-1.jpg

As you can see, I'm very excited :grin:

Wastegate will need to be extended slightly due to my having changed the angle of the up-pipe flange and down-pipe mouth:
https://sl-i.net/FORUM/

So, this is the exhaust I'm talking about in the above posts.

That's a sweet up-pipe, is that a muffler shop special? I'm thinking about something like for future setup.

[Garrison]

Yeah, I had an idea and a good welder. Between these two things, most things are possible.
Read my build thread for actual pics of my new uppipe

[nikolaus.conrad]

I shall look it up :smt023

Edit: Promotion FTW! :smt026

[Garrison]

Update for anyone curious about the fitment.

I would say that the basic skeleton is there to make the exhuast, but as mentioned above, the legacy is a longer car (about 11"). The exhuast shop charged me $100 to install it, which I think is a little excessive because they literally made me a system out of 2.25" and charged me $65 for the whole thing. I -give- them most of the system that requires a little chopping and measuring and boom, their labor rate goes up. Either way, I guess I really can't complain, the system sounds incredible, very quiet at highway/low throttle situations, but opens up nicely (classy) when you get on it a little bit.

Conclusion: Ebay exhausts are decent quality, stainless steel, well welded and depeneding on your setup, a lovely sound. Also, they're relatively inexpesive. Labor rates vary from area to area, budget at least what I was charged to have it installed.

[rennkafer]

Was the 2.25" system you had them make stainless? Looked like the 3" you had them modify was and that could be the difference in price, stainless tube ain't cheap.

[Garrison]

Sorry for not getting back to you, I looked under the car to be sure, but no their piping isn't stainless.