I did something similar with my RV-3 13B decades ago. It split open at the welds around one of the pipes from the manifold into the the big outer tube. True, it did use individual manifold base plates, not the connected factory manifold and the big tube was only 0.035.

Still, I would recommend slip joints on two of the three pipes, like I added on one of the pipes (cut through and a surrounding bigger pipe -- missing in picture).



Can't remember why I went from the above to individual runners into a perforated pipe under the fuselage. Probably got lured by promise of increased power by tuned lengths and still uncomfortable by the muffler being inside the cowling.

Finn

On 12/28/2019 12:10 AM, Matt Boiteau mattboiteau@gmail.com wrote:

This is what I'm going to try in a few weeks. 

"Exhaust valve opens and a pulse of hot gas puffs out through a short pipe, then tangentially into a cylindrical canister. Being tangential, the pulse flattens out and travels helically (rather than bouncing and reverberating around) along the inside curved wall of the can, spiraling toward the exit, where it comes out more uniform in flow and so pretty quiet."

Outer pipe = 321 ss 0.050 thick. Flat plate bent to a 5" tube

Inner pipe = 321 ss 0.036 thick. 2.5" diameter

(I might use 302ss 0.065 since I already have it)

From my understanding, the area of the holes should be double the area of the inner pipe. 

- Matt Boiteau