I know BMW does there exhaust like this, im not sure what other companies do.

There is a vacuum-actuated flap at the end of the exhaust. so on the x, since there is dual exhaust, it can be put on one of the sides. it is sprung open and attached to a vacuum line. when there is vacuum, it closes the flap. so during idle, cruising or whenever there is vacuum, it will be closed. thus, quieter. so during WOT, and when you need more flow, the flap will open up to allow the needed flow.

here is a diagram of how one is set up. the bottom is the actual flap(ignore the modules).


it will satisfy everyone... quiet during idle and cruise, and loud only when power is needed

id buy it!

 

You want a quiet Evo? I think that massive 700 lb muffler for your "dual" exhaust should quiet it down plenty.

Plus, last I rode in/drove a X, it was pretty damn quiet anyway.

 

Exactly; maybe a contraption that mutes road noise would be more beneficial.

 

my 04 vw r32 had that flapper thing. everyone just pulled the vacuum line

 

Z06's have a similar system....

 

I also disconnected the flapper on my R32 and RS4.

 

I want an aftermarket exhaust that is loud when WOT and quiet when cruising.

 

Then buy one of those high priced JDM Exhaust.

ARC, Amuse, HKS, Apexi.

Those are all quiet at cruising. Make sure you use a Hi Flow Cat, and not a test pipe.
A test pipe really makes things louder, at both idle and WOT.

Good luck.

-Chris

 

They do that vacuum Valve to increase low end torque. With the valve closed yes it is quieter but it also increases exhaust back pressure thus increasing low end torque. When the valve opens the back pressure falls off and the flow helps build high end horsepower. Really simple system but significant results.