Photography: Courtesy of Bosch
Before he returned to Germany in September, Diesel World magazine arranged an exclusive interview with Dr. Johannes-Joerg Rueger, senior diesel systems engineer for Robert Bosch LLC. He shared with us his views on the future of diesel-powered vehicles in the United States.
First, we riffed on a previous conversation at the 2010 SAE conference, where he said that a return to 2008 fuel prices (remember paying $4 a gallon?) would change consumer behaviors. Surely you also remember how panic switched people out of trucks into tiny cars? Maybe you got your truck that way.
Rueger says that, inevitably, there must be, and will be, an oil substitute, whether natural gas or a synthetic fuel made from natural gas, bio-fuels or electricity. However, he says the death of the internal combustion (IC) engine can occur suddenly only if a sustainable replacement is available. So far, we have seen none.
Gas Vs. Diesel
Before we considered diesel’s future, we talked more about IC engines in general. Rueger noted that gasoline IC engines are getting smaller and more powerful with the addition of turbocharging and direct injection, technologies that have been on diesels for a decade. These advanced technologies allow smaller-displacement gas engines to provide similar power (not just horsepower) to larger traditional port fuel injected engines and he says the gas IC engine can become more fuel-efficient “almost easily. ”
However, he speculates that all the technological low-hanging fruit will soon be picked and the move toward diesel engines is inevitable. This, he says, raises the point whether the rapid shift to smaller vehicles, as seen in 2008, is sustainable without higher fuel prices and whether North American consumers will make small cars a sustainable trend.
Rueger says that as we approach 2016’s mandated 35 1/2 -mpg CAFÉ standards, the cost of the kinds of advanced technologies necessary to achieve ongoing improvements no longer favors gasoline engines <for automobiles of current size.> That is a very important point. If customers shift away from large vehicles to smaller ones, small diesel engines may not be relevant in the U.S.
But if we keep our desire for larger vehicles, what the world calls C- and D-sized cars, CUVs, SUVs and, of course, pickups, they would benefit greatly since diesel engines provide their typical 30-percent better fuel economy and lower CO2 emissions, whether driving stop-and-go, towing a boat, or cruising on the highway. And rumor has it, GM is already rethinking the demise of the 4.5L Duramax and strategizing about when and where it would be appropriate.
A Growing Global Diesel Market
We asked about the European importers—the Audi-VW group, BMW, and Mercedes—where some name plates report up to 50-percent sales volume. Globally, European sales dropped in 2009 and bounced back to 50 percent in 2010. In India, diesel is growing in passenger vehicles and trucks, while China uses diesel mostly for small, medium, and large trucks.
Engines are mostly inline-four and a variety of six-cylinder engines, both V and inline. “Interestingly, maybe the eight cylinder will be abandoned, replaced by six-cylinder turbo engines. There will also be more effort on the air [induction] side and creating the same power output with smaller engines. So the base engine for larger luxury cars will have six cylinders.”
The Bosch exec says that, in India, there are many small diesel engines and that Europe is shifting to “three-cylinder and even two-cylinder engines. That’s not so much available as in the works at automakers. And its the kind of transition we see in North America, replacing old port-fuel injection to engines with turbochargers and direct injection—just not diesels.”
Tighter Emissions Regs
The meat of diesel’s future is in emissions technology as regulations become tighter and national standards in the U.S., Japan, Europe, and China move closer together. Globally, these regulations typically show emerging markets follow European regulations, with a five- to 10-year offset, though China seems to govern cities more rapidly and stringently than rural districts.
Europe will adopt Euro VI in 2014-2015 and its NOX (nitrous oxide) emissions will closely resemble the stringency of the U.S. market. At the same time, the U.S. moves towards LEV III standards that begin around 2016 and extend in a long transition to 2022.
“Still, the world is not unified in terms of emissions regulations or in test cycles There are different interests in various regions and different philosophies which have narrowed over the last decade or so, from Europe going in the direction of moderate NOX reduction and strict particulate reduction and a strong focus on CO2, and the U.S. being extremely stringent on NOX and CO2—not too much. Now the U.S. has changed direction with CAFE regulation and much more emphasis on CO2. The truth is, you’ve got to compromise.”
Absolutely. It’s well known that if you optimize the system in one direction (NOX), it is not optimum in the other (CO2). The question then becomes, <what direction to drive the compromise?> Well, at one time, diesel particulates were a factor. But with modern particulate filters standard on every new vehicle, particulates are no longer a problem—at least for now.
The Problem With NOX
Admittedly, a diesel engine costs more and emissions treatment is hugely expensive as compared to gas engines. According to Dr. Rueger, “It’s all about NOX after-treatment technology. Currently we have two technologies: LNT or NSC (lean nitrous-oxide storage catalysts, which we see on the VW Jetta and its 2.0-liter engine) and SCR (selective catalytic reduction using urea).
Typically, the efficiency of the LNT is lower than an SCR/urea system. That’s the reason for larger vehicles, particularly in North America. The SCR-urea system is more favorable under stringent emissions regulations. In the future, still for North America the SCR is the most efficient technology we know of.”
The future likely sees a combo platter between NSC and SCR, a combination system. The science is complex, having to do with engine startup when, currently, engines of all types generate most of their emissions until the catalyst reaches operating temperature. The storage catalyst (NCS/LNT) offers, according to Bosch, very favorable cold start performance but has some problems maintaining efficiency as it ages in engine hours.
New Emissions Technology Worldwide
What Rueger thinks is important to the future of diesel is the world outside the U.S., adopting more stringent emissions regulations that more closely resemble our emphasis on NOX reduction. As that occurs, millions of new diesel emissions systems will be built in Europe versus the few thousand in the U.S., and that increases volumes and economies of scale will apply. Another overlooked issue is that the latest lean burn gasoline engines may, under LEV III, require particulate filters and therefore increase their powertrain cost. However, nobody knows what the LEV III final regulations will be.
Because we care about what’s inside our engines and what makes them operate more efficiently, we also care about the latest SCR and LNT after-treatment technologies. For instance, Honda’s clever self-ammonia-generating small-engine catalyst, those that use other urea-generating methods—anything that lowers a diesel’s cost. Dr. Rueger says regardless of technology involved, the cost is based the amount of costly precious metals used in each unit. Then, as production is increased, the cost of production comes down.
“An example is gasoline. We started with catalysts and they were not chea; today, nobody is talking about it. Particulate filters for diesels. And once there were in the millions, they are not that significant.” (Bosch supplies injection, engine management, and after-treatment parts to GM and Ford.)
Rueger says that the cost of a diesel engine will never drop to that of a gasoline engine. “There are higher inherent costs, but compared to advance gasoline direct injected, downsized and turbocharged, you’ve got a downsized diesel engine that still has a fuel economy improvement of 30 percent or more.”
But if we move the question to that of power, specifically torque necessary to achieve a performance goal, “We can do that easily. A diesel engine delivers the best fuel economy no matter how you use it. If you drive it hard and very fast, or tow, which is different from other technologies that are very good under certain conditions, and if not used appropriately, the benefits are gone.”
Rueger doubts any scenario where small, turbocharged, direct-injection engines will not power the preponderance of automobiles in North America. He compared these new-generation engines to those of even two to three years ago. and says the new engines have great advantages over older PFI motors.
Combined with stop-start and other simple technologies, the engines have at least a decade’s life span. However, beyond that his well-informed crystal ball says that sometime after 2020 TGDI, or even electric and hybrids in low volumes won’t be enough. Then, “diesel offers another major step without a complete new technology> It’s proven, and it can clean up to meet future legislation.”
We also speculated what kinds of diesel vehicles might appear in the near term and how popular a 2.0-liter diesel minivan or 2.0L mini pickup might be (though Ford says it is discontinuing Ranger). Either might get 25-plus miles per gallon. Since VW already has certified power trains, “I would expect that to occur that at some time,” Rueger said. “They have such large volumes [of that engine] that it would make sense…BMW and Audi could use their six-cylinder engines for a minivan or smaller pickup (or CUV), and Mahindra and Mahindra will be here with a two point eight-liter pickup. It is simply a [manufacturer] and their strategy.”
Diesel versus Hybrids
Bosch supplies VW and Porsche with hybrid technology and the company makes batteries through its SB Linotile joint venture with Korea’s Samsung SDI. It also sells electric motors and hybrid powertrain controllers so Rueger’s argument that vehicles with under 200 miles range might be a second or third vehicle underscores his position that Electric Vehicles are far from sustainably competitive pricing, and that a 50 percent reduction of battery and associated components cost will be required for EVs to become major global players absent continued government subsidies.
At the recent SAE World Congress Dr. Rueger said that of the 2020 global fleet, 3 million pure Electric Vehicles and Partial Hybrid Electric Vehicles remain an ambitious, but achievable, 8-10% target; 40%, he says, is unrealistic. Also, including the production of electric energy in well-to-wheel emissions when comparing EVs or PHEVS to vehicles with IC engines is necessary. “Once we do that, we see that Electric Vehicles, at this point, are not as clean as they seem to be.”
According to Rueger, the metrics are simple: “the number sold is not relevant and could be highly influenced by subsidies, not necessarily reflect a real trend. From that perspective, it is really the cost of the battery … and availability of the components to make those batteries. That is much more important. Then, once you have something that is attractive from cost and performance perspective, people will buy it. …”
“It was interesting to see, in my presentation (at this year’s SAE World Congress,) that the panelists were more realistic in assessment of the potential all kinds of differing technologies than in the last one or two years. It was always Bosch’s perspective that we have to be realistic and there are a variety of technologies available and we have to fulfill customer needs as well as cost needs.”