I'm still green so please bear with me.

I notice on my 545i there are two mufflers with the tips. One muffler outlet has a valve on it before the tip. At idle it is not open.


Does it open only in low vacuum (wide open throttle)?


If so has anyone put just a straight pipe in there (in place of the muffler but leaving valve intact and working) to see what happens?


I'm hoping it would have a nice stock sound to it until wide open throttle.

 

I believe it opens based on RPM, not throttle. In the lower gears, i.e., lower road noise, I believe I can hear the second path open up around 3,500 RPM. There is also a noticed boost in thrust. Since we have continuously variable valve timing, I do not believe this is related to a different valve timing program, but the exhaust.

 

I went ahead and removed everything the two mufflers it has and installed one free flow exhaust with double tip and man i can tell you my car sounds incredible you can barely hear it from the inside of the car but the engine of the 545i sound really nice and deep. I did not noticed any lack of power and on high speeds feels even better.

I hope this helps

Luis

 

Thanks but I actually wanted to keep the stock primary muffler for around the town and seeing my clients type driving.

I want the secondary bypass to open up during wide open and quick squirts.




Allen

 

You can do a bypass mod to keep both mufflers in play....go to autozone and get a universal vacuum line connector...open trunk...remove left side cover.....next to tail light there is a solenoid that has two vacuum lines connected to it....unplug both from solenoid and connect directly inline to universal connector....this will keep both mufflers in play at all times....called the golf tee mod for the 3 series
I have not noticed a change in exhaust sound...throttle response is a little better

 

No, it is related more to fact that the variable length air manifold has 'kicked in' to its shortest length.

Unless other modifications are done to the engine, playing with the exhaust system will only result inmodifying the sound and possibly reducing power.

Salut, Bob P.

 

In doing my own research before getting my exhaust done I believe I read that the "golf tee mod" doesn't work for the 545, as the spring keeps the valve closed normally, rather than open normally - versus the 3 series of those years where the valve spring would normally keep the thing popped open, and all you've got to do is stop telling the valve to close by plugging the vacuum line. I tried strapping the valve open, but gave up as it was too much of a pain.

To the OP, just get a nice exhaust system and drive in a reserved manner with people in the car. popping the valve open all the time doesn't make that big a difference. If it's a nice system people will like the sound anyway.

 

With the 545i you have to connect the vacuum line instead of plugging it and the valve will stay open. ..super easy