BennyP

Hi there,

New to the board after recently purchasing a hawkeye 2.5 WRX.

Chuffed with the car, except for the rather muted exhaust note.

Am looking to buy an exhaust and have done a number of searches on here, but I am still baffled so was hoping somebody could help?

As I understand it, my car has 2 cats, one in downpipe and one in front pipe.

I think it also has a resonator box in centre pipe?

Firstly, is this info correct?

Secondly, if I keep the front cat and replace the second one and resonator box, am I likely to get the engine mgt light coming on?

Finally, should I be going for a 3" bore (Milltek, Magnex etc) or would something like a TSL centre section suffice?

Thanks for the patience and for any help

jasonius

iTrader: (1)

If it's just a better sound you're after then a decent back box will give you what you want..

If you're after a 'bit' more performance then removing the centre cat (which is the last of three btw. Up-pipe/down pipe/centre) will help the turbo spool a little earlier and still pass emissions test.

Removing anymore cats will require a remap to be of any advantage..

A 3" system is really only required if your going to push >400bhp..!

v8voodoo

Hi Benny and welcome.

I was disappointed too with my 06STi until I took it to Hayward & Scott to sort it out same as I did on my 03 WRX.

Firstly lets answer your questions: Yes, there is a cat in your downpipe and also one in the front centre followed by a resonator centre section then the backbox.

I believe the wrx also has a cat in the up pipe, but as I understand it, that makes little difference to the sound at the end.

If you replace the front centre cat and the resonator section with straight through stuff you won't get the management light coming on (speaking from experience with the 03 and 06).

Your best bet for extra added burble is, as you say to ditch the front centre cat and the resonator section, then whack a decent back box on. The back box only swap on my old car released a good bit of burble, but I wanted "added extra" burble a few weeks later.

I also believe the downpipe and front centre cat pipes on the 2.5 are of different length to the 2 litre cars, so be mindful to get the right parts when you order.

If you are anywhere near them and are happy with the price then Stainless steel exhausts manifolds and headers from Hayward and Scott are the business and will fit for free. I had my original stuff (03wrx) off them and now have a full downpipe back system (06 sti) from them and love the quality, price and burble.

Also agree with Jasonius, 3" system isn't really needed.

Here are some parts you might like the look of....

Stainless exhausts manifolds headers

Stainless exhausts manifolds headers

Stainless exhausts manifolds headers

The above is what I now have and am very happy with.

Hope that clears things for you....

Nige.

BennyP

Brilliant, thanks for the helpful replies.

One last question, would fitting a 'sports cat downpipe' enable me to remove the cat in the upipe as well?

53

iTrader: (41)

Different pipes mate. You can bin all three cats and replace the down Pipe with a sport cat version and decatted versions of the other two. You will then defo need some supporting parts and a remap.

53

iTrader: (41)

If you just want burble I would stick with removing the center pipe for a straight through version and then an alternative back box.

Performance wise you are better off deciding what you want the car to do, talking to someone like Mocom Racing - Performance car and trackday products before you spend any serious money on decats/sports cats.

BennyP

Thanks again for the help.

I should have been clearer in my original post, I am not just interested in a louder exhaust but am more interested in performance and will definitely be looking for a remap at some point in the not distant future.

fivetide

iTrader: (1)

Just had my WRX done for the same reasons as you. Went with the centre decat, deresonated centre and back box and upgraded the intercooler hoses (standard is quite restrictive)

Had it mapped by Andy Forrest and it now has 1.3 bar boost at 2700rpm and just over 270bhp. The real shift has been the torque though, it is now at the same level as the bhp.

I was advised that any decat - safety wise - should have a remap. Some cars are ok, some aren't apparently, if you get a boost spike and blow something your warrenty is in the bin if you caused it.

5t.