So whats the difference between a stock 3" exhaust and a "cat back" exhaust?

Yeah, my car still has the stock exhaust manifolds but I after the Y pipe I have stock 3" pipin going all the way except when it gets to my muffler...

I dont know, but how much of a difference does the so called "cat back" really do? Now I know headers will but Im asking about the exhaust....

thanks guys

 

Stock exhaust is 2 3/4", not 3". Also its not mandrel-bent, so there are crimps and stretches in it at the bends. That disturbs the airflow and creates turbulence. Mandrel-bending is a process that keeps the bends straight, reducing the turbulence that costs power. If you look at the bends on your stock pipe now, especially where it goes over the axle, you'll see what I mean. Also, the aftermarket cat-back exhausts are a true 3" in diameter, so the extra volume helps too.