Soo want to go single, no Cat with a N/A S5 13b.
But dont know what size to use for tubes and if the size matters in dual or single?
plan to go TII later on soo is single better or worst in power?

sorry if its ben coverd before, and if it has and i missed it on search post a link to the topic.

TY in advance

Edit to add why i need the help in a better way.
i have 2 extra mufflers but 1 is a old Hayame 3inch inlet and i have a HKS hi power 2.5 inlet. dont know witch to use on what size piping.

 

A 2.5" single is as big as you'll want to go on an NA, and as small as you'll want to go on a mild TII. It will be light, low-restriction (for the NA), and LOUD!! I have seen just one single that wasn't obnoxiously loud, which was an Apex'i WSII owned by another forum member.
I ran a Mindtrain header, Bonez high-flow cat and Corksport single for about 2 weeks. I measured 124db at 10 feet! Inside the car, it was loud enough to make me nauseous. BTW, the cat takes some of the barfk out of the exhaust, so without it, you would be even louder...

 

Inside diameter of 1.75" +/-0.05" for either single or dual.

The proper exhaust system for a turbocharged engine is totally different than a non-turbo engine. Also, if you want to go TII later on, then it is better to just sell your car and buy a TII. Single is slightly better for power, and slightly lighter, but much louder.

 

ty for the reply's

as for the TII part already have everything planed out for it (exept) exhaust setup but tnks again its been cover. As for noise i dont care , i know ppl nextdoor will when i go to work @ 5 am XD but F it! hehehe