MGB & GT Forum

I've removed the center resonator with a straight pipe that goes to a Bosal rear muffler.

The sound is great but I would like to eliminate some of the high frequency rasp that I only get on hard acceleration.

I wondered what effects a baffled exhaust tip resonator would have, one like in this photo.

Steven,
The "high frequency rasp " is from removing the front 'chamber' resonator/muffler, but then you knew that.
I think you are aware that the Bosal exhaust system was made as a two box system, and pretty much represents the OE sound. You have half of it so you may want to think about reinstalling a front 'chamber'.
It is these 'chamber' that allow the sound frequency to change and be attenuated.
Another approach could be to install a larger single rear 'chamber' .

I will admit I have no idea what the that tip you show will do.

Good luck.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

Steven,

I, too, can not tell you what the resonator tip will do. In my case, the PO thought the OE resonator was "too quiet" and replaced it with a glass pak. Unfortunately, whoever did the replacement fudged it in, and the pipe from the headers to the glass pak rotated and I could not get it back in place. Too much exhaust crept into the cabin, so I took the car to a muffler shop that a MG friend recommended. There were too many bends in the exhaust system that they could not figure out, and I replaced everything from the where the headers ended to the back of the car.. This shop worked on MGs and Triumps, so they knew that the middle resonator was not needed. All I can tell you is that the muffler, which sits next to the gas tank, is a Lifetime Muffler Brake and Radiator #3018. With a straight pip where the resonator used to reside, my feet no longer get hot.

This is what my car sounds like. I am going up Renton's version of Lumbardi Steet. You start out at about elevation of 50 feet, and end up at about elevation of 380. There are a few choice words at the beginning of the clip, as I discovered later that my timing was not quite right, and I though the MG was going to stall.

gee , I suppose in some eyes here then , I would be considered as thrashing mine maybe....give it the ugga duggas

As others have said, you have removed the bit that does the job of reducing the rasp.
Short answer to effect of adding a glorified chrome(?) trim pipe is, nothing

Quick answer, almost none. If it was that easy, MG would have done it. Instead of spending money on "magic" solutions, check out a book:

http://www.bentleypublishers.com/automotive-reference/engineering-and-motorsports/scientific-design-exhaust-and-intake-systems.html

You will learn why things like that won't work. There are only a couple of ways to reduce noise. The correct answer is to put the resonator back in. Besides, you have no space for that tip. The muffler is very close to the rear of the car. You could add a SuperTrap to the tailpipe and tune to your desire. They actually do work. They use the restriction principal. ( restriction or absorption are your only choices)

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Cogito ergo sum periculoso

I know that road (192 St) I've driven on it with my Norton motorcycle. We lived in Renton (149 Ave SE) when I working for Boeing at the Kent Space Center.

The benefit of having less heat transmitted through the floor is worth the modification alone and I'm not at all bothered by the extra low frequency noise.

I wouldn't go so far as calling an exhaust tip resonator a gimmick though I would not expect a significant amount of noise level to decrease with its use.

What I was looking for is more of a high frequency notch filter for the exhaust.

Thanks for the replies.

How about putting in a section of chambered exhaust pipe? http://www.classicchambered.com/classic/products.html

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Pogo is right.
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The power of reasons is an illusion. The belief will not change when the reasons are defeated. The causality is reversed. People believe the reasons because they believe in the conclusion.

The "chambered" pipes are actually well known for having pretty high restriction. They are handy when you just don't have enough room for a real muffler but they are not even as quiet as a Cherry Bomb. If you are concerned with floor heat, put on a heat shield. Just like all modern cars.

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Cogito ergo sum periculoso

I also removed the center resonator, or rather it fell off (rust). Replaced the entire exhaust system using a header, straight 2 inch pipe back to a thrush glass pack. Sound? Kind of raspy and harsh, I may do what you are doing, but not until spring. I am not "restoring" my MG, as such, although it could be done if one wanted to. I love the car and I find that small subtle changes, improvements, are good. It's my car and I can hot rod or modify it anyway I want too, and so can you! ( removing the pesky catalytic converter was more an act of mercy...) I do not agree that the stock MG exhaust setup's had any particular value other than being OEM which for some is how they roll. Carburation, exhaust, ignition improvements/ changes are all very easy to do on these cars, and it's fun! No it probably will not add HP, but a little bling here and there? Priceless.



Edited 1 time(s). Last edit at 2016-12-10 01:02 PM by ernzo2.

That's not my only concern. My main concern is ground clearance. Back when these cars were born there was no such thing as speed bumps.

Besides, modern cars even with larger engines have a single muffler with tip resonators.

Yes they do Steven, but don't forget new cars are designed with this in mind. And these cars, "with larger engines " certainly sound good, and usually more than 4 cylinders..

Also keep in mind, that most single box exhaust systems of the era, (and perhaps new?) have a smaller diameter outlet to the muffler than the inlet. Just how it was done to reduce noise level.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

It's curious as to why Bosal decided to only offer an oem style rear muffler.

My take on this is most owners did just as you did and simply omitted it for reasons as you suggest, or $$ or not thinking or _ _ _ _ _ (fill the blank)

B

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Life's most persistent and urgent question is, "What are you doing for others?"