2002 bugeye wrx, standard apart from milltek catback and a panel filter. Am wanting to decat prior to getting a remap but searching on here has left me confused as to which pipe to replace (am a bit dumb!) so could someone kindly point me in the right direction? Uppipe, downpipe?
Searching on ebay just made it worse as all the pipes look identical but prices vary massively (£40-250)?

 

I've just gone through all this.......
My mapper says the most restrictive pipe by far is the downpipe - effectively the front section of the exhaust.. the standard cat downpipe restricts outflow a lot.
The uppipe may have a cat on yours (not on my MY06 2.5ltr) but I don't think that matters so much.
I was told to get a 3inch decat downpipe which I did.....
Please note though I bought a milltek centre section and catback but I couldn't get a decat downpipe to go with it so had to send it back for an exchange. As far as I'm aware you need to fit a sportcat downpipe (circa £700) to go with a cat back.
Give Charlie at Millteksport a call - he is very helpful.....

 

Thanks for the response. Could you elaborate on why the decat wouldnt go with it? As the Milltek is a direct bolt-on for the standard downpipe I would assume that a replacement downpipe would match it exactly?

 

I bought the following
MSSUB117 (resonated centre section)
MSSUB115 (sportcat back box)

These are 2.75' and I would fit onto standard system or so I'm told.

Then bought MSSUB129nc (decat downpipe) which is 3' and won't fit onto the 2.75'.

I was told by Charlie they don't do a decat downpipe that will fit onto the sport cat back, only a sport cat downpipe (mssub131)

However the 2.75 system is listed as what is right for the 2ltr car, but even tho it is not listed for the 2.5 it would be ok. The issue was they don't do a decat downpipe that will fit with a catted back system.
There are various systems coded at the following address which I used for reference but there are also other bits not listed - Charlie told me they also do a resonated decat 3' downpipe (mssub133) for example

http://www.roadrunnermotorsport.co.u...ust-subaru.asp


Give Millteksport a call
01332 227280 because they will know what will go on your car as mine is a hawkeye it might be different

 

De cat the up pipe it will make a difference to spool time = more response
find an sti one they dont have a cat in them

 

Point taken about the Milltek system, but surely if I bought from a different company it would be designed to mate to a standard system, so would have the same fitting as a standard downpipe and therefore connect to my Milltek cat-back?

Thanks Pete, the STI up pipe doesnt have the cat or the STI downpipe doesnt?

 

The sti up pipe has no cat and will fit your car, the sti down pipe has a normal cat unless its a ppp then it will have a sport cat as standard

 

The STi up-pipe has no EGT sensor boss and you will have to get both the P0420 (missing cat CEL) and the missing EGT CEL mapped out......just need to tell the mapper

Shaun

 

The STI up-pipe has no cat. All std downpipes are catted.

 

Hi Shaun, My wr1 up pipe has the hole with sensor ? Sorry Shaun my mistake its in the manifiold just before the up pipe so you was right, its been a while since i was under there.

 

Something like this?

http://www.ebay.co.uk/itm/93-06-SUBA...item5d2c51e5fd

 

If I was you I would find a sec hand sti one, some after market types can actually slow down spool time and ive heard all sorts of stories of them cracking blowing etc, speak to harvey on here he is more clued up than me on this subject.

 

I really should have a chat with Harvey as I dont live far from him and have actually met him before on another forum.

Does anyone know much about the construction of the subaru cats? I used to run a mk5 Escort and on there it was simply a case of pushing a broom shank down the pipe to smash the contents of the cat and let it all fall out

 

how about something like this tony?
http://www.ebay.co.uk/itm/SUBARU-IMP...ht_2481wt_1199

 

I looked at that but the outlet is 3" which apparently is larger than standard?

 

this looks more promising 3" bore with 2.5" end onit to connect to centre.
http://www.ebay.co.uk/itm/SUBARU-IMP...ht_2359wt_1199

 

Right, am as confused as I was before really. Am going to get a downpipe but I dont understand why a standard fit decat downpipe wont match to the Milltek system. The Milltek system is designed to mate to a standard system, so surely swapping a standard bore cat pipe for a standard bore decat pipe should mean that everything mates up nicely?

 

Have a look here mate:
http://www.scoobyworld.co.uk/catalog...hp?cPath=24_53

 

When people mention decats for mapping it's normally the downpipe that is talked about being replaced as that is the most restrictive one.

When you say you've got a cat back milltek system is that just the centre section and back box or have you replaced the 2nd cat for a straight through pipe aswell?

Have you thought about getting a milltek sportscat instead of a decat. You wouldn't lose that much horsepower over a decat and wouldn't have to worry about your car passing it's MOT.

 

There's quite a good picture that some members have of the exhaust layout on the newages showing the different parts. I'm sure someone could post it up as it's easier looking at it than trying to explain lol

 

Pic to explain:

http://www.scoobyworld.co.uk/new_age...ust_system.jpg

 

Thanks for all that, much clearer. I have the non-resonated cat back system, which comprises of a back box and one centre section.

My main question is why do the downpipes that are available come with a variety of bores (2.5", 2.75", 3") when they all claim to be standard size? Surely the flanges match up no matter the bore of the pipe?

 

No problem, I remember being as confused as you when I 1st started looking at changing bits.

Some downpipes and pipework come in true 3'', which is 3'' diameter pipework and flanges the same size, so that you arnt restricting the airflow at the joints.

Other 3'' systems can have 3'' diameter pipe but reduce down to a smaller flange size.

One option for you could be to get a prodrive 2nd decat pipe and sportscat. Both are the standard size pipework and should fit onto your milltek system.

Theres a sportscat in the sales section going for £150 and the 2nd decat pipes can be had for £50.

 

Agree with above get a prodrive sportcat and 2nd decat pipe and a sti uppipe don't forget new gaskets and a lambda socket then fit these and get it mapped asap fit a walbro fuel pump and Ngk 7 plugs as well. If you want decat then a Haywood and Scott one will mate to your milltek system no worries

 

Thanks for the advice guys. So do the 3", 2.75" and 2.5" pipes have different sized flanges? I ask as it is easy to get hold of a 2.5" decat so am thinking that if it had the same flange size as the 2.75" Milltek then I could just get that?

I still cant get my head around the fact that the Milltek mates to the standard downpipe so why wont it mate to decat pipes that are a straight swap for the standard pipe?