Exhaust diameter

My classic is fitted with a cat-back Apexi system. The pipe is a little over 3" & the outlet is 4.5". It sounds great but on a long trip it gives me a pain in my ears!!!

I want to make up a restrictor to drop into the tailpipe to reduce the noise a bit for long journies but I don’t want to overly restrict exhaust flow.

What is the tailpipe diameter on a standard classic backbox?

2" at a guess!!!!

The sti box i have on at the moment is just a little under 3 and a half inches
can post up a pic if you need

Shur throw up a pic if you have one handy!

I made up a 3" diameter disc for it but it didnt do much for the noise level - my ears were ringing after an hours driving!!

Im going to to try a 2.5" disc next & hopefully the bit of back pressure will help reduce the noise. I dont want to over-restrict the gas flow or it might cause problems...

When you made up the disc did you weld a pipe to it to go into the backbox???
if not your wasting your time, why not just buy this one >>>>> http://www.scoobyworld.co.uk/catalog/product_info.php?cPath=24_52&products_id=1294

The baffle in your link works very well but they can rattle pretty badly if they dont fit the exhaust perfectly. The perforated pipe on it is really the only way to reduce the noise & maintain gas flow.

I might get one of those baffles from your link & weld the perforated pipe from it onto the 3" disc that I made up, that would be the ideal mix of silencing & good gas flow but without the rattles.

In the meantime I have have fitted a 70mm ID disc & it took the hard edge off the exhaust note, so I wouldnt exactly say it was a waste of time. I have 3 studs holding it in place against the ID of the tailpipe & it doesnt rattle at all