# just joined the no-exhaust-valve club :D



## rwg (May 10, 2002)

*Just remembered something else from those other threads on the topic*

I seem to remember someone saying that there is a sensor that might generate a fault code and warning light or that the open vacuum hose might cause problems. There was a discussion about plugging the hose and going into the fender from the inside of the trunk to disconnect something. Obviously, I am not very knowledgeable about thisdunno: ), but you might want to do some research if you plan to leave the hose off.


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## Jspeed (Dec 23, 2001)

You MUST plug the vacuum line. BMW's parts catalog also includes a sports muffler for the 330 which does not have a flap and it comes with a plug for the vacuum line. Failure to plug up the hose will lead to the source of the vacuum being contaminated with dust and dirt.


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## DougDogs (Dec 26, 2001)

SONET said:


> *There have been several extensive discussions about this valve here, at .org, and on the fanatics board. It has been concluded that these valves are on 330* and 325xi cars. Among other things, it adds necessary backpressure for extra torque at lower RPMs. Do a search for 'exhaust valve' for more details.
> 
> *


My 2002 325xi (build week 2) does NOT have this exhaust valve. Maybe it was a 2001 thing. My car no longer has a CDV. That's the best mod I've made so far:thumbup:


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## Patrick (Dec 23, 2001)

I am going to have to go and see if my diesel has this funky valve; if Alan can be in this club, why can't I!  

I'll be back ...

Patrick


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## Patrick (Dec 23, 2001)

Poop.

Nothing but the big rubber grommet or hook that holds the muffler in place. Obviously, the diesel muffler is way different than gasoline engine version.

I know that no one will know the answer to this but: why does my exhaust tip (single outlet) bend down? The 330d has the same muffler as well. I always wondered about this.

Ho hum. Back to my yard work.

Patrick


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## johnlew (Dec 25, 2001)

Patrick 320d said:


> *
> I know that no one will know the answer to this but: why does my exhaust tip (single outlet) bend down? The 330d has the same muffler as well. I always wondered about this.
> 
> *


So that the back of the car doesn't turn black from diesel exhaust?:dunno:


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## Patrick (Dec 23, 2001)

johnlew said:


> *So that the back of the car doesn't turn black from diesel exhaust?:dunno: *


There is no black sooty smoke, even under hard acceleration. It doesn't smell like a diesel in the traditional sense either. Most modern turbo diesels are the same way.

I dunno either.

Patrick


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## DougDogs (Dec 26, 2001)

Patrick 320d said:


> *Poop.
> 
> I know that no one will know the answer to this but: why does my exhaust tip (single outlet) bend down? The 330d has the same muffler as well. I always wondered about this.
> 
> Patrick *


The exhaust tip on my Audi A6 was bent down....but this was from my wife not watching what she was doing while backing up:thumbdwn: :banghead:

Patrick, does your wife drive your car??


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## webguy330i (Jan 9, 2002)

Jspeed said:


> *Just to share what I know. Bentley manual explains that the exhaust flap is there merely for noise reduction and nothing else. So now it depends on how much you trust Bentley. I tend to agree because the exhaust flap only closes when you let off the throttle. If it were there to improve low-end torque then it shouldn't open when you accelerate from low rpm. *


This is exactly what I've observed. Upon letting off the accelerator I can tell now that there is a bit more exhaust note which tells me that the valve would have normally been closed at that point. I've also noticed that (when the valve was enabled) and I was accelerating at WOT from a slow stop, that the valve would open (you can hear it go "clack!").

This lead me to believe that the valve was ONLY there for sound supression. I am not one to fool around with the R&D that a bunch of much-more-qualified engineers have performed, but I truely believe that the valve is only there to make the car more subdued and therefore available to a larger market of prospective customers.

You don't see valves on any M cars now do you? Also why in the world would they bother with a dual-pipe exhaust system only to close up one of said pipes with a flappy valve, if it had any performance ramifications otherwise?


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## Patrick (Dec 23, 2001)

DougDogs said:


> *Patrick, does your wife drive your car?? *


Occasionally! However, all of the BMW diesels are the same. It is a short tip that does not even clear the opening in the rear valance.

Patrick


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## JetBlack330i (Feb 8, 2002)

webguy330i said:


> *
> You don't see valves on any M cars now do you? Also why in the world would they bother with a dual-pipe exhaust system only to close up one of said pipes with a flappy valve, if it had any performance ramifications otherwise? *


Most 6-cylinder engines have dual tips due to the amount of gas flow. If the factory were to put a single tip, it would look like a coffe can (hmm... if I recall, the IS300 does that). As you must have noticed, aftermarket "free-flow" exhausts are loud. You're right that BMW wants to appeal to a wider audience, so they put a valve there to close off one tip when it's not needed, in favor of comfort.
I understand that many of us would be willing to pay the noise price for a few extra ponnies. That's exactly what aftermarket free-flow exhausts claim to offer. But a I don't see how disabling the valve would give us any extra ponnies. It's not like the valve closes when we need it to be open. 
If anything, you stand to loose performance. Do a search on the web with the keywords "scavenging effect" and "starvation" in "exhaust systems"


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## Nick325xiT 5spd (Dec 24, 2001)

It occurs to me to wonder if the noise problem is a wago thing... I could easily see hat the rear end of my car serves as a sort of reso0nance chamber... On the other hand, I've seen lots of cars with exhausts that would make me ill whose owners rave about the "note" and "performance." :dunno:


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## webguy330i (Jan 9, 2002)

JetBlack330i said:


> *
> Most 6-cylinder engines have dual tips due to the amount of gas flow. If the factory were to put a single tip, it would look like a coffe can (hmm... if I recall, the IS300 does that). As you must have noticed, aftermarket "free-flow" exhausts are loud. You're right that BMW wants to appeal to a wider audience, so they put a valve there to close off one tip when it's not needed, in favor of comfort.
> I understand that many of us would be willing to pay the noise price for a few extra ponnies. That's exactly what aftermarket free-flow exhausts claim to offer. But a I don't see how disabling the valve would give us any extra ponnies. It's not like the valve closes when we need it to be open.
> If anything, you stand to loose performance. Do a search on the web with the keywords "scavenging effect" and "starvation" in "exhaust systems" *


Actually most 6-cyl cars don't have dual tips. Some 4-cyl cars do, some don't. Some 8-cyl cars do, some don't. It's a matter of "do we want to spend the money to make this car look like it is performance-worthy or not" as in the case of the 540i for example. The number of tips is absolutely irrelevant.

IMO there is no noise price; it's a fundamental aspect of the car. This engine makes a wonderful sound and I want to hear it whenever possible. There is a reason why the valve opens at WOT: it's for performance, it's for sound, it's for pressure release. There's also a reason it remains closed on the highway and around town when you're not gettin on it very much: it's for sound, not performance, and certainly not for pressure.

This engine produces a hell of a lot of torque as you know, more than 2x that of my older car (2000 Civic Si). Because of that back pressure is a negligible thing and thusly I do not believe the valve is there for any sort of pressure regulation. It IS, however, definitely there for sound supression. Otherwise people like Nick would never have been able to buy their 325xi without stuffing a sock in one of the exhaust outlets.


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## JT - '02 330i (Dec 29, 2001)

ride365 said:


> *
> 
> I don't understand... that seems contradictory.
> 
> kurt *


Try it, might work better for you. It's an odd frequency of droning, and didn't work for my head. It wasn't loud.

As for the contradiction:
Think nails on chalkboard, not really loud, but causes different reactions in different people, many of them severe.


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## Guest84 (Dec 21, 2001)

in_d_haus said:


> *I'm guessing there is some reason for it being there...anybody know what it does? Is there a long term problem running without it? *


I'm with Haus, personally, I'm not for second guessing engineers unless there's plenty of information saying why its there, and what potential long term effects without it could be.


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## webguy330i (Jan 9, 2002)

Rip, I cannot imagine that there are ANY ill-effects that could be caused by disabling this valve. If anyone can offer any information otherwise, I'm game, but to me it doesn't seem like it's that serious of a part/function.

I think it comes down to "do you want the extra noise and the seemingly-better throttle/engine response".


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## AF (Dec 21, 2001)

Patrick 320d said:


> *I am going to have to go and see if my diesel has this funky valve; if Alan can be in this club, why can't I!
> 
> I'll be back ...
> 
> Patrick *


Patrick, If Chris is ok with you being in the club then so am I !!

The only thing is your annual dues will have to be paid in American Dollars . . . . please forward them immediately to my attention


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## bmw325 (Dec 19, 2001)

I think its safe to disable the valve given:
-BMW's own sport muffler for the 330 doesn't have this valve
-plenty of people install aftermarket mufflers that obvviously don't have this valve. Maney of these aftermarket companies are quite reputable and wouldn't want to damage their reputation by selling something which would potentially hurt performance or ruin the engine.
-the 325 (atleast the RWD version) doesn't have this valve- and the 2.5 liter engine is very closely related to the 3.0

It seems like its just a toss-up as to whether you like the extra noise or not.


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## webguy330i (Jan 9, 2002)

Alan F said:


> *
> 
> Patrick, If Chris is ok with you being in the club then so am I !!
> 
> The only thing is your annual dues will have to be paid in American Dollars . . . . please forward them immediately to my attention   *


I am absolutely down with that. It's good to go international! :lmao:


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## JetBlack330i (Feb 8, 2002)

webguy330i said:


> *
> Actually most 6-cyl cars don't have dual tips. Some 4-cyl cars do, some don't. Some 8-cyl cars do, some don't.
> *


That's not true within BMW, but I agree the # of tips is not important. What matters is the flow volume allowed by the tips.



webguy330i said:


> *
> There is a reason why the valve opens at WOT.
> There's also a reason it remains closed on the highway and around town when you're not gettin on it very much.
> *


You've got it backwards.
The default position is open, like on highway. You already get max performance by default.
The valve only closes in certain situations. I've not been able to determine exactly when those situations are, but I've heard of the following two:
1) When decelerating, like when the wheels are driving the engine. You'll agree that there is no need for performance there. The valve closes for sound supression.
2) When you accelerate in low rpm. This is supposedly to improve torque at the low end. You disable the valve, you loose the extra torque. Even if this is not true, you gain nothing by disabling the valve in this situation.

So, to summarize, you disable the valve to get some extra sound.
If you like the sound, keep it disabled.
If the low end torque theory is true, then that's the price you pay for your extra sound.


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