[The Nightman]

I ran a 330i exhaust on my 328i a while back and ended up swapping back to the stock exhaust as the cold starts and highway droning were annoying with the muffler valve always open. Otherwise, I enjoyed the sporty sound of the 330i exhaust and still find the stock exhaust to be too muted. So, I've been toying with the idea of manually controlling the valve in the 330i muffler so that the valve remains closed during cold starts and highway driving, and I can open the valve at other times. This is where I'm at so far:

1. The muffler valve is controlled by "vacuum control valve" (solenoid?) 18307604055. An OE Pierburg control valve is <$30 from FCP. It's also the same valve used on the N54 so it shouldn't be difficult to source. Basically, the valve has a two pin connector and the 12V is always live while the ground is switched by the DME. The valve opens when the circuit is complete (ie powered) and allows vacuum to close the muffler valve.

2. The vacuum source for the muffler valve is the plastic brake booster line (34336769622 on the 330i). The brake booster line has a tee and there is a vacuum line that runs from the engine bay to the trunk, where the solenoid is located. I'm not sure if I can directly swap the 330i brake booster line on, as the vacuum pump connection seems different from the 328i. I'm also not sure how I would splice the tee onto the 328i brake booster line as it is hard plastic. The N54 muffler valve control has the same set up.



3. Wiring would involve a 12v source to a switch, then to the control valve and to a ground point in the trunk. I believe I need a toggle switch or a switch that is normally closed, so that the control valve is energized and the muffler valve remains closed by default. Not sure what to use as a switch. There are exhaust toggle buttons on Aliexpress meant for other vehicles, but may look out of place:


https://www.aliexpress.com/item/1005003673887318.html

4. Where can I locate the switch? It's too bad all the factory buttons use a PCB board/module, otherwise it would've been cool to use a steering wheel button or add another button to the heated seat button row.

Just brainstorming ideas so far. Any input or suggestions are welcome!