Don't forget though, auto manufacturers have long-made their policy of only making additions or modifications that eventually make them money! I was involved in a project in the early 80's designing and building an engine that eliminated the valve train. It used a cam/valve that was a rotating cylinder replacing the valves. It eliminated the conversion of rotating motion to reciprocal motion as in "cam to valves". It worked fantastic! It eliminated a lot of lost HP due to change of motion, less moving parts and less moving mass. Also the system could be designed to operate similar to a turbocharged or supercharged engine. The result was a Chevy 305 engine, producing 400+ HP and still getting close to 30mpg. The other major result was GM buying the patent rights, and NEVER appearing on the market! What really got my co-worker and I mad was this was the prototype, and we had plans on starting the drag-racing version! The same 305 engine with a 600+HP output! Well, it wasn't our design entirely. We just worked out the details and did the machining/assembly work. So...another major improvement in auto/engine technology held back by the major money-makers due to who would benefit from it the most!