Have tried searching but getting conflicting info on the exhaust setup for a 2003 WRX STi with PPP.

As far as i understand it my car will have the PPP Sports Cat downpipe, resonated PPP centre section and PPP back box? along with the PPP ECU remap.

Now if thats true ive also read that there is a 2nd cat on the up-pipe? which if there is, i assume goes from the downpipe to the turbo? But i have also read that the STi doesnt have this second cat

The idea being that to limit the low down lag, you get a up-pipe de-cat, non-resonated centre pipe and a remap.

Is this the case? or does it only have the 1 cat in the downpipe which is removed with the PPP sports cat?

Not only this but if it does have the 2nd cat, and i replace it leaving only the ppp sports one, will it fail on MOT?!?

 

STi has 2 cats but the 2nd cat is in the rear centre pipe between the centre and DPipe. With the PPP it is removed. No cat in the STi uppipe.

 

cheers for info

Subaru Impreza Exhaust decat downpipe, centre section, sports cat. :

I was working from this diagram as a guide

So the 2nd cat is in the "cat pipe" which is replaced with PPP. Does this mean the 1st cat is in the downpipe then?

 

Yes, you have one cat in the downpipe. As a matter of interest, the resonated section is part of the original system and is very slightly smaller diameter than the PPP parts.
JohnD

 

Interesting, so this is why people recommend replacing the centre section and getting remap together?

Just wondering has anyone else replace the std downpipe with a sports cat on a PPP car - does it pass MOT?

 

I am running the exhaust system I had on my 53WRX PPP on my MY06 STI.

Consists of H&S Sports Cat DP, rear decat, H&S straight through centre pipe, Blitz Nur Spec S BB. I fully expect to pass the MOT with just the sports cat

 

thats good news

 

The main change when replacing the resonated pipe with a straight section is to get a bit more noise! Power gains are very small.

Just to clarify - The PPP downpipe has a sports cat. There is little or no point in changing this.

JohnD

 

So does the PPP replace the 2 cats then or just the downpipe one?

As from what i can gather the system has two, 1 in the downpipe and 1 in the cat-pipe after the downpipe

 

The original system consists of: Downpipe with cat.
2nd cat section.
resonated section.
backbox.

The STi PPP system consists of: Downpipe with sports cat.
cat replacement section.
original resonated section.
Backbox.

So, the original system had 2 cats. The PPP has one (sports) cat.

JohnD

 

Excellent, i get it now