[sylonien]

Hello, new member here!
I recently noticed that when I start my car and it leave it to idle, the left valve in the exhaust opens by itself after a while? Thought it meant to do that only after a certain RPM when driving?

I recorded two video to show it here and the RPMs.

[Lulz_M3]

There is alot of speculation but no one has definitive proof of when and what that valve is suppose to do. In my opinion, it is used to limit the noise produced on cold starts since the RPM's are higher and the wastegates are wide open = LOUD. Other theories are that it is used to warm the cats, its suppose to stay closed under certain RPM conditions etc, please add your opinion to the pile LOL.

[enrita]

normal. warm up the cats and limit sound when on light throttle.

[sylonien]

My theory is that it's suppose to make it louder when open and allow more waste gas to escape? :P

But if you watched my first video, what I don't get is that after a while on a cold start, the valve opens automatically even though it's stationary and is sort of quieter when the left side opens up, along with the RPM dropping down to 600rpm instead of the initial 1100~RPM.

I don't really mind either way, just curious why it does that automatically and where all the people do the "golf tee mod" or unplugging stuff when mine does it like that?

[sylonien]

Originally Posted by enrita

normal. warm up the cats and limit sound when on light throttle.

Limit sound by opening up? Does it close again when it's hot then?

[enrita]

Originally Posted by sylonien

Limit sound by opening up? Does it close again when it's hot then?

limit sound by closing. All latest cars have this. just look in the pipes of another Audi or BMW in front of you when driving.

[sylonien]

Thought so, what I don't get is why does it open up when idling then and not even touching the throttle.