sign in sign up
<<
Home , Diesel engine

WORKING PAPER 2017-08

Diesel

Authors: Aaron Isenstadt and John German Date: 10 July 2017 Keywords: Passenger vehicles, diesel, advanced technologies, fuel-efficiency, technology innovation

Introduction improvement in fuel economy of about This paper provides an analysis of 4.1 percent per year. advanced diesel technology In 2012, the U.S. Environmental developments and trends. It is a collabo- Protection Agency (EPA) and the The technology assessments performed ration between ICCT and automotive Department of Transportation’s National by the agencies to inform the 2017–2025 parts suppliers. The paper relies on data Highway Traffic Safety Administration rule were conducted about five years from publicly available sources, as well (NHTSA) finalized a joint rule estab- 3 ago. The ICCT is collaborating with as data and information from the partici- lishing new greenhouse gas and fuel automotive suppliers on a series of pating automotive suppliers. economy standards for vehicles.1 The working papers evaluating technology standards apply to new passenger progress and new developments in and light-duty covering model engines, transmissions, vehicle body Background years 2012 through 2025. A mid-term design and lightweighting, and other review of the fuel economy standards measures that have occurred since then. TECHNOLOGY will be conducted in 2017. Each paper will evaluate: AND EFFICIENCY

Assuming the fleet mix remains • How the current rate of progress Diesel engines possess a number of unchanged, the standards require these (costs, benefits, market penetra- efficiency advantages over vehicles to meet an estimated combined tion) compares with projections in engines. These grow out of significant average fuel economy of 34.1 miles per the rule; differences in how diesels operate. The gallon in model year 2016, and 49.1 mpg diesel engine does not use a • Recent technology developments in model year 2025, which equates to control airflow into the engine or a that were not considered in the to 54.5 mpg as measured in terms of to start ignition of the fuel rule and how they impact costs dioxide emissions with air con- as do gasoline engines. Instead, load and benefits; ditioning refrigerant credits factored is controlled by the amount of fuel in.2 The standards require an average • Customer-acceptance issues, injected. The timing of such as real-world fuel economy, controls timing, as the fuel performance, drivability, reliability, ignites almost immediately after being 1 U.S. Environmental Protection Agency and safety. injected into the hot compressed gas & National Highway Traffic Safety within the . Administration, “EPA/NHTSA Final Rulemaking to Establish 2017 and Later 3 U.S. EPA & NHTSA, “Joint Technical Support Model Years Light-Duty Vehicle Greenhouse Document: Final Rulemaking for 2017-2025 As a result, diesels eliminate the sig- Gas Emissions and Corporate Average Light-Duty Vehicle Greenhouse Gas Emission nificant pumping losses that come Fuel Economy Standards” (2012). https:// Standards and Corporate Average Fuel from forcing air past the throttle in www3.epa.gov/otaq/climate/regs-light-duty. Economy Standards” (2012). https://www3. htm#2017-2025 epa.gov/otaq/ climate/regs-light-duty. gasoline engines. The heterogeneous 2 The air conditioning credits are roughly htm#2017-2025 U.S. NHTSA, “Corporate combustion process of a diesel also 20.6 g/mi in 2025. There are also off-cycle Average Fuel Economy for MY 2017-MY allows much leaner air/fuel ratios than credits, estimated at roughly 8.1 g/mile in 2025 Passenger Cars and Light Trucks: Final 2025, that would slightly reduce the required Regulatory Impact Analysis” (2012). http:// with pre-mixed gasoline combustion.

tailpipe CO2 and fuel consumption reductions. www.nhtsa.gov/fuel-economy These lean air/fuel ratios reduce

Acknowledgements: Thanks to Dave Lancaster of BorgWarner, Pierre-Jean Cançalon of Honeywell, and Sean Osborne of The ITB Group for their input and reviews.

© INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION, 2017 WWW.THEICCT.ORG DIESEL ENGINES

average in-cylinder temperatures and large passenger vehicle market shares A common misconception is that improve by reducing in Europe and India. diesel engines produce a lot of NOX. heat losses to the cooling system and Engine-out NOX emissions from . In addition, the diesel engine is The remaining challenges for diesels engines are lower than from gasoline not subject to the knock constraints of are primarily cost and emissions engines under some conditions, as control. Diesel engines inherently cost a homogeneous-charge engine and can NOX formation is proportional to operate with much higher compression more to manufacture than gasoline combustion temperature. Diesels have ratios for increased efficiency. engines because of the need for much lower bulk combustion tempera- increased structure to contain higher tures than gasoline engines, although An indirect advantage of diesel engines combustion and because of temperatures around the fuel droplets is that the higher density of their more sophisticated and higher- are higher. The problem is that reducing results in about 14% more energy per fuel injection systems. It is also NOX emissions requires splitting NOX gallon than gasoline. This means that more expensive and more difficult to into and . This process diesel vehicles will go 14% farther on control particulate and nitrogen oxide will not proceed if there is excess a gallon simply because of the higher oxygen in the exhaust. Gasoline engines (NOX) emissions from diesel engines, energy content. On the other hand, because of their lean, heterogeneous run at stoichiometric with extremely diesel fuel also has 14% more carbon combustion process. precise air/fuel control that allows per gallon, so this advantage does not three-way catalysts to reduce NOX at apply to CO2 emissions. In gasoline engines, vaporized fuel is greater than 99% efficiency. However, as mixed with air before a spark sends diesels run unthrottled, there is always For all that, diesel engines historically a flame through the mixture. As a excess oxygen in the exhaust, and the have had limited consumer appeal for result, the fuel is completely burned three-way catalyst does not work. The passenger vehicles in the . except for quench layers at the solution for diesel engines is some Diesels used to be hard to start, noisy, control chamber walls and in crevices. The fuel combination of engine-out NOX and smelly, and they did not provide as in diesel engines ignites shortly after through recirculation (EGR) much . also being injected, and droplets of fuel do and injection retard, plus exhaust after- damaged the reputation of diesels in the treatment using lean-NO traps (LNT) not have time to fully evaporate and X late 1970s by rushing out an extremely or selective catalytic reduction (SCR) mix with air before combustion. As a unreliable product in response to the using urea injection. However, these result, diesel combustion is charac- fuel crises in the 1970s. GM converted a systems are expensive; engine-out NO terized by diffusion burning in which X gasoline V8 to a pre-chamber naturally- control and LNT systems increase fuel oxygen cannot fully penetrate the aspirated diesel—a marketing disaster. consumption; and SCR systems require burning flame front surrounding the periodic refilling of a urea . Technology improvements such as fuel droplets, resulting in an unburned direct fuel injection, higher fuel line carbon core. As the gas cools during pressure, and turbocharging have since passage through the exhaust, carbon MARKET PENETRATION TRENDS almost fully addressed the performance particles adsorb uncombusted and According to the EPA’s fuel economy and reliability issues, though diesels partially combusted products, forming trends report4, diesel accounts can still chatter a bit after startup and . Modern particulate traps for a very small portion of the U.S. at idle. These advances, together with are effective in controlling the release passenger vehicle market. As shown fuel-tax policies encouraging diesel use, of particulate emissions, but they are in Table 1, diesel penetration of cars have enabled such engines to capture not cheap. and light-duty trucks (large SUVs,

Table 1: U.S. diesel market penetration trends (passenger vehicles, including light trucks)

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Diesel Share 0.1% 0.3% 0.4% 0.1% 0.1% 0.5% 0.7% 0.8% 0.9% 0.9% 1.0% 0.9%

4 U.S. EPA, “Light-Duty Automotive Technology, Emissions, and Fuel Economy Trends: 1975 Through 2016” (2016). https:// www.epa.gov/sites/production/files/2016-11/ documents/420r16010.pdf

2 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2017-08 DIESEL ENGINES

and , pickups) increased to comparing the diesel against a more Once all the more cost-effective tech- 10-fold from 2004 to 2014, but still efficient gasoline engine baseline. nologies were implemented, manu- accounts for just 1% of the market. The facturers would turn to alternative share of diesel engines among cars The EPA and NHTSA make two main fuel/powertrains, including diesel, the and trucks does not vary greatly from assumptions on why manufacturers agencies assumed. the combined values. might hesitate to increase production of diesel vehicles. The first is that, However, the agencies recognized that In Europe, diesel engines have captured although expanded diesel penetration a number of manufacturers offer diesel about half of the passenger market could help them meet fuel economy vehicles, indicating that these manu- and the large majority of the light standards, manufacturers are likely facturers envision diesel as a viable commercial market. This is primarily to determine that other technologies option for meeting tighter standards. In because much higher fuel taxes overall are more cost-effective for reducing the absence of standards, the agencies’ and relatively lower taxes on diesel fuel greenhouse gas emissions. Secondly, baseline projections include a 2% in Europe encourage consumers to manufacturers may find it difficult market share for diesel engines in 2025. choose more diesel vehicles. to comply with NOX emissions limits Furthermore, several diesel technology without reducing the fuel economy developments were examined in the benefits of diesels or dramatically 2017-2025 rulemaking. These include HISTORICAL ESTIMATES OF increasing vehicle cost. improved fuel injection systems (higher COSTS AND BENEFITS pressure, better fuel atomization, and The National Academy of Sciences multiple injection events), advanced EPA/NHTSA 2017-2025 determined in a 2002 report5 that controls/sensors for combustion and PROJECTIONS: MARKET it would be a challenge to create emissions optimization, advanced PENETRATION, COSTS, AND emission control systems for NOX turbocharging, and expanded use of and particulate matter that could BENEFITS cooled EGR, which helps control NOX be certifiable for a 120,000-mile As shown in Table 2, the agencies with less impact on fuel consumption. vehicle lifetime. At the same time, predict close to 0% market penetra- the academy estimated that a diesel tion of diesel by 2021 and continuing For emissions control, the agencies engine with direct injection, a high- into 2025, although this varies by assumed that all diesel vehicles would pressure , and a variable manufacturer. For example, Mercedes require a catalyzed diesel particulate geometry could achieve is predicted to have 2% diesel market filter, sometimes paired with a diesel a 30-40% reduction in fuel consump- penetration in 2025. To generate these oxidation catalyst and a selective tion compared with a two- per projections, the agencies assumed that catalytic reduction system (SCR)— cylinder gasoline engine. manufacturers would initially concen- usually a base-metal zeolite urea-SCR.

trate on improving gasoline engines. It is unlikely that lean NOX traps In its 2008-2011 rulemaking,6 NHTSA estimated that combustion improve- Table 2: EPA/NHTSA rulemaking estimated future diesel market penetration, incremental ments (high-pressure and direct manufacturing cost (DMC), and fuel consumption reduction EGR) along with improved aftertreat- 2025 2025 ment (LNTs, injectable urea) would 2021 2025 aftertreatment engine Fuel result in a 15-30% reduction in fuel Market Market incremental incremental consumption consumption compared with a con- Penetration Penetration DMC DMC* reduction** ventional gasoline engine, at a cost of Small car 0% 0% $1,134 $618 19.7% $1,000-$5,000. The lower amount of Standard car 0% 0% $1,311 $441 21.5% fuel consumption improvement is due Large car 0% 0% $1,321 $824 22.3% Small MPV^ 0% 0% $1,315 $441 19.3% 5 Transportation Research Board and National Large MPV 0% 0% $1,331 $441 21.7% Research Council. Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Large 0% 0% $1,577 $878 20.7% Standards. Washington, DC: The National Academies Press, 2002. doi:10.17226/10172. * 2025 engine incremental DMC is derived from engine incremental DMC in 2012-16 rulemaking and 6 U.S. NHTSA, “Light Truck Fuel Economy 2017-25 rulemaking total DMC incremental to a comparable gasoline engine; costs in 2010 dollars. ** Compared with baseline gasoline vehicle with equivalent performance. Standard Rulemaking, MY 2008–2011” (2006). ^ MPV: multi-purpose vehicle http://www.nhtsa.gov/fuel-economy

WORKING PAPER 2017-08 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 3 DIESEL ENGINES

(LNTs) alone can achieve the required Because the 2017-2025 joint technical under $2,000 in 2025.10 PGM costs emissions reductions without a sig- support document (TSD)7 did not represent 16-23% of the combined nificant fuel consumption penalty, as separate aftertreatment and engine- diesel DMC. However, the February 2011 fuel is used to regenerate the catalyst, related costs, the separated costs given prices used in the TSD were some of the and LNTs are not as durable as SCR in the MY2012-2016 joint TSD8 formed highest historically: $1,829/troy ounce systems. LNTs may be paired with the basis for deriving the two separate for platinum and $2,476/troy ounce for SCRs or eliminated entirely in favor of 2025 DMCs shown in the two DMC rhodium. By comparison, in December SCRs, as assumed in the rulemaking. columns in Table 2.9 2016, platinum averaged around $930/ It is the incremental cost of these troy ounce and rhodium, $785/troy emission control systems, particularly For all but two vehicle classes, the total ounce.11 Although the specific catalyst for smaller car segments, that the DMC for switching to diesel falls below formulations and amounts assumed agencies perceive as a hindrance to $2,000 as early as MY2019 and is well by the agencies are not known, these wider adoption of passenger diesels. PGM price reductions could result in an 8-15% reduction in emission control Table 2 shows the aftertreatment system cost, or $150 to $400. Future (SCR + diesel particulate filter + diesel aftertreatment systems will reduce oxidation catalyst) and engine-related the effects of PGM price volatility on direct manufacturing cost (DMC). The 7 U.S. EPA & NHTSA, “Joint Technical Support system cost, as we will show. agencies sought to determine diesel Document: Final Rulemaking for 2017-2025 Light-Duty Vehicle Greenhouse Gas Emission costs by comparing gasoline and diesel Standards and Corporate Average Fuel vehicles of equivalent performance. Economy Standards” (2012). https://www3. Status of current The agencies assumed that epa.gov/otaq/ climate/regs-light-duty. htm#2017-2025 U.S. NHTSA, “Corporate production and future Average Fuel Economy for MY 2017-MY developments versus • a 2.4L I4 gasoline engine would be 2025 Passenger Cars and Light Trucks: Final replaced by a 2.0L I4 diesel, Regulatory Impact Analysis” (2012). http:// agency projections www.nhtsa.gov/fuel-economy Many of the developments in diesel • a 3.2L V6 gasoline engine would 8 U.S. EPA & NHTSA, “Joint Technical Support be replaced by a 2.8L I4 diesel, Document: Final Rulemaking to Establish engines are similar to those being Light-Duty Vehicle Greenhouse Gas incorporated into gasoline engines.12 • a 4.5L V8 gasoline engine would Emission Standards and Corporate Average be replaced by a 3.0L V6 diesel, Fuel Economy Standards” (2010). https:// nepis.epa.gov/Exe/ZyPDF.cgi/P1006W9S. 10 It is unlikely that the VW diesel emission and PDF?Dockey=P1006W9S.PDF. Pp. 3-37 scandal will significantly affect these costs. As shown in Table 1, diesel vehicles represent • a 5.6L V8 gasoline engine would through 3-45. 9 First, the total MY2012 DMC was estimated a very small fraction of new vehicle sales of be replaced by a 4.0L V6 diesel. from that of MY2017 given in the 2017-2025 in the U.S. Diesel engine and aftertreatment joint TSD, based on a flat learning curve development is primarily driven by the 7 All classes used SCR systems. The cost assumed by the agencies (3% per year million-plus diesels sold every year in Europe. Diesel sales in Europe may decline in the of diesel conversion included the cost reduction in DMC for the first five years). This back-calculated MY2012 total DMC includes future because of the scandal and revisions of the engine and the associated incre- the increased cost of PGM, reflecting volume in fuel taxes, but they will still most likely mental costs for aftertreatment. increases and PGM prices from Feb 2011, as be well above 5 million per year. Thus, the the agencies assumed. The engine-related 2025 estimated DMC probably would not It was also assumed that manufactur- costs, applying no additional assumptions, change. For a more detailed analysis of the were extracted directly from the 2012-2016 effect of the VW scandal on German diesel ers would meet Tier 2, Bin 2 pollutant joint TSD. Presented in 2007 dollars, these sales in particular, see: Uwe Tietge, “Diesels emissions level criteria on average in costs were $813 for small cars, $1,085 for dip, electric vehicles rise in Germany,” ICCT, anticipation of more-stringent future large cars, $580 for medium/large MPV, $580 December 9, 2016, http://www.theicct.org/ for small trucks, and $1,156 for large trucks. blogs/staff/diesels-dip-electric-vehicles-rise- regulations. To meet this standard, the After adjusting to 2010 dollars, these engine in-germany agencies estimated a 20% increase costs were subtracted from the calculated 11 Johnson Matthey. (2016). Price Charts in catalyst volume over Tier 2, Bin 5 2012 DMC to reveal the aftertreatment [PGM historical price data]. Retrieved from costs in MY2012, as modified by the agency http://www.platinum.matthey.com/prices/ emissions level, a slightly increased assumptions. Finally, aftertreatment and price-charts price of platinum group metals engine DMC in 2025 were calculated from 12 Aaron Isenstadt, John German, Mihai (PGM), and an additional blanket $50 their corresponding 2012 values using Dorobantu, David Boggs, Tom Watson, flat manufacturer learning as assumed by Downsized, boosted gasoline engines of DMC to account for upgraded urea the agencies (3% in the first 5 years, 2% (ICCT: Washington, DC, October 28, 2016). and fuel controls. afterwards). This assumes no major changes http://www.theicct.org/downsized-boosted- in PGM prices through 2025. gasoline-engines

4 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2017-08 DIESEL ENGINES

Examples include advanced friction years.16 As a result, FCA is expanding new CX-5 in the second half of 2017.22 reduction, higher turbocharger production of those engines.17 These (As of this writing, fuel economy data pressures, improved variable vehicles are fuel economy leaders for the -D engine is not yet geometry , downsizing in their respective classes, earning available.) Mazda reduced the cost of and downspeeding, better thermal compliance credits for the future, and the aftertreatment system by designing management,13 greater use of high- the manufacturer plans for the next the engine to operate with a much lower and low-pressure EGR, higher-pressure generation four-door Wrangler diesel than most diesels.23 injection systems capable of multiple to nearly meet 2022 fuel economy The reduced pressures lower the injections, and e-boosting with 48-volt standards.18 Diesels in these segments operating temperature. Combustion mild hybridization. benefit not just from better fuel takes longer, which improves air-fuel economy over gasoline engines but mixing. The lower temperatures and also increased towing capacity and better mixing reduce the formation CURRENT PRODUCTION COSTS better low-speed performance.19 of NO . The weight of many parts of AND BENEFITS X the engine was reduced, which also Because of the cost and complexity While diesels are not as cost-competi- led to reduced friction, on a par with of currently available aftertreatment tive in small vehicles, buyers of smaller some gasoline engines. As with many systems and future requirements for autos are generally more concerned modern, light-duty diesel engines, 20 pollutant reductions, diesel engines about fuel economy. This is reflected the SKYACTIV-D uses piezoelectric may be best suited for larger vehicle in Chevrolet’s efforts to boost sales of injectors to more precisely control types. In the bigger vehicle classes, the Cruze by offering an optional diesel timing and location of fuel injection 21 the costs and fuel economy benefits engine in 2017. Mazda, too, plans to than traditional electromagnetic of diesels over conventional gasoline offer its SKYACTIV-D engine on the injectors. Unlike some OEMs, Mazda power plants are comparable to or uses a two-stage turbocharger. The better than those of strong hybrids.14 better injectors, two-stage turbo, and For example, the MY2016 pickups and 16 In January 2017, the EPA issued a notice of improved variable valve lift enable the the five non-hybrid 4wd SUVs with the violation to FCA for failing to disclose eight software algorithms that revise emission low-compression ratio diesel engine to 15 highest fuel economy were all diesels. control calibrations on MY2014-2016 operate cleanly even upon . Ram 1500 3.0L diesel and Jeep Grand Demand and production of diesels in the Cherokee 3.0L diesel (see https://www.epa. Whatever the vehicle class, diesel larger vehicle segments is increasing. gov/fca). The results of the investigation may affect future sales. engines must contend with NOX and For example, sales of EcoDiesel engines 17 Larry P. Vellequette, “Chrysler seeks more particulate matter aftertreatment. In on Fiat Chrysler Automobiles’ Ram diesels,” Automotive News, July 7, 2014, interviews with suppliers, the Martec 1500 pickup and Jeep Grand Cherokee http://www.autonews.com/article/20140707/ OEM01/307079960/chrysler-seeks-more- Group found that PGM price reductions SUV have surged over the past few diesels and technology improvements have 18 Fiat Chrysler Automobiles. (2016). Business led to significantly reduced costs for Plan Update 2014-2018. Retrieved from today’s aftertreatment systems.24 https://www.fcagroup.com/en-US/ investor_relations/events_presentations/ For instance, in 2008 the cost of a quarterly_results_presentations/ 2015 emission control system for a FCA_2014_18__Business_Plan_Update.pdf 4-cylinder engine was estimated at 13 Sean Osborne, Dr. Joel Kopinsky, Sarah 19 The Martec Group. (2016). Diesel Engine Norton, Andy Sutherland, David Lancaster, Technology: An Analysis of Compliance Costs Erika Nielsen, Aaron Isenstadt, John and Benefits [White Paper]. Retrieved from 22 Hans Greimel, “Mazda solves its diesel German, Automotive Thermal Management http://www.martecgroup.com/diesel-engine- dilemma,” Automotive News, November Technology (ICCT: Washington DC, 2016). technology-an-analysis-of-compliance-costs- 21, 2016, http://www.autonews.com/ http://www.theicct.org/automotive-thermal- and-benefits-white-paper/ article/20161121/OEM06/311219928/mazda- management-technology 20 John German, Vehicle Technology and solves-its-diesel-dilemma 14 As noted previously, diesel fuel has 14.5% Consumers. Presented at Focus on the Future 23 Mazda. “SKYACTIV-D”. SKYACTIV Technology. higher density per gallon than gasoline. For Automotive Research Conferences, slide 13, 2017. http://www.mazda.com/en/innovation/

CO2 emissions, where diesels do not gain this November 10, 2008 technology/skyactiv/skyactiv-d/

benefit, hybrids generally have lower CO2 21 Mike Colias, “Chasing Jetta, Chevy equips 24 The Martec Group. (2016). Diesel Engine emissions than diesels. Cruze with a new turbodiesel,” Automotive Technology: An Analysis of Compliance Costs 15 EPA. (2016). Download Fuel Economy News, June 29, 2015, http://www.autonews. and Benefits [White Paper]. Retrieved from Data [datasets for individual model years]. com/article/20150629/OEM04/306299984/ http://www.martecgroup.com/diesel-engine- Retrieved from http://fueleconomy.gov/feg/ chasing-jetta-chevy-equips-cruze-with-a- technology-an-analysis-of-compliance-costs- download.shtml new-turbodiesel and-benefits-white-paper/

WORKING PAPER 2017-08 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 5 DIESEL ENGINES

$980. In 2016, the system actually cost E ciency Eyebrows Turbine E ciency Eyebrows just $550 and was projected to rise to GTC GTD GTE only $620 in 2025 while complying with stricter emissions standards.

Martec calculated in 2015 that a 2025- compliant 4-cylinder diesel would cost an additional $1,828 compared with a port-fuel injected gasoline V6. In their 2017-2025 Joint TSD, the government agencies found that the same Compressor eciency [-] advanced diesel would cost $2,059 5pts more (or $1,752 more in 2025, as shown 5pts Turbine mechanical eciency [- ] in Table 2). Similarly, a 2025-compliant V6 diesel would cost $2,246 more than Compressor corrected flow [g/s] Turbine corrected flow [g/s] its V8 gasoline counterpart according Figure 1: Evolution of VNT efficiency. Note that the higher the curve, the greater the to Martec. That would be $276 less efficiency. At greater flow speeds—the right side of each graph—newer turbochargers show than the agencies’ estimate. efficiency similar to older generations. The biggest improvements appear at lower speeds— the left half each graph. Here, the eyebrows of newer turbochargers are significantly higher In a report commissioned for the ICCT, than prior generations, indicating improved efficiency. (Source: Honeywell correspondence, FEV estimated that improved EGR Feb 16, 2016) systems for smaller vehicle segments would cost between $40 and $50.25 would cost $1,000 to $1,900 more GTE), the range of operation grows. In larger segments, adding EGR than a comparable gasoline engine. The result is increased low-end cooling across all pressure ranges This takes into account the downsizing or an increase in rated power would cost $109-$122. These costs and cylinder-count reduction of the at reduced low-end speed. Improved cover upgrading the EGR system diesel engine and other modifications. performance makes room for engine to include cooling at both high and downspeeding and downsizing, Most diesels in North America use which improves . As low pressures, which enhances NOX emissions control by lowering in-cyl- variable nozzle turbines (VNTs), or an example, the turbo improve- 26 inder temperatures and reduces the variable geometry turbochargers. As ments shown in Figure 2 going fuel consumption tradeoff. shown in Figure 1, the development from Honeywell’s GTC VNT to its of VNTs by Honeywell shows continu- successor GTD result in as much as FEV also estimated that downsizing ously increased efficiency of the tur- a 6% reduction in brake-specific fuel 27 the engine would create savings bocharger. Successive generations consumption at low rpm.28 for all vehicle segments. However, show improved efficiency on both the as expected, diesel engines with compressor side of the turbocharger, Newer VNT generations show reduced displacement but not as well as on the turbine side. This additional reductions in fuel con- reduced number of cylinders realized improvement is particularly noticeable sumption with maximum declines of savings of only $17-$24. Reducing the at lower speeds, where Figure 1 shows 2%, plus a torque increase of 20Nm number of cylinders leads to savings the blue eyebrows at higher efficiency of $149-$274. than both the red and gray eyebrows 28 P. Barthelet, N. Morand, B. Chammas, L. of earlier generations. Toussaint, L. Sausse, C. Rivière, E. Bouvier. Significantly, FEV found that a (2013). The New Family of VNT™ Turbocharger Developed by Honeywell Turbo Technologies baseline diesel engine with a 2025- For every sequential generation of for Eu6 and Beyond. Presented at the compliant aftertreatment system improved VNT (from GTC to GTD to Dresden Supercharging Conference 2013, 12 September 2013. Retrieved from https:// turbo.honeywell.com/whats-new-in-turbo/ story/honeywell-at-dresden-supercharging- 25 FEV. (2015). 2030 Passenger Car and 26 Correspondence with Honeywell, February conference-2013/ Light Commercial Vehicle Powertrain 16, 2016. M. Pannwitz, T. Tietze, J. Kabitzke, P. Barthelet, Technology Analysis. September 2015. Report 27 P. Davies, D. Jeckel, G. Agnew, G. Figura, D. Jeckel. (2011). Upgrading Diesel TM commissioned by ICCT. Retrieved from P. Barthelet. (2015). 25 Years of VNT TurbochargingSystem to Fulfill CO2 and http://www.theicct.org/2025-passenger-car- Technology – Past, Present & Future. Euro 6 Requirements. Presented by IAV and-light-commercial-vehicle-powertrain- Presented by Honeywell at 20th ATK, Dresden, GmbH and Honeywell at IQPC in Wiesbaden, technology-analysis Germany, September 2015. March 11, 2011.

6 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2017-08 DIESEL ENGINES

and nearly a 1-second decrease in Overall E ciency (iso torque) Load Step (1250 rpm) time-to-torque at 1,000 rpm.

The newest turbochargers designed for 3- and 4-cylinder diesel engines are -50% optimized to handle the higher loads generated by these smaller engines. Because of present and future fuel 0/ +2 pts consumption and greenhouse gas +9 pts standards, turbocharger improvements Boost pressure (kPa) GTC GTD are necessary for compliance using Turbo overall eciency [-] downsized engines. Downsized diesels 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 01 23456789 have the benefit of already being more Engine speed (rpm) Time (s) fuel efficient than gasoline engines. • Massive overall performance improvement • Significant Transient Figure 2: Improvement of Honeywell VNT from generation GTC to GTD (Source: Barthelet Suppliers including Honeywell and et al. (2013). The New Family of VNT™ Turbocharger Developed by Honeywell Turbo BorgWarner are reducing the friction Technologies for Eu6 and Beyond. Presented at the Dresden Supercharging Conference of the bearings within turbochargers 2013, 12 September 2013.) by replacing hydrodynamic bearings 29 with ball bearings. Ball bearings NOX emissions are highest at cold start applied engine and aftertreatment generate as much as a 20% improve- and SCR catalysts need time to warm improvements.33 Compared with the ment in torque, a 5% increase in power, up, suppliers are developing methods gasoline version, the diesel truck 50% better transient response, and of warming up the catalyst faster and achieved 29.8 mpg, a 37% reduction significantly better cold-start perfor- catalyzing or storing NOX at cold start in fuel consumption with a 28% drop 30 mance as a result of lower oil friction. to hasten NOX conversion and limit in CO2 emissions. The engine used 32 NOX emissions. Many systems are emission controls without a noticeable capable of NO conversion over a wide fuel economy penalty. High- and low- IMPROVEMENTS IN X temperature range at rates close to pressure EGR loops reduced engine-out DEVELOPMENT those of three-way catalytic converters NOX and assisted the NOX storage and Aftertreatment and emissions on gasoline vehicles. Examples of SCR systems to dramatically reduce aftertreatment devices that can be tailpipe-out NO to regulatory levels. control X configured to reduce cold-start and Although the engine-vehicle integra- Future aftertreatment systems for operating diesel emissions include tion increased cost somewhat, the compliance with Tier 3 emissions NOX storage catalysts, SCR-on-filter biggest cost contributor was the standards are expected to cost less catalysts, and ammonia slip catalysts. emission control system, at nearly four than $100 compared with today’s Tier Suppliers and manufacturers are exper- times the cost of the baseline system. 2 systems, albeit requiring a higher- imenting with combinations to create 31 pressure injection system. Because durable aftertreatment systems that At low loads, cylinder deactivation are cheaper and more compact. increases the load on the active 29 Marsal, D., Davies, P., Jeckel, D., Tietze, T., cylinders, thereby increasing the Lautrich, G., Sommer, A. (2008). A new developed a demonstra- exhaust temperature more than if Turbocharger Bearing System as a further step to improve the overall TC Efficiency. tion diesel engine for the 2010 Nissan all cylinders were used at low loads. Presented at Aufladetechnische Konferenz half-ton 2wd Titan pickup that meets This increased temperature can be 2008, October 2008. Retrieved from https:// MY2015 CAFE targets and Tier 2, Bin used on diesel engines to help warm turbo.honeywell.com/whats-new-in-turbo/ technical-papers/page/2/ 2 emissions requirements. Designers up the aftertreatment system to the 30 Peter Davies, Damien Marsal, Regis Michel, Paul de Montfalcon. (2013). Ball Bearing goes Mainstream. Presented at IQPC, Wiesbaden, 33 Michael J. Ruth, Cummins, Inc. (2015). ATP-LD; Germany, March 18, 2013. Cummins Next Generation Tier 2 Bin 2 Diesel 31 The Martec Group. (2016). Diesel Engine Engine [Project ID: ACE061]. Presented Technology: An Analysis of Compliance Costs 32 “Cold Start Catalyst (CSC),” Johnson Matthey at the 2015 DOE Annual Merit Review, and Benefits [White Paper]. Retrieved from Automotive Catalysts Technologies, accessed Washington, DC, 12 June 2015. Retrieved http://www.martecgroup.com/diesel-engine- December 2016, http://ect.jmcatalysts.com/ from https://energy.gov/eere/vehicles/ technology-an-analysis-of-compliance-costs- catalyst-technologies-johnson-matthey/cold- vehicle-technologies-office-annual-merit- and-benefits-white-paper/ start-catalyst-csc review-presentations

WORKING PAPER 2017-08 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 7 DIESEL ENGINES

point at which it is most efficient.34 e-boosting and 48V mild hybridiza- recuperation system” reduces 36 Deactivation also has fuel savings of tion. E-boost systems, comprising CO2 emissions by 7% (on the New as much as 25%, but this is only under an electric or an electric European Drive Cycle, or NEDC) low-load operation. motor integrated into a turbocharger, and engine-out NOX by 10-20% on use the 48V electrical system to diesel engines. The 48V electrical As previously discussed, the late directly boost the engine, or to spin up system would also help increase injection of fuel in a diesel engine the turbocharger and greatly reduce efficiency and decrease parasitic causes high particulate emissions. To turbo lag. E-boosting systems also losses of the selective catalytic meet stringent particulate standards, enable the use of larger turbines with reduction systems. More recent diesel particulate filters have been lower backpressure. Better boosting reports from Bosch indicate universally installed. As these filters and reduced lag permit further engine that the system will be ready slowly fill up, they must be regenerated downsizing and downspeeding. Taken for production in 2017 and will at high temperatures to burn off the with reduced backpressure, these decrease fuel consumption even carbon residue, which results in some engine modifications reduce brake- more, by as much as 15%.39 37 CO2 emissions. This process can take specific fuel consumption. as long as 20 minutes and can lead to • Ricardo’s “ADEPT” concept for diesel vehicles parallels the devel- greater fuel consumption and elevated The 48V electrical system has further opments of its gasoline HyBoost NO emissions. The high temperatures benefits if a larger battery is added. It X concept.40 require heat-resistant SCR systems or captures regenerative braking energy It uses a higher- increased packaging to move the after- that can be used to power the e-booster power 12.5kW -drive - generator from SpeedStart, with treatment further away. Just as NO or for propulsion, permits accessory X further energy recovery from conversion catalysts are improving, so operation with the engine off, enables the exhaust using Controlled too are diesel particulate filters. One more-robust start-stop systems, and Power Technologies’ 48V turbine potential alternative is non-thermal can shift the burden of powering certain integrated exhaust gas energy filter regeneration. This method uses accessories to the electrical system, recovery system, known as backpressure—flowing gases backward reducing engine accessory losses. TIGERS. An advanced lead-carbon through the filter. This form of regen- Cooling fans, HVAC blowers, electric battery is used to store recovered eration does not require high tempera- heaters, and other accessories will most energy from braking regeneration tures, eliminating the need for temper- likely be among the first to be powered and exhaust. The battery is easily ature-resistant catalysts and extended by the 48V system. Electric may recyclable and costs significantly packaging. This process also takes be introduced later because they cost less than a Li-ion battery, albeit at seconds rather than minutes, which more than mechanical pumps. lower energy density. The system could lead to fuel savings. However, was fitted to a Ford Focus with collection of the blown-back Automakers and suppliers have the 1.5TDCi ECOnetic diesel and requires some additional space for a reported these developments: achieved CO emission levels as container to store the captured soot.35 2 • Bosch’s electric boosting system low as 80g/km on the NEDC, a helps break the traditional greater than 10% reduction in fuel E-boost and 48V hybrid systems trade-off between NOX and CO2 consumption over the baseline As with gasoline downsized and emissions, according to an early vehicle. Ricardo states that the turbocharged engines, downsized 2015 announcement.38 The “boost diesel engines will soon benefit from 39 Florian Flaig, Bosch Media Service. (2015). 36 Aaron Isenstadt, John German, Mihai The hybrid for everyone: Bosch’s 48-volt Dorobantu, David Boggs, Tom Watson, system makes sense even in compact Downsized, boosted gasoline engines (ICCT: vehicles. Retrieved from http://www. Washington, DC, October 28, 2016). http:// bosch-presse.de/presseforum/details. 34 Dr. James McCarthy, Jr. (2016). Driving www.theicct.org/downsized-boosted- htm?txtID=7384&locale=en Automotive Innovation—Cylinder Deactivation. gasoline-engines 40 “ADEPT,” Ricardo, 2016, accessed June 2016, Presented at the ICCT conference, “Driving 37 BorgWarner (2015). Technologies for http://www.ricardo.com/en-GB/What-we-do/ Automotive Innovation,” September 13, 2016. enhanced fuel efficiency with engine boosting. Technical-Consulting/Research--Technology/ Retrieved from http://www.theicct.org/ Presented at Automotive Megatrends USA adept/ Ricardo. (2016). Advanced ADEPT events/driving-automotive-innovation 2015, 17 March 2015. Slide 26. 48V affordable hybrid on path to meet 35 Bailey, B., “Non-Thermal Active Particulate 38 Jack Peckham, “Novel Electric Boost future ultra-low vehicle emissions, 29 June

Filter Regeneration for Global Particulate Can Slash Diesel NOX, Cut CO2: Bosch,” 2016, retrieved from http://www.ricardo. Matter Reduction while Enabling High Sulfur Downstream Business, May 13, 2015, http:// com/en-GB/News--Media/Press-releases/ Tolerant Low Temperature Urban Effective www.downstreambusiness.com/novel- News-releases1/2016/Advanced-ADEPT-48V- SCR Solutions,” SAE Technical Paper 2015-01- electric-boost-can-slash-diesel-nox-cut-co2- affordable-hybrid-on-path-to-meet-future- 0990, 2015, doi:10.4271/2015- 01-0990. bosch-559016 ultra-low-vehicle-emission/

8 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2017-08 DIESEL ENGINES

“cost-effective focus on the com- 4.5 U.S. No 2 Diesel Ultra Low Sulfur bination of near-market, available (0-15 ppm) Retail Prices 4.0 technologies” gives it the potential for an “extremely high level of 3.5 U.S. No 2 Diesel mass-market appeal, providing Retail Prices arguably a greater overall fuel and 3.0 carbon emissions saving in the 2.5 near to medium term.” 2.0 • Powertrain engineers at VW- U.S. Regular All Price ($/gal) and suppliers have been 1.5 Formulations Retail developing e-boosters with 48V Gasoline Prices hybrid systems for years. When 1.0 combined with regenerative 0.5 braking, the systems may result in fuel consumption reductions of 0.0 7-15%. The higher boost pressure at 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 low loads also reduces particulate Figure 3: U.S. on-road gasoline and diesel fuel prices 1992-2016 (Source: U.S. EIA) emissions.41 And using 48V Li-ion batteries enables electrification the plus side, diesel engines have high Diesel use has been rising rapidly of ancillary mechanical pumps, low-end torque and good acceleration worldwide in the past decade or two, further reducing engine load. from a stop. These two attributes are and refiners have not been able to shift • FEV estimated that a 48V hybrid highly desirable for many consumers. production from gasoline to diesel fast system applied to diesel engines For large vehicles, especially for pickups, enough to keep up. As a result, there would cost $708 to $712 more this low-end torque is especially is a worldwide shortage of diesel fuel, than a 12V stop-start system.42 attractive for increasing cargo and putting prices at a premium compared That is in line with estimates from towing capacity. For all vehicle types, with gasoline. Part of this reflects suppliers that 48V systems cost the fuel savings of diesel engines can be the rapid expansion of diesel sales between a third and half as much quite high. This feature may be particu- in Europe, but a much larger factor as full hybridization while reducing larly important for larger vehicles, which is the explosion of freight movement fuel consumption by one-third to usually have lower fuel economy. in developing countries, almost all of two-thirds as much.43 which uses diesel fuel. Many consumers have outdated perceptions of diesel engines. These Figure 3 shows the trends in fuel CONSUMER IMPACTS include poor starting at colder tem- prices over the past 23 years in the Diesels have a mixture of many undesir- peratures, noise, smell, and slow U.S.44 Historically, diesel fuel was the able and highly desirable features. On acceleration. On the other hand, same price as gasoline, if not slightly consumers also believe that diesels are cheaper, but the trend crossed over more durable than gasoline engines, in 2004, and for the last 12 years 41 E-boosting for VW-Audi’s 2015 V6 diesel. (November 4, 2014). Automotive Engineering. which is also outdated. A recently diesel fuel has been consistently more Retrieved from http://magazine.sae. introduced perception problem is the expensive than gasoline. org/14autp11/ Stuart Birch, “Testing Audi’s VW emissions testing scandal. As with new e-booster reveals turbocharging’s future,” past such cases, the negative impacts Automotive Engineering, August 4, 2014, DISCUSSION: COMPARISON OF http://articles.sae.org/13421/ will probably blow over in time, but CURRENT PRODUCTION, NEW 42 FEV. (2015). 2030 Passenger Car and there may be short-term damage. Light Commercial Vehicle Powertrain DEVELOPMENTS, AND AGENCY Technology Analysis. September 2015. Report PROJECTIONS commissioned by ICCT. Retrieved from http:// The larger challenges for diesels are www.theicct.org/2025-passenger-car- higher vehicle cost, higher fuel cost in Government projections for the costs and-light-commercial-vehicle-powertrain- the U.S. compared with gasoline, and technology-analysis of advanced diesel engines are higher 43 Aaron Isenstadt, John German, Mihai rapid improvements to gasoline engines. Dorobantu, David Boggs, Tom Watson, Unlike Europe, where most countries Downsized, boosted gasoline engines (ICCT: levy substantially lower taxes on diesel Washington, DC, October 28, 2016). http:// 44 Graph downloaded on January 17, 2017 www.theicct.org/downsized-boosted- fuel than on gasoline, the U.S. taxes the from https://www.eia.gov/dnav/pet/ gasoline-engines two fuels at almost the same rates. PET_PRI_GND_DCUS_NUS_W.htm

WORKING PAPER 2017-08 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 9 DIESEL ENGINES

than estimates from suppliers.45 Table 3: Comparison of EPA, FEV, and Martec Group estimates of 2025 incremental prices of PGMs have dramati- manufacturing cost cally reduced diesel package costs. EPA FEV MARTEC Although monthly PGM prices have $441-$824 $530-$1,288 $869-$1,123 been relatively stable or trending Engine downward for several years, they can Aftertreatment $1,311-$1,321 $428-$532 $595-$675 change direction quickly. As a result, Total $1,752-$2,146 $996-$1,893 $1,463-$1,798 suppliers continue to create emission Note: Martec Group estimates for 2025-compliant diesels were derived by applying the same control systems with lower levels of manufacturer learning curves EPA used to Martec Group’s 2015 estimated incremental costs. FEV PGMs. Component makers have been incremental costs were determined by comparing baseline segments C and D diesel and gasoline engines. developing new designs and methods $3,500 for particulate filters, NOX storage/ Rulemaking P2 Hybrid adsorbers, and NOX reducers. There are numerous strategies and configu- $3,000 rations for engines of different sizes tailored for specific loads and tempera- Diesel + tures. These developments are likely $2,500 mild hybrid + to decrease the costs associated with Rulemaking e-boost, Advanced ICCT/supplier aftertreatment systems. Diesel $2,000 Several engine improvements are Advanced Diesel, ICCT/supplier poised to assist in reaching peak after- treatment temperatures faster while $1,500 reducing engine-out NOX and boosting efficiency. These include cooled low- Direct Manufacturing Cost and high-pressure EGR loops and $1,000 cylinder deactivation, for example.

Significant research continues $500 on diesel turbochargers, some of $100 per % fuel consumption reduction whose components are appearing $50 per % fuel consumption reduction in downsized gasoline engines. Each $25 per % fuel consumption reduction $0 generation improves performance and 0% 10% 20% 30% 40% 50% 60% permits greater engine downspeed- Percent fuel consumption reduction ing and downsizing. Major suppliers already have turbochargers ready for Figure 4: Comparison of rulemaking and ICCT/supplier estimates of direct manufacturing cost per percent fuel consumption reduction in 2025. the growth of 3- and 4-cylinder engines. These sharply downsized engines Aftertreatment costs are the incremen- near-production of 48V mild hybrid promise increased fuel economy. tal cost of diesel aftertreatment over systems are likely to lead to diesels that reduce fuel consumption by Table 3 shows the estimated 2025 gasoline aftertreatment. Improvements direct manufacturing cost for engines in emission control systems, turbo- more than 30%. The higher-voltage and emission control from the EPA charging, and combustion/injection electrical system will take the load rulemaking and from suppliers. The may increase costs but will certainly of powering ancillary systems off the values represent the difference in improve efficiency. engine, directly increasing efficiency. cost between a naturally aspirated And the capacity for regenerative In the rulemaking, diesels were gasoline engine and its corre- braking and e-boosting provides as estimated to have around a 20% sponding downsized diesel engine. much as two-thirds of the benefits of reduction in fuel consumption a strong hybrid at half the compared with baseline gasoline 45 The Martec Group. (2016). Diesel Engine cost or less. Technology: An Analysis of Compliance Costs vehicles. Many of the developments and Benefits [White Paper]. Retrieved from discussed previously contribute Figure 4 compares the costs and http://www.martecgroup.com/diesel-engine- technology-an-analysis-of-compliance-costs- to this benefit. However, a host benefits of advanced dieselization and-benefits-white-paper/ of engine improvements and the as estimated in the rulemaking (red

10 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2017-08 DIESEL ENGINES

box) with more recent calculations against VW and FCA cause some Diesels have two significant by suppliers. The rulemaking cost- manufacturers to abandon diesels. advantages over gasoline engines: benefit analysis for full hybrid (P2) Diesel share will expand further as They will always have significantly is also shown for reference. Future incremental costs decline. higher fuel economy, and their ability diesels are expected to cost less and to haul cargo and tow cannot be have greater benefits than forecast matched. Those things make diesels in the rulemaking (blue box). The Conclusions a strong option for customers who costs are lower because of less- Diesel vehicles have had a rough put a high priority on towing or fuel expensive emission control systems time penetrating the U.S. light-duty economy and manufacturers that and improved engine components. vehicle market, reflecting outdated want to market high fuel economy. Adding the costs and benefits of a negative perceptions, higher fuel This can be seen in the market with 48V mild hybrid system and electric prices for diesel than for gasoline, the successful use of diesels in GM’s supercharging (orange box) leads to the cost of complying with stringent mid-size pickup trucks and coming slightly higher costs per each percent U.S. emission standards, and rapidly diesel offerings for the Chevy Cruze, reduction in fuel consumption, but improving gasoline engines. Then, in the diesel truck, and in average total costs remain lower than just as light-duty diesels were Mazda’s diesel CX-5. for full hybrids. finally gaining market share, the VW emissions testing scandal set diesels Diesels offer a promising pathway For the increasingly popular larger back once again.46 for compliance and another option in vehicle classes, diesels provide a manufacturers’ toolboxes. Their use is uniquely cost-effective alternative to Still, improved aftertreatment likely to vary significantly from manu- hybrids for achieving deep reductions systems are rapidly reducing the facturer to manufacturer and model to in fuel consumption. They have plenty cost of complying with emissions model. This will depend on each auto- of room for emission control systems standards, and further cost-reducing maker’s assessment of diesel’s cost- and benefit from the low-engine- advances are expected. While the effectiveness compared with other speed performance of diesels. efficiency advantage of diesels over technologies, such as hybrids, and gasoline engines is narrowing,47 customer desire for the advantages As a result of all these trends, it seems diesel engine developments are also of diesels. Coming cost reductions will likely that diesels will have a larger occurring and will further improve improve the diesel’s competitiveness market share in 2025 than predicted diesel efficiency. The VW scandal will and likely increase its market share in by the EPA and NHTSA, unless the eventually blow over. the future. diesel cases brought

46 The recent Notice of Violation from EPA against FCA’s light-duty diesels is also of concern. However, it is not likely to have the same impact as the VW scandal, as unlike VW, FCA’s software only deactivated the emission control system part of the time and FCA has cooperated with the U.S. agencies in their investigation. 47 As described in other papers in this series, gasoline engines are reducing this fuel economy gap through higher compression ratios, Atkinson and Miller cycles, variable compression, and other improvements.

WORKING PAPER 2017-08 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 11