Exhaust centre section 2004 impreza STI
 

Hi I am after some advice please

I need to get a new Centre Exhaust section for my 2004 Impreza STI Uk Version with PPP pack.

The MOT station advisory says it is the piece between the CAT and rear Tail Box (which includes a small silencer or resonator)

The Car has standard exhaust with whatever the PPP prodrive upgrade is. It has prodrive on tail pipe but not sure what else they changed in the PPP pack.

I have looked on line as stainless options and find so many option it confusing as some mention they are centre decat pipes there are one with resonators and ones without.
2.5 ", 2.75" and even 3" but most say for off road use only.

I am not trying to alter performance or noise level just looking for a road legal (Emissions) stainless steel "centre section" replacement only.

Any recommendations would be appreciated

regards
Ian

Something like this will be fine. The standard exhaust is 2.5", non resonated will add abit more noise but will only make the car sound nicer.

https://rover.ebay.com/rover/0/0/0?m...2F352467586024

Got a standard centre section if needed.

Nah mate. I have changed my full exhaust for 3" bore stainless steel manifold, and sports cat and prodrive ecu and performance filter car runs fine. Such a small change like that won't do much.

I'll be interested to hear how going non resonated affects the sound...

I have the PPP on my 2003 & I can't help but think the back box strangles the burble as it only seems noticeable between 2-3k RPM & then a seems to get muffled.

Would swapping out the centre section for a non-resonated one free up more of the burble (or rumble, whatever the technical definition if for it)? For some reason I have it in my head that going non-resonated increases drone but maybe that's just a side effect.

Cheers :)

Yes will improve the sound nicely. I have a powerflow system on mine which is 3" bore no resonator and just a back box similar to the prodrive.

Mine has a nice note, not much drone, I've had multiple systems on mine, worse for drone was a jap style awful.

With the prodrive it should be abit quieter than mine. Can't imagine it would have drone.

I similarly went with a 2.5" stainless non-resonated centre in my STi PPP. Nothing but good things to say about it - louder, but just enhances the sound nicely. No droning, well certainly no more noticeable than standard.

Got a standard resonated centre pipe if interested top pipe in picture.



Attachment 72367

It's still what I'd call quiet, but the resonator helps a little...

With the non-resonated centre & Prodrive back it's not really any louder (only a fraction), it just just the tone has a deeper not & the rumble burble is more prominent & doesn't get swallowed up by the resonator.

You'll be best off swapping out the centre section & back box at one time to save messing about later if noise is the main goal.

https://cimg4.ibsrv.net/gimg/www.sco...08a0ac9fb8.jpg

I see, so still very quiet after 3000 rpm? My mechanic who is a subaru olspecialist and fanatic told me that removing the center resonator wouldnt make any differece, I guess he is right then!

I agree, I have a stock STI PPP and recently changed the middle resonated pipe for a straight pipe hoping for more sound, and I'm disappointed, I don't notice any more sound under hard acceleration, what I notice is a bit more drone on the motorway. I might have to change the backbox for a louder one.