EXHAUST....WHICH WAY?
 

hi...am fairly new to scooby scene but after having my my05 wrx for 12 months am starting to get the itch for some minor mods with maybe a future remap in mind.
do i go full exhaust system or just parts?.....which best for performance .....and keeping it legal.

if your wanting to go for a full system then you'll be needing a remap. A 200 cell sports cat downpipe will keep things legal.

Maybe start with a back box or something and work your way from there? Theres quite a few parts to scooby exhaust system (headers, up-pipe, downpipe, centre cat, centre section, backbox) so maybe start adding in stages, see how you get on?

Scoobyworld have quite a good selection of exhausts to choose from. Cobra sport exhuasts are well worth a look too!

is it right there are two cats on the exhaust and its ok to get rid of one but not both......if so which one is best to get rid of?

Speak to Ian at Hayward and Scott, he is is very helpfull and knows his stuff, i have just purchased my first system and he advised me to go for a cat back system with the classic style back box, should be here friday so i could let you know how i go on once fitted. There are actually 3 cats on the impreza, a pre-cat in the up pipe, your main cat in the down pipe then another cat in the mid pipe, see this link http://www.scoobypedia.co.uk/uploads..._schematic.gif.

theres a pre-cat in the up-pipe, main cat in the downpipe, and another cat in part of the centre sections.
One in the downpipe is the one thats needed though for emissions.

Any changes to the up-pipe and/or downpipe cats though require a remap as overboosting can occur as a result. IIRC the cat in mid section isnt so much of an issue.

Newage WRX has 3 Cats; Up-pipe, downpipe, centre.
Newage Sti has 2 Cats: Downpipe, centre.

On a public forum I wouldnt like to say 'its ok to get rid of one', however should you feel the need to replace one with a decat I would recommend the Up-pipe first as this is the most restrictive, but its a bit of a pig to do, and if your considering upgrading the little TD04 at some point, then I would leave this until then.

Rob

bump

Why Bump :wonder:

Has you question not been answered?

Rob

Your car will still pass an emmissions test with the up pipe cat and the centre cat removed.... If you opt for the prodrive performance pack the centre cat is replaced with a straight though anyway i believe.

cool...thanx for help.spose if i was wanting a remap the tuner would tell me the best mods to get done

I would imagine every mapper would tell you that the up-pipe cat on a WRX is the most restictive and this would be a deffinate removal. The Up-pipe is pre turbo so resticts the amount of flow, thus no matter what you do to the exhaust after the TD04 the Up-pipe Cat will still restict the amount of gases that can be forced through.

The Newage STI up-pipe is obviously a decat, and as a OEM to that car simply just swap this for one of them as they are more than up to the job, and as they are narrower than some of the aftermarket ones, they also spool very well too. For whats its worth if your chasing a little power and you know you need money for a remap, I would personally save a little more and change the TD04 for a 16G or 18G if one crops up at good money, and keep away from eBay as these are generally chinese copies.

Good luck,
Rob

thanks for that info