Exhaust flap

[Dusty]

Hi Guys, although I saw this yesterday on a E90 330i I am posting this under the x35i section due to the fact that the golf T mod related to this flap has been discussed here before. I was driving behind an E90 330i and noticed that when we came to a standstill at traffic lights the valve inside his left exhaust pipe opened. And once he pulls off the valve closed and did not open again before he came to a stop at the next traffic light. This confused me: open at idle and closed when moving?????Should it not be the other way round? Pull off was gentle and we did not exceed 60km/h so I can understand if revs kept low and valve stays closed but why then open at idle and close once he starts moving?

 

[GK 1]

You're right, I think the golf T mod works the opposite to what's happening here.Maybe that's how it usually works. Confused

 

[abmi0000]

From my understanding, it is normal and closes to reduce noise levels and gain some torque as the back pressure is altered. I disconnect the vacuum pipe for the grunt but it needs to be choked as I am confident that there is a flat spot on low revs when it isn't.

 

[Twinz]

The flap has only two functions. It assist with reducing/muting exhaust noise levels. Secondly, it assists to warm up the cats on a cold start. :thumbs:

 

[moranor@axis]

it makes sense for it to be open at idle to make a nice noise... then close to reduce noise up to 4000rpm where i needs to open to not be a restriction...

 

[boost3d]

I saw a diy where they disconnect the actuator that control the valve...

Would this throw an error that can be picked up?

 

[Philip Foglar]

Hmm, I also was wondering about this just the other day - mine is open when the engine is off, and when started and idling, haven't been able to run along side the car to see what it's doing while on the move... :rollsmile:

But like said, I would gather that it is rev and throttle position sensitive?? So at lower speeds and throttle position it remains closed - and maybe this does explain the common hesitation/flat spot that I experience with mine if driving sedately and then suddenly booting the throttle to accelerate - quite annoying of course! :nonono:

 

[Twinz]

Yes. It will throw a soft code. But there are other ways to do it to avoid the silly code.

I saw a diy where they disconnect the actuator that control the valve...

Would this throw an error that can be picked up?

 

[ASH M]

Mines opened permanently with the vacuum pipe still in place. Even when i get someone to rev it up it still stays open.

Maybe its stuck?

Anyway, i'm gonna throw out all of that exhaust kak :rollsmile:

 

[Twinz]

Haha...nice Ash

I have done the same :thumbs:

 

[Philip Foglar]

The only way I know that mine is working is the mere fact that the left pipe's chrome tip gets dirty quicker than the right side... :thumbs:

 

[ChrisBrand]

I did the golf tee mod on my car. The function of the flap is to reduce noise levels when idling. It is OPEN when the car is off. CLOSED when idling and OPENS after about 2500RPM when moving. The golf T mod removes the pipe to the control arm., closes it with the golf tee and the flap always stays open. Give s a nice deep note when cruising in town

 

[Philip Foglar]

But that's the thing, on the E90 it is open when idling or off, but closes as you drive off I gather and at lower speeds/throttle position, opens at higher engine speeds or throttle position. My father in law's E46 closes when it is started up - can actually hear the flap close as he turns the ignition on...

 

[ChrisBrand]

Yes the flap closes when you start because it was open when it was switched off. Opens when driving. Only thing i don't understand is open when idling. So only difference is idling

 

[Philip Foglar]

Yep, this is what I could not understand, but I gather that when driving in town in normal conditions it opens and closes as needed - be very curious to see how it behaves in general...

 

[Dusty]

During cold start in the mornings I can hear the flap closing and then after about 20 seconds it opens up again. Yesterday when I got home from work I left the car idling to check the flap, it was in an open position. It seems to me that the flap is open during idle, then close when you take off and drive at low speed/revs and only opens up at higher revs and then again when stopping and idling.

 

[abmi0000]

Mine is closed by default...

 

[gavsadler]

I researched this a while back, and found something which said the flap is closed at partial throttle openings (for noise) and then opens again when throttle position is more than 15%.

I generally plod around the suburbs, and I actually found it irritating hearing it open and close all the time.

By doing the golf tee mod, I eliminated that irritation and it also makes a bit more noise low down. Nothing hectic though.

 

[abmi0000]

So in my case (where it is closed when the car isn't running) will the disconnect of the pipe cause it to stay permanently closed? :idea: