Are you referring to the airbox pictured below? If so, it's activated by vacuum, hence the suggestion to plug the line. Otherwise, I'm not sure what you're asking and my bad for getting off track.

 

Count me in for the group buy on Duct Tape

 

Is keeping flap 2 above closed the secret to a louder stock exhaust?

 

No! This has nothing to do with the exhaust. This is thread is about changing the engine air intake sound.

 

so how do you do it?

 

I just put a silicone plug into the Helmoltz resonator outlet hose .
I like the more throaty sound .
Also, the plug can be removed if you want to return to stock .

I got some liquid silicone ( mold making material ) at a hobby shop ,
temporarily closed the connection point to the main air intake and poured it into the hose.
It solidifies (but stays flexible) in a few minutes and you're done.
( Make sure you don't fill it all the way up, leave enough space so that the rubber hose
still fits over the resonator outlet )

 

Why can't you just disconnect and plug the vacum lines that operate the valve?

 

Rolf,

How do you know that the silicone plug won't be displaced distally?

How would you retrieve the plug to return to stock?

I am thinking of doing this but thought I would ask first.

 

The resonator hose curves into the main air intake . The silicone mold material can't go anywhere once it cures..
You can force it out anytime because it stays flexible and does not bond to the rubber.
I have mine in for several months now and it has not budged.

 

For orientation purposes, does anybody have a picture of the Helmoltz resonator in the engine compartment? Which is the outlet hose?

 

The large hose ( ~ 3" dia. ) is the air intake to the engine, the smaller hose
( ~ 2" dia. )is the resonator outlet .