you could always mount an exhaust in the other hole that isn't attached. just have it there for looks. it would be kinda cheesy, but only you would know unless someone goes snooping.

 

ya personally i dont liek sual on a civic i like the single exhaust coming out at an angle, but it does sound good for a dual

 

it'd be overly obvious that only one exhaust works, because when the engine is still not warmed up, smog will only come out of one of the 2 exhausts lol

 

or if you live in a cold place where you see stuff coming out this looks REALLy weird.

 

if you do duals use 1.25" piping from the y split to the mufflers. youll still maintain velocity

 

^^ wow thats really small

 

^ yeah, but you have to remember that it's two pipes, not one. I'd say maybe 1.5" tubing if someone wants duals and plans to do some pretty decent mods to the car, but absolutely no bigger than 2". Actually, I think 1.75" would probably be pushing it. Remember, two 1.5" tubes would be approximately the same as 3" (I'd assume)

 

^ I wouldnt do 1.5" I said 1.25" because when you add it up it becomes 2.50" which is over the ideal size for a single exhaust on a honda civic.

 

if you do go dual, i would say 1.25" for the split, just try and find a dual outlet muffler with a single inlet, that way when you run it out back, you won't have crappy and cheap looking mufflers sticking out (just try and make the exhaust setup look like an s2000 or mustang) and get polished tips. that's what i would do if it were up to me.

 

i just thought i would throw an idea out there. i know how it sounded.