matty094

Hi I've an 04 sti with a prodrive back box and I'm looking to decat the rest, looking at exhaust diagrams and under the car it looks like I have a downpipe , a mid pipe then the centre section , bit of a stupid question but does this mean I need to buy decat down pipe , mid pipe and centre section are can I get away with a decat downpipe or sports cat downpipe stright to the centre section , going to fit it myself but not having done this before this "mid pipe" with the centre cat confuses me !! Any help greatly appreciated !

bugeyejohn

iTrader: (11)

You just need to replace the two cats that are below the turbo which most people just call the downpipe. Although on a newage the downpipe is in two pieces which would account for the second one being called a mid pipe. The centre section is just a resonated section so it doesn't need a decat.

matty094

Cheers buddy you've just stopped me scratching my head !! Sports cats any good ??

Fonzey

iTrader: (5)

I made 315bhp with the prodrive sports cat, and 318bhp with a decat pipe in it's place - both setups involved no mid-pipe cat.

The car sounds better without the sports cat in place, but not too loud (I've still got the prodrive backbox). I'm sorted for MOTs, but if it was a hassle - the prodrive sports cat is easily substantial.

matty094

Not big difference there like , cbf with changing for mot , prob will change the centre section at some stage as it's guna look pretty shabby beside a nice new downpipe , following the decat I'm going to change fuel pump and get a switchable remap hopefully get around the same bhp as yourself

Fonzey

iTrader: (5)

Yeah in hindsight I probably wouldn't have bothered, as it cost me a remap too...

That said, I suppose decat gives me more headroom at higher levels of tune - so is a bit of future proofing if nothing else!

matty094

True , did you remap stright away after decating ?

Fonzey

iTrader: (5)

Yep, never got driven between having it fitted and mapped.

JTinnovations

iTrader: (2)

Just to put the cat (lol) among the pigeons ...my car was mapped with a decat and gave 495bhp on Vpower and 525bhp with 10% meth. Recently refitted the Milltek sports cat (centre pipe) to pass the MOT and decided I couldn't be @rs€d to remove it so tweaked the map accordingly. Same result on Vpower, but only 515bhp with 15% meth.

Oh dear, I lost 2% of my power...but at least I won't have any hassles at MOT time

Guess I can say that 500bhp is the limit for a Milltek sports cat.

YMMV