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M2 Technical Topics > S55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > Exhaust flap activation

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      08-18-2019, 09:52 AM   #1
Scott Z
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Exhaust flap activation

Does anyone know what’s going on in comfort, sport and sport+?

I had assumed in comfort they remain closed regardless of throttle position.

Sport closed at low throttle position, open at full throttle, closed at highway speeds.

Sport+ open most if not all of the time.

Just finished installing the TechnicPnP (TechnicPnP.com) ASD removal harness this morning. Very happy with the results but now a bit confused on the exhaust flap positions within the different driving modes.
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      08-18-2019, 11:08 AM   #2
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I think the flap opens in Comfort mode above 4K rpm
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      08-21-2019, 03:53 PM   #3
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More complex than that.

Comfort does open at higher load / rpm.

Sport open from idle then closes about 3k then opens about 3.5k. Closes higher up on light load.

Sport+ open more than sport but not sure exactly.
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      08-21-2019, 07:11 PM   #4
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Its vacuum/pressure activated so even in Efficient mode, sometimes they can open up under load. Likewise, even in Sport+ mode, if there isn't sufficient vacuum pressure, the valves will stay closed. The modes simply change the threshold to how much pressure is required to actuates the valves opening and closing.

EDIT: I'm wrong on this ^
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Last edited by tokki; 08-23-2019 at 01:09 AM.. Reason: wrong info
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      08-21-2019, 08:23 PM   #5
Scott Z
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Don’t think thats entirely correct. At idle and low rpms you can hear the valves open when switching from comfort to sport.
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      08-21-2019, 08:36 PM   #6
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1. Press the power button without pressing the brake pedal

2. Set Sport+ Mode through M buttons on steering wheel

3. Press on the Accelerator half way through at least (car is off)

4. Start the car while pressing the brake pedal

Now your car starts up with valves open

5. Switch the car off and get underneath the rear after it cools down

6. Remove actuator cables on both left and right side

Now your car always has its flaps open

7. Drive for a week or so with this setup and then you will recognize when it is open or not

With ASD bypassed it's much easier because everything you hear is real
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      08-22-2019, 12:17 AM   #7
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Quote:
Originally Posted by tokki View Post
Its vacuum/pressure activated so even in Efficient mode, sometimes they can open up under load. Likewise, even in Sport+ mode, if there isn't sufficient vacuum pressure, the valves will stay closed. The modes simply change the threshold to how much pressure is required to actuates the valves opening and closing.
That's not right I'm afraid.

They are operated by electric stepper motors and controlled directly by the DME.

They only open / close when the DME requests it in accordance with the software mapping.

Even the old vacuum version pre F8x didn't open due to load. Vacuum was provided by avacuum pump and stored in vacuum canisters for use so it didn't run out.
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      08-22-2019, 09:23 PM   #8
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Quote:
Originally Posted by doughboy View Post
That's not right I'm afraid.

They are operated by electric stepper motors and controlled directly by the DME.

They only open / close when the DME requests it in accordance with the software mapping.

Even the old vacuum version pre F8x didn't open due to load. Vacuum was provided by avacuum pump and stored in vacuum canisters for use so it didn't run out.
Ah, perhaps you are right. This is how it was explained to me by the Eisenmann exhaust vendor.
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      08-24-2019, 06:53 AM   #9
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I'm looking at the Bimmerlink app just so that I can keep the exhaust valves open. Any long term issues with keeping the valves always open? I actually like the sound of the car - just want a little more of it!

If I want the valves open all the time do I have to use the app each time I start the car or is the last setting saved?

Last edited by cb804; 08-24-2019 at 11:54 AM..
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