Well, I figured I'd throw my two cents into the hat here. I actually have a CNC machine in my garage to make the plates and various plenum pieces with, and I definitely will be using a Cyclone manifold on my new build, once I actually find one for sale at a reasonable price.
What are people's thoughts on variable plenum volumes / resonance tubes? It's not a new concept. Just like switching runners, one can use a butterfly valve, a slide valve, or various other methods to open/close off plenum area at a certain RPM.
Take a look at this fantastic SAE paper on the design of Mazda's K-series V6es. Take special note of their design of the VRIS system, complete with dyno graphs of how the 4 possible combinations of the two switching valves affected the torque curves.
http://www.tsentraal.ee/mx6/engine/SAE920677.htm
Seems like engineering something like that, coupled with the pre-engineered dual runner setup in the cyclone manifold would be one hell of a setup.
Would take 4 dyno pulls to get the switching points right with the dual runners and one switched resonance tube / plenum volume, and 8 dyno pulls if you implemented dual switched resonance tubes like the K-series manifolds, but I bet the gains would be worth it. One could even pillage old mazda V6 manifolds for the vacuum switching actuators, shafts, and butterflies, too.
We wouldn't be able to calculate the effects of different volumes as easily as Mazda did, thanks to their engineering expertise and CFD software, but we could make some pretty good guesses based on how they designed their plenum.
I'd be able to easily make an adjustable controller for all 3 of the butterflies for probably $50-75 - it would control both the cyclone actuator and the one or two we used for a variable plenum volume / resonance tube, so this would all work happily with the stock ECU.
I could also definitely get the lower plates for the plenum CNCed if there was interest. Anyone up to the task of designing the upper plenum?
