wankeldude

Just wondering if anyone knows the rationale for why the flap is there in the first place... or is it just like an appendix :-)

Bob W.

...but I think intake temp control might benefit from a closed flap in certain situations.

Vijay

So is it louder w/o flap?

Bob W.

I didn't notice, but that may be because I'm mostly hearing my cat-back.

daveak05

it could be a concern if it's picking up heated air from down in the engine compartment vs an outside fresh air feed like the main supply at front of car.

my guess is that it serves more purpose than just opening at 5000 rpm and 200 kmph(?). some of these could be what you just described, and/or keeping closed for cold operation drivability, noise, fuel consumption, emissions...