Interesting, but I don't buy it.
http://www.motortrend.com/news/at-least-one-automaker-plans-to-produce-an-opposed-piston-engine/
This engine looks like it will... Sound like a diesel.
Also, how do the intake "holes" work? It seems like that design would cause all kinds of issues on the power stroke unless boost pressure was unreasonably high. Wouldn't this also cause a perfect place for a casting failure?
Sounds like it could run, but I have no clue why they think it would be better in any big way. Also, some of the claims are silly, reduced friction because it doesn't have cylinder head bolts? Some guy is making some of that up.
In reply to tuna55:
I understand what he's talking about there, as there used to be an issue with bore distortion issue that required tighter rings. But that problem had a solution decades ago, and it's pretty minor.
In reply to alfadriver:
Bore distortion is still a pretty big deal in heavy-duty engines, and automotive engines for that matter.
alfadriver wrote: In reply to tuna55: I understand what he's talking about there, as there used to be an issue with bore distortion issue that required tighter rings. But that problem had a solution decades ago, and it's pretty minor.
Yes, what you said is what I understood to be the case
You did notice the part where the engine is supercharged? Obviously the only way to get enough air into (and out of) the engine with those ports
maschinenbau wrote: In reply to alfadriver: Bore distortion is still a pretty big deal in heavy-duty engines, and automotive engines for that matter.
But what he was alluding to seems to be the cloverleaf shaped distortion- which, for car engines, has been solved a long, long time ago. The reason it even happened was someone was cheap with the head bolts.
There's still distortion when you torque it down. Still- that amount is so small that the ring tension to keep the gasses in is more important and higher than dealing with distortion.
mad_machine wrote: You did notice the part where the engine is supercharged? Obviously the only way to get enough air into (and out of) the engine with those ports
It's 2 stroke. Has to be supercharged.
I see the list of claims about lower heat loss, lower friction, better port efficiency, but I don't see how what is shown leads to that?
No valve train = less friction. But you've added another crank with it's bearings. More conrods and pistons with more main and rod bearings plus piston rings.
Less mass? But you've added another whole freeking crank, up high with more rotating inertia.
Less heat? How, where?
More efficient combustion chamber shape? What can't be achieved with a regular head on block engine?
Better port shape? Where? It seems to exit around the circumference of the cylinder which will have a pretty long, inefficient shape to get 180 degrees round to the actual exit from the block assembly?
I'm not smart enough to claim this is wrong, just I'm not seeing it. Eric or someone smarter than me, can you explain how these claims stack up please?
Being 2 stroke helps with a few of those aspects. Less heat loss into the block due to less cylinder surface area per hp (both because it's a 2 stroke and because of no cylinder heads). 2 stroke reduces mass because at a given boost pressure, you can theoretically make twice as much power for a given size of engine.
rslifkin wrote: Being 2 stroke helps with a few of those aspects. Less heat loss into the block due to less cylinder surface area per hp (both because it's a 2 stroke and because of no cylinder heads). 2 stroke reduces mass because at a given boost pressure, you can theoretically make twice as much power for a given size of engine.
Good point I should have thought of, but it leads to the same set of Questions for this version Vs a regular single crank 2 stroke. Where is the advantage?
I'm honestly not knocking this design, I just don't have the applied knowledge to understand or make an informed opinion.
What I see with this is in very simple terms, it is a 6-cylinder using 3-cylinders. More efficient and less heat because of the 2-in-1 cylinders, you get 2 power stokes at the same time out of basically the same cylinder. What I see as a weak point is the power from the 2 cranks have to be combined into a single output, appears to be either belt or chain on this. Could be mistaken though, not enough detail to see.
Would be interesting to see it in a car and how it would work. Would it rev quickly? How quick will the power/acceleration be? Etc...
I will say this, my father was almost killed by a navy "rock crusher" back in 1970. A generator in the engine room he was running was about to be started. The guy starting it had to fill the upper oil reservoir before cranking or the upper crank would run dry. He was so busy yapping that he overfilled it before starting.
The ensuing overrun as the oil leaked past the rings into the combustion chamber had them evacuating the room until it finally blew up.
Which leads to my question, how are they going to keep enough oil on the upper main bearings to keep them from getting gouged and worn out prematurely
Adrian_Thompson wrote:rslifkin wrote: Being 2 stroke helps with a few of those aspects. Less heat loss into the block due to less cylinder surface area per hp (both because it's a 2 stroke and because of no cylinder heads). 2 stroke reduces mass because at a given boost pressure, you can theoretically make twice as much power for a given size of engine.Good point I should have thought of, but it leads to the same set of Questions for this version Vs a regular single crank 2 stroke. Where is the advantage? I'm honestly not knocking this design, I just don't have the applied knowledge to understand or make an informed opinion.
Also, with the nature of the two stroke- with the intake at one end and the exhaust at the other, there's far less chance of a short circuit of the charge- which is one huge problem with two strokes. Although, the port temp issue that rotary engines have will be the same (but that's been solved, so...)
On a physics basis, the double volume being swept relative to a single crank 2 stroke also probably helps.
BTW, this will only really work for diesel- on gas engines, the excess O2 in the exhaust makes it virtually impossible to fully convert the NOx that is made.
It will be interesting to see how far this goes- it's both simpler and more complex at the same time.
One of the things that would concern me is the "loose" rings sweeping over the ports all the time. Again, I know rotary engines do this, too- but there still has to be pressure on the rings so that they don't pop out.
I thought these Rootes engines were pretty neat using rocker arms and one crank shaft. Aren't two strokes all but dead though because of emissions regs.
alfadriver wrote:maschinenbau wrote: In reply to alfadriver: Bore distortion is still a pretty big deal in heavy-duty engines, and automotive engines for that matter.But what he was alluding to seems to be the cloverleaf shaped distortion- which, for car engines, has been solved a long, long time ago. The reason it even happened was someone was cheap with the head bolts. There's still distortion when you torque it down. Still- that amount is so small that the ring tension to keep the gasses in is more important and higher than dealing with distortion.
I would be surprised if bore distortion from head bolts and heat is not a concern with automotive gas engines, but that's not where my experience is. It certainly is the case with diesel/natgas engines. The huge cylinder pressures drive huge head bolt loads. Gas sealing is the easy part. Conforming to bore distortion is another story. Truckers don't like topping off oil between changes.
This new engine seems targeted at the medium duty diesel market rather than passenger cars based on its ratings, so removing bore distortion from the equation would be very attractive.
In reply to maschinenbau:
the clover leaf issue is due to the head bolts stopping at the top of the block- so the bolt torque twists the top of the bore. Once you put them down at the crank- that's fixed (yes, there's distortion at the bottom, but that's pretty low pressure anyway).
AND gas engines don't run as tight as diesel engines- since peak pressures are lower (as are compression ratios).
It's not a big deal.
In reply to Wall-e:
For the most part, gas 2 strokes are dead. I don't think 2 strokes can get high enough pressures/temps on the smaller scale of car/truck diesels. But if they did- the flow issues are not that much difference, or I should say- IF it would work, then the exhaust on a 2 stroke diesel is generally the same as a 4 stroke.
alfadriver wrote:Adrian_Thompson wrote:Also, with the nature of the two stroke- with the intake at one end and the exhaust at the other, there's far less chance of a short circuit of the charge- which is one huge problem with two strokes. Although, the port temp issue that rotary engines have will be the same (but that's been solved, so...) On a physics basis, the double volume being swept relative to a single crank 2 stroke also probably helps. BTW, this will only really work for diesel- on gas engines, the excess O2 in the exhaust makes it virtually impossible to fully convert the NOx that is made. It will be interesting to see how far this goes- it's both simpler and more complex at the same time. One of the things that would concern me is the "loose" rings sweeping over the ports all the time. Again, I know rotary engines do this, too- but there still has to be pressure on the rings so that they don't pop out.rslifkin wrote: Being 2 stroke helps with a few of those aspects. Less heat loss into the block due to less cylinder surface area per hp (both because it's a 2 stroke and because of no cylinder heads). 2 stroke reduces mass because at a given boost pressure, you can theoretically make twice as much power for a given size of engine.Good point I should have thought of, but it leads to the same set of Questions for this version Vs a regular single crank 2 stroke. Where is the advantage? I'm honestly not knocking this design, I just don't have the applied knowledge to understand or make an informed opinion.
There is plenty of O2 in diesel exhaust that current aftertreatment technology deals with. Most diesels run a globally lean AFR well over 30:1.
Rings sliding over those intake ports doesn't look very different from rings sliding over a heavily-distorted cylinder liner. Might create a funny wear pattern, but I've probably seen worse on engines with higher miles than this one will ever see!
In reply to Adrian_Thompson:
I'm far from an expert on any of this, so assume I'm probably wrong on some/most/all of it, but this is the best I've been able to come up with so far regarding your concerns.
Think of it as a equivalent to an I6 that has had the head removed, been cut in half, and bolted together in opposed fashion. Same number of pistons and connecting rods. One more main bearing and only a slightly greater total combined crank length. However, it has 2x6 cylinders less cam, 14 fewer rotating cam bearings, 24 fewer reciprocating valve/spring assemblies, 1x6 cylinders less head material...Which is subsequently where the wetted area vs displacement also comes into play for combustion efficiency. Note that the same wetted are vs displacement issue is one of the main advantages of OHV engines over side valve (flathead) engines.
Even though total inertia is probably less than a conventional I6 engine, I don't think they're pushing that. If reduced inertia were that big of a deal in production cars, there wouldn't be cross-plane (heavily counterweighted) V8's "sports cars" with large diameter (high inertia) 30 pound flywheels (still not counting the large diameter/heavy/high inertia clutch) that could easily be 1/3 the weight. With all of the above, I would expect that it's at least physically capble of being more revvy than an I6 of similar bore and stroke, whether or not other factors allow it to be.
I would guess that the improved combustion chamber design comes from not requiring relievs to accommodate valve/piston interference nor chamber shapes that are necessarily based around not shrouding too tightly around the valves. I also believe that chamber geometry is being developed to maximize both intake and exhaust flow from the same side of the cylinder. If the flow path from intake to exhaust was essentially unidirectional, with no need to control a flow reversal, maybe this can allow for more efficient combustion chamber geometries. Sort of along the lines of going from reverse flow cylinder heads to cross flow cylinder heads.
As far as the ports go, I can't speak to the shape of them, but consider the area. The intake port area is HUGE compared to what is possible with poppet valves. The exhaust area is obviously by design much more constrained. I can also see how the numerous, quite small, and continuously open exhaust ports might (or might not) provide a similar net effect to they more typical 2-stroke exhaust port layout.
maschinenbau wrote: There is plenty of O2 in diesel exhaust that current aftertreatment technology deals with. Most diesels run a globally lean AFR well over 30:1. Rings sliding over those intake ports doesn't look very different from rings sliding over a heavily-distorted cylinder liner. Might create a funny wear pattern, but I've probably seen worse on engines with higher miles than this one will ever see!
Which is why I'm pointing out that this will only really work for diesel... 
In reply to alfadriver:
They actually claim to have figured out Gasoline-Compression-Ignition with this engine:
http://achatespower.com/opgci-an-evolution-that-revolutionizes-the-internal-combustion-engine/
In reply to alfadriver:
Ah I see! On the other hand...if this thing does burn gas, but spews NOx and O2 out the exhaust like a diesel...shouldn't diesel catalysts/dosers be able to break it down? Also, no spark plugs...so yeah it probably runs on diesel.
EDIT: Oh cool, it burns gas without spark plugs! According to that link, CI gas has a cool combustion compared to SI gas, so NOx is lower but UHC and CO is higher, which are easier to mitigate than NOx. Very interesting...
In reply to maschinenbau:
The problem with gas is the limited a/f range that it can nominally run. Most of the time it has to run near stoich, which means high HC, and SCR's don't run well with that.
Or I should really say Otto/Spark ignited engines.
The gas version of this engine is really a Diesel/compression ignition gas engine. (note Diesel not diesel- we are talking cycle not the fuel)
I'm not sure if I agree with the claim that gasoline is a better Diesel fuel than diesel. If it were, we'd be using it.
For sure, lean gas isn't cheap, especially the way they imply that it's a direct replacement. There are lean burn gas systems out there, but they all require some time at stoich or rich to restore the NOx storage capacity. And I'm 100% sure that running excess O2 in the exhaust means that gas catalysts wont work at all. I've done a LOT of work looking at that, and it doesn't take much O2 to really shut conversion down.
In the end, the only real theoretical difference in an equivalent output compression injection gas vs. diesel would be particulates*. But gas DI make particulates, too. Many EUROVI gas DI engines have particulate filters in them.
*(when running using the fuel as the throttle, you get those 30-40-50:1 a/f mixtures- at that point, HC is almost negligible, and NOx is fairly low- but not low enough, and still really hard to convert- head to head, the engine output of a diesel is cleaner than a gas. Just that gas is really easy to clean up to almost nothing, whereas diesel is really, really hard)
im gonna guess this will probably fall to the wayside just like the many other 'alternative' piston engines do.
like the duke engine:
or the 5 stroke engines:
or this 'Paul Motor Engine':
I have no doubt that these engines do/would work but I'm guessing since they haven't caught on that they weren't as simple/efficient/reliable to ever get picked up by any major players. As for the OP-3 engine i just cant see how there wouldn't be oil issues with the 3 upside down pistons. I could see it working better as a 'flat' engine, that would keep the 3 inverted cylinder from having oil issues. but ill believe it to be a good engine when a major manufacture decides to use it.
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