What exhaust parts do I need?
 

I have a 2005 WRX with the standard exhaust setup with the exception of an STI rear backbox on it. Before I get it mapped I want to make sure that I have made enough adjustments to the exhaust system to get the best value out of the map. I also want it to be:

1. MOT friendly, which from my reading I think means that I can't go fully decat and would be better going for a sports cat (is this bit correct?).

2. Not very loud. I don't mind a slight increase in sound but would prefer for it to be minimal, which again from my reading suggests going for resonated rather than non-resonated parts (is this bit correct?).

Could anyone help me out and suggest what individual parts I would need (and roughly how much you would expect them to be) to get to where I want as I will need to spread the purchasing out over a few months so I'd prefer to get them one-by-one rather than as part of a full system (but if that is the better option, then just say).

Cheers!
Mark

If you want the most from the remap get a decat uppipe, one from a classic or newage sti will do, a used ppp downpipe and second decat, prodrive intercooler hose and a panel filter best to get a deresonated centre and possibly used prodrive backbox as well should give about 280bhp, If you want to save a bit just fit a second cat delete, panel filter and prodrive intercooler hose and prodrive backbox, a remap on this will give about 265bhp as thats what prodrive pack on wrx is, so only about 15bhp less for a much smaller cost. depends how much you want to spend really.

Yes you are correct :thumb:,if you want to keep it mot friendly then opt for a sports cat ,you can then get away with a straight through centre section which will gain you a bit more bhp,and if you dont want it very loud could opt for a prodrive or a racebox or a haywood & scott backbox.Having said that a lad on here had his car mapped recently with a sti backbox for the same reasons as yourself and his car still made good power gains with supporting mods. The link below will give you a fair idea of prices :


http://www.scoobyworld.co.uk/catalog...hp?cPath=24_53

1. yes for the car to be friendly you will need a sports cat, you can either get one second hand from the for sale section on here or new from scoobyworld or another performance site.
2. yes get the resonated centre section, again, new or used and i think a used prodrive back box would suit your needs, it is very civilized.

Fooking double post

OK, thanks for the responses, I think I understand. Just to be clear though, if going for new parts I could go for something like:

1. Centre Section (Resonated) http://tinyurl.com/2wbyno8 £125
2. Front Pipe & Sports Cat (is this also known as a downpipe?) http://tinyurl.com/38zljq6 £225

I also saw while browsing a Second De-Cat Pipe (is this also known as an uppipe?) which said when fitted that although it was de-catted it would still allow the MOT to pass:

3. Second De-Cat Pipe http://tinyurl.com/2wpsewx £55

So could I also fit this as an extra to help with the airflow?

Cheers for the help, I'm doing loads of reading and think some of it is starting to sink in! :lol1:

yes will help the extra airflow but don't forget the pro-drive back-box. also a full down-pipe in the link you have provided eliminates or involves two cats the main one and then a second one. so if you buy a full down-pipe like the one in the link the you don't need a second de-cat pipe as it is already eliminated.

OK, thanks so if I read that right that looks like I'm back to just having to buy:

1. Centre Section (Resonated) http://tinyurl.com/2wbyno8 £125
2. Front Pipe & Sports Cat (is this also known as a downpipe?) http://tinyurl.com/38zljq6 £225

But I also need a prodrive exhaust instead of the one I got from a standard STI? And will this add much extra noise though as if it adds a fair bit I think I'd rather miss out on some bhp and keep a similar level?

Cheers!

I had a prodrive backbox with a decat uppipe, ppp downpipe, decat 2nd pipe and deresonated centre, ie straight through no silencer and it was not overly loud at all, in fact sounded just right on cruise and wot. I later fitted the std uppipe back on and the std downpipe, so just had std wrx ppp exhaust with deresonated centre and that was not much different to be honest. The prodrive back box is very quiet but does unlease a nice burble that is lacking on std exhaust.

OK cheers, if there isn't much noise difference then I don't mind going for it. Out of interest do you think there would be much bhp difference between a standard STI and PPP backbox when remapped?

The back box will make very little difference to the performance

there wont be much of a difference between the two exhausts power wise unless you are going for big power, as some exhausts choke the car past certain power levels, the prodrive exhaust is ok till around 370 bhp.

Excellent, thanks to everyone, I think I know what I need now :)