Porsche's Six Stroke Engine

[stevej37]

Glad to see the ICE is still being advanced.

https://www.yahoo.com/autos/porsche-dreamed-6-stroke-engine-160300596.html

from the article...."The secret to making this novel ignition is a crankshaft that rotates around two concentric circles (also known as an annulus)"

[rfuerst911sc]

Interesting concept .

[stevej37]

It's nice to see that they haven't given in to the "It must be Electric" mission.

[herr_oberst]

Crap.

It took me a long time to be able to recite "suck-squish-bang-blow" at a moments notice. I'm not sure if I can remember 50% more words to describe the cycle.

[3rd_gear_Ted]

1 power stroke to 4 cycles
2 power strokes to 3 cycles
Simple physics

[CurtEgerer]

It's interesting that the mock-up is a flat 6 turbo. There are other 6-stroke engines but they all seem to use water injection and steam.

[SiberianDVM]

No matter how I try I cannot visualize this.

And, yes, I looked at the diagram.

[cockerpunk]

id rather see sleeve valve engines come back. they seem like the most obvious next ICE development.

[David Inc.]

Originally Posted by cockerpunk

id rather see sleeve valve engines come back. they seem like the most obvious next ICE development.

This appears to include some sleeve valves, actually. This article does a better job explaining:

https://www.motortrend.com/news/porsche-engine-patent-stroke-explained/

After the first power stroke the crank gearing lowers the bottom-dead-center of the piston and exposes some sleeve valves that allow a charge of fresh air in. It's compressed as normal, fuel is injected and you get another power stroke.

Seems... kind of odd? I wonder what the benefits are.

[stevej37]

^^^ Power...from the additional power stroke?
Not sure...the article is kinda vague.

[Tervuren]

It has an extra long stroke for power stroke #1 .
At the Bottom Dead Center of that extended stroke the diagram has "scavenging".
I interpret that as intake and exhaust valves are opened pushing air out the exhaust and letting air in the intake.*
Between turbo charging, the lower pressure of extended stroke, some spent air and fuel leaves and some fresh air comes in, and then it compresses and goes for shorter distance power stroke #2.

Originally Posted by SiberianDVM

No matter how I try I cannot visualize this.

And, yes, I looked at the diagram.

[john70t]

(thank you Tervuren)

It looks like the compression is varied by altering the height of the piston/rod/crankshaft.
So instead of a single location for the lobes/balancer/rods, the entire middle of the crank moves in an elliptical?

I've seen patents for mechanically lifting the piston-to-rod pin to vary piston height. Extra weight at the end.

Yeah I still don't get it.
-I don't get how that extra power (especially turbo kick) can be efficiently handled even to straight cut gears at high speed.
-Gear teeth wear down and make noise. Small contact area. Not a good look for LeMans.
-Lots of variable-compression techniques have been attempted: https://nap.nationalacademies.org/read/21744/chapter/27
-And Infinity https://www.caranddriver.com/features/g15084183/under-pressure-the-science-behind-infinitis-variable-compression-ratio-engine uses an intermediate crankshaft like the Prius https://en.wikipedia.org/wiki/Atkinson_cycle
-Not applicable but worth noting.

The first 'long stroke' is very efficient for lower rpms.
The extra cycle is what I don't understand.

The "compression-power-exhaust" sounds like the first exhaust has left but there is still pressure in the cylinder with more squash.
Do they keep and use that stored exhaust pressure as another short-stroke under turbo?

How does the cylinder stay clean without using hydrogen/methanol/etc?

[unclebilly]

Will it have sealed for life bearings in it?

[David]

I think a 6-stroke is overly complicated but this guy explains it well as usual: