Trem

iTrader: (3)

I have a 1994 STi, I have recently got a decat Magnex downpipe and left the rest of the system standard. Is there any other power restricting areas on the exhaust? I was told that they only have 1 cat on them so I thought I would just get the downpipe fitted......like I did. Just wondered if anymore power can be gained by replacing the whole system.

Marky-San

This is a difficult one to answer.....I'll explain

Indeed you can replace the centre section (it has a CAT also) and it does makes an increased noise difference and helps the gas flow a little quicker. The decat downpipe is a the biggest difference you can make, but getting the rest done is a good option. Seemingly the standard STI backbox is meant to be pretty good. Just depends what sound you want from your car. There is a full range of options available to you. Just remember the MOT time stuff....

If its any use Trem, I've got a spanking new Magnex decat unresonated centre section which was supposed to go on my car, but I've got a 3" system and the pipe is slightly smaller. If your interested mail me (thats the difficult bit - trying to give sincere impartial advice )


PS - meant to say, not forgotten your mail - will send you an answer on it all tomorrow.

Trem

iTrader: (3)

Thanks for that Mark, will mail ya later today.

D8UGF

Marky,

Dont want to contradict but I thought the middle section on the STi system is only a resonator, theres no cat in my middle section only the downpipe (and its an STi pipe).

Markys right tho, put a scoobysport downpipe on mine and it sounds more "throaty" but the tailpipe is not noisy so its more engine noise than exhaust noise

Dougie

Marky-San

Hello Doug - you could be right - I'm just going on info from other posts about MOT's, and not passing with the decat dp. However there seems to be some talk that folks have just passed with the centre one intact.

To me it looks like a resonator - can't see point of 2 restrictive cats on an exhaust. But to confuse me its advertised as a 'cat-replacement pipe'.

So after all that we're none the wiser

D8UGF

Mmmmmmm Not sure then buddy, but thought all the confusion about the Mot situation was cleared a little as most of these cars arent on the mot database so they should only get a cat idle test not the full shabang(sp)

Was also told that if they cant read the engine codes properly due to rust or (ahem)letters missing/unlegible then it was the same story?

Heres hopin cos the mots due shortly

Dougie

TBMeech

Bit of a grey area this one.....

My original exhaust from my old STI 5 only had a cat in the d/p and the centre section was resonated with no cats.

Some STI's have cats in both the d/p and the centre section, it could be the fact that a aftermarket exhaust was fitted in Japan and car was returned to std with a wrx centre before importing to the UK.

The std STI backbox is very restrictive, you only need to look at the way the car boosts with a de-cat d/p and std centre and bb, my old STI5 used to hit 0.95 (on my defis) with Scoobysport 2.5" d/p and std Resonated centre and STI bb, it then hit 1.15bar of boost with Scoobysport 2.5" Centre and BB.

It all boils down to noise issues as well, if you have a de-cat d/p and centre and the std STI bb you won't have a noisy car at all, so good for everyday driving, but if you like noise too then changing the bb will make a load of difference, plus an aftermarket bb wont be full of baffles so therefore less restrictive over std.

Trem

iTrader: (3)

So for more power do you recommend I swap the centre and backbox? Got a chance of a cheap Magnex centre so I'm taking it I should buy it. Kinda worried about emissions come MOT time though.

TBMeech

Depends 'how' much power / noise you want.

Personally i'd only go for decent spec jap exhausts but they do make a lot of noise, cost a lot and will deffo fail the mot.

You could always put a catted centre section in come mot time, its only a 15 min job on axle stands.

Trem

iTrader: (3)

Its pretty loud at the minute to be honest, I certainly wouldn't say its quiet. The Magnex exhausts always seem quiet, although not many people on here seem to use them. God its so fooking complicated

911

Too much information is a real pain!

I have an STi V3, 1997.
It has a full Magnex system, runs well, reasonably quiet, no neibough complaints, fully de-cat. MoT man does not check emmissions.
Fitted the STi centre/box for last MoT incase he did check it . Performance was much worse, mainly due to dulled engine pick-up, more feeling of turbo lag and such like.

If you want to feel/hear improvement, fit the whole system from one manufacturer.

Graham.