I got myself really confused about exhaust sections and could do with some friendly advice.

I have a MY01 WRX and as far as I know there are 4 sections from the turbo back - 1/. Downpipe (with Cat) 2/. Cat Pipe 3/. Long center 4/. Back box. - Is this correct??

I have a Ninja back box and STi panel filter at present and have been looking to get a few more bhp from my scoob so have decided to change more of the exhaust, but I don't want to fully de-cat it as I don't want the hassle of swapping sections for the MOT (or failing a spot emissions check), also I've got a limited budget (about £275)

My question is this, which will give me the greater increase in torque/bhp - changing just the downpipe (leaving the original cat pipe & center) or leaving the downpipe & changing the 2 center sections?

Any comments/shared experience would be appreciated.

DJ

 

The best improvement in performance terms is to remove the downpipe cat, this is the most efficient cat for emmisions, but the most restrictive, not sure on MY01, I think it has 3 sections & 2 cats

 

Thanks Andy - I suspected the downpipe might be the one to go for, but i'm still confused whether the MY01 is 3 or 4 sections? Any one?

DJ.

 

Just to add, its the most difficult section to change but u should get through a mot with a centre if you get it nice & hot, you can if you choose to go full decat defer a roadside test for 7 dayswhich would allow you to change your centre back to original.

 

Thanks again Andy - I didn't know you could defer a roadside check.

 

Ive just checked TSL's site, they list MY01 as 4 piece D/P (cat), centre cat, resonator, backbox, yes you can ask for a roadside to be deferred, especially if you know your cars running like a bag of spanners

 

Cheers - looks like it's the downpipe then

DJ.

 

I have an MY03, I think its the same pipe as your MY01 ?
I was told by TSL, that fitting a de-cat down pipe will put an engine check light on the dash ! & re-map would sort it out, but I didn't realy want to shell out on a Re-map just yet.

 

Now i'm unsure again. I can't aford a re-map at the moment - I asked scoobyclinic which would give best improvement for the money and they said downpipe, but never mentioned anything about needing a re-map at the same time or that the CEL would come on.

So come on chaps - how about a little more advice please?

DJ.

 

You can get a CEL fix!
It's a little box of tricks that fools the sensor in to thinking the cat is still in place It shouldn't cause any side effects.
Speak to TSL, Scoobyclinic etc about it. They should know were to get it.

 

...Agree or solder a 10 MOhm resistor in your blue wire on rear O2 sensor and you won't have problem, I already have 6000 "decated" kms with the resistor and no CELs so far!
JIIM

 

Thanks - I'll ask about the price.
DJ

 

I was at PowerStation last week. They do a full Miltex system - which includes a front CAT - 100 cell so apparently much better flow, and as it has a CAT in, no issues of emmissions for MOT, ECU light etc.

Full system was about 750 + VAT. I heard one on an STI they had - also pretty quiet.

They said it makes significant improvement. Guess you can trust them - they helped with the Type 25 - see review in Evo mag this month.

 

dj wolud you be interested in a powerflow cat n sti back box £250 ono of a sti v7