Hi all first post, did a bit of searching but couldn’t see answer.

So I bought a Toyo exhaust for my standard 135bhp Abarth but it’s loud AF and tbh I was toying with getting rid however someone has suggested getting a silencer welded into the system to quieten it down which seems a much more cost effective option than me buying a whole new exhaust.

My question is what size silencer would I need in terms of making it fit the existing exhaust pipe? I.e what is the standard diameter? Also I have seen one that is around 14 inches long would that be too long?

Sorry if questions seem stupid I have no idea about cars really so just after some advice 

I have a 2015 U.S. Fiat 500 Abarth.  I replaced the exhaust with a high flow cat and a 2.5" diameter exhaust system, expecting it to not be too loud.  However, I was astounded at how loud it was, considering the stock exhaust doesn't have any kind of muffler or resonator.

Where I live in the U.S. the cops don't mind loud exhausts, but my Fiat was unreasonable and since I like to speed a little bit, I thought I had better tone things down before I got arrested.

The simple answer was to buy a 14" straight through resonator and weld it into the exhaust pipe more or less below the driver seat.  The reduction in noise was impressive and now I have a pleasant exhaust note not too far from what the stock car was like with it's restrictive cat and small diameter exhaust tubing.   The fix was cheap, easy, and resulted in just the kind of noise reduction I wanted.

Why not measure your mid-pipe diameter and buy an appropriate straight-through resonator and either weld it in yourself or take it to a muffler shop and have some else do it?