Sub-Subaru

So I have decided to fit a new VF35 turbo and pink injectors etc. I need to start buying a new exhaust for my WRX 2004 Impreza. I already have a prodrive back box and would like to buy the rest second hand if I can.

I have come across an article that sort of explains the exhaust system on WRX Imprezas but I really don't have a lot of knowledge in this area.

From what I understand in order to stay legal and pass the MOT this year I need a decat up pipe, sports cat downpipe, decat centre section?

Is there any particular makes which I should be looking out for or avoiding?

Is there anything else about exhausts that I should know about that people can give me some pointers on as I'm doing all this in the dark a little.

Do people buy different sections of the exhaust made by different manufacturers or is it better to try and get a complete system from one manufacturer?

Is the prodrive backbox sufficient or should I be looking to change that for something else? Also is 2.5" sufficient or should I be looking at 3"?

BBB3

iTrader: (7)

Hi,

Miltek full system is probably the best bet.

RS_Matt

200cel on the sports cat might be a better option? A bit more restrictive but lowers emissions a bit more than a 100cel.

Sub-Subaru

I just don't get how people choose between all the different make of exhausts out there. I see so many different types on this forum alone.

Why do you recommend Miltek out of interest?

Is the sports cat different on each make of exhaust?

BBB3

iTrader: (7)

It's a full true 3" exhaust even in the back box, most other exhausts are 2.5 in the box.

The quality and build is very good, the fit is perfect along with good power gains.

IainMilford

iTrader: (15)

I ran my 2005 WRX at circa 330-340 bhp with a 2.5" exhaust, this included a decat uppipe, Prodrive sports cat and an rcm backbox. The rest was similar to your set up vf35, pinks and an sti tmic etc. passed mot no problem

Reshard1977

iTrader: (17)

Exhausts, especially second hand can be a minefield!

There a lot of manufacturers that make exhausts that only fit with their own make pipes. I.E. they are not interchangeable. Miltek is an example of this.

Have a look at the diagram further down the link to see the OEM exhaust, and the parts that make it up. If you look at the other pipes and back boxes you'll start to see and understand the total number of pipes that you can change (3 or 4 depending on the downpipe). http://www.scoobyworld.co.uk/catalog...roducts_id=179

Whether you chose 2.5" or 3+" should really depend on the power your after and the noise your willing to live with. My car is a daily driver, and I've gone from 2.5" to 3" back to 2.5" as its quieter. To make things a little more complicated, the back box itself will play a very large part to the final volume and drone of the exhaust.

From my own experience, i noticed the 2.5" systems that i have had to be quieter than the 3" systems, with slightly more torque lower down. But the 3" undoubtedly produced more power up top. I've also had all types of back boxes, and some of the 2.5" back boxes were louder than the back boxes with 3" pipes on boost (i had the 3" revolution system) but on cruise, the 2.5" pipes are generally quitter.

The sports cat will make only a slight difference in volume, but a big difference in power delivery.

As a VERY rough rule of thumb, if you are aiming up to 350bhp 2.5" will be more than enough. Anything more, you would really want to go to 3". Having said that, I really recommend against aiming for more than 350bhp on a WRX, unless you are planning on forging the engine and swapping the gearbox.

To make things worse, choosing an exhaust is a very personal choice, everyone has a different view and opinion on exhausts. The only way to know what your looking for is to meet other members and decide what kind of sound you want, or trial and error until you get what your looking for.

With some indication of what your looking for, some pointers to brands and types can be made. Youtube clips can help you a tiny bit, but most cameras don't pick up bass very well, so you don't get an accurate sound.

On a side note, i have a Newage STI PPP sports cat on my car at the moment, that will be coming off soon. Looks like this: http://www.ebay.co.uk/itm/Subaru-Imp...item43cf6e1bf4

If your back box is in good nick, I'd be happy to do a straight swap with you.

Sub-Subaru

Thanks for the replies especially the very detailed one.

Ian that sounds good. The mods you mention are what I intend to do but have not actually done yet. I am really trying to do all this as soon as possible because I have had the car now coming up two years and not done any mods. Are you in the Yeovil area by any chance, I live very close to Yeovil.

Reschard that is very informative and helpful thanks. Perhaps if I gave you a little more info you could make some further suggestions. I currently have the prodrive back box with the oval shaped tip but the rest is standard. I want to make about 300-320bhp if possible. My current exhaust sounds not too bad but it is a bit quiet. I would love to have it louder but also keep the nice Subaru burble. It is also my daily driver.

Is it possible and cheaper to fit all the prodrive exhaust sections to make a decent exhaust system or will that still be more restrictive than an aftermarket one like Scorpion, Blitz, Janspeed, Miltek etc? I don't know if the prodrive back box I have is good or too restrictive?

For instance the sports cat that you mention you are removing shortly. Would that be as good as an aftermarket style sports cat? Presumably if your answer is that the prodrive stuff is all good and adequate then I would want to keep the back box really?

I guess the only other issue is that the prodrive exhaust sections are not stainless steel and will rust?

IainMilford

iTrader: (15)

I'm in weston-super-mare mate, but the club I help run Somerset Scoobys is er in Somerset lol We have plenty of members down yeovil way you should join up!

RS_Matt

Any guesses on this back box?

Sub-Subaru

So just so I understand is the Prodrive exhaust sections as good as the other aftermarket stuff or is it a bit restrictive. I am thinking I could keep my prodrive back box and get the rest of the sections.

Could I therefore built a full decent exhaust from the prodrive sections.

Are all the sports cats the same? I don't understand this 200 and 100 cell stuff?

WRX 2312

Been reading this post with some interest... I am still a 'rookie' with in depth information but I will share what I do know...I am also intending on fitting a VF turbo (not decided on which yet) plus 550cc pink injectors. I currently have an Afterburner Vortex catback which is quite good to be honest, not overly loud and can only be mildly heard in the car but has that authentic deep subaru growl with the occasional pop/bang.

On another forum I was told an STI up pipe, prodrive down pipe and decat centre would be an ideal setup along with what I currently have for power/daily drivability. I am only aiming for around 320bhp, if I can hit that or near to then I will stop at that point.

I have pieced my parts together one by one and have got some good deals on here (as an example, scoobyworld advertises the sports cat down pipe for £350, I paid £115 from a nice fella on here and it included the centre decat...OK not brand new but a hell of a saving) highly recommend Matt at MB developments for an STI up pipe, the one I bought is in great condition. I am using my phone so I can't see your location but if you are, by chance, near the East Anglia area I'm more than happy to let you hear what mine is like

WRX 2312

Apologies, I skipped over the 'Somerset' part...ignore the come and listen comment above lol