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Opposed Piston Opposed Cylinder engines have two pairs of pistons facing one another, each in a cylinder on opposite sides of the crankshaft. There is no cylinder head, just a ring of ports for intake and exhaust in the cylinder walls near where the pistons bottom out. With a slight timing offset, the exhaust ports will open before the intake ports. It is a fascinating design, simple and elegant, with very few moving parts and a high power density. The engine is completely balanced, and all of the linear forces cancel, leaving little load on the bearings, just torque. There are other interesting concepts out there, but this one is actually being mass produced today.

Electric cars are certainly attractive, but the reality is that hydrocarbon fuels are going nowhere. The energy density and flexibility are simply too great, and we have an immense amount of infrastructure and equipment that make use of them. The fastest way to a greener world isn't through electric cars, but rather synthetic carbon-neutral fuels, which can be efficiently produced using heat from nuclear reactors. Nuclear Ammonia is particularly interesting, because the feedstocks are readily available from air and water. Other replacement fuels can also be synthesized, but extracting carbon from air or water will add to the cost.

I'm really surprised no one has put the pieces together yet.
Yes this is a 2 stroke diesel, and the opposing pistons are really not such a big deal by them selves.
However there's the "Electrically Controlled Turbocharger", which is really a "part-time" electric supercharger.
Why does this change everything? Because you can be 100% certain to flush out all combustion products from the cylinder at all times.
You can eliminate crankcase "aspiration", resonance tuning, and turbo lag and all the attendant problems.
In this context the opposing piston may be just as much an optimization of the valves and ports for this new regime.

To summarize.
2 stroke: high power density
diesel: no unburnt fuel goes out with the exhaust as it is flushed.
electric turbo: no exhaust ever left in cylinder for next cycle, no oil from crankcase etc.
opposing pistons: larger symmetrical ports optimize flushing, balance oscillating mass etc. but have other costs.

Of course it's not that simple. Like all attempts at innovations in a mature technology this is a delicate balancing of trade-offs by someone who thinks they know the game well enough to get away with it. It amazes me how confidently some people here dismiss this in one sentence, while obviously having no clue.

heh, you made me dig up this:
http://ecomotors.com/technology

until i looked at the CAD there, i thought "opposing piston" was just another way of writing that the pistons where aligned on either side of the shaft.

You mean someone like...HITLER?!

I think you are on to something....

OPOC Video

I not a car guy. So, will someone explain to me how this differs from a boxer engine?

Everyone seems to be struggling with this this morning. Watch the linked video. Each cylinder has two pistons pushing away from each other. Each pair of opposing cylinders is a unit that can be connected to other units using a clutch that allows some units to be shut down when energy needs are smaller.

If you go to the site he has a bit more info including a graphic rendering of the engine >> EcoMotors International

As I understand it, "traditional" flat engine, or opposing cylinder engine technology uses multiple crankshafts and cylinders and are often based on two-stroke engine technology. Certainly none of the examples I saw or read about in the wikipedia article (Opposed-Piston Engine) seemed less complex, nor efficient.

This engine, uses two cylinders, each containing two opposing pistons, and only a single crankshaft to obtain 4-stroke emissions benefits without the added complexity of synchronising multiple crankshafts. Also, they're proposing that multiple such powerplants could be daisy-chained together to provide additional power when it is required. In theory, 1-4 of these modules connected thusly could give you performance up to that of an 8cy car, but use as few as two cylinders when the extra horse-power isn't necessary (by "turning on" extra modules as necessary, then turning them back off again when it isn't).

In theory at least, that should radically improve the available efficiencies of modern engines without needing to alter the existing fuel-distribution network, and without a loss of available horsepower when such is required. In that light, I would say it does represent "something new" (as opposed to your assertion to the contrary).

-AC

go back a bit further, radial engines used on most pre ww2 aircraft.

This is similar to radial engines but it's quite different in having two pistons per cylinder. See video.

Like a VW, Subaru, or BMW bike? This is new?
Ok, they may be taking this to a new level, but this design has been around for quite a while.

No. I thought the same and wondered why it was different from a flat 4 layout. This has two pistons per cylinder, each pushing away from each other. It's also an advanced two-stroke. (I remember in the late 80s and early 90s when all the talk was about how two-strokes were going to be the next big thing.)

You need to watch the linked video to see how it works. It's actually kinda cool. Each pair of opposing cylinders can act as an independent unit, so you can shut one unit down when you need less power. The guy claims significant fuel consumption savings.

Indeed, hybrids are far more practical, but it seems that you are misrepresenting the promise of microturbines. From the wikipedia article:

Typical microturbine efficiencies are 25 to 35%. When in a combined heat and power cogeneration system, efficiencies of greater than 80% are commonly achieved.

In automotive applications, the waste heat goes unused; so the efficiency will be in the 25 to 35% range.

Another promising option for hybrids is the OPOC engine, which is a simple, efficient, and clean 2-stroke engine. It is a very interesting design, with a number of other advantages as well.

When coupled with a capacitor/flywheel/etc. to allow for regenerative braking and acceleration, the requirements for the power source in a hybrid are actually very minimal. This allows for the creation of an extremely efficient vehicle, and as far as energy density goes, you can't do much better than hydrocarbons.

I wonder how this compares to the OPOC engine that is being developed by the same guy who did the TDI for VW. Check out the nifty flash animation: http://www.ecomotors.com/ . I think the new found focus on economy is starting to (finally) spur some innovation in this area.

Not with an OPOC diesel: http://www.ecomotors.com/