I was told that my exhaust was a full 3" but I measured the ID and it's 2 3/4", is this normal? I thought that 3" was the ID. I wonder what an actual 3" or 3.5" would do for the performance of the car? I have a 3.5" DP on my Superduty and it made a huge difference

 

should be 3" ID, what exhaust do you have?

 

That is par for the course. All 3" mandrel bends or straight exhaust piping I have purchased over the years from over a dozen differnet sources has been 3" OD.

Best of luck finding 3" ID. I would just look for 3.5", which is probably just 3.25" ID.

 

tubing, whether square or round, is specified by the outside dimension. This way the wall thickness can vary and the OD will always be constant.