I wanted to bump this back up and add to my findings..
First, once the RAVE valve fully opens the exhaust note does become more aggressive – more edgy sounding. This sound can vary in volume based on the engines’s state of maintinance: exhaust matting, gaskets, etc. But the note takes on a slightly harsher or shrill sound once the valve opens.
But here’s a few more questions for the experts:
1. Does the valve snap open when the pressure overcomes the spring rate? Or is it a gradual opening over a few 100/1000 rpms?
2. Does the Rotax ignition programing actually change the timing at <7500 rpm to allow the firing of the cylinder to occur as the piston draws even with the closed exhuast valve (on the down stroke)?