OK.
From a quick hunt around, and having disposed of a lot of my books, the only reference I could find last night is from "Coltrane's Planes and Automobiles - Engines that turned the world" (Not the most authorative tome I'll admit, but a good read none-the-less and all I could rootle out last night)
Quote:
Engines that didn't turn the world - The six-stroke cycle
Four stroke not fastidious enough for you? See if you can get your hands on a venerable old British six-stroke engine. The six-stroke only produces one power stroke for every six strokes of the piston - that's three whole rotations of the crankshaft. The two extra strokes are used to draw in clean air from the atmosphere and flush it back out again, ridding the cylinder of every last trace of exhaust gases before the fresh fuel/air mixture is drawn in from the carburettor. If you like novelties and don't care a hoot about the weight, size, cost or complexity of your engine, it's great. Its mechanical efficiency is only five or six percent less than that of a four-stroke - that's the cost of having the piston do that extra work- but its overall fuel efficiency is almost the same as the four-stroke, so much more powerful is combustion when all traces of exhaust gas have been removed.
End of quote.
Of course I would expect a modern engine to be more efficient at scavenging the cylinder than the six-stroke's contempories, so maybe the efficiency figures would be comparatively worse nowadays.
I'd like to see one working though. I wonder what it would sound like?
"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams
