What does the center muffler do?

BP1

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The center muffler on my coupe was deleted by a previous owner. I have a b35 with Stahl headers and stock front and rear mufflers. How would the addition of the middle muffler change things? Quieter exhaust? Different sound? Or ??? Why do people delete it?
 

restart

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I think the long middle muffler under the drive shaft is referred to as a resonator.

I have a car with no middle muffler and one with no rear muffler.

Not sure if I ever heard them both in the same week but
IIRC
The one with only a cheap cherry bomb Center resonator is quieter than the rear muffler only.
Ymmv?
 

JimV

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As Markos wrote, the resonator (it's not a muffler) helps greatly to eliminate an annoying drone which can be present at highway speeds. A brief explanation:
Exhaust pulses entering the exhaust system at the engine are filled with high and low-frequency sounds. The sounds bounce back and forth inside the pipe, changing a little bit as they go, especially when they change direction inside the pipe. The engineers realized this and decided to look for a way they could take advantage of it. They learned that if they designed an essentially empty chamber for the exhaust to travel through, the pulses would bounce around in there — resonate — and some of them would cancel each other out. As luck would have it, the annoying higher tones were more likely to be canceled out. This made the job of the muffler much easier without robbing any efficiency or power from the engine.

I opened my stock resonator with a cut-off wheel and inspected its insides just out of curiosity. It's as described above; an empty chamber with a few metal baffles and no sound deadening material. I zipped it up and put it back on. My take is that the resonator serves a useful purpose (as described above) and though I might someday change the entire system to hopefully sound a bit more snarly, I would continue to utilize a resonator of some design.
 
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BP1

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So, if I understand things, if my exhaust has gotten very loud I should be looking only at the rear muffler as the source of my problem and not the front resonator (if there are no leaks in the resonator then it must be good, or can they fail internally?). Correct?
 

JimV

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So, if I understand things, if my exhaust has gotten very loud I should be looking only at the rear muffler as the source of my problem and not the front resonator (if there are no leaks in the resonator then it must be good, or can they fail internally?). Correct?

I would suspect the muffler. An unlikely failure of the resonator shouldn't cause a "loud" condition.
 

HB Chris

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I think you need the long front resonator, perhaps the small center muffler and you need the large rear muffler. I did add the small center one and like the sound of my exhaust.
 

Cornishman

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Mine only has the rear box which is mounted across the car. It does not have the other two boxes, or resonators as I learnt above. It is also stainless, I do not know the brand. Most people say it sounds great and compared with a three box car when static but revved up does not sound so different. However, on a motorway I would like it to be quieter, it is noisey.
I am told that a full three box system will add to lower end torque, can anyone confirm if that is true?
Is it true that a system made of both stainless and mild steel will be quieter than one made entirely of stainless steel? Apparently all to do with resonance. If so it may be worth adding a central box made of mildsteel, or perhaps a piece of mildsteel straught pipe.

But to reduce noise I also need to address other things eg fit of bonnet (hood), actually fit my 5 speed OD transmission, fit the last two door seals, adjust the sunroof. So the extra exhaust box is not so high on the priority list.
 

BP1

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I replaced the long front resonator and the large rear muffler and it sounds soooooo much better. Thanks all. Happy Thanksgiving!
 

Bmachine

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I replaced the long front resonator and the large rear muffler and it sounds soooooo much better. Thanks all. Happy Thanksgiving!
Looking at exhaust system options right now...
You say you replaced it and it sounds better. Would you mind explaining what you replaced it with?
 

Ohmess

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I did stainless and wish I had gone stock. I prefer the tone of the stock exhaust.
 

eriknetherlands

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Stock mufflers are thick walled steel. Stainless is usually quite thin.
The mass of that thick metal wall blocks high tones better then a light thin wall does. So comparing just thick to thin, yes they sound different; thick being more "heavy" in sound.

This comparison does not take into account that new mufflers can be tuned to be either nice and sophisticated or downright obnoxious.
 
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