If I recall correctly, the valves are not sealed when you remove your foot from the gas. There is a 10 minute movie from the Honda website that demonstrates the engine from the HCHII in great detail. In particular, valves are opened during coasting to lower resistance. Does anybody else remember this? I don't want to watch the movie again. I do not have the link at the moment, but I can post it later--or somebody else can post it.