As the title says, when looking at building a custom exhaust system I've heard the reference called pie cut exhaust but I was unable to find any definition or terminology so I was curious to know what does it mean?
This is a term used to describe the shapes of the pieces of tubing used to create exhaust pieces with very hard turns. Imagine an apple pie. Now cut it in 8 individual pieces (triangles). You can now make complex shapes by arranging the pieces in different ways.
In the image below, you can see how each weld marks off each piece of tubing. If you pay attention to the shape of the piece, you can see that it resembles a piece of pie. Thus the term pie cut exhaust.
This is done when bending the tubing is not an option for whatever reason. Sometimes its done because it just looks bitchin'. ;-)