Normally a piston completes an up-down movement in 360 degrees. With this setup the top of the piston has an additional up-down movement in approx 60 degrees. So with the engine running at just above idle at 1000rpm this piston top will be moving back and forth as quickly as if it were 6000rpm on a conventional engine. It won't be able to rev up without *enormous* forces and consequent breakages to contend with.

Feel like that cam pushing the piston back up will have some massive wear with such a big leverage and pushing the piston up so quick.

Cool idea but adding so much complexity to an engine is rarely worth it. Simplicity is king

Those bits of metal banging together will be quite spectacular.

Excellent video. My gut tells me this wouldn’t last in the long term. You’ve basically built piston slap into the system. With it firing like a 2 stroke it’s going to generate heat like a two stroke. I reckon it will make good power. But I don’t see it lasting 200,000 miles without expensive maintenance inbetween.

Making a 4 stroke combust twice as often is a good idea, theres a reason 2 strokes and Wankels have such good power to weight and power to displacement ratios. But with all of the added parts, the friction and intertia losses would sadly reduce those gains again.

I see a lot of added complexity and points of failure. It looks great on paper, and for very short term ownership I bet it works great. I bet I won't see too many of them with 300k miles on the odometer.

TBQH the entire video I was thinking that the crown piston wouldn't be very eager to move down on its own, which you addressed in disadvantage #11, including a desmo-like solution. Oh well, it seems that the standard 4-stroke Otto-cycle engine sits really in the Goldilocks zone for what regards complexity and performance/efficiency. With a Wankel or 2-stroke you get simplicity and performance, but not efficiency. With complex post-Otto designs you get better efficiency and power at the cost of complexity. Otto is just about good enough in all three departments.

Kudos for covering the disadvantages so well

It's hard to call the ball on this one since it needs a lot of development and materials selection/testing. I believe that the mating surface between the two pistons is going to be very difficult to achieve. I'd like to hear one of these guys running and watch hp and torque numbers on a dyno.

Finally something interesting for heavy duty low revving diesel engines. Interested to see a huge-ass naval engine with this tech.

A turbocharger provides the same kind of increase in power without all the additional wear surfaces. A modern two stroke uses direct injection which avoids the oil burning, and you can avoid it completely with a blower (detroit diesel) or even a turbocharger if you have a way to start it a blower or saved air pressure.

Finally a good and critical video on an experimental engine

The fact that we use the design of the 4-stroke as it is for a century now without major modifications speaks for itself. Maybe its simply that good.

The upper piston and crown piston constantly collide with each other so those are gonna need to be changed way more often. Also the upper piston might not compress the intake gases efficiently because it has no skirts so a slight tilt will increase friction and decrease compression A better solution in my opinion is to have compressed air (maybe supplied by a auxiliary pump) blow out the exhaust fumes right after the combustion

Excellent video. The discussion of pro- and con- adds so much to the visuals 😃 Really sets your hard work apart from other creators

The thing that strikes me about this design is the number of moving parts. Yes, it is far more efficient, but at what cost? I can see maintenance issues galore here.

Maybe it was just me but the pro vs con ratio was definitely slanted against, I hope decision-making isn't based solely on 20% increase in HP. Sounds like this needs more tweaking before being practical.

I see all the working parts of an ordinary engine and turn a bunch more parts that need to move. More moving parts means friction and inertial resistance. I can see the belt or chain drive and the lobed kicker that pushes the piston top wearing a lot and quickly. The idea is to remove as much parts and weight as possible resulting in more faster acceleration, more speed and smooth balanced operation.

the ratling, noise and unrealibility of such desing is remarkable

I really like your 3D animation style, the thumbnails always catch my eye scrolling through KZfaq. Do you model everything yourself? What kind of software do you use to animate and render everything?

I see another couple of problems: One is the lack of skirt in the crown will increase the wear on the bore. As it ovalizes, piston will go in sideways. Second is balancing issues. It already has a secondary shaft than can be used as a counterbalancing shaft, like 3 cylinders engines already have. I think a better solution than the spring would be replacing the entire cam concept by a linking mechanism. It is the most efficient and also prevents the piston from going rogue on the mechanism. However, that would have the most parts, not to mention a lot more points to lube. It would also need to be very precisely sinchronized or the linking mechanism would takes the entire force of the combustion stroke. Kinda similar to the Atkinson cycle tbh.

Fascinating ! I love things like this. Thanks for showing us.🌞

This engine is essentially a four stroke, but with an asymmetric motion so that the two lower-effort strokes are performed via cam instead of via crank. The intake stroke is only low effort at wide open throttle, however. On a gasoline engine, closing down the throttle would make it necessary to have a spring that's stiff enough to draw vacuum (negating some of the other advantages) or else using delayed intake closure as a means of controlling power.

Also the gas is exerting all it's force on the piston in a fraction of it's stroke length before it is expelled, so the transfer of force to the piston is probably less efficient

This is brilliant and I have faith in it , providing few modifications such as; offsetting the crank , hydraulic tensioner for the ( ring piston), xtra oil galleries and better bearing for rod

I'd love to know how high they revved those test engines up, and what problems they came across out of so many potential extra problems. The two piston halves clapping eachother, the sheer amount of force being put on that arm and its tiny roller bearing, piston slap from that pancake-flat crown piston, flex in that split con rod, extra balancing issues, etc etc.

Now thats what i call a one stroke engine

( Notes for D-cycle - following are not obvious, call to discuss: 1. Most piston skirts need not be windowed. 2. Ring sections can be made of stronger thin steel just to hold rings and oil to cool. 3. The same rings stop the oil leaking. 4. The piston-train can run directly from the crankshaft. 5. Crown doesn’t run at higher speed and having Atkinson cycle. The full air intake can be provided via an air 2x pump. 6. Valves don’t run at higher speed, except for fewer cylinder engines. 7. Piston-train spring is compressed during intake. )

How high will the acceleration of that piston be? Maybe works at low revs, but never at higher revs.

I see why they made a diesel version, because they rev less. I've been thinking of making a wall that helps move the gasses like this, i wouldn't have imagine f1 speeds. Interesting that it's essentially a valve :).

You don't need the second cam to lift the crown piston. You could just have the rocker arm on the second cam ride the crankshaft with a second lobe attached to the crankshaft for the rocker arm on the second cam to ride along

It looks like the extra power output is coming from essentially tweaking the engine to put out more power (like street racers do). As noted by others, this drastically reduces the longevity of the engine wear items. Once the design has been balanced for longevity and desired power output, then we can determine the advantage of the split piston. The turbocharger is a good way to harness the energy dumped by the exhaust stroke to return it to the intake stroke. It is not clear to me whether this is a better solution for energy conservation than the current EcoBoost system that Ford has for the Fiesta and other engines. Ultimately, it's a balance between power output, durability and mass. All of that said, I would love to test this in real world conditions, with or without a turbo!😃😃

This is the first time I am hearing of this technology. Great presentation! I wonder how it would do in large, slow turning applications such as Marine Diesel propulsion systems? I know most of the largest engines are already two stroke. Perhaps it would just be unnecessarily complex for any gains to be had.

In essence, this design splits the pistons into two parts: One part (crank, camshaft, and piston skirt) that all run at same speed. A second part (piston top) runs at twice the speed. It is evident from the animation that the piston skirt makes its trip once every crank revolution. But the piston top makes its trip twice during that time. So at 1000 rpm the piston skirt moves 1000 times, crank runs at 1000 rpm, and camshafts runs at 1000 (instead of 500 as in conventional engines), while the piston top moves 2000 times. The reduction in spinning inertia (mass @ speed) is basically the source of its advantage. However, complication & added reciprocating parts are its main enemy. An extended test over time is needed to clearly identify pros & cons of this new design, not just building a testing sample and demonstrating that it runs.

Could this engine be a good candidate for "free valve" technology? Seems reasonable to me, as this would solve the cam issues completely.

There are so many six stroke engine types that also try to combine the benefits of 2 and 4 strokes and they need less parts like the Griffin, Färber, Bajulaz, Velozeta, NIYKADO or Crower engine. Can you show the difference? Thanks, love the channel.

very good thank you!!!

I appreciate your analysis.

Nice video. I wonder about the upper crown stability and the chance of it shifting in the bore.

The cam arm moves the crown piston under exhaust and intake - the easiest of the 4 strokes and so the lightest loading .. really interesting idea .. by changing the timing of the “hop” (the cam timing on the crown piston lifter arm) it would be easy to short stroke the intake (create an Atkinson cycle for better fuel economy) .. hoping development pans out !!

instead of running it off the crank there should be a smaller cylinder and piston (50-100cc) that pushes the exhaust stroke arm thing in sync with the actual piston. (no spark plug needed, just put a small channel from one of the normal cylinders to allow some hot gas in when it fires).

Fascinating!

I think the piston clashing so fast would demolish the "upper" piston in no time.

This may hit a roadblock: the cam/follower arrangement simply can't turn very fast before the return stroke on the piston crown starts reducing. The cam would just eject the piston crown

Amazing!

Excellent analysis of a fascinating concept.

I imagine this added complexity and subsequent additional moving parts will add to wear and tear significantly. Interestingly though, it might be useful in race and drag engines where engines are typically rebuilt after each use.

I bet it sounds amazing

Looks like the crown piston should be made of a ceramic material, to withstand the high heat problem w/o the need for extra oil to cool it. Ceramics not only withstand heat but also are insulators, preventing as much heat transfer (vs. a metal crown piston) from the combustion chamber to the crankcase.

What I love is that you assume that the upper part of the piston will come down by itself, which at that point in the 4T cycle is impossible. It's not the atmospheric pressure that's going to make it come down; on the contrary, it's the piston that sucks the fresh gases into the engine, and there are no mechanical parts to make it come down. With a desmodromic operating principle on the cam that allows this to work, it could work, but certainly not in this configuration.

Superthanks!👏

i feel like some form of super charger would get about the same effect with less vibration. funky idea though.

As mentioned in the video and in comments, the accelerations and thus forces required to actuate the auxiliary piston are enormous. There’s probably a better trajectory (displacement vs time) than what’s illustrated in the video. Decades ago Mercedes Benz raced a car with a desmodromic mechanism driven by a circular cam lobe - eliminating jerk and higher order accelerations. But that mechanism had serious overlap which meant the engine could not run well at low rpm. It won races, though.

nice vid!

My first question is why? We had a 2 stroke engine decades ago already that didn't utilize a total loss oil system. The Detroit Diesel. It needed a supercharger to force air through the cylinder at a fraction of a bar over atmospheric (some used turbos as well in the later years to introduce true forced induction), but was a 2 stroke combustion cycle with 4 stroke valves, crankcase, and combustion chambers. Especially with direct gasoline injection and modern turbos and superchargers, this could very easily be implemented on modern gasoline engines rather than this overly complicated destined to fail design.

Ingenious!

Although I do not think this idea will go anywhere, I do applaud the people who divised it. I like seeing outside the box thinking and ways to improve the internal combustion engine. The light bulb did not work on its first attempt either.

One point: there is enough place to increase the mass (=thermal capacity) of the piston itself, so that point can be easily improved. But still - the main question is if we really need this technology and is it financially reasonable, not only in the development ohase but also in repairing costs.

This will create nightmares tonight!

A separate crown piston crank instead of a cam would be more reliable. Turbo/supercharger's solve the partial charge air intake issue.

This is the problem with engineers: They never stop engineering

Még egy hiba lehetőség 🤌 gratulálok, biztosan nem fog kopogni mint az állat

Connecting rod peak load is actually at top dead centre - the tension needed to bring the piston to a screeching halt and pull it back down the barrel. Its worse on the exhaust stroke (of a 4 stroke) with little gas pressure above the piston to assist the process.

perfect application for the scotch yoke

Maybe it is difficult to be realized, because of acceleration concerns and lubrication. But it is a BRILLIANT creation!!!

This could work well on a stationary diesel that aims for constant rpm like a generator but you'd have to adhere to runtime maintenance intervals or scheduled services, whichever comes first. Big diesel generators can spend a long time un-started so they need to be test started on an interval (back up generators) but they can also do constant runtime in service (locomotive). Large boats in the other hand generally can tolerate having at least one generator out of service and ships usually double that (redundancy while one is being serviced by the ship's engineer).

Very interesting. Be cool to more on alternative engines 😊

ChrisFix: *makes piston return springs joke D cycle engine: "Am I a joke to you?!"

This looks pretty promising. Nothing too fragile.

Super thanks

It is an interesting concept and I think it has merit. There are some kinks which need to be ironed out, but I could see this being used commercially.

Hi, I really love this channel, I have a recommendation. Could you make a video on Porsche's flat 6 engine? Or Subie's boxer engine?

A very intresting engine design. Right now I dont think it would be able to be sold in cars but maybe in the future when its more developed.

Even though this seems highly unrealiable, I would still enjoy very much to see a working engine with this setup.

Developer: it is not durable but... Cars manufacturers: shut up and take my money

7:26 Ahh… yeah. Piston return springs are needed.

The piston is going to float on the intake stroke. It's also going to need a way of addressing vibration

I really had doubts about the title, because there are a lot of KZfaq channels like "Here’s the techonology of the future!!! OMG [Emote]", also during the 3d animation at the beginning, I suspected that there was more stress on some pieces. But as a result, I’ve really been a hundred years that you’ve been talking about these points, with executably the same skills I thought. This video was really a good surprise, it’s exactly the guy I’m looking for. I’ll follow you and wait patiently for your next videos.

What is going to pull the piston down on the intake stroke? Will there be a spring between the skirt and the piston? Also what are the chances the slap between the skirt and piston will hold up?

That Lil cam lobe shooting the piston up at the bottom of the stroke. That's gonna need to be built tough or be a grenade

This probably would suit a diesel as a diesel will get by on low revs and already has stronger built engines that because it's built for higher compression ,ied love to see this engine built and tried out , surly it's better than electric right now because there no cheeper to run than conventional fuel if you do a lot of miles like I do

nice... really nice... now let's see if it can take any load or rpm at all. best case scenario, this might become a very efficient engine for some specific edge cases like a generator...

i can only imagine the absolute racket that thing is gonna make while running. the piston crown connecting back to the skirt, the crown arm running over that highly aggressive cam as well as the more aggressive valve cams. that thing is gonna chatter like hell especially when it gets up in the rpm range. valve/cam float is going to be a huge issue for that extra cam and it will likely beat itself to bits i would say

It seems to me that the piston will hammer itself into oblivion the moment that any wear changes min distance between the top and bottom part of the piston. Also the inertia forces inside the engine will be tremendous. Fuel injected two stroke is the future. Simple ,light and powerful.

Super.

Atkinson cycle also achieves all 4 cycles in one totation of the crankshaft. And there are now millions of succesful examples since every Prius has one.

Qué maravilla de producto! Ojalá algún día podamos hacerte llegar uno de nuestros equipos para que los evalúes así. Abrazo grande!

It's surprising, that this concept makes more Power, even with the added Camshaft for the Piston...

I don't think this design would work for vehicles, due to the wider RPM band needed. The challenge with the double stroke is getting the crown piston to drop to bottom dead center on intake. In order to achieve higher RPMs, something has to bring the crown piston down hard and fast, and that is going to take a lot of force that is never returned. It would end up working like jake brakes. Additional force is required by the crown piston to expel gas, then additional force is required by the crown piston to draw gas in. Low RPM generators might be an application.

You've heard of Valve float, Now get ready for PISTON float!!

My concerns would be how do they handle carbon build up on the piston skirt and piston slap.

I am surprised that there is only a 20% gain in ideal test conditions, considering the real world applications would be subject to the increased potential problems when considering the added complexity.

It will be interesting to see where this goes and if it ever goes into production. Then, the real testing will happen. Can this engine stand up to the rigors of real people driving every day?

how can that cam & leaver pull down the piston crown during the intake stroke? From what you can see in the design illustration, the piston crown should stop at the top of the cylinder after the exhaust stroke unless it is forced down.

nice idea , especially for diesel !

Looks to me there are more negatives than positives, great getting more power for the same fuel consumption but the reliability could be the kicker, nobody wants the risk of catastrophic failure

now is the time to talk about the infernal noise that this engine would make

Maybe a good generator design. Can tune to a fixed rpm. Better torque for sudden loads starting. Can overbuild high wear components since weight is less a issue and normally low run hours will help. This won't be in a cheap residential unit but if it keeps good efficiency and size it could be a fit.

Timing belt: **jumps** Engine: **fucking explodes**