New Direction
Many of you are aware of my battles with the R460 and the associated noise this little engine produces. I've tried many different muffler designs and my last one has proved the most effective. It also brought to light another noise source, intake noise. My solution was to put a silencer over the air filter to gain a little edge on the noise, the muffler and silencer are documented in this thread. Not totally satisfied (who would have thought) with my results, I added some fiberglass air filter material between the stock air filter and the end of my silencer. This helped a great deal but decreased air flow as evidenced by an over rich condition, which I corrected by adjusting the carb. Again not content, I began research into another method method to cut intake noise.
I began searching intake noise and found an interesting article about a guy with a Tomos 55 moped. He had installed a HP air filter and gotten pulled over for illegal muffler, which I recount to illustrate the significance of intake noise. What I was actually after was information on the Helmholtz Resonator and how I could employ it to help my problem. The two methods that I found to correct this issue were pre air filtration silencing and post air filtration silencing, the Helmholtz Resonator or as it's more commonly known an air box. Air boxes are widely used on engines today, especially in the automotive industry and I thought this might be the answer.
During my searches, I found an intake silencer for a Rotax ultra lite engine (IMG 1), this seemed pretty simple to me, an air box between the filter and carb with the filter at 90 degrees to the carb bore. Working on this principle, I began looking for a suitable box and settled on one of my old friends, a 4 x 4 x 2 inch electrical box from Home Depot. This plastic box has no ports or openings (drill your own) and has a "marine" rating, due I guess to the O ring sealed lid. After determining how I wanted to mount and brace the air box, I did a little drilling and painting (Krylon Fusion) and put it together. I have photos of the mounted box (IMG 2), the brace (IMG 3) and the assembled unit (IMG 4 & 5).
My first test ride was amazing, first off I had to lean the carb back out and for the first time I realized just how effective my muffler is. This has reduced my engine noise by at least 50%, absolutely unbelievable!