Does this solem length information apply to a 20B. I would also assume that "(two pipes with a muffler on each)" would read 'three pipes with a muffler on each'  when using a 20B.'

 

Joe

I would say yes, based on no knowledge whatsoever specifically in this area. I look at the number of rotors as just a number of small engines sharing a muffler, in the case of collected systems. The primary header length being equal is just to keep any two pulses from interfering with each other, rather than hoping for additional scavenging. I believe that once you have two complete pulses in one tube, there will not be better scavenging, and anything else that happens, like adding tubes or additional length is reducing the best situation available.

 

The challenge of a large volume of gasses moving at the speed of sound has overcome some fairly clever people. I had some luck with a half dollar sized button of 1/4" steel suspended in the center of a 4" exhaust pipe, and down flow a bit a 3/8" ring standing inside the 4" pipe. Like a necked down section but only a 1/16" thick ring with a 3 1/4" hole in the center. It made for a cheap tinny sound, but it was quieter. Might work in a smaller pipe. I did it at a track because we were over the 105 dB allowed at the time. (now 103 dB). It worked that time, so we got to race, but it sounded strange. Didn't seem to affect power.

 

The factory muffler looks like a large diameter steel pack muffler with an open chamber in the front. The pulse is allowed to drop to subsonic in this chamber, and beyond that its just a steel pack. They are stainless but still blow apart from time to time. The ID is about 3 1/2". Very pricey, so I never owned one.   

 

So, a design with a volume set aside in the flow to allow the pulse to drop to subsonic, and once done to re-enter the main flow minus the shock wave. Then its just muffling as in a Chevy.

 

Or a combination of the spiral flow around the outside of a tube full of small holes, to break up the flow and change the pulse into two smaller pulses that reach the end of the tube at different times because of the longer path one takes. Or, that and the front chamber to allow for subsonic changes and then whatever combination you want to try.

 

Build the prototype in carbon steel (SAE 1010)  and if it works OK, make the flight version in stainless.  

 

 

Lynn E. Hanover