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A closer look at the basics of Volkswagen Group’s important new 2.0L diesel MDB engine

22 March 2014

Ea288
The EA288 2.0-liter diesel, prominently showing the closely attached exhaust aftertreatment system. Click to enlarge.

The Volkswagen Group’s new 2.0-liter TDI diesel (EA288) will eventually replace all the 2.0-liter TDI Clean Diesel engines fitted in Audi and Volkswagen TDI Clean Diesel models, and as such, is a strategically important engine. (Earlier post.) The Group was responsible for 79% of all light-duty passenger diesel sales in the US in 2013; worldwide, every fourth car sold by the Group is a diesel, said Dr. Johannes Arning, of Volkswagen’s Powertrain Product Management group.

The new 2.0L TDI is a turbocharged, common-rail, direct-injection four-cylinder engine based on the Volkswagen Group’s modular diesel toolkit (MDB, Modularen Diesel Baukasten). (Earlier post.) Volkswagen also has a modular gasoline engine toolkit, the MOB (Modularen Ottomotor Baukasten), which includes the new EA211 series. Both MDB and MOB play critical roles in the Volkswagen Group’s larger MQB modular toolkit, which is in turn one of the four main modular toolkits (modularen Baukästen) of the Group: the MQB (transverse); the MLB (longitudinal); the MSB (standard drive); and the NSF (New Small Family).

16-17_MQB_Grafik2
The MQB strategy of the Volkswagen Group extends from the A0 to the C-segment. There is some overlap at the low-end with the NSF and in larger vehicles with the MLB. Click to enlarge.

The MQB allows the integration of alternatives, for example, natural gas, hybrid and electric drives, in addition to the conventional gasoline and diesel power units. As one clear example, the new Golf, which is MQB-based, offers gasoline; diesel; natural gas; plug-in hybrid (the GTE, earlier post); and battery-electric (the e-Golf, earlier post) versions, all of which can be manufactured bumper-to-bumper on the same assembly line. Further, the hardware of the plug-in hybrid drive in the GTE is also that of the Audi A3 e-tron plug-in hybrid.

The new MDB EA288 diesel

The 2.0L EA288 diesel engine delivers 150 hp (112 kW)—an increase of 10 hp over the current engine and 236 lb-ft (320 Nm) of torque. Technical development targets for the development of the new MDB-based EA288 diesel engine were CO2 reduction; emissions reduction; performance; comfort; and costs.

Chart
Basic specs of the older 2.0L (left) vs. the new (right). Click to enlarge.

The new diesel shares only the bore spacing with the previous 2.0-liter diesel. A number of changes have been made to help reduce emissions, such as the use of a complex exhaust gas recirculation system (with high pressure EGR and a cooled low-pressure EGR); integration of the water-cooled intercooler and the EGR valve with the intake manifold (which also improves throttle response); and packaging the exhaust after-treatment components close to the engine by combining the DPF with the SCR Catalyst.

The EA288 is designed to meet the requirements of different markets. For example, depending on the emission requirements, 3 different types of exhaust gas recirculation (EGR ) can be used:

  • cooled high-pressure EGR without low-pressure EGR;
  • cooled low-pressure EGR without high-pressure EGR; or
  • cooled low-pressure EGR and non-cooled high-pressure EGR.

Similarly, the closely-attached after-treatment devices—including an oxidation catalyst; diesel particulate filter; and NOx storage or selective catalytic reduction system (SCR)—can be used singularly or in combination depending upon the needs of the vehicle (e.g., weight) and market regulations.

Crankcase. The crankcase—as in the previous TDI—is made of gray cast iron. The objective was to reduce crankcase weight while integrating further components. Volkswagen engineers achieved this by:

  • integrating balancer shafts above the crankshaft;
  • a short water jacket for the fast component heating;
  • cooling of the area between the cylinders;
  • integrating of thermal management measures in oil and water management;
  • head bolt threads below the water jacket;
  • optimization of oil guides to minimize flow losses; and
  • extension of the oil return and blow-by channels to the parting plane of the oil pan.

Design criteria were:

  • even cooling of the crankcase;
  • cross-flow in the cylinder head from the outlet to the inlet side;
  • good flow through the holes to cool the cylinder fins;
  • uniform distribution of the flow to the cylinder; and
  • optimization of the flow guide with additional consideration of the requirements in the warm-up.
Oilvacuum
The dual oil and vacuum pump unit. Click to enlarge.

Oil and vacuum pump. The oil/vacuum pump is designed as a dual pump, driven directly from the crankshaft by a toothed belt in oil. Both pumps are arranged in a common die-cast aluminum housing below the cylinder crankcase flanges in the oil pan. Pretensioning of the belt is specified during installation by the center distance of the components; this leads to a particularly friction-optimized drive.

The oil supply is realized by a volume-controlled vane pump. A solenoid valve can also be connected depending on the load in a low- or high-pressure stage. Thus, an optimum between lubrication and power consumption can be achieved in engine operation.

The arrangement of the vacuum pump resulted in new design requirements that required a low drive torque at cold start, among others factors. Using a double-reed valve, a sufficiently large cross section for the ejection of the oil is realized in the vacuum chamber. Thus, the drive torque can be kept low even at low temperatures . The connection to the vehicle-side vacuum line is via bores in the vacuum pump and in the cylinder crankcase.

Cylinderhead
Cylinder head. Click to enlarge.

Cylinder head. The cylinder head intake and exhaust valves are arranged one behind the other. This arrangement results in a mixed camshaft, each having an intake and exhaust control. Since the valve assembly has been changed compared to its predecessor, the channels had to be redesigned, with a focus on increasing the maximum flow with good swirl numbers.

A further innovation of the MDB concept is the thermal management system in which the cylinder head plays a central role. A micro-cooling circuit—one of three cooling circuits in the engine—is integrated into the cylinder head.

The outlet is located in the bottom plate with connection to the cylinder block, which takes the return of the water.

To increase the heat dissipation in the region close to the combustion chamber, the water jacket is divided into a lower and an upper water jacket core, each with a cooling channel. The two cooling channels are separated from each other and are guided together only at the outlet.

This enables a more uniform distribution of the cooling capacity between the individual cylinders compared to the predecessor engine.

Valvetrain
Valve train. Click to enlarge.

Valve train. The valve train of the new MDB 2.0-liter TDI engine differs from its predecessors through the use of an integrated valve drive module ( iVM ). Thus, the camshaft bearing frame can be separated from the cylinder head to prepare it for future emission requirements. In addition, the bearing frame was optimized for friction.

Functional advantages of the iVM include:

  • Valve train is designed as an independent module with appropriate manufacturing and cost advantages.

  • Reducing the friction loss of the camshaft through the use of a needle bearing.

  • Internal oil supply to the bearings with a separate integrated into the bearing frame oil gallery.

  • Additional supply of oil to the cylinder head.

Regardless of engine capacity, the blank, valve train and cylinder head cover module are always identical. Only the size of the hole and of the valves is different.

Intercooler
Intercooler. Click to enlarge.

Intake manifold with integrated charge air intercooler. The MDB TDI features an intake manifold with an integrated charge air intercooler. The predecessor 2.0L TDI had already used indirect water-cooled charge air cooling were used. As a further development, the water-cooled charge air cooler for the MDB engine—as in the 1.4 liter TSI engine—is integrated into the intake manifold.

This constitutes a separate low-temperature coolant circuit with air-water heat exchanger in conjunction with a variable-speed water circulation pump.

The charge-air duct is extremely compact, and the water-cooled module enables a shorter and more compact air intake circuit. The reduced charge air volume improves the transient response of the engine significantly. Further, flow losses are reduced, and icing or condensation in the intercooler be avoided.

Chargeairintercooling
Comparison of the new charge air intercooling system (right) with its predecessor (left). Click to enlarge.

The integrated intercooler is supplied by Valeo and is made entirely of aluminum. The cooling body, which consists of coolant plates, fins, cover, bottom and side panels, as well as coolant connections,is fully soldered. The inlet and outlet boxes are then welded to the heat sink.

The radiator network consists of 10 pairs of brazed cold plates. The coolant flows through plates are W-shaped counter-currents to force a complete utilization of the radiator network at a reasonable pressure drop.

Through a special geometry of the coolant plates, the cooling agent flow is distributed across the width of the flat tube, and is deflected at the same time. This provides for a low pressure loss for a good heat transfer from the aluminum sheet to the coolant. At the same time the design of the cooling plates offers a high robustness with respect to the change in pressure resistance.

Air side fin thickness and fin spacing were optimized so that the cross-sectional area of the lamella can derive the maximum quantity of heat to the coolant plates and at the same time the pressure loss is minimal. Small punched openings which are arranged alternately like gills provide for a good heat transfer and also allow a flow in the transverse direction.

Exhaust
The exhaust side systems. Click to enlarge.

Exhaust-side. The exhaust side of the MDB engine consists of the exhaust manifold module with exhaust gas turbocharger; the exhaust after-treatment system module; and the low-pressure EGR system. As noted earlier, the components within the aftertreatment module vary depending upon the emission standard, as do the three different types of exhaust gas recirculation.

The compact design of the aftertreatment module and its close mounting to the engine enable low heat and pressure losses as well as the fast starting of the oxidizing catalytic converter and speedy heat-up of the diesel particulate filter.

EGR. At high combustion temperatures in the engine result in NOx emissions. The higher the combustion temperature in the cylinder, and the longer its duration, the higher the proportion of NOx in the exhaust gas. Exhaust gas recirculation (EGR ) is used to reduce engine-out NOx, which, in conjunction in come cases with further aftertreatment, results in meeting emissions targets. The rapid oxidation of fuel molecules in the combustion cylinder is inhibited by the presence of the exhaust gas molecules; peak temperature and the resulting NOx emissions are therefore reduced.

Both the forthcoming EU 6 emission standard as well as the even more stringent US EPA Tier 3/ California LEV III standards, call for further significant reductions NOx compared to today. Volkswagen engineered the MDB TDI engine to be able to meet all those coming standards.

The engine features high-pressure and low-pressure EGR loops.

The recirculated exhaust gases of the high-pressure EGR have a high temperature; mixing this exhaust gas to the fresh air in the intake manifold is intended to reduce the air mass, resulting in operation with a lower air-fuel ratio. Also, the average temperature of the fresh charge increases. HP-EGR is used to address dynamic and cold start issues.

The low-pressure EGR system, integrated with the exhaust aftertreatment system, is upstream of the exhaust gas turbo; the recirculated gas is cooler, and low in particulate matter. This allows the reduction of the cylinder air mass without heating the intake air; further, the exhaust gas mass flow upstream of the turbocharger is not reduced, which enables maintaining the high exhaust gas enthalpy. Volkswagen improved the pressure losses in the LP EGR system by some 90%, bringing it down from 200 to 20–25 millibars.

EGR
Exhaust gas recirculation system. Click to enlarge.

Thermal management. The thermal management of the 2.0L TDI MDB has three cooling circuits which can operate independently.

  • Micro-circuit. The micro-circuit consists of the cylinder head, the EGR cooler, the heat exchanger and an electric coolant pump.

  • Main water circuit. The main water circuit includes the crankcase, engine and transmission oil cooler, front radiator and a switchable water pump.

  • Low-temperature circuit. The low-temperature circuit consists of the integrated intake manifold intercooler, a front radiator and an electric coolant pump.

After cold start only the micro-circuit is operated. With increasing cooling demand, the switchable water pump is switched on. The low-temperature circuit is responsible for the indirect charge air cooling. The high- and low-temperature circuits are operated independently of each other. The aims of the thermal management system are to shorten the warm-up phase after a cold start; bring the emission-reducing components to temperature; and deliver an optimized temperature to the passenger compartment.

Thermal

March 22, 2014 in Diesel, Engines | Permalink | Comments (17) | TrackBack (0)

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I can't wait to see what we get one day, when manufacturers put even HALF this much effort into optimizing electric motors, inverters, and especially batteries.
They'd be getting 800 mile ranges with 2 minute charges and cars doing 0-60 in 4 seconds on ordinary passenger cars.
Well, one day it will be in their interest and they'll put the effort into it.

DaveD, that's simply incorrect. Nissan/Renault has anted more than USD4.5Billion and counting on products that barely appear in their total vehicle delivery numbers. GM shows more than USD1.2Billion on the balance sheet for the Volt --- the real total was considerably higher, with some portion written off during the "bankruptcy". BMW took a 4% hit on share value the day they confirmed more than Euro1Billion to be invested in the i series as investors realized yet another huge expenditure placed for cars that would sell in miniscule quantities at a loss. Ford took a relatively inexpensive way out with "only" a few hundred million on the FFE, but combined with Magna Automotive's CanD500Million, there was still more than a Gigabuck spent to put thus far fewer than 3000 cars into the hands of owners/lessees (each of those at a further loss). Mitsubishi probably has some of the best large-scale power electronics component manufacturing around, and has operated several versions of a SiC-based inverter in extensive road testing. Their iMiEV experiment has been a dismal money loser, netting over Y150Billion in writedowns (as I understand but cannot reference).

What about Tesla? A great story indeed, but even their total non-GAAP profit from the entire run of Model S to date is negative net of ZEV/regulatory credits. They carry -USD1Billion Retained Earnings on their balance sheet.

Note that I am not opposed to EVs. I briefly leased a Volt (great car), and did a lease swap for a Leaf in November (also a great car). I have built a 700w/1.2kwh electric bicycle and I have many parts for a "someday" EV conversion sitting in a relative's barn. But the economics for EVs have been disastrous and will continue to be without an unforeseeable battery breakthrough (Gigafactory notwithstanding as a potential significant event).

The total amount of industry money invested in Electric propulsion technologies is enormous, and stunning on a per-vehicle basis. Add in the plethora of money-losing component suppliers like UQM who build some VERY competent technologies, or the large suppliers like DENSO who are refining auxiliary elements like HVAC and the expenditures are likely well over USD15Billion since 2008. This doesn't include other PHEV efforts like refinements to Prius, which amount to over Y75Billion annually since the tsunami.

If you can achieve the performance you mention for half the cost of developing a new diesel engine, you should seriously go find the investors and make it happen. Honestly the money is out there and you could be a Godzillionaire. Good luck.

When EV sales approach sales of conventional ICE vehicles, R&D will most likely be equal as well.

I suggest those who comment on this site to stick to the topic of the article. There are enough articles on this site where EVs can be discussed. Having said that, my primary conclusion from this article is that future US emission limits (LEV III) does not seem to be a hurdle for diesel cars in the USA. Customer acceptance seems to be the biggest problem.

That customer acceptance may be a while in coming.

The advantage of diesel used to be high efficiency and cheap fuel.  Now that ULSD is required, the fuel is no longer cheap.  I'm seeing $4.009/gal around here vs. $3.579/gal for unleaded 87 octane gasohol.  Guessing at 140 kBTU/gal for diesel vs. 115 kBTU for gasoline, diesel only delivers about 10% more energy per dollar.  With boosted GDI engines getting close to diesel efficiencies, it takes a lot longer to amortize the expense of the diesel.

Gasoline will be required to be "ultra low sulfur" starting in 2017, and it's anyone's guess what that will do to the price of gasoline (up to $0.09/gallon by some estimates).

It will sell like hot cakes in Europe - the US will just be a blip in sales.

People often say than new development X will cost Y extra, but it is usually much less than that after a few years once manufacturing experience and competition kick in.

So I wouldn't worry to much.
What I fail to understand is why very large, underpopulated regions of the US don't use diesel more - I can see why California and New York don't - but Nebraska ?

Maybe it is just fashion - Ireland is 70% diesel, which is crazy in such a small country with short commute distances, but it is the fashion - the resale values of anything petrol > 1.6 L is abysmal, so the default is to go diesel, and pay the extra up front and deal with the urban pollution.

Turbocharged and downsized GDI engines have improved but they do not even come close yet. Ford has been hailed for the new 3-cylinder engine. Few other gasoline cars come close in fuel consumption. In Focus, this engine consumes 5 l/100 km. The corresponding Focus diesel consumes 3,4 l/100 km. That is a factor of 1.47, or 0.68 the other way. (If you think this comparison is out of line, consider the data for VW Golf, where the fuel efficient models consume 4,9 and 3,2 l/100 km respectively.) In Sweden and many other European countries, diesel and gasoline cost approximately the same per liter, so we could forget about energy content for the moment and use volume as basis for our calculations. Bearing in mind that the yearly improvement of specific fuel consumption has been on the order of 0,5 % per year, we realize that it would take very long for the gasoline car to catch up. If we presume a linear extrapolation of the mentioned trend, it would take 64 years. If we assume 1% per year, it would still be 32 years. Recognizing that further improvement will be increasingly difficult, we could anticipate that the relative improvement is exponential (e.g. 0,99*0,99*0,99,…). With this assumption, it would take 38 or 77 years depending on if we assume 1% or 0,5%. All these calculations are under the assumption that diesel development would stop and not continue any further from today’s state-of-the-art. In reality, you aim at a moving target, implying that gasoline cars may never catch up. Remember Achilles and the tortoise, in the paradox of Zenon? Hybridization and improvement of the “rest” of the car most likely have bigger potential than just improving the engine itself. A potential breakthrough in (gasoline engine) technology might be another factor to consider but I will leave that topic for later…

@DaveD,
The Modular construction nature of the MDB and MOB series with sharing of common parts among engines of different displacement actually will save on development cost and inventory cost. Due to the coming EU6 and EPA US Tier3 emission regulations, new engine development will be inevitable anyway.

Why do you bet that electric motors will be the only way to utilize non-fossil-fuel energy in the future? All these refinements in ICE technology will come handy to use electrolytic H2 and synthetic Methane as future fuels, or the combination thereof, in ICEV or HEV, with very high efficiency that will rival the efficiency of BEV's.

For example, what would happen if one would substitute diesel fuel with H2, or a mixture of H2 and CH4? Compression ratio about 14:1 or higher, late injection of gaseous fuels to avoid detonation, and multiple injections per power stroke to reduce peak pressure to comfortable levels, and high-voltage spark-assisted or laser-assisted ignition when conditions calls for it? The high cost of high-pressure carbon-fiber fuel tank will be offset by absence of DPF (Diesel Particulate Filter) and the absence of the ultra-high pressure (2000-bar) diesel fuel system. The already-high pressure of the gaseous fuel can be administered directly as direct fuel injection without any ultra-high-pressure fuel pump, whereby this high pressures can be partially recuperated as power for the piston. The NOx emission system already present will come in handy to meet any future emission regulation, while using H2 will eliminate the CO and HC part of the exhaust. With H2 onboard, there will no longer any need for using a separate Urea tank in SCR, as the H2 can be injected directly, instead of using Urea.

What is your opinion on this, Peter?

A hybrid diesel would have co2 levels so low that they would match Co2 from most EVs charged on normal grid electricity (say about 70 gms/km), with the exception of France and similar very low CO2 electricity countries.

They would still create local pollution, and so would not be optimal for cities, but would be fine for rural and suburban (or exurban) use.

Also useful would be small battery PHEV(d)'s with enough battery to get you through urban regions (say <= 10 miles E travel).
I include these because they would not add too much cost to already expensive diesel hybrid powertrain.

Peter XX,

The efficiency gap between gasoline and diesel may never dissapear, but the difference can become so small as to be immaterial. A 1 l/100 km gap means 200 l per 20,000 km (a representative yearly driving distance).

The cost of those 200 l of gasoline has to be weighed against the extra initial cost of buying a diesel-powered car, as well as extra regular maintenance costs (and urea refills if so equipped). Add to this a social backlash against diesel (WHO calls it a carcinogen, large cities want to ban it, it's more likely to leave a odour on your hands after filling-up), and diesel may not be cost-effective for most regular users.

It's not a coincidence that the latest city cars from Citroen, Peugeot, Renault and Toyota are gasoline-only.

Bernard,

You are right about the small city cars. Their sales price can not bear the cost of diesel engines. Due to their small size and weight, they are already 'economical enough'. Furthermore, short-distance city driving can be quite damaging to diesel engines, particularly the ones fitted with particular filters. Last, but not least, small cars like those rarely amass enough mileage to warrant diesel engines in the first place.

For larger classes of vehicles, this changes.

There is no social backlash for diesels in Europe. The overwhelming focus on CO2 over other forms of pollution cast diesels in a positive light. It will be interesting to see whether the recent smog-incident in Paris changes this?

As the light-duty fleet gets progressively more and more electrified, I wonder what will move the fastest:  GDI and downsizing, diesels, or hybridization and outright electrification.  With HCCI waiting in the wings and the switchable 2/4 cycle engines as a wildcard, the efficiency of gasoline engines at part load seems set to jump.  Batteries make the engine less relevant, however efficient it is.

@E-P,
As ICE will get more and more efficient, it can use renewable fuels such as synthetic H2 and synthetic CH4, using the Diesel principle to maximize efficiency. Diesel engine is expensive due to the emission control system and the ultra-high fuel system. Using highly-compressed gaseous fuels, the fuel is already compressed and sparing the expense of fuel pump. Emission control will be much simplified, if at all: CO and HC will be zero, while NOx can be much reduced to below regulatory limit, using very lean mixture and highly mixed charge. Pehaps only Lean NOx trap will be needed to trap the NOx at higher power level. With electric boost in HEV, thereby avoiding frequent high power use, LNT can even be dispensed with.

So, future LDV's may need a battery pack capable of 10-20 mi range for short trips, while longer trips or winter use can use a low-cost and simplified ICE running on H2 and CH4 mixture, or just H2, in order to avoid having to use a large battery pack.
Kit P's famous statement kept resonnating in my mind: "Hauling around a lot of battery is never a good idea!"

The efficiency of diesels cannot be dismissed in one or two sentences. Who bothers if it is 30 or 50 years of time before the gasoline engine could catch up. It is not going to happen in the near future anyway. Part load efficiency cannot jump up just like that. Recall that BMW already use their Valvetronic, which practically eliminates pumping losses at low load. Those of you who think this measure (and improving part load efficiency in general) is the Holy Grail could just compare two representative BMW cars and still find a big diesel advantage. Atkinson? Well, the Atkinson cycle, as Toyota use it on a naturally aspirated engine, increase fuel consumption at part load, since the engine size must be scaled up to provide the same power and torque as a conventional engine. This cannot be compensated by higher efficiency at high load. This is why we do not have any Atkinson engines in conjunction with conventional drivetrains. It only works on hybrids! Miller system (i.e. Atkinson with turbocharging)? Yes, it is basically a good idea also for conventional drivetrains but it can be used on both otto and diesel engines. I did an evaluation on the potential for diesel engines myself more than 20 years ago. I know it works! HCCI? Well, this can be used on both gasoline and diesel engines. Eventually, if we assume that HCCI could be used in a “diesel-like” cycle but with gasoline and over the full load and speed range, definition of what we actually have becomes increasingly difficult. Make the generalized duck test: “If it looks like a diesel, runs like a diesel, and quacks like a diesel, then it probably is a diesel”. Eventually, according to my opinion, this is the only possible way for the gasoline engine to compete on the long-term future. It would be a diesel engine that burns gasoline. The same base engine could be used for both diesel and gasoline fuel or, as the most efficient option, run on a fuel in between, kind of something like kerosene fuel that would also boost efficiency in refineries. If all this could be done due to practical and other reasons, remains to be seen.

Immaterial, says Bernard. I made the cost calculation myself when I bought a Ford Focus. In Sweden, payback time was two years if we just take fuel cost into account and assume similar resale value. In reality, there are governmental incentives that reduce payback time to little more than one year. Further, the resale value for the diesel version is higher than for the gasoline counterpart. In addition, the diesel version is much more fun to drive and does not need annoying high revs and frequent downshifting on the highway. It is a win-win-win solution! My friend just made the same choice as I did based on his own calculation. Finally, we should not only look at the first owner; at 5 l/100 km and a useful life of 300 000 km, fuel cost is higher than the cost of the car.

Again and again, I see comments about smog, carcinogens emissions and such topics when diesel is debated at this site. Scientific evidence I have referred to in the past is just overlooked or dismissed, so I will not bring up some old studies. However, there are new ones... Bernard, in particular, should carefully read the article about diesel and gasoline cars in the latest issue from Engine Technology. FYI, the article starts at page 42.

http://viewer.zmags.com/publication/e5b6bd2e#/e5b6bd2e/1

Peter,

I said that the gap can become immaterial, not that it was immaterial right now.

Obviously, this starts with smaller cars. They use less fuel (which means that potential savings are less), and are more cost-critical. They also have limited space for things like particulate filters and urea tanks, and their suspension/brakes may be less tolerant of the weight penalty of a diesel powertrain. As we've seen, some automakers no longer offer diesels on their smallest platforms.

If, as you predict, the gap between gasoline and diesel gets smaller over time, then we can expect that the smallest diesel-friendly segment will grow every few years. Right now, sub-minis (A segment) no longer derive an economic advantage from diesel. We can expect this to move to the marginally bigger B segment (Ford Fiesta, VW Polo) quickly, and to the C segment (Golf, Focus) by the end of the decade.

Of course, this trend may be accelerated by the fact that the cost of diesel compliance keeps increasing, whereas the efficiency of diesel has not improved significantly in quite a while (since the first high pressure injection models of the mid 1990s).

Also, while I am sure that diesels can be made just as clean as gasoline cars (at a cost, obviously), I'm not sure that the social stigma of diesel can be negated soon.
Previously pro-diesel markets such as France and Italy are now openly rebelling against politicians who subsidized diesels in the past. Diesel market shares are dropping significantly (down 5% since their peak 10 years ago), and air pollution alerts are being blamed on diesel (smog days in Paris last week). That's a lot of bad PR to fight, and I am convinced that automakers will seize the opportunity to sell new gasoline/hybrid/electric cars rather than being seen on the loosing side of a debate that prominently features kids with cancer.
It doesn't matter who is wrong or right, no big corporation wants to be associated with that image.

It's rapidly coming down to one question:

Where's money better spent, on the additional costs of a diesel engine, or on batteries?

As Peter XX says (and I agree 100%), Atkinson-cycle engines have lower specific output than conventional.  On the flip side, the switchable 2/4 cycle engines will allow close to a doubling of effective displacement (needing only a blower of some kind in 2-cycle mode).  With the CVT nature of the Ford and Toyota hybrid drivetrains, managing engine RPM to get the proper gas flow for positive scavenging from a turbocharger is not a big issue.  We could see a 1-liter, 2-cylinder packing 110 kW or more, using the electric drivetrain systems as power buffer and source/sink for power to/from the turbocharger, slashing size, weight and parts count and managing drivability using the battery for throttle transients while the engine catches up.  This would not be feasible without the hybrid systems.  I would not be surprised if Fiat is first to do this by small changes to its TwinAir engine.

Eventually batteries will get cheap enough that almost everything on the road will dispense with the engine.

Don't put blind faith on those published F.E. figures, they are pretty much meaningless, especially when some automakers choose to "game" the test: Exhibit A: Hyundai was forced to revised downward it's published EPA mileages; Hyundai suffered another black eye when the F.E. for the 2015 Sonata was found inflated in S. Korea. Ford Motor also have to reduce its over-optimistic fuel rating for its C-Max hybrid in the U.S.

Over in Europe, BBC reported that automakers "manipulated" emission/F.E. test:

'Slick tyres are pumped hard to reduce rolling resistance. Brakes are adjusted, or at times even disconnected, to reduce friction. Cracks between body panels and windows are taped up to reduce air resistance. Sometimes they even remove the wing mirrors.

For carmakers, preparing for compulsory fuel efficiency and emissions tests has become a race in its own right, as they set out to make themselves look as clean and as frugal as possible.

"It's lots and lots of small tweaks," according to Greg Archer, clean vehicles manager with pressure group Transport & Environment.

"And they all add up." '

http://bbc.com/news/business-21759258

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