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Exhaust db reduction mod


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Created this inexpensive DIY spark arrestor/silencer device. It’s a 1 1/2” to 2” exhaust pipe adapter, with a 2” washer welded on the end with a 3/4” center hole and 8 - 3/16”. There is fine stainless steel mess right behind the washer. The inside of the 2” portion of the adapter is filled with one stainless steel (Scotch-Brite) scrub pad. A self tapping bolt holds it in place. The existing tail pipe had to be bent upwards to make room to slide the silencer on.

There is no change in engine performance other than the machine is a little less responsive at the upper most rpm range, it takes just a little longer to reach max mph. Hasn’t effected engine temperature either. Tailpipe surface temperature increased about 26 degrees.

You may look at my db readings and think it’s not that much of a difference, but the tone of exhaust is much more mellow, and doesn’t have any sharp sounds. It’s a really nice change. The decibel system is not a linear scale of sounds, it’s a average of two factors, so just a couple decibels can be a big change.

Here are my db reductions, measured with the iPhone app from NIOSH:

-5 db standing 6’ behind the machine at idle.

-2.5 db in the cab at idle, all windows closed.

-3 db driving on paved road at 25 mph, all windows closed.

-2 db driving on paved road at 50 mph, all windows closed.



Edited by Mndefender
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Interesting mod, if you want to reduce back pressure (response on the top end) you would want the mod to have a flowing area that is at a minimum the same as the area at the end of the stock exhaust (pie x diam) and potentially larger to allow for some plugging of the steel wool over time. If you are already there enjoy the reduced noise.👍

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certainly a creative idea for a problem you had.  nice job, as long as it works for you, thats what matters.  those dB reductions are pretty good, regardless of the hp loss.  thats probably 2 hp worth of reduction (unless it flows the same overall like andy stated) id bet but certainly worth the trade off for someone who wants it quiet instead.  just the screen alone will reduce it enough to lose some hp, even with nothing else changing.  ive seen it on dynos when we pull the spark arrestor out of the exhausts, it makes a difference.


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I knew there would be a HP trade off, that’s just how things work, but I think there’s a little more low end grunt. The surface area of the holes in my silencer are the only slightly less than the stock tailpipe opening. I did this intentionally, knowing I could drill them out larger if needed later. I was hoping to create more reverberations in the silencer. So far I’m happy with the HP trade off, time will tell as I put through more tests.

My Defender is a exploring machine for my wife and I, usually tooling around at 25 mph or less, checking out the neighborhood wildlife. It’s amazing how much a couple decibel reduction makes when trying to relax and have a normal conversation. If I want loud and wild I have other things to satisfy me.

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  • 6 months later...

I have about 325 miles now with this modification, including a lot of snow plowing, no negative impacts so far, other than what I spoke about in original post.

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