Exhaust pipe damper

[bbally]

The second way is the correct calculation, but you need to add 10 percent onto it.  Since you are below 5000 feet just add 10 percent to the area and you are ready to go.

 

[fourthwind]

And for RF between 5400 and 8000 feet?    Wont find out the size of what tanks I can get till next weekend, but it's looking like a 150 size tank.