NineVettes

I thought I went through the menus to keep the exhaust open all the time - normally drive in "Sport" mode. Outer exhausts dark as expected, inner exhaust flaps do not seem to be opening? Yesterday during my dyno session, the shop attached some sniffers to the inner exhaust pipe and got zero readings during the first pull. Even during idle, the flaps are not open. Why? Guess it cost me 5 or so ponies yesterday but I am pretty pleased with 589 rear wheel..

cyi1

The inners only get dark in quiet exhaust modes Eco/touring.

My inner 2 have been spotless since day 1 since I pulled the fuse.

ahero4eternity

This should help you understand.

NineVettes

I appreciate the diagram, but it does not explain to me why the outers get dark and the inners stay clean. Or why, if I set the exhaust to be open in the engine management screen, the dyno shop guy thinks the inner flaps may have never opened??

SnowyATX

There are no inner flaps. Only outer. When outers are open majority of flow goes through outer tips thus black.

TXshaggy

NineVettes

OK, now I understand. I thought opening the valves runs the exhaust through ALL 4, which gave the additional flow. I didn't realize the valves were on the outer pipes, thought they were on the inner pipes. So with my valves being open through the engine management menu, the vast majority of exhaust is going through the outer pipes - which would explain what we saw at the dyno shop on Monday.

Thanks!

Warp Factor

You were right. It does run the exhaust through all four when the valves are open.
When the valves are closed, the "straight-through" section is shut off.

RegnaR

yep my outer pipes turn black pretty quick with the valves always open.

C5-VERT

Yep even my aftermarket Borla ATAK mufflers do the same thing hence similar design and flow. Just louder.

MacRoadie

Exhaust is always flowing through the inner pipes, but as it is running through the muffler baffles, most of the soot is deposited in the muffler leaving the tips clean. When you close the valves, the exhaust is all run through the muffler/inner pipes. When the valves are open, SOME of the exhaust is allowed to flow throug the outer pipes, bypassing the muffler and allowing soot (and a lot of extra volume) to exit unimpeded, causing the outer tips to turn black. The rest is still running through the inner pipes and still depositiong most of the soot inside the muffler.

ahero4eternity

Warp Factor

At higher throttle openings, when the mixture is much richer (sootier), the valves will be open, allowing most of that sootier exhaust to exit through the less restrictive path on the outer pipes.