Downpipe

[PalmerWRX]

Good afternoon, how much of a difference noise wise does getting rid of the cat and popping in a new downpipe make. Looking to do this then get a small map done.

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[Rdlangy1]

removing the cat will make a difference to the noise - especially at full chat.

[NL03Scooby]

My 3” de-cat down pipe and 2.75” Milltek (non-resonated) exhaust are too noisy on full chat for the likes of a Brands Hatch track day, despite ‘comfortably’ passing the static test.

Also bare in mind emissions and MOT testing.

[scotty]

Watching with interest as a newbie newage owner

[PalmerWRX]

Mot isn't an issue as brother in law is a tester. Is there any brands which seem to be better than others as the price varies.

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[Banstead Stig]

Originally Posted by scotty

Watching with interest as a newbie newage owner

Your exhaust is based on a Classic Impreza though... assuming you're referring to the Forester...

[Red Baron]

I put a Decat downpipe on mine, still running the centre cat and at the time had a Prodrive back box, definitely made it a little louder as cat acts as a bit of a silencer.

No idea about brands, mines just a second-hand stainless open mouth downpipe, someone mentioned it may be a japspeed one but don't know.

[Neil97rs]

Are there not 2 cats in the system one on the downpipe as well ? If your removing both you will get more noise but depends what system you have as too how loud in total it will be.
Pro drive system will be fairly quiet
Nur spec will be ear bleedingly loud

What cat back do you have on the car now ?

[PalmerWRX]

It's a japspeed cat back. Just would prefer to de cat before mapping.

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[boggissimo]

My car now has a Prodrive sports cat downpipe and a decat up-pipe, as was as the WRX PPP centre and rear sections, and was measured at 82 decibels the other day, at 4-5K revs. Don't notice it being louder than with the standard cat downpipe and catted up-pipe.