Variable valve timing seeks to combine the low-rpm torque of a Harley-Davidson Big Twin with the high-rev power of a sportbike engine. This is especially useful in helping downsized engines to do the job of bigger engines with fixed valve timing. The ideal system would be one that could vary opening and closing timings independently, and even vary valve lift, too.
Coming close is an electromechanically driven system from an outfit called LaunchPoint Technologies. Because solenoids must move a heavy iron magnetic core, LaunchPoint chose to drive its design with lighter-weight voice coils just like those used to rapidly drive loudspeaker cones in sound systems.
Like some other electromagnetic valve-drive setups, LaunchPoint’s system employs the “throw-and-catch” mode. When the valve is to be opened, the voice-coil driver throws it upward and an unspecified arrangement catches and holds the valve at full lift (8mm or .315 of an inch, for example) until a valve-closing signal is sent. Then, the voice coil “unsticks” the valve from its full-lift position and throws it toward the seat. The points of opening and closing can be varied at will while the system is operating.
Because seating velocities over about three feet per second cause valve bouncing and rapid seat/valve wear, a catch-and-hold system similar to the one that held the valve open now decelerates it to its seat with a moderate claimed seating velocity of four to 12 inches per second.
A 500cc Rotax single-cylinder engine is being used to test this system, and you can see additional short videos of it in operation (with valve motion visible) on the LaunchPoint website.