Anyone heard of exhaust 'chambering'?
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Joined: Sep 2008
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From: Vegas
02 C32
Anyone heard of exhaust 'chambering'?
I picked up a new-to-me C32 this weekend. It drives tight and looks great, records all look good. The one thing bugging me is what sounds like an exhaust leak. I took it to a 'performance-oriented' exhaust shop and had them put it on the lift and crawl through the engine compartment with a stethoscope.
The tech said they could find no leak. His explaination was that since the previous owner had replaced one of the secondary cats with an aftermarket catalytic converter, what I am hearing is an effect called 'chambering.' He said it was due to the dissimilarity between the two secondaries setting up a pressure wave in the exhaust pipes and manifesting itself as a high-pitched sound similar to an exhaust leak. It disappears over about 3000 RPM, so maybe there is something to it.
This seemed dubious, but I couldn't argue intelligently against the diagnosis so I accepted it. While they had it on the lift, I had them cut out the resonator and weld a piece of 3" stainless in it's place ($60).
I visited a Midas today at lunch and they looked at the car for about ten minutes and then gave it back with no charge, stating they could find no leak but also stating they didn't like to fool with Mercedes manifolds.
I have an appointment with a good local indie shop in two days, and I'll have them give me a good answer on how to make this sound go away forever but I am hoping the answer won't have to be a new Mercedes cat. Anybody ever hear of 'chambering' as used in this scenario? Any ideas on what I might really be experiencing if it is not a leak? Any ideas on a possible fix? I just hate things that have mystery causes...
Thanx!
The tech said they could find no leak. His explaination was that since the previous owner had replaced one of the secondary cats with an aftermarket catalytic converter, what I am hearing is an effect called 'chambering.' He said it was due to the dissimilarity between the two secondaries setting up a pressure wave in the exhaust pipes and manifesting itself as a high-pitched sound similar to an exhaust leak. It disappears over about 3000 RPM, so maybe there is something to it.
This seemed dubious, but I couldn't argue intelligently against the diagnosis so I accepted it. While they had it on the lift, I had them cut out the resonator and weld a piece of 3" stainless in it's place ($60).
I visited a Midas today at lunch and they looked at the car for about ten minutes and then gave it back with no charge, stating they could find no leak but also stating they didn't like to fool with Mercedes manifolds.
I have an appointment with a good local indie shop in two days, and I'll have them give me a good answer on how to make this sound go away forever but I am hoping the answer won't have to be a new Mercedes cat. Anybody ever hear of 'chambering' as used in this scenario? Any ideas on what I might really be experiencing if it is not a leak? Any ideas on a possible fix? I just hate things that have mystery causes...
Thanx!
Senior Member
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From: Brooklyn
2009 Mini Cooper Clubman S
If the problem truly is that you have mismatched cats, you might consider just chopping the secondaries, which would in all likelihood eliminate the noise as well as possibly gaining some power. It doesn't seem to me to make a lot of sense their explanation unless the secondary cat is significantly more restrictive than the primary, although I could only see that causing back pressure, not "pressure waves".
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02 C32 AMG
cut them off. you don't need your secondaries. improve flow a little bit and make the exhaust sound louder. while you're at it, the resonator is also nice to chop off.
i have heard of chambering and what your exhaust guy says sounds plausible, but IMHO i would just chop off the secondaries and resonator and have yourself a nice exhaust sound. you wont pick up much power between the two (maybe with both, 2hp?) but you will see some weight savings, especially with the resonator delete, and slightly improved flow. congrats on picking up a great car!
i have heard of chambering and what your exhaust guy says sounds plausible, but IMHO i would just chop off the secondaries and resonator and have yourself a nice exhaust sound. you wont pick up much power between the two (maybe with both, 2hp?) but you will see some weight savings, especially with the resonator delete, and slightly improved flow. congrats on picking up a great car!
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From: Livingston, California.
2002 c32 AMG 2012 c250 Coupe
wouldnt cutting off the secondary cats give you smog problems..? if anybody here from cali has ever done this, did you ever had problems smogin the car..? how was the sound..? any noticeable power gains..?
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From: California
06 C55, 09 E350
I have been told that as long as you have the primaries you will pass smog. I kept my secondaries just in case there is an issue. I will just have them weld them back on if so.
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From: Keesler AFB, Gulfport, MS
C32 AMG
All you need for smog check is the primaries. Delete the rear cats and kill two birds with one stone. You won't be sorry!
On a side note, welcome to the forums and greetings from Keesler.
On a side note, welcome to the forums and greetings from Keesler.
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Thread Starter
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Joined: Sep 2008
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From: Vegas
02 C32
I had the guy remove the resonator (it actually is pretty heavy), but he flat refused to remove the secondary cats. I even asked if he could weld in a set of 'test pipes' for me, but he refused to do that. If I had any idea how to weld I'd cut them out myself. As it is, I am stuck unless I can find a place flexible enough to bend the rules for me but still trustworthy enough to wrench on my new toy.
In the meantime I am stuck with a car that sounds more like an old dump truck than a high performance machine.
In the meantime I am stuck with a car that sounds more like an old dump truck than a high performance machine.
Thread Starter
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Joined: Sep 2008
Posts: 173
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From: Vegas
02 C32
MBWorld Fanatic!
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From: Keesler AFB, Gulfport, MS
C32 AMG
Thanx! I've never been stationed there but passed through many times en route from Maxwell to New Orleans. I was told today I may have an opportunity to PCS to Ramstein in the near future. I'll just have to get the speed limiter removed before taking this beastie out on the Autobahn
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Joined: Apr 2007
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From: Orange County
2019 AMG C43
I had the guy remove the resonator (it actually is pretty heavy), but he flat refused to remove the secondary cats. I even asked if he could weld in a set of 'test pipes' for me, but he refused to do that. If I had any idea how to weld I'd cut them out myself. As it is, I am stuck unless I can find a place flexible enough to bend the rules for me but still trustworthy enough to wrench on my new toy.
Thread Starter
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Joined: Sep 2008
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From: Vegas
02 C32
You say it is legal to remove the secondary catalytic converters? I hope this is true. Can you cite your source for this information so that I can print it and present it to a muffler shop as proof they are allowed to make this modification? This would be the ideal solution I think. Thanx!
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Joined: Nov 2008
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I DON'T COME HERE ANYMORE
I dont think it is-removing any of the factory installed emissions parts and not replacing them with similar/like parts is where they get hooked-they can take the cats off, but they have to but something similar in its place (and no, a TP/Race pipe is not similar 
)
replacing many in my past (10+ cars worth front and back)-I have not found a muff/exhaust shop that would do it (tuner shop.... )
)replacing many in my past (10+ cars worth front and back)-I have not found a muff/exhaust shop that would do it (tuner shop....
)
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Joined: Oct 2006
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02 C32 AMG
https://mbworld.org/forums/c32-amg-c...-question.html
look at post 23. the secondary cats are those bulkier looking things at the end (your right side when looking at the diagram) of numbers #10 and 15
look at post 23. the secondary cats are those bulkier looking things at the end (your right side when looking at the diagram) of numbers #10 and 15
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From: FT POLK LOUISIANA
1992 Toyota Corolla, 1994 Chevy C1500, 2002 C32, 2012 Prius, 2013 Toyota Sienna
From a Soldier that has been in Germany twice I can tell you that a modded C32 is nearly untouchable on the Autobahn.
Thanx! I've never been stationed there but passed through many times en route from Maxwell to New Orleans. I was told today I may have an opportunity to PCS to Ramstein in the near future. I'll just have to get the speed limiter removed before taking this beastie out on the Autobahn
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From: Cave Creek, AZ
2012 Mercedes S63 P30, 2015 Mercedes GL550, 2009 BMW 650i Convertible
Local undercover authorities are known to take a car to exhaust shops to have them modify the exhaust with non-approved (or non-CARB-approved) parts, and then they bust them.
If the shop has a smog machine and, in turn, passes the vehicle (or any vehicle that shouldn't pass the visual inspection), the authorities likely have a case to confiscate the smog testing machine. Smog tests are huge money-makers for shops, so the risk is just not worth it in the long run.
