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      03-13-2013, 10:38 AM   #11
Used2be
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Drives: F90 M5 DG/Aragon
Join Date: Oct 2012
Location: Michigan, USA

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Quote:
Originally Posted by jmh View Post
It is operated by a vacuum pump underneath the trunk (a common mod on the E90s is
to disconnect the pump via the electric connector in the trunk to keep the valve open).

Where at idle speeds, up to 2500 RPM: the exhaust flap is closed with vacuum applied to the actuator. This causes the exhaust gas to pass through the long resonator pipe, reducing the low frequency noise that is generated.

On the F10 it is now reverse where vacuum applied means the exhaust flap is opening
Interesting info, thanks. Since BMW seems to be concerned with the drain on the battery from the various systems in the car, and will actually shut down non-essential components if the battery is getting low to allow the car to continue to run, for those of us who will be/are using exhausts without the valve, is there an easy way to remove the vacuum pump entirely? I'd prefer to physically remove it, but I suppose a simple fuse removal would stop the electrical drain? Just thought of another question. If the vacuum needed to open the valve is generated at the pump beneath the trunk, and presumably the pump is activated electrically from a RPM sensor on the engine, why would leaving the vacuum line open affect the running of the engine?

Last edited by Used2be; 03-13-2013 at 10:45 AM..
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