Saw this while under the car, which looks just like the one on the 335, that controls a flap in the exhaust that opens up to give a sportier sound. It also opens up after a minute of idling when the car is cold.

I assume it's the same part as on the 335? I haven't noticed a sportier sound though when I get on the gas.

Anyone here done the mod to it where they either plug the tube with a BB / zip tie the tube to prevent the flap from closing, or unplugged the actuator controller in the trunk (#2 in the pic)? Only problem with the latter method, while simple to do from inside the trunk, is that it throws a harmless code, so you should plug it back in before dealer visits, whereas the other methods throw no codes.

Here are some pics from the 335:




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And here is what I saw under the car, and in the trunk when you open up the left side panel:
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So I went ahead and tried to see how the actuator works, and I see that by default, the spring loaded mechanism in it keeps it closed.

On the E9X series cars, it seems that the flap mechanism works the opposite way, in that vacuum in the line keeps the flap CLOSED. So by simply unplugging the tube, the vacuum pressure is gone, and the flap remains open. But in this car, it seems to work the opposite way...

Unplugging the tube didn't do anything, as it seems the tube uses vacuum to OPEN the flap under WOT or higher RPM's...

So I played with it while the car was idling just to see (by using my hand to open and close the exhaust flap) and it sure made a difference in noise!

So then I figured I'll see how I can leave the flap open all the time, to get a deeper exhaust note during regular driving. I ziptied the arm that keeps the flap open, and went for a drive.

Unfortunately, I could barely hear a difference in the cabin, probably because the cabin is so well insulated, but even with the windows down, I couldn't hear much more, unlike in the E9X series, where it makes a big difference.

Bummer!

 

So I came across this mod on another forum, and figured out how the flap works on this car, which is the opposite of on the 335.

On the 335, vacuum is applied to the valve to hold it closed. So removing the vacuum line (and plugging it with a tee so you don't have a leak) will result in the valve remaining open all the time. Or you just unplug the wire powering the solenoid in the trunk...

The system is reversed on the E6x where engine vacuum is used to keep the valve open. So removing the vacuum line will have no affect other than ensuring that the valve will never open. What you need to do is make sure the valve always has vacuum.

Open the panel and inside you'll see a vacuum line coming from the front of the car to the solenoid as well as a vacuum line going to the same solenoid from down below. The hard black plastic tube on the left that's zip tied to a bunch of wires (and has white tape on a section of it) was the one that came from the front of the car. It connected to the rubber tube that went to the bottom of the solenoid. The tube coming out the side of the solenoid was the one going to the flap, so you disconnect that, and attach it to the hard plastic tube, and you're done!

Leave the short length hanging unused on the solenoid. What you've done is bypass the solenoid and will be applying vacuum to the exhaust flapper at all times. To reverse the mod, simply plug the lines back in as they were before. And if you took over the other line too, and you've forgotten which vacuum line connected to each solenoid inlet, don't worry -- it doesn't matter. Just make sure the line coming from the front of the car connects to one inlet and the line coming from the flapper connects to the other. The solenoid is just a simple electronically operated on/off valve and the input and output flow direction doesn't matter.

The pics below are the "after". It makes it a bit louder, but unfortunately, nowhere the difference it makes on the 335, but oh well, it's free!