There was a lot of buzz around the Coates valvetrain circa 1995. (Animation is too good to miss)
Two decades later, I still don't see mass adoption of this "revolutionary" technology.
So what gives? Is there a technical reason to warrant the lack of adoption?
Volumetric Efficiency
The primary limitation would be the intake charge timing. The rotating chamber for the intake charge is limited to the volume of the chamber rather than the poppet valve style valve train that can be timed to allow for a longer period of intake as well as gaining the efficiency of an intake charge that is flowing into the combustion chamber without restriction.
Restrictions
Limitation of intake flow
Limitation of intake charge due to volume of the rotating chamber.
Although it appears the reliability gains of removing a poppet style valve from the system seem to be meaningful the performance restrictions of overall power potential for the engine seem to be quite restrictive.
One thing I did read about this was that it worked best with fuels of natural gas and the like. Perhaps the lack of infrastructure for this fuel prevented any sort of penetration of the technology in modern designs.
It might also be too soon. If the technology needs to be proven, the design cycle for modern cars is about 5 years or so isn't it? If it took 4 or 5 years to prove out the technology, work on it's issues, like sealing, measure it's longevity, performance, fuel economy, emissions performance, etc, etc, it might not be ready for inclusion yet.
