Thanks, Mike. The days are short here. Long nights and foul weather. Lots of time for machining. This morning there was a bright glow to the south. I thought the Russkies nuked California. Then I remembered. The sun. That is what it looks like.
This is not LSR. It is interesting. The old race mufflers on Bonnie, the race bike, were some stainless steel glass paks. A couple of tuners told me they were not adequate for a big bore motor. They looked great Clyde the street bike. Unfortunately, the internal diameter is 1.75 inches and they are far to loud for street use. The job is to quiet them down without killing street performance. Also, the changes need to match the EFI mapping.
First, I tried a simple choke ring as shown on the left in the photo. It made the bike quieter but performance was poor. It seemed to run too rich or lean at different rpm compared to the mapping. The choke ring has a flat surface perpendicular to the flow that reflects a strong and distinct pressure wave back down towards the exhaust valve. Maybe this is the problem.
Next I tried a baffle with a single step at a 45 degree angle, as shown to the right in the photo. This worked much better. It reflected a less distinct wave.
Finally, I made the baffles shown in the second photo. They step down from the 1.746 original pipe diameter to 0.975 inches in five increments. All steps are beveled at 45 degree angles. The heights of the steps and the distances between them are not the same. This is intentionally done to reduce the intensity of any reflected waves. These baffles work great. They quiet the bike down and do not hurt performance on the street, as best as I can tell. They match the mapping.