340i Exhaust

[iluvkefalonia]

I'm sure this is a simple question for the knowledgeable people on here. I have a 340i M Sport auto which sounds lovely on start up, but it looks like only the right hand exhaust is working, is this only on start up or is the left hand one a dummy? It's also evident after 1000 miles that the right hand exhaust tail pipe is getting noticeably dirtier than the left, I know I could crawl underneath and have a look but I'm the wrong side of sixty so will leave it to the younger folk to advise! And before you ask, yes someone of my senior years can utilize and appreciate a car with this performance.

[BlownImp]

Hmmm, looks like you have a flap controlling one pipe and the other is in continuous use?

[Max M4X WW]

On cold start the left tailpipe will be closed, I assume to aid in heating the catalytic converter(s) quicker.

With my M135i I'm almost certain both worked at all other times, though some did say that it opened during sport mode.

I actually removed the clip between the flap and actuator and wired the flap open as it annoyed me!

[ladderino]

Yes, similar to the 335i, one of the exhausts will remain closed until the engine is up to temperature. As a result, one side will get dirtier because it's in use more often.

With the 335i, it was possible to stop the vacuum pump from operating, which would mean both pipes were in action all the time. Provides a much better exhaust sound.

If you want to do a similar thing to yours, take a look at this - http://f30.bimmerpost.com/forums/showthread.php?t=...

[Mike335i]

I have the same on my e90, it is to speed up the warming up process to reach more efficient running quicker.

[interstellar]

Use Autosol to keep the exhaust tips clean. works a treat on my 340i.

[Monty Python]

Noticed this on the current Audi TT - there's a flap on the nearside exhaust that closes when the car is moving slowly, then opens as speed increases. At first I thought the nearside one was just for show.

[interstellar]

Having read more abut this on bimmerpost it is closed and opens after a couple of minutes. It is possible to mod the exhaust to stay open permanently by unplugging the lead on the left exhaust and it wont throw a fault but will make it louder most of the time.

Follow the bimmerpost further up this page if you want to try it.

Edited by interstellar on Thursday 1st December 13:39

[Nick_C]

I disconnected the valve on mine when open. Car has thrown up no errors and it's a touch louder inside. From what I can find its due to drive by noise regs.

Nick