I was so disappointed in the first video, that I quit watching after the dissertation on spring pressures. Yes, it takes energy to open a spring, but that same spring is pushing the cam around its rotation after the peak of the lobe has passed the follower, so in theory, that counters some of the next cylinder whose lobe is opening the spring...yet he doesn't even mention that. Also, peak valve lift discussion cannot be compared to peak port flow until one includes the ramp profile and how much longer that "useless" lift is a by-product of keeping the longer period area of that profile beyond port's flow. He may address this later, but right now, I've lost interest in it.