440i exhaust sounds

Billy Cheeseman · 08-09-2018, 03:35 PM

Noob question - how does the exhaust actually work? - on start up, it is in automatically in comfort mode and sounds amazing but very quickly gets much quieter - I assume there is a moving flap at work - I also assume that going into sport mode re-opens it for more noise?

Any facts from the gurus on here would be much appreciated - cheers

NotGotABimmer23 · 08-09-2018, 03:48 PM

On start up the exhaust valves are closed but turbo waste gate is open, thats why its extra loud. In sport or over 4k revs in comfort the valve opens for more noise.

225 · 08-09-2018, 04:30 PM

The left pipe has a flap as well and first thing you need to do is make it stay open!

Few threads about it but drive round in sport mode so the valve opens, then park up with engine running, there is a small connection you can unplug and the valve stays open.

Cold starts are that extra bit louder and you get more burble and pops when driving.

08-09-2018, 03:35 PM	#1
Billy Cheeseman Fender bender 115 Rep 514 Posts Drives: Sky Grey 330e tour msport pro Join Date: May 2014 Location: Surrey UK iTrader: (0)	440i exhaust sounds Noob question - how does the exhaust actually work? - on start up, it is in automatically in comfort mode and sounds amazing but very quickly gets much quieter - I assume there is a moving flap at work - I also assume that going into sport mode re-opens it for more noise? Any facts from the gurus on here would be much appreciated - cheers __________________ "you only live once - enjoy yourself!"
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08-09-2018, 03:48 PM	#2
NotGotABimmer23 Colonel 834 Rep 2,114 Posts Drives: 340i touring - incoming Join Date: Oct 2016 Location: Leicestershire UK iTrader: (0)	On start up the exhaust valves are closed but turbo waste gate is open, thats why its extra loud. In sport or over 4k revs in comfort the valve opens for more noise.
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08-09-2018, 04:30 PM	#3
225 Brigadier General 2281 Rep 4,933 Posts Drives: 340i Join Date: Jan 2016 Location: Uk iTrader: (0)	The left pipe has a flap as well and first thing you need to do is make it stay open! Few threads about it but drive round in sport mode so the valve opens, then park up with engine running, there is a small connection you can unplug and the valve stays open. Cold starts are that extra bit louder and you get more burble and pops when driving.
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