[DBU]

I have read several threads for other models on this subject and observed the behavior on my own X4 M40i.

Some folks believe it is there to speed up warming of the cat. And other folks believe it is there to reduce exhaust noise during cold starts. I dunno.

What I have observed is that the flap was closed at cold start regardless of mode selected. It will then open after 1-2 minutes after cold start. Certainly this was the behavior on SoCal "cold" mornings - say 50F (in my garage).

The weather is warmer now say, 60-70F in my garage, and I have noticed that the flap simply stay closed now

So, the first question is: Does ambient temperature affect the flap behavior?

I find the exhaust noise from the driver's side exhaust, where the flap is, too loud in my garage. When the flap used to open, the exhaust tone and level was much more pleasing.

On the X4, the flap is held closed by a spring. A vacuum opens the flap. You can see the vacuum solenoid in the trunk behind the driver side panel.

Has anybody modified their X4 to keep the valve open at all times? If so, how did you do it? I can disconnect the wires to the solenoid, but that will leave the flap closed at all times. I want just the opposite.

[hardparker]

Connect the two vacuum lines together to have the valve stay open.

[DBU]

Originally Posted by hardparker

Connect the two vacuum lines together to have the valve stay open.

Of course! Thanks.

[DBU]

Originally Posted by DBU

I have read several threads for other models on this subject and observed the behavior on my own X4 M40i.

Some folks believe it is there to speed up warming of the cat. And other folks believe it is there to reduce exhaust noise during cold starts. I dunno.

What I have observed is that the flap was closed at cold start regardless of mode selected. It will then open after 1-2 minutes after cold start. Certainly this was the behavior on SoCal "cold" mornings - say 50F (in my garage).

The weather is warmer now say, 60-70F in my garage, and I have noticed that the flap simply stay closed now

So, the first question is: Does ambient temperature affect the flap behavior?

I find the exhaust noise from the driver's side exhaust, where the flap is, too loud in my garage. When the flap used to open, the exhaust tone and level was much more pleasing.

On the X4, the flap is held closed by a spring. A vacuum opens the flap. You can see the vacuum solenoid in the trunk behind the driver side panel.

Has anybody modified their X4 to keep the valve open at all times? If so, how did you do it? I can disconnect the wires to the solenoid, but that will leave the flap closed at all times. I want just the opposite.

Replying/updating my own words above (underlined above).

Yes, I did observe a more pleasing exhaust sound level and tone when the exhaust flap opened. BUT, now that my flap is open all the time, I have come to realize that the change in tone actually is caused by, what appears to me to be, a change in the fuel mapping or timing - NOT the opening of the exhaust flap.

With the flap permanently open the sound level for the first 30-40 seconds after startup, is very high. Then something changes in the engine and the sound becomes quite pleasing.

Also, with the flap permanently open there is some "droning" during normal cruising in all modes. The droning corresponds directly to the amount of torque the Sports Display indicate.

Hoping my observations are of value to others.

[FSociety]

I noticed something similar on my cold start up before and after catless downpipe.