03 JDM STI exhaust question
02 November 2011, 11:00 PM
#1
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03 JDM STI exhaust question
Hi all. I have a jdm sti my03 with an afterburner centre section and back box. If im going decat then do I need just one down pipe or does it come in two sections or is it just one like on a classic. I've seen diagrams which show two cats: one in the down pipe and one in the mid pipe. Is this still the same in my jdm?
Thanks.
Thanks.
02 November 2011, 11:17 PM
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There's two mate. there's the downpipe and then the cat pipe. They both have cat's in them. I used to have a fully decated afterburner system.
It's a nice loud system
http://www.scoobyworld.co.uk/catalog...roducts_id=447
http://www.scoobyworld.co.uk/catalog...roducts_id=179
I've got the cat pipe decated left for sale mate. PM me if interested, I'll do it half price.
It's a nice loud system
http://www.scoobyworld.co.uk/catalog...roducts_id=447
http://www.scoobyworld.co.uk/catalog...roducts_id=179
I've got the cat pipe decated left for sale mate. PM me if interested, I'll do it half price.
02 November 2011, 11:20 PM
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There's two mate, I've still got my old subaru ones in the garage and they've defo got cats in them. I also changed my pipes in stages and both times gain a fair bit of power etc
Have a look at the scoobyworld links. Afterburner is their own brand
Have a look at the scoobyworld links. Afterburner is their own brand
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03 November 2011, 06:30 AM
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Thanks guys. next question- when I go fully decat I'm pretty sure that It will be too loud (motorways etc) if that is the case then can I swap out the back box for something quieter, say a prodrive one, without losing power?
03 November 2011, 07:47 AM
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When I had a fully decated afterburner system it was really loud. I never really went over 70 cruising just due to noise. I was at 105db at 5k revs. I had an sti backbox spare that I was gonna swap over for track days.
It's a very loud system. I loved it, sounded great but was a bit too much if I was gonna do a lot of motorway miles. I only changed to a milltek because of track noise restrictions
It's a very loud system. I loved it, sounded great but was a bit too much if I was gonna do a lot of motorway miles. I only changed to a milltek because of track noise restrictions
03 November 2011, 09:21 AM
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When I had a fully decated afterburner system it was really loud. I never really went over 70 cruising just due to noise. I was at 105db at 5k revs. I had an sti backbox spare that I was gonna swap over for track days.
It's a very loud system. I loved it, sounded great but was a bit too much if I was gonna do a lot of motorway miles. I only changed to a milltek because of track noise restrictions
It's a very loud system. I loved it, sounded great but was a bit too much if I was gonna do a lot of motorway miles. I only changed to a milltek because of track noise restrictions
Tony, slightly confused. Is the after burner centre section longer meaning that I need a classic fitment down pipe?
Thanks guys
03 November 2011, 09:48 AM
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IMHO I would if you're gonna do motorway miles, it's too loud. You can just swap the back box, no problem. My original plan was to keep the afterburner system and just change the backbox for track days.
You could go full afterburner decate system and use a STI or prodrive backbox to bring the noise right down
You could go full afterburner decate system and use a STI or prodrive backbox to bring the noise right down
06 November 2011, 08:10 PM
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Ok thanks. I want a little more noise than standard so was thinking ninja2 or miltek backbox after a decat. Still too loud for motorway miles?
I had a look under the car and it seems that I have a down pipe and then a short pipe before the central afterburner section. Do they both have cats in on a JDM?
I had a look under the car and it seems that I have a down pipe and then a short pipe before the central afterburner section. Do they both have cats in on a JDM?
06 November 2011, 08:20 PM
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You will need to remap the car if you go decat, if you go sports cat you will also need to remap the car, so its a no win situation, its best just leaving the standard cat on, saves lots of hassle come mot time 
Tony
Tony
06 November 2011, 08:57 PM
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I'm pretty set on the remap anyway so the decat seems logical. I'm not worried about the MOT. I just need to know if there are 2 cats or just one in the downpipe?
What do other people call the other pipe- is it a mid pipe?
Just want to say thanks, you've ended up answering a lot of my JDM questions so far and now I'm a very happy owner of a great JDM STI 03. its such a different car to my uk classic I cant quite believe it. Grinning from ear to ear.
06 November 2011, 10:18 PM
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You only have one in the down pipe AFAIK. I also have a jdm sti and love the extras like the rear wiper and folding mirrors. If your changing the exhaust you might as well swap the whole lot for a 3" system anyway, this will future proof you for inevitable "Im going for 400+" lol
07 November 2011, 12:07 AM
#16
My car was running 420bhp / 406ft lbs with the cat in the down pipes, no restriction caused, to quieten it down we cut the tail section 3" pipe off (108db @ 4,800rpm > track days where a 
) and installed a 2.5" tail section, now running at 102db & no loss of power at all 
Keep the cat & concentrate on the tail section to take care of the noise
) and installed a 2.5" tail section, now running at 102db & no loss of power at all Keep the cat & concentrate on the tail section to take care of the noise
07 November 2011, 10:47 AM
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Alright mate!
The factory downpipe is two sections with one or two cats in it but a decat downpipe will be one section and replace both bits so it doesn't matter how many cats you had, you will be left catless.
Oh and the backbox has hardly any effect on power
The factory downpipe is two sections with one or two cats in it but a decat downpipe will be one section and replace both bits so it doesn't matter how many cats you had, you will be left catless.
Oh and the backbox has hardly any effect on power
07 November 2011, 11:36 AM
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My car was running 420bhp / 406ft lbs with the cat in the down pipes, no restriction caused, to quieten it down we cut the tail section 3" pipe off (108db @ 4,800rpm > track days where a ) and installed a 2.5" tail section, now running at 102db & no loss of power at all
Keep the cat & concentrate on the tail section to take care of the noise
) and installed a 2.5" tail section, now running at 102db & no loss of power at all Keep the cat & concentrate on the tail section to take care of the noise
I'm afraid that I don't understand what you mean by no restriction being caused. Almost everything I have read (not taking it all as gospel) and looked at suggest that the cats will cause a restriction due to the exhaust gas not being able to flow as easily. I've no doubt that you have a sweet ride (420bhp / 406ft lbs) but for me I would gain more power by removing the cats and having a remap no?
What's the retail on a second hand one then. Should I look afterburner so that it fits with my centre pipe?
07 November 2011, 11:59 AM
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Your centre section is a probably 2.5" so any bellmouth to 2.5" down pipe will do the job.
I got a Japspeed one on ebay for £60 new.
Might as well get some new gaskets while your at it.
I got a Japspeed one on ebay for £60 new.
Might as well get some new gaskets while your at it.
07 November 2011, 01:20 PM
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Sorry i meant i got mine off ebay for £60. I don't have one for sale at the moment but there are shed loads out there.
Oh and you should change your avatar now to an sti
Oh and you should change your avatar now to an sti
Last edited by DonNedly; 07 November 2011 at 01:21 PM.
07 November 2011, 02:05 PM
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didn't think you had one. That's a great price. I'm gonna check out ebay more carefully but they look double the price.
I'll try with the avatar. Hmmm
I'll try with the avatar. Hmmm
07 November 2011, 02:39 PM
#23
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Toffee failed to mention that he has sport cats.... not OE cats which is what you're referring to.
Removing the OE cats on the JDM is a great way to unleash more go go. The choice is simple imo, either remove the OE cat's (decat) or fit a sports cat.
Removing the OE cats on the JDM is a great way to unleash more go go. The choice is simple imo, either remove the OE cat's (decat) or fit a sports cat.
07 November 2011, 03:32 PM
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If you are replacing the whole exhaust why not go 3".
This one on ebay is for 3" but its only on £18 with 4 hours to go:
http://www.ebay.co.uk/itm/GD-SUBARU-...item2c6079c1a4
This one on ebay is for 3" but its only on £18 with 4 hours to go:
http://www.ebay.co.uk/itm/GD-SUBARU-...item2c6079c1a4
07 November 2011, 04:26 PM
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If you are replacing the whole exhaust why not go 3".
This one on ebay is for 3" but its only on £18 with 4 hours to go:
http://www.ebay.co.uk/itm/GD-SUBARU-...item2c6079c1a4
This one on ebay is for 3" but its only on £18 with 4 hours to go:
http://www.ebay.co.uk/itm/GD-SUBARU-...item2c6079c1a4
Tony
07 November 2011, 04:36 PM
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no need for 3 inch. Only if its cheaper but then don't I have to find a 3" back box to match it to or can I get some sort of 2.5 to 3 adapter.
07 November 2011, 10:56 PM
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The dp for a Newage Twinscroll JDM MUST BE a twinscroll dp. The UK ones for the same year are single scroll and the shape of the flange to the turbo is totally different and won't fit.
08 November 2011, 05:59 AM
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Thanks Shaun, needed to know that. Any idea on makes or brands? I'd prefer to pick up a cheaper second hand one if I can but I guess they might be quite rare.