I think the Ducati guys already took the name 6-stroke though. Oh, here it is. I believe it involves moving the head up and down so as to increase volume (and thereby compression) on the intake stroke, but reducing it on the exhaust purge stroke, so as to avoid losses. They tested it on a Ducati and it sounded pretty sweet. Should work too, but it's not going to get you to 40% thermodynamic efficiency as this guy claims his can.
http://www.sixstroke.com/
There is nothing like a fuel-cell though, 100%, perfect efficiency. No thermodynamic cycle can ever exceed 50%, so there is no reason to bother drastically changing the combustion cycle any more, it'll be obsolete before a major new cycle change can become mainstream.
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Did you ever see the Wiseman cycle? It's a brilliant idea that takes very little effort to implement. It's basically a planitary crankshaft. The connecting rods go only up and down on gears, no angles at all. It was said that there was so little friction because the rod never pushes at an angle, that the gas engine needed no lubrication at all.
Power gains were quite good and torque gain was immense, as you completely eliminated cylinder-wall friction and the force from the connecting rod was always creating the maximum moment rather than changing with crank position (the force was always applied at the same distance from the center of the crank, as opposted to running directly through the crank at tdc and slowly moving away as the stroke proceeds). http://www.wisemanengine.com
There are some cool technologies, but as soon as fuel cells are practical, they'll destroy any combustion process, period.
