MadUsa1

Hi All, I have a 3" HKS back box that I want to fit to my 2005 STI. The rest of the exhaust is standard so I assume 2.5". Do I need an adaptor to mate the 3" back box to the 2.5" mid pipe or does it bolt right up?

Cheers, Jake

MadUsa1

any help?

RobsyUK

iTrader: (2)

You can buy a reducer. Inthink rcm & h&s do them

Vxr2010

it may just bolt up as it is , give it a go 👍

MadUsa1

Thanks. I have seen the reducers / adaptors, but they are usually listed for the cat / mid-pipe connection so I'm curious if I can get away with it for the back box.

Anyone else have experience with this?

IainMilford

iTrader: (15)

As been said give it a go, exhausts can vary so much so it’s hard to give a definitive answer. If it doesn’t line up then go to a specialist exhaust fabricator who can make up any bits you need or extend your current exhaust, adding a small piece of tube doesn’t cost much

Vxr2010

i’ve bolted it up before going small large and visa versa , you will only know when you bolt it up as it comes down to design and flange type and where the holes are in the flange , i have a two 2.5 inch centre deletes on different cars , one with a 3 inch jdm back box , but due to designs being different it’s a suck it and see 👍 if it’s a no any decent exhaust place can do a coupling , obviously better all one size but it’s not the end of the world to be different