Actual diameter of 3" exhaust?

[John B]

When I got my 2.5" catback I was disappointed to find that it was actually 2.25" ID. What is the actual ID of the 3" exhaust tubing? I am porting my 2.5 SV housing and need to know so that it will match up to a 3" downpipe when I get the money to put one on. Thanks, John B

[lametec]

Typically, 3" will refer to the OD. ID depends on the wall thickness of the pipe. ID = 3" - (wall thickness * 2)

[turbovanman]

I had to expand my 2.5 inch DP slightly to fit inside the 3 inch DP, then welded it up. Worked great!!!!