The expansion chabers are generally set to a specific rpm band where the torque tubes increase torque from start to the highest rpm. Thus you just got more torque when you ran one period. No specific "boost effect" at a certain speed.
I don't know if you've looked at this animation of how a expansion chamber works or not but the last illustration shows it working. Makes it much easier to understand.
This thread had a good run as we talked about chambers, listed free chamber design download software etc. Some of the guys here were into building them after taking all the measurements of their engine and plugging it into the boxes in the software wizard........which spit out the measurements to make, roll up, weld/braze together, and asembel to fit your bike.
It would be nice to build a data base of the most popular engines now of the best ones to post in a thread with the free design software. Then any owner could just download the software and plug in the dimensions to calculate with. Some of the softwares are for sale but don't cost much. I was figuring some guys could go in together on them with somenone who has a shop and can build them. Like partons. Then the holder of the program could build the
chambers for them reasonably enough. With the most popular motors it would
justify turning wooden forms to roll the cones on. (like out of old wooden baseball bats) and have a frame with a dead engine in it to asemble the chambers on to tack weld them before the final welding/brazing. (in which case they could send them tack welded semi finished or fully finished and painted if they wanted) Thus if the ones buying them had a way of finishing the chamber they could do so and save even more. Or the shop could just sell the cones and tubing knocked down to ship.
Whatever. The possibilities abound.