STi exhaust mod

[Philip Procter]

I understand that the stock up pipes on the US spec STi are packed
with palladium catalyst. There are several manufacturers of catalyst
free pipes, which claim to reduce throttle lag and midrange hp.

Question: Is it possible to unbolt the stock pipe, remove the catalyst
and get the same performance gain?

Would the chip need to be reflashed?

Thanks

Philip

 

[WRXtreme]

I understand that the stock up pipes on the US spec STi are packed
with palladium catalyst. There are several manufacturers of catalyst
free pipes, which claim to reduce throttle lag and midrange hp.

Question: Is it possible to unbolt the stock pipe, remove the catalyst
and get the same performance gain?

Yes it can be gutted, but you MIGHT not get the same performance gain.
Reason being that most aftermarket exhaust components are 3" or 3.5" and the
factory is 2.5". If all you are doing is pulling the cats I would suspect
the performance would be similar to aftermarket by gutting them. If you
plan on full turboback exhaust, I'd look into aftermarket pieces personally.
The one thing I'm not sure about is if the STi uses a 3 cat system like the
WRX does. If so, you might want to look into just replacing the up-pipe &
downpipe w/ a cat-less APS unit (really any up & down pipe will be fine, APS
is my personal favorite for subaru parts...even though I use a Perrin
up-pipe and PDE downpipe which I bought before I knew about APS), it will
cost you, but it will be worth it IMHO.

Would the chip need to be reflashed?

No. BUT you might want an ECU reflash (EcuTec) or go w/ some sort of
aftermarket engine management (UTEC, Element Tuning ECU, Vishnu, Etc...) to
extract the most performance out of the vehicle. Also, you may get a check
engine light if you remove/gut the cats as well. There is a CEL eliminator
you can buy OR you can search www.nasioc.com as I believe there is a DIY mod
to eliminate the CEL as well.

Thanks

No problem

Philip

Chuck

 

[Patrick Fisher]

I understand that the stock up pipes on the US spec STi are packed
with palladium catalyst. There are several manufacturers of catalyst
free pipes, which claim to reduce throttle lag and midrange hp.

Question: Is it possible to unbolt the stock pipe, remove the catalyst
and get the same performance gain?

Would the chip need to be reflashed?

The STi does not have a catted up-pipe - only the WRX does. The STi up-pipe
is cat-free, so a lot of WRX guys buy them (from STi owners who upgrade
their headers and uppipe), to avoid having to try to gut theirs.

 

[David Edgley]

Does the STi up pipe fit without any modifications? The up and down pipes
are on my list of desired mods to my currently stock silver 04 WRX.

David

 

[brentlz]

Fitment is fine: "factory fit" one might say. The STi up-pipe is a
much better choice IMO than most aftermarket up-pipes due to the
inclusion of heat shielding and a flex joint.

The only mod you'll need to do is to add a 2.2k resister in place of the
WRX EGT sensor as the STi up-pipe has no EGT bung to mount it...the EGT
sensor is no longer needed as it is only there to protect the (now
nonexistant) cat.

Brent.