Reply To: Exaust and Body

[Gregory Long]

Fonts, fountains etc.

I went through a time when I was trying to quiet down an aftermarket exhaust system on a diesel truck, it had some weird drones and an odd tinny sound at idle.

One of the things I noticed was the aftermarket muffler was half the weight of the original equipment one. But about the same size.

I had a rusted original so I cut it open and it had a double outer skin. No insulation, just two layers of thin steel, with many spot welds keeping the two attached to each other.

I duplicated the idea, I just added a second skin, of 16ga steel, rolled so it had to be expanded to slide over the muffler, I just tack welded it in a few places and then tested the idea for a few trips to the airport. I had gotten pretty serious about this noise reduction project and had a Db meter. The double skinned muffler was noticeably and measurably quieter. and the dinging and tinny sound was gone when the truck idled.

I finished attaching the second skin with a few more welds and welded the lengthwise seam closed, Eventually this muffler succumbed to Michigan salt and rusted out, I bought a Stainless steel system next, and inquired of the manufacturer/seller how thick the skin on the muffler was, he asked why? I told him about my double skinned muffler for noise reduction, He offered to make a muffler for me out of 14 ga SSteel, instead of the standard 16ga. And it was plenty quiet.

So, I believe either a second skin, or a rather thick and heavy single skin will change the radiated sound from just about any muffler. You can experiment quite inexpensively with the correct diameter chimney flue pipe, and two or three large diameter hose clamps. just open the metal flue pipe at the seam, put it around the muffler, and hold it in place with two or three hose clamps. See if you notice any difference. Most flue/chimney pipe is either 24 or 28 ga. Rather thin, but it should make some difference in the radiated sound. You can use the results of the experiment to see if you want to go with a real double skinned muffler or not.

Greg L.