Intake silencer more
Intake silencer more
Ken, The challenge for silencing the 912 is much different that of a twin cylinder two-stroke.
Matt, you are right, the flow difference is not much,... sometimes, though, slight differences in resonance frequencies, manifold lengths and widths can change the result a lot.
Rest assured, there is tuning in the exhaust system. It may not be a huge tuned chamber like RD Aerosports, but it is a purposefully designed set of compromises for size, noise, weight, cost, and performance. Just try to alter it in some way and see what happens.
Also, the rotary valves tend to cause less intake noise, not more. Your intake tuning has more noise, than one with reed or rotary valves. The difference isn't much, but it does point out more of a need for a silencer.
It would seem that having three cylinders instead of two would be a help to you, since the primary frequency is 50% higher than for an equivalent twin cylinder motor, thereby reducing the size of the silencer required. As the frequency goes up, the size of the box needed to stifle the resonances goes down.