Has anyone fab'd an exhaust with a flap or butterfly?
 

I'm not talking about cat-cutouts that you have to turn open and close with a switch. I'm talking about ones that automatically adjust to throttle inputs, similar to Golf .:R32, C6 Vettes, etc, and open valves in the muffler or pipes to the muffler.

I'd like to build an exhaust with one; stock exhaust is too quiet, but most systems out there drone too much. Since I shuffle customers from time to time, I need to keep things quiet sometimes.

Plus, the Mech Eng geek in me wants to try something new.

Something liek this? http://www.more-japan.com/home.php?cat=551

Also I know apexi has an exhaust something like this...

The sedan muffler already has this flapper in the canister. It opens when there is enough exhaust volume to open it. It doesn't have solenoid like the R32, Z06, etc. The same muffler techology was used on the prior gen Skyline GTR, Sentra Spec V, and 2000-2003 Maxima.

If you want to attempt something like this, you'll need an RPM switch, a vacuum canister and lines, vacuum solenoid, vacuum actuator, and exhaust valve. The vacuum canister stores vacuum and is attached to a vacuum line on the motor. The RPM switch is connected to a coil pack so that it can pick the rpm signal. You program the switch to trigger at the choosen rpm. The solenoid connects to vacuum canister and the rpm switch. When the desired rpm is achieved, the rpm switch triggers the solenoid valve to open which releases vacuum to the acuator which opens the exhaust valve.

summit has them. But IMHO putting them at the end of the system won't lead to much performance but it will lead to noise.

I was thinking of something like this.

http://sap082.channeladvisor.com/p-1...cutout-25.aspx

That's pretty close, but I'm not willing to swap a cat for it (unless it's a cat WITH the valve.)

That is exactly what I described in the first sentence in the original post. Don't want that.

That might work, but I wonder if I could do with without a signal from a coilpack. I'd rather pull the signal from a hall sensor, like a Cam Pos/Sen or Crank Pos/Sen.

I've never done it that way. It's very easy to simply tap into the #1 coil pack rpm signal wire and call it a day.

Wouldn't you want it based on throttle position rather than RPM? Seems to me that you only really want it loud under WOT? Curious to see how this goes though. The in-house solution sounds the most practical to me.

The sard unit is interesting. Would be kind cool to have a cat inside the inner portion and have a flapper that went around it.

But that one works simply on the amount of exhaust force past the flapper. Simple and probably is more indictitive to when you would want it. As you could be reving in neutral and a rpm flat would open up.

The oem Nissan muffler flaps are based on simply how much exhuast force is going though the pipe.