Hey all,
I've got an 03 FX4 with the 4.6. I'm looking to have an exhaust installed but I was just curious of what size pipe is on the truck.. All the web sites I've googled have come back to me with anything from 1.75 inches to 3. At best look, I can come up with that it is 2.5 inches. Anyone with experiance? Thanks alot.

 

Take a tape measure, the kind you would use for sewing, and wrap it around the pipe and get the circumference. Then divide that number by Pi, which is 3.1415 etc, etc, etc. That will give you the diameter of the pipe, which is what you are looking for.

The equation that works here is: circumference = Pi x diameter.
In reverse: diameter = circumference/Pi

Good Luck!

 

It has 2.5 on it now. If you run true duals 2.5 inch pipe is good for up to about 700 hp.