I have a 89 Civic with a B16A and was wondering what size exhaust piping shoud I go with?

 

The exhaust size depends on your motor setup. If you are going forced induction, three inch is what you want.

For just the basic bolt ons, since you have a B16 I would reccomomend a 2 3/8 size, but for a nice juicy all motor setup, 2.5 inch piping.

*edit* Dont forget to upgrade your cat to the same size as your piping as well.

 

I believe 2.25'', , unless turbo'd you should go 3''.....