The centre CAT on my '94 WRX import has been removed already, would like to remove the other one (Downpipe).

Just wondering, what would the difference in sound be? At the moment its a deep, soft rumble they make, I've heard 30bhp gains, but what really would I be looking at.

Also, I'm gonna get my local garage to fit the de cat downpipe for me, how long would that take, thinking about labour, and the fact I'd have to put the standard CAT back on for MOT/EMMISIONS tests.

Would removing the last CAT left be worth my while?

 

removing the cat from the downpipe would have more benefit than the cat from the centre pipe. It would allow your turbo and waste gate to breathe better so therefore better spool. It will be a little louder as well but that depends on the size and shape of your downpipe.

 

You won't pass the MOT without the DP cat and you won't really want to be forking out for this to be changed every MOT as it's a considerably more difficult task than chaging the centre section (between approximately £50-100 to change once and you'd need it done twice). The obvious solution is to get a DP sports cat, better flow, but MOT friendly. H&S have a group buy on at the moment. Scoobyworld are also doing a special on the Ninja sports cat DP.

Otherwise see if you can find a friendly garage that'll swap your centre pipe for one with a std cat prior to emissions test and then the decat on afterwards (much smaller job than the DP).

Decat DP means the sound wil be a little deper and you'll hear more of the turbo spooling up, but nothing drastic. Power fains vary from car to car, you'll need a remap to get the most from it. If you dont already have one, I'd also seriously consider getting a knock link too.

NS04

 

how do you re-map, and whats a knocklink?

 

You don't, a professional does it for you. Although since yours is a 94 Scoob, you'd most likely need an aftermarket performance ECU and appropriate mapping from someone like www.andyforrestperformance.com

A Knocklink is a device that monitors your engine for detonation, commonly caused in imports by the UK's lower grade fuel and exacerbated in cars with mods that might make the car run leaner, like a decat.

What fuel do you run the car on and are you using Octane Booster?

Ns04

 

I'm running optimax 98 rons with octane booster.