Learn me stepped headers

So, tell me why stepped header tube diameters get larger as they get farther from the exhaust port?

I remember when these were introduced for the fox mustang.

I think the theory is that the exhaust gas cools and expands as it travels away from the port. This is supposed to help maintain velocity and scavenging of the cylinder.

Hopefully, someone who really knows will be along soon.

The short version I always head is small tube headers are better for low and mid range power, and large tube are better for top end, (with low/mid loss). 

Apparently, stepped headers are a decent compromise of both. 

Slightly more technical, involves the pulses and scavenging. I’ll let the smarter folks go from there!

Floating Doc (Forum Supporter) said:

I remember when these were introduced for the fox mustang.

I think the theory is that the exhaust gas cools and expands as it travels away from the port. This is supposed to help maintain velocity and scavenging of the cylinder.

Hopefully, someone who really knows will be along soon.

Does not compute.  

The steps have two uses: transition a small, fast port to the right tubing size for broadest power; give wider power band through additional wave reflections (which happen at the steps). I have tested 2 and 3 step headers and they do tend to be able to have a better compromise than a single tubing size.