They basically uses an additional power stroke to utilize the heat and give some added output. The stroke is called the steam power stroke. The result is less heat to dispose off and a saving in fuel.
It would be best if you use the search engine for "six stroke engine" I saw a nice link but cannot remember what it was.
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Never do today what you can put of until tomorrow - Student motto
Good Good I'd went to the recommended site and it's super well consise I do like it. A lot to learn from it too. However the concept I'm trying to bring up is about an engine that some how we can mutate and prototype from using the same mechanical advantage of the gas engines into an electrical powered one. I do specialy seing something more for such conversion into the 'Wankel' engine because it's rotary properties which can be probably easier to apply with an electrical technology in this example.
The other idea I seing will be trying something like that with the reciprocal engine or pistons which can be again using their mechanical advantages but instead replacing theirs regular pistons with a set of big strongs set of 'Solenoids' to simulate the reciprocating motions in it and propulse the cranshaft for power. I don't know I'm just brainstorming don't bring it to the bank yet, he he ha, but Who Know's ?...
Eventually will be great to builds some Non-Gas power plants for automotive down the road with such sky hi gas prices around. Have fun and a good day...