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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > 2012-2019 BMW 3 and 4-Series Forums > General F30 Sedan / F32 Coupe / F36 Gran Coupe Forum > Before you ask why your exhaust is broken and why only one side is dirty: READ THIS!
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      01-15-2018, 02:50 PM   #67
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Originally Posted by BMRSEB View Post
To address the muffler delete question, since I recently did the muffler delete.. No, no check engine lights or any codes stored.. I just wrapped up the connector neatly and tucked it under the bumper.. There's a nice little "shelf" for it..

However, be prepared for drone at low speeds, high load and cruising! To the point where, I am considering putting the stock muffler back on and perhaps at some point getting the AA exhaust or similar.

At (cold) startup it sounds loud as hell, then drops down to a nice rumble, would be nice if this low rumble was the "stock" sound, post muffler delete.. I will miss the pops and crackles at gas let off, but growing tired of having to shift to combat drone..
Well, went ahead and did it! Put my muffler back on.. I guess le$$on learned.. lol.. I could not take the droning at low speeds and also when you give it (more) gas at higher speeds without downshifting..

I do miss the crackles and pops at "let off" though.. still there but much, much, more subdued.. At some point will consider complete exhaust/muffler options, AWE, MPE, etc..

Just a PSA for those considering muffler delete, my personal opinion of course..
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      01-15-2018, 09:02 PM   #68
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I actually got flagged down by a guy in slow bumper to bumper traffic who had been following behind my car. He rolled alongside and motioned to roll down my window, he was all concerned and wanted to let me know my exhaust had something “stuck in it” on the left side. I laughed and said its a flap and they all were like that!

True story and third day with the car!
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      01-22-2018, 12:58 PM   #69
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Quote:
Originally Posted by paimon.soror View Post
PS. the bit about backpressure is hogwash. wayyyy too far downstream to impact backpressure lol.
I disagree go and get a potato and plug the pipe and see what happens to back pressure lol. I bet you can't drive far
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      01-22-2018, 01:52 PM   #70
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Well sure if you block a flow, that flow has to go somewhere... but i would have been surprised if a simple flap that doesn't fully seal off the outlet would have really caused that much additional back pressure.

But I can admit my ignorance if it really does
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      02-15-2018, 10:54 PM   #71
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Originally Posted by Blubaron79 View Post
On my MPE both pipes open up after warm up even in comfort. Which my previous two 35i models did not with the stock exhaust.
I also have the MPE, and both valves (at least on mine) are open - all the time. I checked using a flashlight, and the valve actually does not close when the car is off either, although I did read that that's probably normal.

I know normally the one valve is supposed to be closed on a cold starts, but I have started my car in the winter in literally -15C temperatures, after being parked overnight and I notice smoke coming out of both exhaust pipes.

Not sure if that's a good thing, anyone know if its a problem if both valves stays open on cold starts?
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Last edited by Carbon.F30; 02-15-2018 at 10:59 PM.
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      02-15-2018, 10:56 PM   #72
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Quote:
Originally Posted by floor_it View Post
Quote:
Originally Posted by Blubaron79 View Post
On my MPE both pipes open up after warm up even in comfort. Which my previous two 35i models did not with the stock exhaust.
I also have the MPE, and both valves (at least on mine) are open - all the time. I checked using a flashlight, and the valve actually does not close when the car is off either.

I know normally the one valve is supposed to be closed on a cold starts, but I have started my car in the winter in literally -15C temperatures, after being parked overnight and I notice smoke coming out of both exhaust pipes.

Not sure if that's a good thing, anyone know if its a problem if both valves stays open on cold starts?
I can say both are open all the time on the 340 with the MPPK. :-)
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      02-16-2018, 12:16 PM   #73
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i tried on my 320d 2014 coud'nt even locate where is my actautor?
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      02-21-2018, 03:41 PM   #74
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Quote:
Originally Posted by Blubaron79 View Post
Moral of the story is: buy the MPE
I have a 2016 340i and mine has 1 dirty and 1 clean exhaust and on cold mornings I see more white smoke out of 1 pipe than the other...this is an awesome sticky thread, btw...kudos to the OP!
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      03-21-2018, 07:42 AM   #75
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Very useful information, thank you!
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      04-13-2018, 11:22 PM   #76
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It's interesting because I don't notice a difference in exhaust tone whether the flap is open or closed. Maybe just a little bit more burble when decelerating in 1st in a parking garage with the windows down.
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      04-22-2018, 03:02 PM   #77
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BMW 335i

Any tips for buying a used 2015 335i
Things to look for like
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      07-22-2018, 12:58 AM   #78
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Excepet warming up, i cannot make sense of why the car wanna close one exhaust even, or especially at eco pro mode. More exhausts means Less back pressure means better fuel economy right?
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      08-06-2018, 03:23 PM   #79
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Quote:
Originally Posted by Cyanfall View Post
Excepet warming up, i cannot make sense of why the car wanna close one exhaust even, or especially at eco pro mode. More exhausts means Less back pressure means better fuel economy right?
Exhaust backpressure has to be balanced. I'm not going to pretend that I understand it, but there is a point where it's more efficient to have a certain amount of backpressure. That's why headers and exhaust design is actually more important than just making big pipes from the car go out the back.
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      09-06-2018, 11:45 AM   #80
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Possible to make it come out of both pipes

I recently got a valve controller in which i can control my valves without having to switch my car into sport. They are not too expensive and go a long way for both the sound of the car and having exhaust exit from all pipes/tips
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      09-14-2018, 07:00 AM   #81
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Hey, as a new member it says I have to reply to an existing post first!

I have a 2014 320d (F30) that's done about 115k miles.

Recently I've noticed that when switching the engine off, the exhaust makes a rough 'purr' sound as everything winds down. It sounds fine at all other times though.

It sort of reminds me of the sound an old VW Golf made when it was running without a silencer box, but I doubt there's a hole in the exhaust since it was serviced and MOT'd just back in May.

A search via google and on this forum hasn't turned anything up - lots of people talking about rattling and ticking sounds but nothing quite like this.

I'd be grateful if anyone has any insight please!

Thanks
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      09-18-2018, 12:51 PM   #82
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Nice to know!
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      11-02-2018, 12:55 PM   #83
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Quote:
Originally Posted by Cyanfall View Post
Excepet warming up, i cannot make sense of why the car wanna close one exhaust even, or especially at eco pro mode. More exhausts means Less back pressure means better fuel economy right?
Back pressure increases torque at low revs..makes the car more driveable which would also reduce MPG because you use less throtle to get going. But closed flap is bad for BHP at higher revs so you want to open the flap to reduce back-pressure to get better high end performance and free reving engine, thats why they have a valve. Its a bit like vanous on the camshafts which gives better torque at low revs and more BHP/higher rpm. Simples
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      11-02-2018, 01:41 PM   #84
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This flap broke on my car before causing a terrible rattle when accelerating, embarrassing to drive around like that to say the least. It was fixed by the dealer under warranty but I was sick of having one dirty tailpipe already so I upgraded to the dinan exhaust with black tips and haven't looked back since. Life is better with no exhaust flap
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      12-03-2018, 01:46 PM   #85
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Quote:
Originally Posted by smithf80 View Post
This question comes up all of the time, so I have asked a moderator, Dackelone, to sticky this so it can be at the top of the forum for everyone to see, although I'm sure this won't stop people from asking still.

[SIZE="3"]It is completely normal for exhaust gas to come out of only one of your two exhaust tips, and for only one to look dirty most of the time. [/size]


This is because the exhaust on our cars is valved, meaning it has a "flap" inside one of the pipes, and can be controlled electronically by the car for various reasons. In most cases, the flap will be closed, and this is the default setting for both Eco Pro and Comfort mode, this is why you see one tip clean and one tip dirty. In Sport and Sport+, it is open.

Here is a summary of the function of the flap (to my best knowledge):
  • Flap closed on startup to help warm up the cat's faster.
  • Flap will open itself when the car reaches idle, and will typically open itself when the car is idling.
  • After driving away in either Comfort or Eco Pro, the flap will close, and remain closed unless you give the car hard throttle.
  • The flap will remain open in Sport and Sport+ mode.

If you car doesn't do what I described to the T, don't worry, it doesn't mean somethings wrong, the car's computer is very smart, and only under certain conditions will that flap open itself, so if you go out and start your car and it happens to be open, don't worry, maybe your cars already warm, etc, etc.

Hopefully this thread will help put to rest all of the questions about this function so we can all get back to complaining about other small, unimportant things.
what to do if the exhaust flap actually stays closed for the whole cold start ?
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      12-03-2018, 06:00 PM   #86
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Quote:
Originally Posted by vinzcast21 View Post
what to do if the exhaust flap actually stays closed for the whole cold start ?
On cold start(on a x35i car)... the engine will idle fast(high) after a minute or two... the idle will come down to around ~800 rpm's, this is when the exhaust flap opens.

I think the SW level(version) also changes "when" exactly the exhaust flap opens on cold starts.

Dack
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      12-03-2018, 06:01 PM   #87
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Quote:
Originally Posted by Dackelone View Post
Quote:
Originally Posted by vinzcast21 View Post
what to do if the exhaust flap actually stays closed for the whole cold start ?
On cold start(on a x35i car)... the engine will idle fast(high) after a minute or two... the idle will come down to around ~800 rpm's, this is when the exhaust flap opens.

I think the SW level(version) also changes "when" exactly the exhaust flap opens on cold starts.

Dack
hmm its a b58 engine 40i
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