Should sell well in Europe where it (in the Civic) will give the Golf a run for its money.
2.2 litres is too large for mainstream diesel cars these days: 1.5-1.6 litres is more usual.

Nice to see more > 64mpg(US) cars being produced, even if the number is a bit aspirational.

These are my favorite kind of articles here on GCC - details about new efficient engines.

I know near-zero about chemistry, so most of the electrode/electrolyte/etc. articles might as well be written in Russian for all I care ;-)

Not that I don't like batteries. I hope they get cheaper and lighter fast, because hybrid cars need more powerful batteries to justify the added complexity and really take a load off the ICE. That way ICE power can drop below 100 hp without sacrificing 'driveability' and performance.

Meanwhile, engines such as this one will save a lot of fuel per kilometer driven. Please put it in a car without the horrible rear of the current Civic hatchback. The CR-V has no interest for me either for my personal taste.

I second mahonj's statement that 2.2 litres is too large for mainstream B-C class cars in Europe. And the Civic should be able to reach around 200 km/t with this gem of a diesel.

The only problem with diesel engines has to do with emissions and in particular NOx. I am pleased for the holistic approach in terms of reducing weight and internal friction.

An engine that can be placed in a variety of platforms will eventually produce profits for the company and also help the end consumer to reduce its cost sheet during the useful life of the vehicle.

Reduced weight
It is possible to make a lightweight diesel engine without using aluminum. For example compacted graphite iron (CGI) can be cast in thin sections and save weight in comparison to grey cast iron, i.e. come very close to an al-engine. CGI also enables higher cylinder pressures and thus, higher power density and/or downsizing. However, some manufacturers consider CGI too expensive for a 4-cylinder engine. So far, CGI is mostly used for V6 and V8 engines and on heavy-duty engines, of course. Returning to aluminum, it has also been considered expensive for this class of engines. However, Honda is not the first one to use aluminum in diesel engines. BMW, for example, solely use aluminum since a couple of years in all their diesel engines. While BMW is a “premium” car manufacturer, we can also note that PSA (Peugeot/Citroën) have used aluminum for more than a decade in their engine families (1.4-2.2 liters) that have emerged from the co-operation with Ford (and other manufacturers). This is a 1.6-liter diesel engine with, to my knowledge, the highest production numbers in the world. It is also very light but since Honda did not provide any absolute numbers, we cannot compare. The PSA engine is also supposed to be cost-effective, so apparently, PSA has solved the cost issue. One often cited issue with aluminum engines is the low limit for maximum cylinder pressure and thus, performance and power density. This would apply to the PSA engine that has an output of 115 PS in the most powerful version. However, as noted above, the PSA basic design is now pretty old, so the progress by Honda (120 PS) seems negligible. Furthermore, other aluminum engines, such as the BMW, have much higher power density than the Honda engine. The cylinder pressure limit for the BMW engines has been 180/185 bar but was recently raised to 200 bar for the tri-turbo 3-liter 6-cylinder engine. Honda does not state the cylinder pressure but I doubt that it is much higher than 165 bar. Regarding durability with aluminum… well, I think it has been proven by so many other manufacturers that these pressure levels can quite easily be handled with aluminum. If they would aim for >200 bar, I would have some doubts. However, this does not imply that Honda might not have made some mistakes…

Fuel injection
Bosch solenoid-actuated fuel injection with an injection pressure of 1800 bar is definitely mainstream, not state-of-the art. While top of the line FI with piezo actuators and 2200 bar would probably be too expensive for this engine, one could at least envision that 2000 bar could have been an ambition for those who want to be in the front line in the development. Engineers of course wish much more, i.e. in the range of 3000+ bar but we will have to wait many years before we see this in a passenger car engine. As a comment to HarveyD, this is the area where you should look if you want to track the progress for the last 15 years (CR started at 1350 bar, 15 years ago) and in the long-term future. Of course, it is not only about the pressure but I will skip all other parameters for a later contribution.

Air flow
It seems as Honda use both high and low-pressure EGR (high-pressure EGR is what all manufacturers used in the past). Well, this is the first area where we can say that there is a state-of-the-art level. Honda was not first, since the VW Group and BMW have used this technology for engines certified for USA during a couple of years. We also have examples from “non-premium” manufacturers, e.g. the new 1.6-liter Renault engine. With low-pressure EGE, Euro 6 can be met without any kind of NOx aftertreatment. This is definitely more cost-effective than a NOx catalyst. Again, Honda does not mention anything about the emission level. Surprising! If they would not meet Euro 6, they do not reach the state-of-the-art level regarding this parameter either.

Summary
Honda has made a nice little 1.6-liter engine that appears lightweight and compact. However, it reaches state-of-the-art level only in a few areas. In comparison with larger engines, it is lagging behind even more, albeit that such a comparison might be somewhat unfair. Similar conclusions could be drawn for the Honda 2.2-liter engine. However, it should be noted that this engine is much older than the new 1.6-liter engine.

@Nick69
It is obvious that Honda is in for aluminum, regardless of if it is a diesel or a gasoline engine.

The additional information from Honda does not really contribute very much to an assessment of the progress. I would like to compare the weight with the PSA engine, where I have data. This engine is very light and I doubt that the Honda engine could be much more than just a few kg lighter. The comparison with the 2.2-liter engine is also irrelevant, unless the difference in size is taken into account. If we anticipate that the 1.6-liter engine weighs in the range of 120-130 kg, the 47 kg heavier engine would weigh ~40% more. However, this engine is also ~40% larger, so where is the progress? I am not so surprised to find that the crankshaft of the smaller engine is 36% lighter and the same could be said about many other data. With a very gentle approach, we could anticipate that Honda tries to explain the advantage of downsizing by implying that the smaller engine can provide similar power as the larger engine. However, even that is not fully true either, since the larger engine is more powerful. The remaining small advantage is that the new engine has somewhat higher power density (and cylinder pressure) than the older and larger engine but a comparison with, let´s say, a 2-liter engine might have been more appropriate. On the other hand, if you design a new engine, why would you not aim for higher power density?

I am not at all impressed with an engine that does not have a balance shaft. Most 4-cylinder engines below 2 liter capacity do not have a balance shaft. The cost is high, increased friction and the simple fact that the engine is smaller reduces vibration and customer acceptance for smaller engines might allow for a somewhat higher vibration level. Gasoline engines of this size usually do not have balance shafts either; for the same reasons.

D Wrote:
"The proof of the success of this new diesel will be durability and reliability. Previous attempts at lightweight diesels have not met expectations in this regard. Marginal strength from weight reduction has not previously shown able to contain diesel operating pressures. To my knowledge there are few full aluminum diesels for that very same reason"

Yes, there are few aluminium turbodiesel in Europe, but one of them is maybe the most popular, the 1.6 (90-115 hp) jointly developed by PSA (Peugeot-Citroën) and Ford. It's used also by Mazda, Volvo and Mini. There is also, since 2002, the 1.4 (75-90 hp) by Toyota, used by Yaris, Auris (kind of European Corolla) and Mini (before the PSA-Ford). Then there is the 2.2 by Honda and another 2.2 by Toyota, plus a V6 by Peugeot and ALL range of Bmw made turbodiesel (from 2.0 to 4.2), some of them will be adopted by Toyota in the near future.
Besides that, in the Le mans Series Peugeot and Audi have clearly showed that an aluminium 600 hp turbodiesel could run 24 hours/5000 km in racing conditions (and win the race).
Widespread diffusion of aluminium diesels is probably limited by unit cost. And by the need for very good R&D, since, you're right, it's not that easy to get the standard target of at least 250,000 km (155,000 miles) trouble-free, target strictly required by automakers before launching a new engine in Europe. At least Toyota, Honda and Bmw-Mini don't give up on reliability.