[scupper]

As you might recall, I am new to these E46s - our 330CiC is sitting at the dock soon to board a ship bound for NY - - -
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Curious to know if the twin outlet muffler is a true dual - that is, two pipes in and two pipes out, or is it one pipe in and two pipes out, i.e., simply a styling thing?

 

[Fisch330ciTB]

2x2 we come marching in....varoooom, varoooom.

 

[scupper]

Excuse me for being dense, but are you implying that indeed there are two pipes coming into a split chamber muffler, and that each chamber exits via its own tailpipe? Each pipe/header, is taking exhaust gases from 3 cylindars? Not trying to ba a smart ass, just curious.
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On the SC, with the flat six, each header handles 3 cylindars - and normally feeds into one pipe, then into the cat, and then into a single muffler inlet and outlet. Some of us, however , bypass the cat, and run separate headers directly into the two-in/two-out muffler, or a two-in/one out muffler (less noise).

 

[Fisch330ciTB]

This is what I know technical wise. :dunno: this is not my car, it is from www.activeautoworks.com

 

[J. Kidd]

Two separate outlet pipes....but

they share a resonator and muffler.

All 6 cylinders dump into two header banks - 3 cylinders per. The 3 tubes squeeze down into one and continue the length of the car (times 2 - one for each header bank). These pipes share what seems to be some sort of resonator and then finally they share the muffler. This is a very efficient exhaust. A performance mod available for other cars with dual exhaust is an "x-pipe" where, on a V8, each cylinder bank goes down the pipe, meets at an "x" and then splits again. The theory is the x does not restrict exhaust flow but actually balances out exhaust pulses aiding in performance. Sharing the resonator the way our cars do seems to me like it would accomplish the same thing. Also having the dual pipes share the same muffler saves in the weight of an additional muffler and still flows very well (as long as there are just as many outlets as their are inlets - which our mufflers have).

Hope that answers your question.

 

[31st330i]

Re: Two separate outlet pipes....but

they share a resonator and muffler.

All 6 cylinders dump into two header banks - 3 cylinders per. The 3 tubes squeeze down into one and continue the length of the car (times 2 - one for each header bank). These pipes share what seems to be some sort of resonator and then finally they share the muffler. This is a very efficient exhaust. A performance mod available for other cars with dual exhaust is an "x-pipe" where, on a V8, each cylinder bank goes down the pipe, meets at an "x" and then splits again. The theory is the x does not restrict exhaust flow but actually balances out exhaust pulses aiding in performance. Sharing the resonator the way our cars do seems to me like it would accomplish the same thing. Also having the dual pipes share the same muffler saves in the weight of an additional muffler and still flows very well (as long as there are just as many outlets as their are inlets - which our mufflers have).

Hope that answers your question.

great answer but I'm not sure it's the answer to this question....

yes, muffler shops have been adding an "H pipe" (a crossover pipe) between the left and right pipes in a dual exhaust configuration for years. in fact, I wouldn't call it a mod in and of itself. any well designed dual exhaust for a V8 will have this feature built in. the diameter of the pipe as well as its location (relative to distance from the header) are to the best of my knowledgecalculated. forthermore, there is only one crossover point. as I recall, the way that it "aides performance" is that it may induce some pulse scavenging. I'm not 100% sure, though. they taught us this in high school autoshop but it's been a while. I also seem to recall that there was an easy way to calculate which diameter to use for the H pipe based on the diameter of the main pipes and where to place the H pipe in relation to the length of the system.

I just remembered.... my BMW motorcycle (boxer twin) had a crossover pipe inthe stock exhaust as well as in the supertrapp system that I later bolted onto it.

anyway our bimmers are quite different since there *several* points at which the dual exhaust streams come together.

in terms of a 325/330: the manifolds are sepeareate and have their own cat. converters. the secondary converter (maybe it's one of two resonators and not a converter) is shared as well as the resonator and muffler. so there are three points of "contact" here. while there may be some of the same effect here, I don't think it's exactly the same thing and don't think that it's the intended purpose of the shared components in this case. I think the shared components are there to keep noise and cost down more than anything else.

 

[J. Kidd]

Agreed on our exhausts (m)

in the sense that is most likely a cost issue (possibly and assembly issue as well). I was just looking at it in a way that "sharing" those components is necessarily a bad thing.

The x-pipe mod I refer to is an x-pipe that replaces the factory h-pipe. The h-pipe is supposed to balance out exhaust pressure between the banks. This might aid in "scavenging" but I was under the impression that is just equalized pressure between the banks allowing the motor to run more evenly (between cylinder banks at least) thusly improving performance. Along this line of thinking, it was determined that the exhaust gasses were flowing too fast passed the "h" part for it to be effective (at least as effective as it could). The "x" shape replaces the "h" shape (at roughly the same location as the h-crossover) actually joining the pulses before separating them again. There are some professional applications of this x-pipe where the actual cross-section of the "x' area is changed and tuned to provide the most performance per application.

SuperTrapp on a motorcycle, huh?!?!? Must have been able to get some dogs to howl at the upper rpms :yikes: