I currently own a 2018 S6. As we know V8s typically run a dual exhaust. Which I am now. I am on stock downpipes, resonators in place, everything else back is straight through. Now I’m going to ask the question because I can’t find the answer. Maybe somebody knows and wants to help. The vehicle is twin turbo. Downpipes off each. I’m going to be going catless and removing the resonators to be COMPLETELY straight through. The stupid question is, I love single exit exhaust setups. It’s okay if somebody finds it stupid but I love it. Is it possible to merge the downpipes in replacement area of the resonators. So that I can run a single exit setup. Or will this end up cause back pressure issues etc. I can think of a pretty clean way to weld it all up my self but I don’t know enough of the mechanical or engineering side of this and looking for help. Thank you so much.

 

To be technical, calculate the area of the down pipes, add them together and back figure the diameter you need for a single.

 

Im retaining the factory twin turbo set up. There’s two down pipes that run off each turbo to the underside of the car for it to be exhausted out. My curiosity is can these two downpipes be merged underneath the car and ran out as a single exit exhaust.

 

Yes. But if you want to avoid exhaust restrictions you will want the single outlet to have the same area of flow as both downpipes. So from the merge it will need to be larger.

 

ahhhhhhhhh ok I’m understanding now. So this is possible. Referring back to your first comment. Sounds like I have to just send it. Thank you for you time brother. Happy new year.

 

Measure the exhaust pressure in the existing system just prior to where you intend to merge into a single. Hopefully you have less than 2 psi at max power. Do the mods and measure again to see if your single tailpipe is big enough. (It doesn't usually need to be as big a CSA as your combined downpipes because exhaust gas shrinks as it cools and the volume flow rate at the tailpipe is not as high as the turbine discharge)