Does an exhaust’s spec’d diameter typically refer to the OD or the ID? I’m sure there are exceptions to every rule, but in general…
The od is not really important(obviously) but, some companies list the od so it seems larger.
I think most people assume the id is listed because it more matters.
Edit: I actually called a place and they admitted on the phone that their exhaust is not really 3". They told me it was 2.750 with a .062 wall so it was 3" od.:smash2: Nice math skills.
schedule pipe is neither. But the ID is closer to the nominal size.