I'm considering de-cating my 01 WRX PPP. I understand that the bug-eyes have 3 cats - 1 in the downpipe, 1 in the middle section & 1 in the back section.

Does the 1 in the back section get taken out when the PPP is fitted???

If not would there be a noticable difference by removing the middle and end cats - while leaving the one in the downpipe in place??. I'm still under warranty so don't want to do anything that will be too hard to put back to normal

Thanks

 

u do have 3 cats-they r one in up pipe before turbo-one in downpipe and one in ur centre section

 

The only one you can easily remove is the centre section one, the downpipe's a bit awkward if you need to put it back in a hurry, as is the one in the up-pipe!

Ron.

 

cheers Ron - it the centre worth doing on its own???

What is the ideal combo???

 

bttt

 

Centre will give a touch more noise and you may notice a slight performance improvement. Nothing major!
Do the other two and you will gain good horsepower

 

The ideal combo is all 3
I can't remember exactly what's in the PPP, but doesn't it already include a partial de-cat & sports cat in the DP? Or is this the MY03 PPP?
Anyway, if the PPP is simply a piggy-back ECU...
The one in the up-pipe is a compete bugger to change, but can offer quite an improvement I believe (I have a 'classic' & far fewer cats in the first place ). The DP also offers a large improvement, is much easier to change (although still not much fun) and I think is the only one that needs to be left in. The centre doesn't do very much at all, and won't make a difference to anything until the other two have gone.
If you want 'performance & flow' it's quite possible to get a high-flow cat: not as good as no cat, but a significant improvement over the standard one. This would be in the downpipe. The up-pipe one I think can go, but then you'd probably need to do something about overboost (the ECU doesn't necessarily cope particularly well with the faster spool-up given by the missing up-pipe cat). Easily done with a Dawes, best set in parallel (to act as a 'pressure release' system to stop overboost but still allow the ECU to remain in control of the boost overall.
I think piddling about with anything is going to void your warranty, BTW

 

Cheers nom!

 

Cheers nom!

 

Just a piccy to show what is what (no up pipe though)



and another with no downpipe (nicked from Buzz)

 

pippyrips

Your WRX PPP only has two cats, downpipe & uppipe. Dealer removes the third cat as part of the PPP. The popular choice seams to replace up-pipe and downpipe at the same time. You will also need a CEL fix which is easy enough. Any overboost could be sorted with a restrictor change, again dealer has already installed one of these in your PPP. Have seen full decat my01 PPP cars make between 275-285bhp on the rollers, so does give a worthwile improvement.
Nigel
UK300 PPP

 

top man nigel,

Have you done anything similiar to yours???

 

I change my exhaust from the turbo back.

I have been told that this will not effect my warrenty (but changing the cat in the up pipe will).
Also by doing this the car will still pass an mot test, and there was no need for the cel fix.

I will change the up pipe for the greater power when the warrenty runs out.


Just an idea....Lee

 

notice any difference??? mine is a uk300 too