Fifth stroke 3

[poorinventor]

I have readen and heard a couple of times of so called "fifth stroke (or cycle)" in a four stroke (or cycle) engine. What does that mean? I have grasped an idea that could be something like that, if it would work, and would not want to waste my time.

Poorinventor

 

[RobWard]

I know that six stroke engines exist. (5th and 6th strokes purge the cylinder and allow more powerful combustion of the fuel which almost makes up for the increased frictional losses)

5 stroke? I doubt it, as the piston has to perform 2 strokes for every revolution of the crankshaft, so an odd number wouldn't be possible.
I'm always willing to stand corrected, so try posting this in the "engine and fuel engineering" forum, as there are some SERIOUSLY clever people who post in there.


"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[alr]

In glorious South Australia we have a man who makes the Six Stroke

http://www.sixstroke.com/index.htm.

Tony

 

[RobWard]

That's a different type of "six stroke" to the one I was refering to, but valid non-the-less. Still don't know about the "fifth stroke" as referred to in the original posting though.

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[Tmoose]

Once upon a time a cam grinder (maybe Iskenderian?) advertised a "5th cycle." I think I recall maybe the claim was imaginatively based on the intake process continuing past BDC as a result of cam timing.

 

[RobWard]

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

 

[jpete]

I think the most common 5 stroke engine, if I can say that, is the Atkinson cycle engine. You can see it on

http://www.sixstroke.com

The new hybrid Ford Escape advertises an Atkinson cycle engine even though I believe it's just a 2.5L Zetec motor with different cam timing.