I have owned 2 engines that lacked cams and valves that ran great (Wankel/Mazda rotary). I guess the .5 inch stroke “crankshaft” could be called a “cam” but I have never heard it called one. Mazda calls it the “eccentric” shaft.
I believe it is the future. If a solenoid were to fail, it could be easily replaced. It would also be possible to design the whole valve assembly (valve, spring and solenoid) as a single replaceable screw in module, much like a spark plug. The Mitsubishi 1.4 engine of the late 70’s had a screw in intake valve.
By controlling the valve timing, the engine could change its dynamic compression ratio as mentioned in the article, so it could not only run in all the modes mentioned, it could also go into a gas diesel mode for cruising and not need a different fuel and separate fuel tank.
An inline 6 cylinder version with two exhaust valves could also go into a 6 cycle mode where after the power stroke, one exhaust valve opens to a enclosed manifold, the exhaust gases would go to the open exhaust valve of another cylinder that has just finished its exhaust stroke to push the piston down for the 5th stroke and then back out the other exhaust valve to the exhaust system for the 6th stroke.
During 4 stroke mode, the enclosed manifold would open a large valve to dump the exhaust gasses directly into the exhaust pipe instead of another cylinder.
Good idea Keith,the diesel and gas engines still lack a long way from being really thermally efficent,the “adibatic” engine concept has been around for awhile,the turbo compounded engine should have some nice efficency gains(especially with a thermoelectric generator in the exhaust stream after the turbine stage)actually I dreamed up an idea similar to this about 40 years ago,with no idea how to implement of course.Another advantage of this design would be an engine brake mode,easily implemented.
@Sarge,that is correct,I guess most 2cycle(small ones) engines and turbines too.