E46 Fanatics Forum banner
1 - 16 of 16 Posts

·
Registered
Joined
·
91 Posts
Discussion Starter · #1 ·
Just wondering why BMW incorporated such cable into their mufflers?

Does it mean once opened muffler turns to straight flow? How is it controlled?

How's the internal of the muffler as compared to non valved muffler version?
 

·
Super Moderator
'03 325iT Mystic Blau
Joined
·
5,448 Posts
Just wondering why BMW incorporated such cable into their mufflers?

Does it mean once opened muffler turns to straight flow? How is it controlled?

How's the internal of the muffler as compared to non valved muffler version?
It's vacuum controlled and ostensibly is meant to provide extra flow under heavy acceleration. How effective it is? 🤷‍♂️
 

·
Premium Member
Joined
·
3,605 Posts
I always thought it was just a noise tuning thing- give it a bit more growl down low,
with less fart can overtone off idle...

t
 

·
Registered
Joined
·
291 Posts
There is no non-valved version, only mufflers without valve. Big difference.

Stock 330i muffler has the valve. Sport muffler also has a valve. Perfomance package muffler doesn't have a valve. Performance muffler also doesn't have a valve. All 4 of these are different from each other (not because of the valve but because they are different mufflers).

You can just disable the valve on the 330i and sport muffler. By now they should almost all be disabled anyway due to getting stuck.

If you want more sound I would just get a sport or performance package muffler.
 

·
Legendary like a schoolboy
Joined
·
6,400 Posts
By now they should almost all be disabled anyway due to getting stuck.
haha, made me laugh,

Yes it is sound control
helps with startups too so that you wont wake up the neighbors.
My stock exhaust valve had a rattle when taking left turns and accelerating lightly when the car was only a few years old.

then the golf tee mod was born in like 2002-2003 which fixed my issue until I got the Rogue DMS
For performance, replacing the heavy section 3 with a dual muffler system (on the 330s) was the only performance benefit
it just happen to come with great heavenly sound.

Only after super charging and then uncorking the stock headers with technik headers did I see some real horsepower gains.
 

·
Registered
2001 330i (pre-facelift)
Joined
·
684 Posts
On my 330i, the valve was stuck open when I bought it. It didn't seem loud to me. But after I freed it up, the valve would close at idle and light throttle, to (presumably) make it quieter. Personally I don't see the point, unless you're extremely sensitive to exhaust noise.

Edit: I forgot about the idle flare at start-up. That could be another purpose for the flap.
 

·
Premium Member
Joined
·
3,605 Posts
Oddly, 325xi has the valve, 325i does not.

Bmw make no sense.

t
was it a noise reg? The stock cars are pretty quiet, it seems...
 

·
Premium Member
E30M3 Race F10 535 R1150Rt M Coupe
Joined
·
7,839 Posts
What I was taught at BMW:
The installation of the valve was a small part of the (EU4?) package. It was to reduce vehicle noise in inner-city uses.

Under less than 50% load the butterfly valve stays closed. Under higher demands, the vacuum controlled butterfly valve opens.
 

·
Registered
E46 325Ci
Joined
·
5 Posts
Mine is a EU4 package (meant for Spain) and it doesn't have the valve. It is very quiet though.
 

·
Premium Member
Joined
·
3,605 Posts
In this case, the xi in question is an xit. Wagon, even.

t
 

·
Registered
2005 330xi, Jet Black w Black Interior
Joined
·
95 Posts
My 330xi is not quiet. It's not loud but definitely not quiet. I wonder if it has an after-market exhaust. When I first read this thread, I thought maybe my valve was stuck open but since it doesn't have such a thing...
 
1 - 16 of 16 Posts
Top