TRAKCAR

I always ran the 997's "unplugged" so that the flap was always open.

As soon as you rev it a tiny bit the flaps close anyway.
Seems like at idle is the only time the flap does anything.

The flap is closed below 3x00 RPM and open above no matter if the button is on or off..
Are the flaps there only for performance; to make a bit more TQ below the 3x00 RPM and "opens" the exhaust for more HP above 3x00 RPM and the button is only there for sound at idle?

Am I missing something? Seems like the flaps could open at idle automatically also without the button? Id prefer it really be open or closed all the time with the button when you want more noise than TQ below the 3x00 RPM??

alaint101

I think you got it.

The way I understand it, flaps closed below 3600ish allows you to drive in at night w/o waking-up wifey, kids, dogs or neighbors. That's pretty much it.

Someone did dyno a 3 last year and showed improved torque at low revs w/ flaps open but of course, it would not matter as soon as you stomp on the pedal or drive in a spirited manner.

Bartron

Paging Money2536!

Personally I get really annoyed with how abrupt the flaps are and useless at low RPM's. Loud idle at Starbucks and then neutered on the drive off the lot.

Once I installed the GMG, I stopped using the button.

Serge944

There are numerous threads on this. Simply put, the valves are there to meet EU noise emissions. The secondary effect is that the engine produces more power below 3500 rpm with the valves closed.

And yes, I wholeheartedly agree, it's extremely annoying. I ran unplugged on my 997 too, despite the low end power loss.

inactiveuser7616

I had a fully manual control unit put in. It totally circumvents the ECU and allows me to use a controller to open or close the valves.
Personally, I totally prefer this method. We dyno'd before and after and there was zero HP loss. And there was about 7-8 Hp loss with the valves closed vs open. Otherwise, I don't feel any difference in the 'butt-dyno'. So it was 'full win' for me.

TRAKCAR

How did I miss that, tell me more!

Charles@dundonmotorsports

Peter, we are actually working on the map programming for the exhaust valve operation. We are working to make it so with the button on, the valves are left open 100% of the time. And with it off, they are closed until a desired RPM that we choose, load dependent. Hopefully we have this finalized this month.

allans

Phil, Please share details of this set up w/ us. Thanks, Allan

Money2536

Sign me up for that! I'm hitting the dyno for the Stage 2 tune this week.

Money2536

I found in my testing with the Sharkwerks center section these results:

Button OFF: Choppy lower end Torque and Horsepower
Button ON: Smoother, more linear power delivery

So my guess is the button does a little more than just opening the valves at idle. When my valves were disconnected, I still pressed the button ON.

See Runs 1-4.

https://rennlist.com/forums/991-gt3-...st-valves.html

Jamie@dundonmotorsports

We have an RS coming for a week to do a bunch of tuning, including exhaust flap control and cold start bark delete!

inactiveuser7616

Well, to be honest.... I haven't wanted to get into a debate about it.

Hence why I didn't mention my tune, dyno runs or exhaust valve controller.

But, I've asked John from Fabspeed to chime in and explain.

Basically it's simply a controller that just needs power and ground and it controls the exhaust valve actuators (or whatever they are) using a simple lock/unlock style remote.

meaker

+1

Charles@dundonmotorsports

I actually completely forgot about that option that Phil has. There are 2 manufacturers that I know of that make universal exhaust flap controller options that are wireless and use a separate actuator and remote. You basically have a separate solenoid control that you wire in and then it connects in place of the factory exhaust valve electronic solenoid, then you have a wireless remote control inside the car that can turn them on and off when you want.

meaker

I like the remote control idea to keep them on all the time or off. But two concerns, is closed all the time cause too much heat? And does open all the time cause any less torque or HP through the rpm range? I have Gmg but absolutely hate the valves open and closing. Not sure I want to disconnect the valves do to droning while highway cruising and don't want any drop in power. I used to run sharkwerks with it disconnected but Gmg is much louder. Love the loud most of the time.