Adding Discs to the SuperTrapp

More Power = More Noise

So with power almost back to its previous level, the next question to answer was how much louder did the bike get? It was time to put the decibel meter back to work.

Before I report on the results, I should make clear the methodology I used to record the sound levels. I positioned my bike in exactly the same location on my driveway as I had in my previous two sound tests, and once again measured 20 feet from the tip of the exhaust to the Radio Shack meter mounted on a tripod. Although the sound from the bike traveled between my house on one side, and a thick growth of cedars on the other (which no doubt affected the readings due to sound waves bouncing from so many objects), the values that I recorded are meaningful in that they can be compared to each other. The only variable that I cannot account for was the ambient air temperatures. How much of an effect they had on sound measurement? I have no idea, but hope that for the purposes of this test that they were minimal.

The following table documents the results from both exhaust systems.

So it appears I am pretty well back to where I started; a bike that is too loud. Except at idle, where it is still noticeably quieter, and at 4000 rpm (and higher I assume), the bike is as loud as it was before I made the change to the SuperTrapp's. The difference now, however, is that I can adjust the level of sound in a few short minutes by changing the number of discs installed. In fact, my next experiment will be to fabricate a clamp that will be used to temporarily (and quickly) cover a half dozen or so discs for those occasions when reducing noise is much more important than producing horsepower. You know, those times when you are about to be inspected by an officer of the law, or when you want to maintain a low profile while riding through a residential area late at night.

I had also ordered a Snuff 'R' Not end cap many months ago, and it has been on backorder ever since. If I ever actually receive it, I will test how well the SuperTrapp performs when switched from a closed end cap to one that is open for a freer breathing muffler.

SuperTrapp claims that an open end cap with nine discs is the equivalent of 20 discs and a closed end cap. I believe I also read somewhere that more than 26 discs is not beneficial as it would perform just like an open end cap at that point.