Greek Opposed Piston Diesel

[pietenpol2002]

Fascinating stuff. And I noticed the pump and injector look suspiciously familiar.

http://www.pattakon.com/pattakonPatOP.htm

[Kristof]

Awesome.

[gilburton]

Some interesting ideas. Certainly a lot of these designs would suit motorcycles but do they work??
I expect they are looking for someone to invest

[Blunt Eversmoke]

Some interesting ideas. Certainly a lot of these designs would suit motorcycles but do they work??
I expect they are looking for someone to invest

At least one of the Pattakon designs exists as a working prototype: http://www.youtube.com/watch?v=EpdoAlqPHgs

[Rhynri]

These designs are functional. Some of the Junkers designs have been in use for decades in various applications. Another engine, a six stroke engine, interests me for diesel applications: It consists of a normal four stroke design, but after the exaust stroke, water is injected through a seperate nozzle into the cyclinder, giving an additional (high)power stoke, cooling the cyclinder, and removing any carbon. There is then a seperate valve that exausts the water, and it is condensed and reused, or it can go out the same exaust port with the normal exaust. The net effect is increased power, and a cleaner engine that runs cool enough to not need additional cooling, as well as longer life for turbos and other high-temperature components.

[espe]

I personally think that 2 stroke is the way to go. It has a far better powerband, stays cooler, has less parts that can break down, can easilly run with water injection, can run on virtually any kind of fuel (even methanol) ,is more compact and makes a lot more noise . Almost all the big ship engines are two stroke diesels, a lot have water injection and at the same time can run on crude oil if necessary.
To prove this in the future I have scavenged two old engines, a Sachs 500 L and a JLO 660 . One of those is going to be installed in my next build, after I finish the DIZH. First however the old ladies need a pretty intensive makeover because for now they are looking like two piles of rust. They have been resting in a junkyard for over 25 years and especially in Holland that is not a good thing!

[Rhynri]

Two-stroke diesels have great output, but they require forced induction and are not very clean running (it's a two cycle problem). They do run cool though! In addition, they are quite loud. I don't particularly feel like sitting in a pile of nasty emissions at every stoplight on my motorcycle!

[Kristof]

Two-stroke diesels have great output, but they require forced induction and are not very clean running (it's a two cycle problem). They do run cool though! In addition, they are quite loud. I don't particularly feel like sitting in a pile of nasty emissions at every stoplight on my motorcycle!

Biodiesel is the way to go.

[Rhynri]

As nice as biodiesel is, incompletely burn any hydrocarbon and you wind up with a nasty mess of hydronitrowhatsits. You may not have it always available, and then you'll have to mix fuel anyway, (and you may as well with blended biodiesels), you might still have to with straight biodiesel. The other downside is that you have to overcome not only the momentum of the engine but of the blower change RPMs on your two-stroke.

[espe]

Currently, the focus in engine development is mostly on 2 stroke. Just because its a better principle. The work temperature and fuel/air mixture need to improve. Smoking is caused by burning lubrication oil. If you can get an oil with good lubrication qualities wich is also combustable without producing smoke than 2 stoke will become widely accepted again.

[Tamber]

If you can get an oil with good lubrication qualities wich is also combustable without producing smoke than 2 stoke will become widely accepted again.

I'm not quite sure what burning lubrication oil has to do with anything. It may interest you to note that two-stroke diesels don't work in the same way as two-stroke petrols; that is, they do not use a pressurised crank-case. Thus, the oil in the engine as lubrication, stays in the engine. (Well, barring unspeakable accidents that tend to lead to bigger issues than a little oil smoke.)

Minitru has a wonderful page on the matter: http://en.wikipedia.org/wiki/Two-stroke ... ots_blower

[Tamber]

Further to above, I'm still not going to weigh in on whether or not they're any cleaner running than 4-stroke engines; since I don't have enough data. I shall, however, make a note to add it to my ...voluminous list of things to do.

As a matter of opinion, though; to my mind, it should be no worse than a 4-stroke diesel. It's still just breathing in the same air, compressing it, then injecting fuel at somewhere around TDC. Of course, I won't stand behind that until I have some figures. (And, of course, I could always be wrong; it does happen occasionally. )

[Rhynri]

Your best example for this is also the most common use of big diesel power: trains.

The cleanliness issue stems from the fact that two stroke engines have to scavenge the cyclinder of exaust in the same stroke as the power stroke. Without the dedicated exaust stroke, this is ALWAYS incompletely accomplished, so the next cycle has some exaust gasses. There are a few solutions for this, but the high-compression environment of the diesel precludes some of these. This is why you do not see two-cycle operation in emissions sensitive engines.

[Tamber]

Without the dedicated exaust stroke, this is ALWAYS incompletely accomplished, so the next cycle has some exaust gasses.

Isn't a similar thing done deliberately for emissions reasons? (And, naturally, one of the things ripped out by people who don't care about emissions reduction; since it costs you a few HP here and there, and emissions controls are a sign of being a liberal, hippy treehugger! ) I know a dedicated EGR system is a wee bit more controlled, but it'd have the same result in the end, surely?

In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates. Most modern engines now require exhaust gas recirculation to meet emissions standards.

Exhaust Gas Recirculation

Either way, this is interesting to look into. (...and will no doubt result in me disappearing into a wiki-walk until ridiculous o'clock in the morning, again.)

[Rhynri]

Yes, it is. However, soot and other byproducts remain in the cylinder as well, The EGR page you link specifically states "Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters. EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity." Not to mention lower fuel economy (3%). EGR is a mostly negative edition on a diesel engine. This effect, however, explains why two strokes have poor emissions.

This may change somewhat in the future. Notice how the verbage on this page mentions reducing "the NOx emissions by enabling higher than normal EGR rates". This is because their engine uses an airpump (electromechanical turbo) that is independent of engine speed. Who knows, maybe we'll see one in a build someday.

Two-Strokes aren't bad once you get them running at full tilt continuously, but this is hardly an option for anything that doesn't have an electrical drivetrain (trains, generators, boats, etc). Also, enjoy this video of a beatifully restored Oliver Super 99 two-stroke diesel pulling on a perfect day.

EDIT: This Article is also interesting and germane to our conversation.

[espe]

If you can get an oil with good lubrication qualities wich is also combustable without producing smoke than 2 stoke will become widely accepted again.

I'm not quite sure what burning lubrication oil has to do with anything. It may interest you to note that two-stroke diesels don't work in the same way as two-stroke petrols; that is, they do not use a pressurised crank-case. Thus, the oil in the engine as lubrication, stays in the engine

Well, it may interest you that your totally wrong on this point! Maybe you should google a bit more before making these kind of statements. You are talking about a variation on the 2 stroke principle that uses one or two valves. I am talking about 2 stroke engines without valves. For instance Sachs, JLO, Deutz OMZ, bolness etc. These engines use lubrication oil to lubricate the cilinder and piston. Any surplus oil drips in the crank -case witch in fact is pressurized, and is taken in with the inletstream. I know so, because I own and/or work on a couple of these engines. No wickypedia for me, half of it is incorrect annyway

[Dan J]

Large 2 stroke diesels used in trains tend have both cylinder exhaust valves and also a supercharger. This principal means as the exhaust valve opens towards the bottom of the power stroke all of the exhaust gas is purged from the cylinder. This of course does mean some energy is lost in the power stroke and plenty is spent on driving the supercharger. Regardless of that though you are stll having a power stroke every single revolution of the engine so power is increased significantly (though for reasons above and plenty more not doubled) over an equivalant 4 stroke.

Various auto manufacturers have looked at 2 stroke diesel technology (I know for sure at least one of the big 3 American firms has) but the fact is it is easier to stick with the status quo. In addition because of both supercharger and cylinder power loss it is near impossible to get the same high levels of economy that you're seeing in modern day 4 stroke diesel car engines.

[Tamber]

Well, it may interest you that your totally wrong on this point! Maybe you should google a bit more before making these kind of statements. You are talking about a variation on the 2 stroke principle that uses one or two valves. I am talking about 2 stroke engines without valves. For instance Sachs, JLO, Deutz OMZ, bolness etc. These engines use lubrication oil to lubricate the cilinder and piston. Any surplus oil drips in the crank -case witch in fact is pressurized, and is taken in with the inletstream. I know so, because I own and/or work on a couple of these engines. No wickypedia for me, half of it is incorrect annyway

So I'm not totally wrong, then, just mostly? I will admit that I am a bit of^W^W^W an idiot, and keep completely forgetting that there are two-strokes diesels out there that don't use externally-blown uniflow design with at least one valve, though. (Well, aside from the Commer TS3; not sure how I'd be able to forget that. )

(And you could always correct the half that's wrong; that's rather the point of wikipedia anyhow. But then, that's a separate discussion, with a separate mess of bitterness behind it.)

Yes, it is. However, soot and other byproducts remain in the cylinder as well, The EGR page you link specifically states "Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters. EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity." Not to mention lower fuel economy (3%). EGR is a mostly negative edition on a diesel engine. This effect, however, explains why two strokes have poor emissions.

But my point was that it's not just limited to two-strokes. (Although, yes, you're right; it being inherent in a 2-stroke, rather than a deliberate, removable add-on is rather a problem; due to not being able to just unplug bits and magically make it cleaner.)

This may change somewhat in the future. Notice how the verbage on this page mentions reducing "the NOx emissions by enabling higher than normal EGR rates". This is because their engine uses an airpump (electromechanical turbo) that is independent of engine speed. Who knows, maybe we'll see one in a build someday.

Hmm, very interesting. That would be neat to see in a build, some day, yes. I'll have to grab a copy of that, and keep an eye on developments.

Two-Strokes aren't bad once you get them running at full tilt continuously, but this is hardly an option for anything that doesn't have an electrical drivetrain (trains, generators, boats, etc).

Diesel-electric trike, perhaps? Hmm, now, there's an idea.

Various auto manufacturers have looked at 2 stroke diesel technology (I know for sure at least one of the big 3 American firms has) but the fact is it is easier to stick with the status quo. In addition because of both supercharger and cylinder power loss it is near impossible to get the same high levels of economy that you're seeing in modern day 4 stroke diesel car engines.

Yup; Saab, GM, and more. And they all gave up on it, since (no surprise, really; you've all been shouting it at me. ) the two-strokes were too hard to bring into compliance with environmental regulations. Still, though, I think that there are things to be learned from the improvements that have been made in the arena of four-stroke diesel engines. (And, even if it doesn't improve things enough; well, at least we tried, rather than saying "It didn't work back then, so we didn't bother trying again".)


Anyway, I think I've dragged this far enough off-topic (and made enough of a fool of myself) now; so I'll sit down and shut up again. (Until the next time, anyway.)

[Rhynri]

Can-Am was looking at building a hybrid-powertrain Spyder, so you might not be too far off the mark!

[Blunt Eversmoke]

Classic two stroke is not the only way of getting one power stroke per revolution. There's also the split cycle way of doing it, and, lo and behold, it has finally been implemented in a working design:

http://tourengine.com/

Splitting intake/compression and combustion/exhaust means that:

You compress air in a cold cylinder and not in a hot one, thus reducing power needed for compression stroke.
You may have to cool the hot cylinder less than on a two-stroke of same operational characteristics.
You can push out the exhaust gas completely and get to keep four stroke gas exchange, meaning no incomplete burn, no residual exhaust gas in the working cylinder, and no ports to lose lube oil through.
Compression and expansion ratio can differ vastly, meaning higher expansion efficiency.
Variable compression ratio built in.

Put off by a whole cylinder needed to do the intake/compression stuff? Just have a turbo do the low compression work, and have a much, much smaller intake/compression cylinder do the high compression and push the compressed air into the work cylinder, thus allowing for a way smaller cool cylinder, so you can afford one per each hot cylinder, weight-wise.

[coachgeo]

Classic two stroke is not the only way of getting one power stroke per revolution. There's also the split cycle way of doing it, and, lo and behold, it has finally been implemented in a working design:

http://tourengine.com/

Splitting intake/compression and combustion/exhaust ....

I emailed them for the hell of it to see if they had considered this format in a diesel configuration

[Rhynri]

I'll be watching this space for their reply, coach, that is one hell of an interesting engine.

[coachgeo]

I'll be watching this space for their reply, coach, that is one hell of an interesting engine.

On second thought..... I mighta made a fool of myself. A diesel engine works by so hightly compressing an "oil" and air mix in a hot environment that it ignites. So with that in mind this design may not work for a diesel engine.

[Blunt Eversmoke]

I'll be watching this space for their reply, coach, that is one hell of an interesting engine.

On second thought..... I mighta made a fool of myself. A diesel engine works by so hightly compressing an "oil" and air mix in a hot environment that it ignites. So with that in mind this design may not work for a diesel engine.

That is wrong, in a diesel, fuel is injected only when air is compressed and hot already. So while it may thus be hard to get a split cycle to run as a direct-injecting diesel, no one says a pre-chamber will not work, since injection happens quite early there. On the contrary, I actually wondered why they didn't do it as a diesel in the first place.

[Rhynri]

I imagine the cool cylinder is only cool on the scale of engine temperatures, because it still has the compression (what actually does most of the heating of the air), especially once the engine reachese operating temp. This sort of engine may require a glow-plug to start at anything outside of texas temps, but even an air-compressor gets quite hot in operation, so I imagine once rpms come up the issue is no longer such. You could also just massively increase the compression ratio (say, to 30:1) to start it, which this engine has the capability according tho their site, then modulate it to the most efficient compression ratio for current operation.

I don't know how much of what I said is right, but just my .02

[BertTrack]

Why on earth would they make it like this? Possibly except for flat out this will have a worse efficiency than any other normal fuel engine.

They add a cylinder with mechanical losses just to compress air. Then allow that air to flow into another cylinder which is hot. Causing this air to rise in pressure. So they have to make the initial compression pressure even higher.

And they want to transport that amount of compressed air into the other cylinder which will introduce extra drag on the air meaning they will have to compensate for that as well by increasing the initial compression even more.

If the first cylinder makes 26 bar of air in the remaining space @ t.d.c. and that has to flow though channels, and fill up the volume on the other side. They’ll maybe have 13 bar remaining. But this has to happen before ignition (or start of injection) Which happens before t.d.c. of the second cylinder. So that isn’t even at its smallest volume yet.

They have to choose to get a well scavenged 2nd cylinder or a high rpm engine with ignition/injection before t.d.c.

And if they open inlet and outlet valve in the 2nd cylinder they will push out air… and in case of non direct injection also fuel. Ah also another small detail having to compress the air (and fuel) mixture that much in the first cylinder to be able to fill/scavenge the 2nd cylinder will likely lead to detonation in the first cylinder.

And for all this they are using crankshaft power too! Not even exhaust gas energy like a turbo.

It’s not the brightest lights on the engine development scene. Just look at the construction of the thing. With both cylinders touching each other also transporting heat.

If someone wants an alternative, try the “5stroke” engine. Very high compression ratio, turbo AND an extra cylinder for every 2 primary cylinders. Catching the bulk of the extra available energy from the high compression ratio in the third cylinder.

[Blunt Eversmoke]

Why on earth would they make it like this? Possibly except for flat out this will have a worse efficiency than any other normal fuel engine.

They add a cylinder with mechanical losses just to compress air. Then allow that air to flow into another cylinder which is hot. Causing this air to rise in pressure. So they have to make the initial compression pressure even higher.

Sorry for late answer!

Keep in mind that the split-cycle is not a two-stroke but - well - a split-cycle four-stroke. Compare it to a two-cylinder four-stroke, if you want to compare mechanical losses: If in a standard four-stroke you have two equal cylinders doing all sorts of things, here, you have two different cylinders with work diversification. This means:

1) That you are free to keep the compression cylinder as cool as you can so compression work is done easier (increasing overall efficiency), and working cylinder can use inner cooling instead of inefficient external WITHOUT the risk of undercooling. Also, the comparatively cool, compressed fresh gas charge will help expansion once it touches the hot cylinder walls, adding to expansion from combustion.

2) That you can use a way smaller cylinder for compression, getting LOWER friction losses. Remember, you can change working cylinder "headspace" on the fly, so if you use a strong turbo arrangement with wastegate, you get permanent WOT on a petrol engine, or can balance efficiency and power on the fly with a diesel engine. Also, this nets you a high expansion to compression ratio, aiding efficiency.

3) In a diesel version with a high expansion/compression ratio, you might even have to thermally isolate the combustion cylinder so it doesn't undercool - Rudolf Diesel's wet dream come true

And they want to transport that amount of compressed air into the other cylinder which will introduce extra drag on the air meaning they will have to compensate for that as well by increasing the initial compression even more.

They report compression ratios of up to 14:1 run on standard gasoline. Can't be THAT grave a problem.

If the first cylinder makes 26 bar of air in the remaining space @ t.d.c. and that has to flow though channels, and fill up the volume on the other side. They’ll maybe have 13 bar remaining. But this has to happen before ignition (or start of injection) Which happens before t.d.c. of the second cylinder. So that isn’t even at its smallest volume yet.

Apparently, they have solved the pressure loss in the channels by putting compression and combustion cylinders head-to-head against each other, between the heads some sort of a very flat valve, which happens to be their know-how. Regardless, this is a moot point: They propose a heavily turbocharged arrangement, and with that, you can compensate any compression loss - as long as you can account for the exact loss figure.

Regarding the timing:
Remember! At ignition, working cylinder ain't at its smallest volume ANY MORE, because ignition - indeed, even charge transfer - is AFTER TDC. For this type of engine, effective compression ratio is higher with an earlier transfer and ignition. Indeed, working cylinder does not compress anything at all, it gets the pre-compressed fresh charge that might or might not even expand a bit before ignition.

They have to choose to get a well scavenged 2nd cylinder or a high rpm engine with ignition/injection before t.d.c.

Huh? NO scavenging. NO compressing the fresh charge in the combustion cylinder. NO need for early ignition. Timed transfer and ignition, according to desired CR.

And if they open inlet and outlet valve in the 2nd cylinder they will push out air… and in case of non direct injection also fuel.

No, they won't. Why on earth would they have to open both valves at the same time when the dead("head") space in the working cylinder is close to zero?
Remember, on a four-stroke(especially petrol), you always have dead space in the head from which you cannot drive the burnt gas with the piston but need to overlap valves so exhaust gas, leaving the head, sucks some fresh gas into the head.
Here, dead space is almost zilch! Work done, exhaust gas pistoned out near to COMPLETELY, exhaust valve closes, transfer valve opens, fresh gas gets pressed into working cylinder.

Ah also another small detail having to compress the air (and fuel) mixture that much in the first cylinder to be able to fill/scavenge the 2nd cylinder will likely lead to detonation in the first cylinder.

That was my fear as well; apparently, compressed fresh charge is cooled enough during the transfer not to self-ignite even at 14:1, see above. None the less, I'd prefer them to do a diesel, there you wouldn't have to worry about that

And for all this they are using crankshaft power too! Not even exhaust gas energy like a turbo.

D.U.H.(c) That's what ANY athmospheric engine does, pull power from crankshaft in order to compress the inhausted charge before ignition or injection. Again, using a turbo is proposed (even if not yet implemented) so compression cylinder can be kept small.

It’s not the brightest lights on the engine development scene. Just look at the construction of the thing. With both cylinders touching each other also transporting heat.

Better than any other split-cycles to-date. Heat is only transferred through the flat valve, you can separate the heads from each other with asbest or somesuch.

If someone wants an alternative, try the “5stroke” engine. Very high compression ratio, turbo AND an extra cylinder for every 2 primary cylinders. Catching the bulk of the extra available energy from the high compression ratio in the third cylinder.

Aye, this, too, is very interesting, and easier to implement than a full-out split-cycle.

Or, better yet, a gas turbine with a free-piston gas generator (diesel with CR above 30, anyone? WITHOUT increased friction losses, with crank gone?) where the combustion chamber normally is. 40% overall efficiency without breaking a sweat.

[BertTrack]

Keep in mind that the split-cycle is not a two-stroke but - well - a split-cycle four-stroke. Compare it to a two-cylinder four-stroke, if you want to compare mechanical losses: If in a standard four-stroke you have two equal cylinders doing all sorts of things, here, you have two different cylinders with work diversification. This means:

1) That you are free to keep the compression cylinder as cool as you can so compression work is done easier (increasing overall efficiency), and working cylinder can use inner cooling instead of inefficient external WITHOUT the risk of undercooling. Also, the comparatively cool, compressed fresh gas charge will help expansion once it touches the hot cylinder walls, adding to expansion from combustion.

This will not be the case for a diesel version where you need hot air to ignite diesel. So there is no benefit in keeping the compression side as cool as you can. Keeping a compression cool doesn't make it more efficient. Keeping it cool means you take away energy that has been put in through compression and again in a diesel version this would be vital. As the comparatively cool compressed fresh gas charge expands it will suck up more heat. Heat which wasn't available after compression because that has been "cooled" out of it.

2) That you can use a way smaller cylinder for compression, getting LOWER friction losses. Remember, you can change working cylinder "headspace" on the fly, so if you use a strong turbo arrangement with wastegate, you get permanent WOT on a petrol engine, or can balance efficiency and power on the fly with a diesel engine. Also, this nets you a high expansion to compression ratio, aiding efficiency.

Friction increases with piston speed. Making a smaller cilinder still needing to be able to compress the same amount will lead to a higher piston speed.

3) In a diesel version with a high expansion/compression ratio, you might even have to thermally isolate the combustion cylinder so it doesn't undercool - Rudolf Diesel's wet dream come true

Insulate sure but it would be smarter to add heat from the compression of the compressor to the work piston. You'd need a medium for that. In a Diesel i'd go for air Also getting even close to undercooling would also lead to diminished mechanical efficiencies. Small loads on any type of engine isn't efficient.

And they want to transport that amount of compressed air into the other cylinder which will introduce extra drag on the air meaning they will have to compensate for that as well by increasing the initial compression even more.

They report compression ratios of up to 14:1 run on standard gasoline. Can't be THAT grave a problem.

If the first cylinder makes 26 bar of air in the remaining space @ t.d.c. and that has to flow though channels, and fill up the volume on the other side. They’ll maybe have 13 bar remaining. But this has to happen before ignition (or start of injection) Which happens before t.d.c. of the second cylinder. So that isn’t even at its smallest volume yet.

Apparently, they have solved the pressure loss in the channels by putting compression and combustion cylinders head-to-head against each other, between the heads some sort of a very flat valve, which happens to be their know-how. Regardless, this is a moot point: They propose a heavily turbocharged arrangement, and with that, you can compensate any compression loss - as long as you can account for the exact loss figure.

The point isn't exactly mood. Having a resulting volume all be it small (1/12th aprox of original) it will still need to expand that air into the other cilinder. There is no way to evacuate the air from the one cilinder so you will always have a significant loss. And that loss will proportionally be bigger at lower loads and at lower temperatures! Is this turbo going to pick up energy from it's under cooled exhaust gases?

Regarding the timing:
Remember! At ignition, working cylinder ain't at its smallest volume ANY MORE, because ignition - indeed, even charge transfer - is AFTER TDC. For this type of engine, effective compression ratio is higher with an earlier transfer and ignition. Indeed, working cylinder does not compress anything at all, it gets the pre-compressed fresh charge that might or might not even expand a bit before ignition.

In diesels it's common to start the uncontrolled burn before TDC. Especially when it's a high rpm one. In normal fuel engines it's even more common to Ignite before TDC.

They have to choose to get a well scavenged 2nd cylinder or a high rpm engine with ignition/injection before t.d.c.

Huh? NO scavenging. NO compressing the fresh charge in the combustion cylinder. NO need for early ignition. Timed transfer and ignition, according to desired CR.

Not compressing in the second cylinder will only increase the waste of compressed gas from the first cylinder. If they don't start their pressure build up before TDC their efficiency of the work piston will be less than ideal. Another loss.

And if they open inlet and outlet valve in the 2nd cylinder they will push out air… and in case of non direct injection also fuel.

No, they won't. Why on earth would they have to open both valves at the same time when the dead("head") space in the working cylinder is close to zero?
At what point are they going to push air into the cycle? Right after exhaust stroke? Or around TDC?


Remember, on a four-stroke(especially petrol), you always have dead space in the head from which you cannot drive the burnt gas with the piston but need to overlap valves so exhaust gas, leaving the head, sucks some fresh gas into the head.
Here, dead space is almost zilch! Work done, exhaust gas pistoned out near to COMPLETELY, exhaust valve closes, transfer valve opens, fresh gas gets pressed into working cylinder.

Ah sorry i should have read on. So you're saying here that the compression piston will deliver it's air as the work piston is around TDC and still has to travel down. Or did it suddenly not become a 4 stroke?

Ah also another small detail having to compress the air (and fuel) mixture that much in the first cylinder to be able to fill/scavenge the 2nd cylinder will likely lead to detonation in the first cylinder.

That was my fear as well; apparently, compressed fresh charge is cooled enough during the transfer not to self-ignite even at 14:1, see above. None the less, I'd prefer them to do a diesel, there you wouldn't have to worry about that

In theory with a diesel they'd be able to control the amount of air delivered so that the resulting air temperature is just enough to ignite the diesel fuel. Of course this air would have to be 350c so why cool the compression cylinder. Or why use one at all? And part of the Diesel's efficiency is because it runs at a high compression ratio all the time. So the control of amount of air delivered is useless. Temperature of that air would be more useful.

And for all this they are using crankshaft power too! Not even exhaust gas energy like a turbo.

D.U.H.(c) That's what ANY athmospheric engine does, pull power from crankshaft in order to compress the inhausted charge before ignition or injection. Again, using a turbo is proposed (even if not yet implemented) so compression cylinder can be kept small.

With ANY atmospheric engine the compression energy of air/fuel mixture of air in a diesel is recovered through expansion stroke and possibly the use of a turbo which will increase the efficiency because it uses "waste" heat. Separating the compression cycle and throwing away that heat and energy through added channels all be it small doesn't improve the efficiency at all.

It’s not the brightest lights on the engine development scene. Just look at the construction of the thing. With both cylinders touching each other also transporting heat.

Better than any other split-cycles to-date. Heat is only transferred through the flat valve, you can separate the heads from each other with asbest or somesuch.

In case of the Diesel version heat needs to remain. So separating is not needed at all.

If someone wants an alternative, try the “5stroke” engine. Very high compression ratio, turbo AND an extra cylinder for every 2 primary cylinders. Catching the bulk of the extra available energy from the high compression ratio in the third cylinder.

Aye, this, too, is very interesting, and easier to implement than a full-out split-cycle.

Or, better yet, a gas turbine with a free-piston gas generator (diesel with CR above 30, anyone? WITHOUT increased friction losses, with crank gone?) where the combustion chamber normally is. 40% overall efficiency without breaking a sweat.[/quote]

Unfortunately there are always friction losses, especially in gas turbines running at lower loads this is a major factor. They only run efficiently at or near full power. Oh and the free-piston gas generator is 2 stroke. Otherwise it wouldn't run. http://www.youtube.com/watch?v=yyUcXPNc ... ure=relmfu