wrxmania

Hello all,

I currently have a JAP custom backbox on my WRX which is great. My mate who built it for me is going to wok on the exhaust in a weeks time and I have two real options:

(1) Upgrade the exhaust pipework to 3 inch, remove the small cat and silencer, and fit my backbox at an angle (exit) to make the pipe work run straight. In essence, Manifold cat, 3 inch pipework through to the angled-exit back box.

OR

(2) Angled exit backbox to remove bend in pipe, upgrade the pipework to 3" and remove the silencer leaving both cats in place.

What is the best?

Is there any power benefit in removing the small cat? What will Subaru think of this in terms of warranty. They do not give a stuff about the back box being changed and I know the dealer's own car had the cats removed.

Anyone done this - leaving the main cat and just removing the small one on an 2003 WRX? Any issues with running?

Thanks for all your answers in advance.

Brian.

wrxmania

Anyone?

wrxmania

? anyone

wrxmania

Come on someone?!?

jas03WRX

Brian....

A small gain will be made but nothing to right home about....

Warranty will always be an issue once CATs have been disturbed. All depends on the dealer you use. The only REAL power gain is made by ditching the original downpipe for either a decat or SportsCAT (see Millteks website). There is also another small cat in the Up-pipe, it is advisable to change this at the same time as to replace you have to remove the down pipe. This will totally tranform the drivability of your car.

wrxmania

Thanks Jas03WRX - anyone else?

wrxmania

? Anyone else ?

wrxmania

This is like a ghost town in here?

wrxmania

Someone else must reply eventually.

New To Scoob

Brian.
Firstly you will probably lose your warranty removing the center cat, will also probably get a CEL warning light IIRC due to the sensor in that part of the exhaust getting an incorrect signal/or it being removed, you can get a HKS thingy to fix the CEL light. You probably will get some power increase dunno how much though, but you might get some overboost probs due to the reduced back pressure (this might only apply to the D/P though so not too sure). As for the flow path - as straight as possible = less resistance and less back pressure. Also IIRC there is no CAT in the up-pipe on the '03 cars.

John.

Butty

iTrader: (2)

There is a cat in the WRX up-pipe, but not in the STi up-pipe.
The removal of the third cat (small section after downpipe) is part of the PPP, so I guess it removes some back pressure . As to adding power, it may do as long as the cat removal doesn't confues the ECU too much.
Its a final polishing cat to get within the emission stds for a new car.
I would ask your dealer about its removal and voiding the warranty. The backbox isn't a problem with warranties.

I don't understand the need to make the mid section complicated? Why not just copy the Subaru shape but in 3"?

Nick

wrxmania

AT last some answers.

Thanks John and Nick!!

wrxmania

Anyone else?

hugo

Brian,
Your exhaust dillema is causing you to be unable to sleep given the time of last post! Why not get her PPP'd and keep the big back box, the dealer is already OK with it. The extra pennies will give you peace of mind. You will be rid of a cat, have a remap that will deal with its effect, have a few extra horses which are much more driveable, and still have a great sounding piece of pipework. Just an idea
H.

wrxmania

Cheers Hugo,

I was just in from work hence the late post. I think I have sorted it out now.

hugo

What are you going to do?