[leemj84]

Hey, very new to BMW in general. Just got my 340i last week. Might be a totally idiotic question....but I don't know what I don't know.

Noticed that when I start the engine, exhaust fumes come out only from the passenger side of the exhaust? Is that normal? Do I need to check for any issues in the exhaust to see if the other side is being plugged by something?

[Zanity]

Absolutely normal, your driver side exhaust flap is closed on start up, only in sport+ or when you floor it, it opens up, if you want it opened up all the time, you have to code it, I coded mine because i hate having one tip black and the other new like never used. It'll look like that after a year if you don't open it.

[cfm56d7b]

Welcome! Please post pictures of your car with a list of options as the world at large will be asking fairly quickly.

This is totally normal behavior to reduce emissions.

[leemj84]

Originally Posted by Zanity

Absolutely normal, your driver side exhaust flap is closed on start up, only in sport+ or when you floor it, it opens up, if you want it opened up all the time, you have to code it, I coded mine because i hate having one tip black and the other new like never used.

Thanks!! And is it because it's closed I don't hear the popping noise like every YouTube video shows or is that because I don't have MPPSK?

[Zanity]

Originally Posted by cfm56d7b

This is totally normal behavior to reduce emissions.

Its actually to reduce noise, not emissions, all exhaust goes through the same catalytic converter regardless which tip it comes out of.

[Zanity]

Originally Posted by leemj84

Thanks!! And is it because it's closed I don't hear the popping noise like every YouTube video shows or is that because I don't have MPPSK?

You will hear popping sounds a lot more when you open the flap, just rev it in sport+ mode, when you switch to sport+, you can hear the flap open up

[cfm56d7b]

Originally Posted by Zanity

Its actually to reduce noise, not emissions, all exhaust goes through the same catalytic converter regardless which tip it comes out of.

Well - a bit more details are always helpful. With one valve closed, catalytic converters warm up faster reducing emissions. The decibel level reduction is an additional benefit for the sleeping neighbors.

[Zanity]

Originally Posted by cfm56d7b

Well - a bit more details are always helpful. With one valve closed, catalytic converters warm up faster reducing emissions. The decibel level reduction is an additional benefit for the sleeping neighbors.

I never bought that, being an engineer myself lol. The heat comes from the engine, not the tailpipe, an extra 3" tip (or whatever the size is) isn't going to matter, how fast the engine warms up depends on how you drive and how long you've driven.