Advanced Engine Technology

WORKING PAPER 2018-14

Fuel-efficiency technology trend assessment for LDVs in China: Advanced engine technology

Authors: Guowei Xiao, Zifei Yang, Aaron Isenstadt Date: 17 September 2018 Keywords: engine technology, fuel efficiency, passenger car

1 Background to advance post-2020 standards for of 3.2 L/100 km was set. To evaluate light-duty vehicles. whether and how these targets can be Fuel-consumption standards drive met, it is essential to understand what down China’s use of fuel by the In its “Made in China 2025” strategic technologies will be available within on-road sector and encourage the initiative (MIIT, 2015), China set a 2025 the 2020-2030 timeframe and what uptake of advanced vehicle-effi- fleet efficiency target of 4 L/100 km the costs of applying those technolo- ciency technologies. Understanding for passenger cars, a 20% decrease gies in the Chinese market will be. the need for a policy roadmap and from the 2020 target of 5 l/100km. In long-term strategies to provide cer- the Technology Roadmap for Energy This series of technical briefings tainty for long-term fuel consump- Saving and New Energy Vehicles aims to provide a comprehensive tion, technology advancement, and published by the Society of Automo- understanding of the current potential compliance costs for man- tive Engineers of China (SAE China, availability, effectiveness, and ufacturers, China is looking ahead 2016), a 2030 fleet efficiency target future market penetration of key

ABBREVIATIONS 2-TCI Two stage CVVL Continuous variable IMA Integrated motor TCI Turbocharger with turbocharger with valve lift assist intercooler intercooler DCP D ual cam phasing IMG Integrated motor VCM Variable cylinder ACT Active cylinder DEAC Cylinder deactivation generator management technology DLC Diamond-like carbon ISG Integrated starter VCR Variable compression AFM Active fuel DSF Dy namic skip fire generator ratio management DVVL Discrete variable MDS Multi-displacement VGT Variable turbine AGM A bsorptive glass mat valve lift system geometry AVS Audi valve-lift EGR Exhaust gas MPI Multi-point injection turbocharger system recirculation NA Naturally aspirated VT-C Variable compression BMEP Brake mean effective GDI Gasoline direct OHC Overhead-cam ratio turbocharging pressure injection OHV Overhead-valve VTEC V ariable valve timing BSG Belt-driven starter GSG Geely Stop-Go PFI Port fuel injection and lift electronic generator HCCI Homogeneous SCI Supercharger with control CATC China automotive charge compression intercooler VVEL Variable valve event test cycle ignition SI Spark ignition and lift CCP Coupled cam ICP Intake cam phasing SPCCI Spark controlled VVL Variable valve lift phasing compression ignition VVT V ariable valve timing

Acknowledgments: The authors thank the Energy Foundation China for sponsoring this series of studies. We greatly appreciate the generous contributions of time by the following experts: Ameya Joshi (Corning), Peter Davies, Ning He (Honeywell), Sean Osborne (ITB), Akichika Yamaguchi (Denso), experts from MAZDA, and John German (the ICCT).

fuel-efficiency technologies that Fuel e ciency manufacturers are likely to use in technologies China by 2030. This information enables a more accurate, China-specific understanding of future technol- Advanced Vehicle Thermal Hybrids and ogy pathways. Transmissions engines technology management electrifction We group technologies into several categories: advanced engine, Figure 1 Categorization of fuel efficiency technologies in the briefing transmission, vehicle technologies, thermal management, and hybrids and 2 Introduction Since about 1980, ongoing devel- electrification (Figure 1). The specific opments in computer-aided design Internal combustion engines convert technologies we considered include and simulation, as well as on-board the chemical energy in fuel into vehi- those that are available today and electronic controls, have enabled rapid cle kinetic energy through specific others that are under development technology improvement to reduce thermodynamic cycles. The theoreti- and expected to be in production in these sources of energy loss. These cal maximum efficiencies of the ther- the next 5-10 years. technologies not only improve engine modynamic cycles indicate that not efficiency but also reduce vehicle This research relies on information all the fuel’s energy can be converted fuel consumption in other ways. For from publicly available sources, third- into vehicle movement. Indicated effi- instance, apart from its benefits in heat party databases, and information ciency is defined as the proportion losses and mechanical losses, turbo- from the participating partners. Our of fuel energy that gets transmitted downsizing can also reduce vehicle approach includes: to indicated work, or the work that fuel consumption by simply reducing the high-pressure in-cylinder gases the weight of the engine and lowering • A detailed literature survey, do to the pistons during an engine’s engine speed. Stop-start technology including both Chinese and global power stroke. Factors that affect an reduces fuel consumption by shutting regulatory documents, official engine’s indicated efficiency include off the engine during idling. Some announcements, and industry incomplete combustion and wasted advanced stop-start techniques are and academic reports. heat. Energy loss from incomplete also equipped with regenerative brak- • Analysis of databases from Polk combustion is negligible, but heat ing, which recovers energy from brak- and Segment Y. losses account for more than 60% of ing and uses it to power accessories, the fuel energy in current engines, reducing accessory losses. In this • Conversations with manufactur- half of which is wasted by the cool- section, we will evaluate technology ers, tier one suppliers, research ing system and half by exhaust gases. progress and new developments of entities, and domestic and inter- Moreover, not all the work done to key technologies. national experts. the pistons makes it to final engine shaft output. This conversion rate is For each key technology, we discuss 3 Current status how it reduces passenger-car fuel termed mechanical efficiency, since consumption, its effectiveness in the losses are basically due to move- 3.1 GASOLINE DIRECT reducing fuel consumption, and its ment of other components. Fac- INJECTION current level of application or poten- tors that result in mechanical losses tial application in the China market. include pumping air into and out of Gasoline direct injection (GDI) injects Wherever applicable, we compare the engine, friction, and powering highly pressurized gasoline into the technology trends in China with those accessories, such as the alternator, combustion chamber of each cylinder. in the United States and the European oil pump, water pump, and com- Since GDI provides direct cooling to the Union to reflect potential technology pressor for air conditioning. There in-cylinder charge via fuel vaporization, pathways in the long term. are also idling losses, although not it allows an increase in the compression directly reflecting engine efficiency. ratio of approximately 0.5 to 1.5 points This briefing assesses technology These losses are highly dependent by improving knock resistance relative progress and new developments in on the type of driving, so total losses to naturally aspirated or turbocharged internal combustion engines. can vary significantly. engines using port fuel injection (PFI)

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(EPA, 2016a). In addition, the cooling 50% effect results in more trapped intake charge, thus increasing engine volu- IHS metric efficiency and engine power 40% and torque. GDI engines also improve exhaust scavenging at low engine speeds by increasing valve overlap 30% and delaying fuel injection until after CATARC the exhaust valve is closed, further Segment Y increasing engine power and torque at lower engine speeds. A study by 20% Chang’an (Zheng et al., 2016) shows that, by replacing the multi-point injection (MPI) system of a 1.6L naturally 10% aspirated 4-cylinder engine with a GDI system, fuel consumption was reduced by 3.9% over the New European Drive 0% Cycle (NEDC) through increasing the 2009 2010 2011 2012 2013 2014 2015 2016 2017 compression ratio from 10.5:1 to 11.8:1. Furthermore, this replacement would Figure 2 Market penetration of GDI from different data sources increase engine torque by 5%-23% the Haval H6 model; Chery’s 1.6T GDI 3.2 COOLED EGR depending on engine speed, and engine is expected to appear on the maximum power by 4.5%. Some man- Commonly used on diesel engines as market in 2018; and in 2016 Chang’an a method to reduce emissions, cooled ufacturers are also pursuing dual injec- introduced its Blue Core 1.5L turbo exhaust gas recirculation (EGR) has tion by combining PFI and GDI. dual port injection (1.5 TDPI) engine, also been found effective for improv- which combines GDI and PFI on a In China, GDI penetration in the pas- ing fuel efficiency of gasoline engines. turbo engine (Chi, 2016). senger car fleet has increased rap- EGR systems introduce some of the idly. Although market penetration The uptake of GDI is much higher in engine-out exhaust gas into the intake estimates from different data sources the United States. In model year 2016, air stream, reducing combustion vary (Figure 2), the rising trend is con- 50% of new U.S. passenger cars used temperature by increasing the spe- sistent. In 2016, the China Automo- GDI, compared with 3.1% in MY2008. cific heat capacity of the in-cylinder tive Technology and Research Center The projected 2017 GDI penetration in gas. By lowering the combustion tem- (CATARC) estimated GDI penetration the United States is 54% (EPA, 2017). perature and rate, EGR enables higher of 25% in China (CATARC, 2017) while Unlike the Chinese market, more compression ratios, allows spark IHS data showed 32%. than half of GDI installations were advance, reduces heat losses, and on naturally aspirated engines (EPA, therefore reduces fuel consumption Based on the ICCT’s analysis of Seg- 2016b). The application of GDI on new of both naturally aspirated and ment Y data, 87% of GDI applica- gasoline vehicles sold in the European turbocharged engines. Cooling the tions in 2014 were on turbocharged Union in 2016 was 44%. exhaust before mixing it with the intake engines. Most GDI installations in stream further exploits this technol- China are applied by joint venture In China, the main suppliers of GDI ogy’s potential for improving engine OEMs. Independent manufactures, systems are United Automotive Elec- efficiency. Cooled EGR also reduces such as Great Wall, Chang’an, and tronic Systems Co. (UAES, a joint fuel consumption by decreasing fuel Chery, have also started to introduce venture of Bosch and eight domestic enrichment, which is used to reduce GDI on passenger cars. For example, OEMs or suppliers), Dongguan Keihin exhaust gas temperature at high engine Great Wall’s 1.5L turbo GDI (or 1.5T (a wholly owned subsidiary of Japa- loads. On turbocharged engines, the GDI) engine is already deployed in nese Keihin), Delphi, and Denso. lower combustion temperature also

WORKING PAPER 2018-14 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 3 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: ADVANCED ENGINE TECHNOLOGY

results in higher turbo pressures and Application of cooled EGR in hybrid turbine. They found that the high- higher engine output, enabling further vehicles can be found in Toyota’s pressure EGR system reduced fuel con- engine downsizing and downspeed- lineup. Toyota’s 2ZR-FXE engine, used sumption more at the highest engine ing. The addition of inert exhaust gas in the fourth-generation Prius and speed and load—as much as 18%—while to the intake system means that for a Lexus CT200h, is characterized by a the low-pressure EGR system showed given power output, the throttle needs geometric compression ratio of 13.0:1, improvements over the entire engine to be opened further, thereby reducing cooled EGR, and Atkinson cycle to road map and better average fuel econ- pumping losses at low engine loads. reduce knocking. This engine realized omy (Morey, 2014). A test of high-pres- Various EGR strategies can be applied a peak thermal efficiency of 38.5%. sure EGR on a 1.4T GDI engine by Ten- to the engine at different operating According to Toyota, the 8ZR-FXE is neco Inc. demonstrated a 12% reduction conditions to achieve optimum overall the domestic China model of the 2ZR- in fuel consumption near peak power, fuel economy. FXE, so it is believed that the domestic and a fuel-economy improvement of China Levin HEV and Corolla Hybrid 2%-3% was demonstrated by a simu- According to BorgWarner, cooled also use cooled EGR as a method of lation on the Worldwide harmonized EGR can reduce fuel consumption of improving fuel efficiency. Toyota also Light Duty Test Cycle (WLTC) (Fischer, a turbocharged GDI engine by 5%-8% demonstrated ways to push ther- Kreutziger, Sun, and Kotrba, 2017). (Zhou, 2014). Mahle Behr estimates mal efficiency to 40% (Takahashi et this improvement to be 2%-5% (Morey, Currently there is no application of al., 2015). One way is to expand the 2014). A study that applied cooled cooled EGR in production turbo- engine EGR rate limit, or the ratio EGR on a 1.8L vehicle1 increased the charged gasoline engines in China. between the recirculated exhaust gas compression ratio from 10:1 to 10.8:1 Mazda’s SKYACTIV-G 2.5T engine, flow rate and the total charge air flow and reduced average fuel consump- which is applied on the CX-9, is an rate, thus reducing heat and pump- tion by 4.6% (Wang et al., 2016). example of such application avail- ing losses. The drawback of a high able in the global market. The engine EGR rate, however, is lower combus- Cooled EGR is deployed on a variety features a compression ratio of 10.5:1. tion speed. To improve combustion of production models in the Chinese The use of high-pressure EGR in this speed, the tumble ratio of this engine market. Like GDI, cooled EGR can be engine improves knock resistance was increased from 0.8 to 3.5 by long regarded as an underlying technol- at high engine loads and allows the stroke and straight intake. By those ogy that typically combines with other engine to maintain the ideal air-fuel means, the new 2.5L I4 Dynamic technologies for lowering fuel con- ratio over a wider output range, thus Force engines, which appeared on the sumption. Mahle Behr expects cooled reducing the need to retard ignition market in the 2018 Camry, realize a EGR to be especially effective on timing (Mazda, 2016). downsized turbocharged engines and thermal efficiency of 41%. EGR usage Atkinson-cycle engines used in hybrid has also been extended to non-hybrid In China, major suppliers of cooled vehicles. These engines are designed vehicles with this engine, while the EGR systems are Wuxi Longsheng to run at higher loads and speeds, or peak efficiency of the non-hybrid ver- Technology Co., Continental in the operating region in which knock sion is 40% (Toyota, 2016). Automotive Systems US, and limit and mixture enrichment seriously BorgWarner Automotive Components Application of cooled EGR in turbo- affect fuel economy. The U.S. Envi- (Ningbo). charged engines is considered an ronmental Protection Agency (EPA) option for current in-development tur- conducted a benchmarking study on bocharged engines but has not yet been 3.3 TURBO-DOWNSIZING a 2.0L four-cylinder vehicle with a widely adopted. The EPA estimated 14:1 geometric compression ratio and Compared with natural aspiration, the potential benefit of adding cooled found a 6% reduction in fuel consump- turbochargers increase intake charge EGR systems to conventional down- tion under the U.S. CAFE test cycle air density to raise the mass flow of air sized turbo direct injection engines to (Schenk and Dekraker, 2016). to the engine and thus require extra be 3.6%. Mahle Behr tested two types fuel to maintain stoichiometric con- of cooled EGR: a high-pressure system ditions. These greater amounts of air that diverts exhaust before it enters and fuel increase engine power for a the turbocharger turbine, and a low- given engine displacement volume. 1 The vehicle is equipped with multi-point pressure system that diverts exhaust injection, four cylinders, DOHC, and VVT and Consequently, turbocharging allows an has a power of 101 kW. from downstream of the turbocharger engine to be downsized while retaining

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the same level of performance. Given 100% US-EPA 2012 a constant power demand, a smaller- China-CATARC displacement engine operates at higher loads during normal driving 80% conditions, resulting in lower pumping loss due to wider-open throttle and smaller heat loss. Smaller engines 60% also have lower friction losses due to smaller cylinders and/or fewer moving parts. Turbochargers are driven 40% US-EPA 2016 by exhaust gas, so part of the wasted heat energy carried by the exhaust can be recycled. Turbo-downsizing 20% also reduces the weight of the engine itself and its supporting mechanism. 0% While this does not increase engine 2016 2017 2018 2019 2020 2021 2022 2023 20242025 20262027 2028 2029 2030 efficiency, it does decrease the work Figure 3 Projection of turbocharging penetration in passenger car fleet in China and needed to move the vehicle, reducing the United States. fuel consumption. China, Europe, and the United States. charged car market share increased Turbochargers are almost 100% In China, turbocharger penetration from 10% to 40% between 2010 and accompanied by an intercooler to in the passenger car fleet increased 2016. More than 90% of those gaso- reduce the temperature of the intake from 7% in 2010 to 21% in 2014 (Zhou line turbocharged engines used GDI air to increase charge density and and Yang, 2018) and to 32% in 2016 accompanied by downsizing (Wol- reduce knock risk, making the most of (CATARC, 2017). The vast majority of fram and Lutsey, 2016). the technology’s benefits in fuel effi- joint ventures—almost 95%—coupled ciency and power. In 2012, EPA/NHTSA projected that turbochargers with GDI in 2014, while the future market penetration of most independent automakers still The benefit of turbo-downsizing in turbocharging in the U.S. light-duty apply turbochargers with PFI. The vehicle fuel consumption can be var- vehicle fleet would be 64% by 2021 1.5 TDPI engine used on Chang’an’s ied, depending on the boost level. and 93% by 2025 (EPA and NHTSA, new CX70T is one of the signs that The EPA and National Highway Traffic 2012). But the estimate was revised independent manufacturers are Safety Administration (NHTSA) con- down to 36% by 2025 in the EPA’s introducing GDI technologies into sidered three boost levels based on latest evaluation reflecting improve- turbocharged engines. the engine brake mean effective pres- ment in other technologies (EPA, sure (BMEP), 18 bar, 24 bar, and 27 bar. For comparison, in the United States, 2016a). Based on the model predic- These correspond to fuel-consump- the gasoline turbocharged car mar- tion of CATARC, 65% of the conven- tion reductions of 10.7%-13.6% at 18 tional passenger cars in China will ket share was 23.8% in 2016 and bar, 15.0%-18.9% at 24 bar, and 16.4%- have turbocharging and downsizing increased to 30% in 2017. More than 20.6% at 27 bar, depending on engine in 2020. That market share would 60% of the gasoline turbocharged type. CATARC estimated the fuel con- increase to 91% in 2025 and 98% in cars in 2016 were combined with four- sumption benefit of turbo-downsizing 2030, according to the CATARC pro- cylinder engines, and more than 90% to be 7.2%. Based on this, we assume jections as shown in Figure 3. of gasoline turbocharged engines also a 7.2%-13.6% fuel-consumption reduc- used GDI (EPA, 2017).2 Turbocharg- tion benefit for this technology. In China, almost 100% of the applica- ers are more prevalent in European tions of turbocharging in the passen- Even though gasoline turbocharged countries, where the gasoline turbo- ger car fleet use single-stage turbo. vehicles were introduced decades Two or more stages of turbocharging ago, it was not until recently that 2 GDI statistics also include light trucks, which and supercharging, which uses engine are categorized as light-duty vehicles in the turbocharging and downsizing led United States, with gasoline turbocharged crank output to power the charger, to favorable market acceptance in engines. are not mainstream in China. They

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account for just 0.1% of the passenger flexible design, controlling intake and Beijing-Hyundai, Donfeng-Nissan, car fleet (Figure 4). exhaust valves independently. Dis- Shanghai-GM, Dongfeng-Yueda-KIA, crete cam-phasing VVT systems offer FAW-Toyota, and Guangzhou-Honda SCI 2-TCI two or three discrete phasing angles, equipped almost all of their passenger 0.07% 0.03% whereas continuous VVT can vary cars with VVT. The adoption rates of phase angle constantly. Compared independent manufacturers increased with discrete VVT, continuous VVT from 7% in 2010 to 40% in 2014. greatly enhances engine flexibility. Continuous DCP system examples In addition to VVT which changes only include Toyota’s VVT-i system, BMW’s the opening time of the valves, VVL TCI Double-VANOS system, Nissan’s enables variable valve lift and dura- 32.79% C-VTC system, and Honda’s i-VTEC. tion, offering greater control over Today, all of Toyota’s new passenger engine air flow. vehicles are equipped with a VVT-i MA VVL changes the length and/or height 67.11% system to enable control over intake of the valve opening. VVL control and exhaust valve timing. can further reduce pumping losses, The majority of current cam phasing increase engine power, and potentially applications use hydraulically actuated reduce overall valve train friction units, powered by engine oil pressure (EPA, 2016a). VVL is normally applied and managed by a solenoid that con- together with VVT in China. Figure 4 Turbocharger distribution by trols the oil pressure supplied to the type in 2016 in China (NA– naturally phasing system. Electric cam phas- There are two major types of VVL: dis- aspirated; TCI– turbocharger with ing, such as used by Toyota on the crete VVL and continuous VVL. Dis- intercooler; SCI– supercharger 2018 Camry, allows a wider range of crete VVL (DVVL) switches between with intercooler; 2-TCI– two stage camshaft phasing and faster time-to- two or three discrete camshaft pro- turbocharger with intercooler) position. The EPA estimated the ben- files to enable variable valve lifts. efits of VVT on fuel consumption to be Pioneered by Honda in 1990, it is a 3.4 VARIABLE VALVE TIMING 1%-5.5%, depending on VVT type and mature technology with relatively low AND LIFT number of cylinders. CATARC also esti- cost. Continuous VVL (CVVL) offers greater effectiveness since valve lift Variable valve timing (VVT) and vari- mated the fuel-consumption reduction can be optimized for any engine load able valve lift (VVL) offer greater of VVT. Although they do not specify and speed. However, it is considered control over the intake air and/or the VVT type and cylinder number, to be more complicated and costly. exhaust gases. their prediction of a 2.18% reduction in fuel consumption is within the range The EPA estimated that DVVL reduces VVT alters the timing of valve opening estimated by the EPA. fuel consumption by 2.8%-3.9% com- and closing. It reduces pumping losses pared with VVT, while the benefits when the engine is lightly loaded by VVT has now become a widely of CVVL were estimated to be 3.6%- reducing the amount of valve overlap adopted technology. In China, VVT 4.9% compared with VVT. In China, and increases power and torque when penetration in the passenger car fleet VVL penetration in the passenger car needed by increasing valve overlap. increased from 44% in 2010 to 64% in fleet increased from 19% in 2010 to 2014. In 2014, 29% of passenger cars 64% in 2014 (Zhou & Yang, 2017). Currently, cam phasing, which changes were equipped with intake VVT only, the phase angle of the camshaft with while 35% of passenger cars had VVT Honda’s VTEC (Variable Valve Timing respect to the crankshaft, is the most on both intake and exhaust valves. As and Lift Electronic Control) system is commonly used form of VVT. There a comparison, more than 98% of new an example of DVVL technology. Cur- are three major types of VVT: intake passenger cars sold in the U.S. are rently all Honda passenger cars sold in cam phasing (ICP), coupled cam estimated to use some form of VVT China are equipped with this technol- phasing (CCP), and dual cam phasing (EPA, 2016b). Generally, joint ven- ogy. The VTEC system features a lock- (DCP). CCP and DCP can modify the tures had much higher adoption rates ing multi-part rocker arm and two cam timing of both the inlet valves and the than independent manufacturers. lobes/profiles, one optimized for low- exhaust valves, but DCP is the most Among the top-selling joint ventures, speed fuel efficiency and the other

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for high-speed performance. Switch- an electric-driven CVVL system. A lift profiles. Whereas a closed sole- ing between the two cam profiles is rocker and two types of links close the noid transmits the pressure gener- enabled by coupling or decoupling intake valves by transferring the rota- ated by the camshaft’s intake profile the rocker arms using a hydraulic sys- tional movement of a drive shaft with to the valve in the normal fashion, an tem. Audi’s AVS (Audi Valvelift Sys- an eccentric cam to the output cam. open solenoid breaks the hydraulic tem) is also a DVVL system but works The movement of the output cam link between cam and valve, decou- in a different way. The system features can be varied by rotating the control pling their operations (Ashley, 2010). two cam profiles and a single rocker shaft within the motor and changing This technology first appeared in the arm. Switching between cam profiles the fulcrums of the links. This makes Alfa Romeo MiTo at the 2009 Geneva is enabled by pushing the cam lobes a continuous adjustment of valve lift Motor Show. Currently, in the Chinese to slide on the camshaft. In China, possible (Nissan, 2008). VVEL was market, engines that have MultiAir AVS appears in Volkswagen’s EA888 first introduced to the U.S. market applied are used on the imported Fiat engine, which is used by many pas- in late 2007 on the 2008 Infiniti G37 500 and GAC-FCA’s Jeep Compass senger cars made by FAW-VW and Coupe equipped with the new VVEL and New Cherokee. Shanghai-VW, including the Magotan, VQ37VHR engine. It is available in the CC, Tiguan, and Audi Q5 models. Chinese market on the Infiniti VQ37 3.7L V6 engine, used in the imported 3.5 CYLINDER DEACTIVATION Applications of CVVL come exclu- Infiniti Q50 and QX70, and on the Cylinder deactivation (DEAC) keeps sively from joint ventures. Examples VK56 5.6L V8 engine, used in the valves closed to disable or deactivate can be found in the passenger cars imported QX80. cylinders when the load is significantly of BMW, Fiat, and Nissan. BMW’s Val- less than the engine’s total torque vetronic is the first mass-production In contrast to those electromechani- capability, thus reducing friction, heat CVVL system. It offers continuous cal CVVL technologies, Fiat’s MultiAir losses, and pumping losses. DEAC and precise control over variable uses managed hydraulic fluid to pro- reduces vehicle fuel consumption intake valve lift, from 0.3 to 9.7 mm3, vide variable valve control. The Multi- without sacrificing maximum power. and duration. Valvetronic cylinder Air system features a single camshaft heads use an extra set of rocker arms, that has three nodes per cylinder: two There are basically two types of cyl- called intermediate arms, positioned to actuate the exhaust valves and a inder deactivation technologies in between the valve stem and the cam- single inlet cam which pushes a small the market. For overhead-cam (OHC) shaft. These intermediate arms pivot pump that either opens the valves engines, the rocker arm has one part on a central point by means of an extra, hydraulically or pushes the engine oil that follows the cam lobe and another electronically actuated camshaft. This into a separate spring-loaded, high- that opens the valve. A lashing or movement alone, without any move- pressure reservoir. An electrohydrau- latching mechanism either connects or ment of the intake camshaft, can vary lic actuator—a high-response, elec- disconnects these two parts, thereby the intake valves’ lift from fully open, tronically activated solenoid—controls activating or deactivating the valves or maximum power, to almost closed, the pressure applied to hydraulic fluid, and their cylinder. For overhead valve or idle (Boeriu, 2016). The Valvetronic which is engine oil drawn from the (OHV) engines, a pushrod is used to system has been widely used by BMW. sump, that fills a thin passageway con- connect the cam lobe and the rocker Application of this technology in the necting the intake valves and the cam- arm. Solenoids are used to release oil Chinese market can be found in Bril- shaft. The solenoid valve regulates the pressure in the tappet and to collapse liance-BMW’s 3 Series, 5 Series, and amount of oil that is pumped by the the lifters and deactivate the pushrod X1 models as well as in the imported cam action either to the valve or a and its respective cylinder. 7 Series and X5, among others. PSA bypass reservoir. When pressurized, (including Chang’an DS, Dongfeng- the hydraulic line behaves like a solid The EPA estimated that DEAC would PSA, and the imported PSA) also have body and transmits the lift schedule improve fuel economy by 0.5%- a couple of models that use BMW’s imparted by intake cam directly to 6.5%. The lower end of the estimate Valvetronic system. the intake valve. When the solenoid is excludes the benefit of reduced disengaged, a spring takes over valve pumping losses from advanced valve Similar to Valvetronic, Nissan’s Vari- actuation duties. This electrohydraulic trains such as DCP and VVL. For able Valve Event and Lift (VVEL) is link allows independent operation of baseline engines with no application the two components, which enables of advanced valve train technolo- 3 Valvetronic II and III offered 0.18 mm to 9.9 mm near real-time control over the valve gies, the benefit of DEAC would be

WORKING PAPER 2018-14 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 7 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: ADVANCED ENGINE TECHNOLOGY

4.7%-6.5%, depending on the num- engine loads. The EA211 1.4T engine, pumping losses by 20% (Isenstadt, ber of cylinders, V6 or V8, according which features ACT, can deactivate German, and Dorobantu, 2016). to the EPA. This estimate applies to cylinders 2 and 3 when operating at OHC engines which are commonly part load. This engine is the first appli- An effective way to decrease the risk used on passenger cars in China. cation of DEAC on a mass-produced of knocking is to reduce the amount I4 engine. However, the domestically of hot exhaust gas remaining inside In MY2016, only 2% of the new produced EA211 engine does not fea- the combustion chamber, lowering passenger car fleet in the United ture ACT. the gas temperature at the end of the States used DEAC. Light trucks had compression stroke. Mazda made sig- a higher DEAC penetration of 21%. In These technologies allow a fixed nificant efforts to reduce the risk of China, DEAC penetration in new pas- group of cylinders to be shut down. knocking at high compression ratios. senger cars is not clear. There are a Thus, they normally are applied on First, a fabricated 4-2-1 exhaust mani- couple of examples of models, exclu- larger engines with an even number fold reduces the amount of exhaust sively from joint ventures or import- of cylinders so that symmetrical cyl- gas that flows backward into one ers, with DEAC in the Chinese market. inders can be deactivated to avoid cylinder from another. Second, a intense torque fluctuations and vibra- combustion chamber optimized with One is Honda’s Variable Cylinder Man- tion. As described in section 4.2, high-tumble flow and a small bore, agement (VCM) system, which works more-advanced DEAC technologies together with other improvements by closing the intake and exhaust that allow variable cylinders to be shut such as increased injection pressure valves using its i-VTEC technology, an down are being developed. and split injection, creates a more example of DEAC for OHC engines. homogeneous air/fuel mixture, and The 3.0L i-VTEC V6 engine, which is as a result, shortened combustion specially designed for the Chinese 3.6 HIGH COMPRESSION RATIO duration, which also decreases the market, can disable the three cylinders Increasing the compression ratio of risk of knocking. Third, a piston cav- on the rear side and work in 3-cylinder naturally aspirated engines improves ity improves combustion stability by mode during specific driving condi- thermal efficiency. However, doing preventing the initial flame from con- tions—for example, highway driving. so also increases the risk of knock- tacting the piston head. Currently, this engine is used on Hon- ing, or the abnormal combustion da’s Crosstour and Acura’s MDX and Combining increased compression phenomenon in which the air/fuel RDX models. It was also once used on ratio with the other improvements dis- mixture ignites before the flame front Honda’s Accord in MY2014-2015 but cussed, Mazda realized a 15% increase arrives because of high pressure and was discontinued in MY2016. in fuel efficiency under JC08 test temperature. This leads to reduced cycle and an increase of 15% in torque. Examples of DEAC for OHV engines efficiency and engine power. Manu- are GM’s Active Fuel Management facturers need to resolve the higher The SKYACTIV technology was intro- (AFM) system and Chrysler’s Multi- risk of knocking associated with high duced in Japan in 2011 on the Mazda Displacement System (MDS). GM’s compression ratios. 2 and in the United States in 2012 on AFM was once used on the 2014 the CX-5 and Mazda 3. The SKYAC- Mazda’s SKYACTIV-G engine LaCross model. Chrysler’s HEMI 5.7L TIV engine was first introduced to achieved one of the highest compres- V8 engine, which features MDS, can China in 2012 on the imported CX-5. sion ratios among mass production shut off four cylinders under light load Starting in 2013, the CX-5 with a vehicles (Mazda, 2010). The adver- to improve fuel economy. However, SKYACTIV engine was domestically tised geometric compression ratio this engine was available only on the manufactured in China. Subsequently, imported Chrysler 300C and Grand was 14.0:1 in the European Union the SKYACTIV engine was applied on Cherokee in MY2005. and 13.0:1 in the United States and the Atenza of FAW-Mazda, the Axela China, reflecting a relatively lower of Chang’an-Mazda, and the CX-4 of A DVVL system can also be used for fuel octane value. In the case of the FAW-Mazda. Currently, all of Mazda’s DEAC if the low-lift cam lobe is modi- SKYACTIV-G engine, the Atkinson passenger vehicles in China use SKY- fied to have a zero-lift profile. Used in cycle concept and direction injection ACTIV engines. Volkswagen’s Active Cylinder Tech- are used. Atkinson cycle is enabled nology (ACT), this strategy deacti- by delaying intake valve closing by Beside Mazda, Toyota’s newly devel- vates two of the four cylinders at low the dual VVT system, which reduces oped Dynamic Force Engine has a

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high compression ratio of 13:1 (Toy- by 8% over the same size engine in this benefit to be 10%-14% (Lutsey et ota, 2018). It is deployed on the 2019 the previous Camry (German, 2018). al., 2017). Corolla but has not been introduced to China yet. Hybrid systems of joint ventures, such as those of Toyota and Ford, 3.8 STOP-START use the Atkinson cycle to achieve A stop-start system temporarily stops 3.7 ATKINSON CYCLE improved efficiency. Toyota’s 1.8L the engine when the vehicle stops and Adopting alternative thermodynamic 8ZR-FXE engine, used on GAC- restarts it when acceleration is needed, cycles is another method to improve Toyota’s Levin HEV and FAW-Toy- thus reducing fuel consumption during thermal efficiency. Compared with ota’s Corolla Hybrid in MY2018, is idling time in urban driving. The China the conventional Otto cycle, the equipped with Toyota’s VVT-i to Automotive Test Cycle (CATC), which Atkinson cycle enables an expan- allow flexible intake valve closing reflects general driving conditions in sion ratio higher than the compres- time, with a geometric compression China, includes an idling time of 22% sion ratio. This allows more work to ratio of 13.0:1. It should be noted that (Li, 2018), longer than the 13% idling be extracted per volume of fuel/air because of delayed intake valve clos- time on the WLTC and the 19% idling mixture by allowing the combustion ing, the effective compression ratio is time on the U.S. FTP cycle. Given the long idling time of vehicles when driv- gases to expand beyond the point lower than the geometric compres- ing in cities in China, stop-start is an at which compression begins. When sion ratio, thus reducing the risk of effective technology for reducing real- applied to modern naturally aspi- knocking. Independent manufactur- world fuel consumption. rated engines, the Atkinson cycle is ers are also starting to apply Atkin- son cycle engines to hybrid vehicles. realized by delaying intake valve clos- In 2016, around 8% of new vehicles sold For example, GAC announced the ing. This results in an effective com- in China had stop-start systems, up GS4 PHEV and GA3S PHEV models pression ratio lower than the expan- from 1.8% in 2012 (Zhao, Wang, Qu, and in 2018, both of which are equipped sion ratio during the power stroke Ren, 2015; Sun, 2017). In MY2016, 9.1% with a 1.5 ATK Atkinson engine. and allows the geometric compres- of new passenger cars in the United sion ratio to be increased. Because Atkinson-cycle engines on non- States had stop-start (EPA, 2016b). Atkinson cycle engines need to hybrid vehicles are usually combined The technology is highly adopted on adjust the intake valve timing, they EU cars with 63% penetration in 2016. with high compression ratios. One require VVT to optimize the effec- example is Mazda’s SKYACTIV-G tive compression ratio. Although the There are generally two types of stop- naturally aspirated engine, which higher expansion ratio improves fuel start system available in the market: was introduced to China in 2012. In efficiency, Atkinson cycle engines reinforced starter systems and direct the SKYACTIV-G engine, the switch sacrifice some maximum power, since starter systems. Both can be com- between Atkinson cycle and conven- part of the charged air is pushed out bined with a limited amount of regen- tional Otto cycle is enabled by Maz- erative braking, sometimes referred to by the piston during the compression da’s Dual S-VT, a VVT technique. The as a micro-hybrid. Mild and full hybrid stroke of the engine. To retain vehicle conventional Otto cycle was used at compulsion systems are not included performance-older Atkinson-cycle high engine load for performance in this paper but are introduced in the engines generally increase displace- and the Atkinson cycle was used at papers in this series on hybrids and ment or are paired with a full-hybrid part load for efficiency. electrification technology. system, where the electric motor returns the power to an equiva- As modeled by the EPA, the applica- Reinforced starter systems are the lent level of performance by adding tion of Atkinson cycle could reduce simplest and most widely adopted additional torque. However, the per- CO2 emissions by 3%-8%, which stop-start system. The main com- formance limitations are being over- includes the effects of high com- ponent is a more robust starter that come by newer designs that include pression ratio and cooled EGR (EPA, can withstand the increased number cooled EGR and wider VVT operating 2016a). However, analysis by the of engine starts and a more capable ranges, such as the base engine in the ICCT, which takes the recent progress battery that can meet the heavier 2018 Camry which increased power of OEMs into consideration, suggests power drawn by vehicle accessories

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with the engine off. The EPA esti- Direct starter systems restart the 3.9 ENGINE FRICTION mated that the potential reduction engine through combustion, rather REDUCTION in fuel consumption with reinforced than relying on a starter motor. Mazda Engine friction reduction technolo- starter systems would be 1.8%-2.4%. is the only manufacturer that employs gies can be categorized into low- direct starter, the i-STOP system. CATARC estimated the benefit to be friction lubricants and engine friction 3.5%. These are close to each other, During engine shutdown the piston loss reduction. CATARC estimated and considering the longer average positions are precisely controlled, that friction reduction technologies idling time on the China test cycle, it’s and during restart fuel is injected in total would reduce fuel consump- reasonable to expect a larger benefit into the appropriate cylinder and tion by 3.5%. in China. The problem with reinforced ignited to generate downward piston starter systems, however, is discom- force and restart the engine. Mazda Low-friction lubricants include low- fort for passengers caused by fre- asserted a reduction of about 8% in viscosity and advanced low-friction quent rough restarts. fuel consumption under the JP08 test lubricant oils. If manufacturers make cycle (Mazda, 2009). Currently, all of use of these lubricants, they may need Typical reinforced starter systems Mazda’s passenger vehicles in China to make engine changes and conduct include Valeo’s ReStART, Bosch’s are equipped with an i-STOP system. durability testing to accommodate Efficiency Line products, and Den- the lubricants. Consequently, cost so’s Enhanced Starter products. The When supplemented by regenera- increases include the costs of lubri- Valeo system is used by Citroën, Peu- tive braking technology, a stop-start cants, engine changes, and testing. geot, Smart, Land Rover, and Volvo, system of either type is sometimes while the Bosch system is used by referred to as a micro-hybrid system. Technologies to reduce engine fric- Volkswagen, BMW, Nissan, and Fiat. By using recovered braking energy tion losses include low-tension piston Independent manufacturers, such to power the electronic systems and rings, roller cam followers, improved as Geely, Great Wall, and Chang’an, engine accessories, regenerative material coatings, more-optimal also apply stop-start technology. The braking can reduce the load placed thermal management, piston surface Geely Stop-Go (GSG) system first on the engine by the alternator and treatments, and other improvements appeared in the EC7 GSG sedan in therefore provide additional ben- in the design of engine components 2012. Chang’an STT system, which efits in reducing fuel consumption. and subsystems that improve the uses Bosch’s solution, also first Many different types of regenerative efficiency of engine operation. For appeared in 2012 in the Eado sedan. braking are being developed. BMW’s example, Nissan first coated the valve Efficient Dynamics uses the alterna- lifter with diamond-like carbon (DLC) Stop-start is expected to develop rap- tor to recharge the battery when on its VQ engines and reduced fric- idly in China. On May 2, 2017, Zheng- decelerating or braking. The battery tion by around 40% (Nissan, 2006). zhou Coal Mining Machinery Group experiences very different load char- A Chinese study looking at reducing Co. (ZMJ) teamed up with the Hong acteristics from a normal car battery, piston and valve friction by apply- Kong-based private equity firm China thus BMW uses an absorptive glass ing DLC film coating found a 3 N·m Renaissance Capital Investment and mat (AGM) lead-acid type of battery. torque reduction and a 2% decline 4 bought Robert Bosch Starter Motors Mazda’s i-ELOOP, produced in 2014, in fuel use on a 1.8L vehicle (Wang, Generators Holding GmbH (SG) uses an ultra-capacitor to capture Huang, and Huang, 2016). Federal- from the German group (Meng & braking energy and provide power Mogul Powertrain introduced a new Shi, 2017). Bosch has been the major for conventional vehicle electronic generation of its coating technology, stop-start system supplier providing systems. When used in conjunction Ecotough, in 2017, delivering reductions in piston friction of as much as 95% of the start-strop systems used with Mazda’s i-STOP, the company 15% and reducing fuel consumption on Chinese cars in 2014 (Zhan, 2014). reports fuel savings of as much as by 0.8% compared with standard The chairman of ZMJ predicted that 10% in real-world driving condi- coatings (Federal-Mogul Powertrain, stop-start system penetration would tions with frequent acceleration and 2016). Chery’s third-generation rise to about 60% by 2020, much braking (Mazda, 2011). The Mazda higher than Bosch’s 2013 estimate i-ELOOP and Valeo iStars system are 4 The vehicle is equipped with multi-point of 30% by 2019 (Meng and Shi, 2017; considered micro-hybrid systems injection, 4 cylinders, DOHC, and VVT and has ChinaEV, 2013). (German, 2015). a power of 101 kW.

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engines, released in 2017, lowered Table 1 Technology penetration and fuel consumption reduction summary engine friction by 20% compared Penetration Estimated fuel with the preceding generation by in Chinese Estimated fuel consumption improving the lubricant system and passenger consumption reduction design of the valve timing system, Technology car fleet reduction (U.S.)a (Chinese sources) crank connecting rod accessory sys- GDI 25.3% (2016)b 1%-3% 4.5%b; 3.9%c tem, and cooling system, according Cooled-EGR n/a 3.63%b; 4.6%d to the company (Chery, 2017). Turbo-downsizing 32% (2016) 7.20%b ICP 33% (2014) 2.1%-2.7% This study does not have detailed b information on the adoption of fric- VVT CCP 31% (2014) 1%-3% 2.18% tion reduction technologies in the DCP 4.1%-5.5% Chinese passenger car fleet. In the Discrete 62% (2014) 2.8%-3.9% VVL technology roadmap drawn by SAE Continuous 2% (2014) 3.6%-4.9% China (SAE China, 2017), the goal is to DEAC n/a 0.5%-6.5% 0.44%b develop 0W-20 lower-viscosity oil by High compression ratio 1% (2014) 3%-8% 2020 and to realize scaled application Atkinson cycle 8.0%-10.3%; 10%-14%e of 5W-20 or 0W-20 oil by 2030. The Reinforced EPA estimated that the penetration 8% (2016) 1.8%-2.4% 3.5%b Stop-start starter of such low-friction lubricants among Direct starter 1% (2014) 8% (JC08) light-duty vehicles would exceed Surface 85% by MY2017 and reach nearly 2%d Friction coatings 100% in MY2025. The penetration of 3.54%b reduction 0.8% (level 1 Others technologies to lower engine friction lubricants) losses would exceed 70% by MY2017, a according to the agency (EPA, 2012). EPA and NHTSA, 2012 b CATARC, 2017 c Zheng et al., 2016 d Wang et al., 2016 3.10 SUMMARY e Lutsey et al., 2017 Table 1 summarizes the contribution to reducing fuel consumption by each 4.1 HCCI and to prevent misfire at low engine loads. Thus, the operating range of of the technologies discussed, based Homogeneous charge compression conventional HCCI is has been limited on different sources. ignition (HCCI) is an engine combus- to a small region on the engine map. tion concept that works by using However, Mazda has addressed these compression, rather than a spark, to 4 Improvements under issues and expanded the operating ignite a homogeneously premixed range for its second-generation SKY- development air/fuel mixture. This technology ACTIV gasoline engine (SKYACTIV-X) There are a variety of advanced promises significant fuel-economy launching in 2019, which uses super engine technologies that have poten- benefits, which come primarily from lean-burn compression ignition (CI) tial to further reduce fuel consump- a combination of highly lean opera- with a high compression ratio of tion of passenger vehicles. Some are tion and a resulting high specific heat around 15:1. already applied on vehicles in other ratio and reduced pumping losses, countries; some will soon enter the typically higher compression ratio, The SKYACTIV-X engine uses a spark Chinese market according to manu- and shorter combustion duration. plug to achieve complete control facturers’ public announcements; of CI combustion. For this reason, and some are still under develop- Although there is extensive under- Mazda terms the technology Spark ment. None of these technologies has standing of HCCI combustion, con- Controlled Compression Ignition, yet entered the Chinese market, but trolling the ignition timing is extremely or SPCCI. With spark control, the most of them have the potential to be challenging. It is difficult to prevent operating range of CI combustion applied on cars sold in China in the explosive combustion at high engine is greatly expanded, and the engine near future. loads due to excessive dense fuel achieves stable switching between

WORKING PAPER 2018-14 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 11 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: ADVANCED ENGINE TECHNOLOGY

CI and spark ignition (SI). At low to 1 3 2 1 3 2 medium engine speeds, the engine Concentional DEAC works in lean-burn CI mode. In this mode, the spark plug ignites the Rolling DEAC homogeneous air/fuel mixture, forming an expanding fireball, which Crank angle 0 240 480 720 960 1200 1440 additionally compresses the air/fuel activated deactivated mixture outside the fireball. At high engine speeds, the engine works in SI Figure 6. Firing orders of conventional DEAC and rolling DEAC mode, with the spark plug as the only ignition source (Figure 5). Among the proposed technologies, engine to operate in 666 cm3 twin-cyl- HCCI combustion is regarded as one inder mode when cruising. The gen- promising way to improve engine effi- eral DEAC system is complemented ciency. Domestic OEMs are advised to by a specially developed pendulum invest in HCCI from the year 2018 and absorber as well as a Schaeffler dual- are expected to apply it on gasoline mass flywheel and a tuned clutch disc engines from 2023. to achieve vibration isolation between transmission and engine, thus mitigat- ing the NVH effects. Ford reported 4.2 ADVANCED CYLINDER a reduction in fuel consumption of DEACTIVATION 4%-6% in a Focus operating in twin- As discussed, conventional cylin- cylinder mode (Birch, 2015). der deactivation technologies allow Figure 5. SPCCI operating range (provided by Mazada) certain cylinders to be shut down, Ford is also researching a rolling, or normally applying to larger engines dynamic, form of DEAC on the same A highly responsive air supply unit with an even number of cylinders to 1.0L I3 EcoBoost engine (Birch, 2015). and EGR allow full control of the in- avoid intense torque fluctuations and The fixed deactivation strategy effec- cylinder gas composition, enabling vibration. Dynamic cylinder DEAC, tively improves fuel efficiency but has optimized CI. By combining these however, can continually change the the disadvantage of an uneven fir- improvements, Mazda reports that active cylinders, therefore offering the ing sequence. By applying the DEAC the SKYACTIV-X engine achieves capability of reducing engine noise, mechanism to all three cylinders, the a 20%-30% reduction in fuel con- vibration, and harshness (NVH) by rolling cylinder deactivation can vary sumption on the WLTC, as well as a controlling the firing order and firing the number and sequence of deacti- 10%-30% increase in engine torque density, or the ratio of cylinders actu- vated cylinders as shown in Figure 6. using RON 91 gasoline, as com- ally fired to the maximum possible. Such a strategy effectively runs the pared with Mazda’s current SKYAC- This expands the operating range, engine in half-engine mode, corre- TIV gasoline engine (Mazda, 2017). approximately doubling the efficiency sponding to a 500 cm3 engine with Additional costs of the SKYACTIV-X benefits, and extends the range of the advantage of an even firing order. engine include a highly responsive applicability to smaller engines. supercharger for the air supply, high- According to Ford, the rolling DEAC pressure fuel injection system, and Ford is planning to apply DEAC tech- strategy has the potential of further in-cylinder pressure sensors. nology to its 1.0L I3 EcoBoost engines, reducing pumping losses at very low which will be used on Focus and Fiesta loads, resulting in better fuel economy According to Mazda’s market strat- ST models in the European Union during low-load drive cycles. The over- egy, vehicles using SPCCI technology in MY2018. This would be the first all load limit of this half-engine mode would appear in China in 2019 or a little application of DEAC on an I3 engine, would be lower than the twin-cylinder later. In a technology roadmap drawn although it is a fixed rather than fixed DEAC mode. Ford reports a 1.2% by SAE China (SAE China, 2017), aver- dynamic form of DEAC. By applying a fuel-efficiency benefit on the NEDC age thermal efficiency of PV engines switchable roller finger follower deac- compared with the improvement is expected to increase to 40% by tivation mechanism to one cylinder, already achieved with the fixed-cylin- 2020, 44% by 2025, and 48% by 2030. this technology will enable the 1.0L I3 der DEAC for the 1.0L Fiesta engine.

12 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2018-14 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: ADVANCED ENGINE TECHNOLOGY

For the larger Mondeo model using the same engine on the WLTC, however, the gain would be negligible.

Delphi and Tula have jointly devel- IVC - Miller cycle oped a dynamic DEAC technology called Dynamic Skip Fire (DSF). P IVC - Conventional Otto cycle Similar to Ford’s solution, DSF also deactivates a cylinder using a switchable roller finger follower mechanism. However, a different controlling strategy is applied. During DSF operation, the decision to fire or skip a cylinder is made right before each ignition V event, based on the torque demand Figure 7. Miller cycle early Intake Valve Closing (IVC), V – in-cylinder volume, and avoiding known resonance pat- p – in-cylinder pressure terns within the engine (Birch, 2017). By choosing the right firing density, 4.3 VARIABLE GEOMETRY too high. Recent advances in material the DSF controller can effectively TURBO technology have improved the turbo’s keep the activated cylinders running ability to withstand high-temperature The vast majority of turbocharged at optimum efficiency and reduce oxidation and wear resistance, and engines in China’s passenger vehicle throttling losses at low engine loads cooled EGR is reducing exhaust tem- fleet today apply a fixed geometry (Tula, 2015). Delphi reported a fuel- perature. Consequently, VGTs have turbo with a waste gate to reduce the economy improvement of 10%-20% started appearing in gasoline engines, maximum boost pressure. compared with conventional engines, especially in sports cars such as the Porsche 718 Boxster. depending on the engine and driving Variable Turbine Geometry conditions (Delphi, 2015). DSF has Turbochargers (VGTs, also known as been demonstrated on a Volkswagen In 2016, Volkswagen announced the variable nozzle turbines—VNTs) are 1.8-L TSi engine. new 1.5L TSI EA211 Evo engine, the a type of turbocharger that exhibits first mass-production gasoline engine GM is introducing the world’s first increased efficiency over a wide range with VGT. This engine is expected production dynamic DEAC system on of flows, enabling better transient to be used in various VW and Audi the redesigned 2019 full-size pickup response and reduced lag compared models, including the new seventh trucks in the United States. This is with fixed geometry turbos. The aspect generation Golf. The major improve- based upon the Delphi/Tula system. ratio of VGTs can be varied by altering ment of this engine over its prede- the geometry of the turbine housing cessor is use of the Miller cycle and Cylinder DEAC for smaller engines and based on the engine operation condi- a high geometric compression ratio dynamic DEAC are expected to expand tion. At low engine speeds, the aspect of 12.5:1. Similar to the Atkinson cycle into additional production within a few ratio can be decreased to allow a lower in naturally aspirated engines, the years. However, it is difficult to esti- boost threshold and reduced lag, while Miller cycle is enabled by advancing mate the benefit of this technology as at high engine speed the aspect ratio the closing time of the intake valve, it is highly dependent on the existing can be increased to avoid exhaust as shown in Figure 7. As a result, the valve train configuration and adopted choking. A study has shown that, com- charged gas expands and cools dur- efficiency technology of the baseline pared with conventional turbochargers, ing the later part of the intake stroke, engine. Ford and PSA estimated the VGTs can increase boost pressure by which places a crucial responsibility additional benefit of dynamic DEAC 30% and reduce backpressure by 10% on the turbo to provide external com- to be 1%-2% over conventional fixed- (Li, 2013). pression. This is equivalent to shifting cylinder DEAC. The ICCT estimated some of the compression work to the the benefit to be 2.5%-3.0% over fixed While VGTs have been developed turbocharger, so the engine operates DEAC with greater benefits for smaller for diesel engines, until recently they with higher thermal efficiency. Use of engines over the U.S. driving cycles were not applied to gasoline engines VGT is critical in enabling the Miller (Lutsey, 2017). as the exhaust temperatures were cycle as it increases the turbo’s ability

WORKING PAPER 2018-14 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 13 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: ADVANCED ENGINE TECHNOLOGY

to satisfy the needs of a Miller-cycle engine across a broader operating range, while the Miller cycle reduces exhaust temperatures, allowing the use of VGT. Compared with its predecessor, the 1.5L TSI EA211 engine is represented as providing a 10% efficiency improvement as well as a 5%-10% reduction in fuel consumption over most of the engine map (Volkswagen, 2016).

Generally, the Miller cycle is estimated to add an additional 5% efficiency improvement over conventional waste gate turbo-downsizing, while the application of VGT can add an additional 1% (Isenstadt et al., 2016). As a result, a Miller cycle engine with VGT is estimated to reduce engine fuel consumption by 12.7%-18.7%, and without, by 11.8%-17.9%. Figure 8 Boosting Architectures (provided by Honeywell)

Although there is yet no volume naturally aspirated engine (Isenstadt thanks to increasing the geometric application of VGTs in China’s pas- et al., 2016). compression ratio of an engine. In senger fleet, some independent Chi- gasoline engines, another benefit is nese OEMs are exploring VGTs and There are two basic forms of electric enhanced knock resistance, which starting to develop their own Miller- boosting architectures: turbo plus an allows the re-phasing of combus- cycle engines to comply with the new electric compressor (eCharger) or tion and further improved thermo- Chinese fuel-economy legislation, electric turbo (eTurbo) only (Figure dynamic efficiency. This requires the according to Honeywell. 8). Both eCharger and eTurbo give turbocharger to provide more boost excellent transient performance, without demanding higher back- while it’s broadly accepted that 4.4 ELECTRIC BOOSTING pressure in areas of the map where eCharger offers the best steady-state the Miller timing is to be exploited. Another improvement considered low-end performance. The bigger challenge is to maintain effective in reducing fuel consump- the engine transient response at an tion in turbo-downsized engines is an 4.4.1 eCharger acceptable level (Pohorelsky, Von- electric boosting, or e-boost, system. ECharger can be considered like drak, Chobola, Jeckel, and Davies, With stricter CO limits, 48V systems 2 a two-stage turbocharger system. 2018). are expected to be more popular and With electric motor help, traditional give e-boost an opportunity to fur- Electrically assisted turbochargers turbo lag is minimal. For performance ther improve vehicle performance also have the functionality to recover cars, eCharger also supports addi- and reduce CO emissions. By solv- energy from the exhaust stream 2 tional low-end torque. If combined ing problems with turbo lag, e-boost instead of opening the waste gate with a gear-shifting strategy, early enables additional engine downsiz- to control speed and boost. This gear shifting can also reduce CO ing and downspeeding. E-boost is 2 process is typically referred to as emissions. estimated to add fuel consumption recuperation. Recuperated electri- benefits of 2%-5% over conventional cal energy may be used directly by single-stage turbocharging, which 4.4.2 eTurbo loads on the vehicle electrical net- translated to a 7.4%-17.9% efficiency Miller valve timing is well known for work, or be stored in the battery if improvement over a conventional its ability to improve fuel economy the state of charge permits.

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ETurbo gives the system more including moving the cylinder heads, thus enabling higher compression flexibility to manage energy from varying the geometry of the connect- ratio through charge cooling by the exhaust manifold. ing rod, moving the crankshaft axis, evaporation of water in the engine’s or changing piston deck height. cylinders. It also increases fuel effi- RTS 95 driving cycle simulations con- ciency by reducing heat losses and firm that it is possible to save 1.5%- FEV proposed a two-stage VCR sys- fuel enrichment, and allows the 3.5% of fuel (Pohorelsky et al., 2018). tem, enabled by varying the length engine to operate with higher boost The technology is demonstrated on of the connecting rod between and earlier spark timing, resulting in the Audi Q7 (Figure 9) and is very discrete high and low points. This greater power and torque. likely to come into production in system requires only minor modifi- 2021 in the C, D, and SUV segments cations to the connecting rods and As a performance enhancement with 1.5L and 2.0L applications. the crankshaft, according to FEV. technology, water injection was used The cost of this system would thus during World War II in reciprocating IAV & HON demo be significantly lower than that of a aircraft engines. The first application continuous VCR system while retain- of this technology in a limited-pro- ing 80% of the potential reduction duction vehicle was by BMW in the in fuel consumption (FEV GmbH, M4 GTS (BMW, 2015). Recent studies 2015). FEV also estimated this system have explored its potential for reduc- would reduce fuel use by 4.2%-6.2% ing fuel consumption as a function on the U.S. combined cycles (Klee- of the location of water injection and berg, Tomazic, Dohmen, Wittek, and the amount of water injected over a Balazs, 2013). broad range of engine operating con- Audi Q7, 2.0l Gasoline ditions. Broadly, these studies point • 215kW with full λ=1 Nissan put the first VCR system into to a 13%-20% reduction in fuel con- • Faster transient production in 2018 on Infiniti mod- sumption at high loads (Pauer et al., Honeywell Boosting els. Its variable compression ratio 2016; Kim, Park, Bae, Choi, and Kwak, • 48V e-Turbo with Advanced turbocharging system (VC-T) uses 2016) and a 4%-6% reduction over an Compressor a multi-link system to raise or lower entire drive cycle (NEDC or WLTP) • GT 25 the reach of the pistons, allowing the (Hoppe, Thewes, Baumgarten, and compression ratio to vary continu- Dohmen, 2016; Thewes et al., 2016). Figure 9 Application of e-Turbo on demo ously between 8:1 and 14:1 (Nissan, vehicle 2016). Nissan unveiled the 2.0L I4 Water injection has ideal synergies VC-T engine at the 2016 Paris Motor with VCR and cooled EGR technolo- Show. The engine first appeared in gies. VCR can compensate for higher 4.5 VARIABLE COMPRESSION Infiniti’s QX50 in MY2019, replac- knock limitations with a lower com- RATIO ing a 3.5L V6 engine. This resulted pression ratio if water injection cannot Increasing the compression ratio is a in a weight reduction of 25kg and a be used due to a lack of water or at low straightforward way to improve the fuel-consumption reduction of 27%, ambient temperatures. At the same thermal efficiency of an engine. Vari- compared with the V6 predecessor, time, high compression ratio can be able compression ratio (VCR) sys- according to Nissan (Kendall, 2016). maintained up to the highest loads if tems change the compression ratio However, this improvement in fuel water injection is possible. Cooled EGR of the engine based on the operat- efficiency was not entirely due to the allows a deep reduction in the amount ing condition—increasing it at low implementation of VCR as other effi- of injected water (Thewes et al., 2016). engine load to promote thermal efficiency technologies, such as Miller ciency, and decreasing it at high load cycle and turbo-downsizing, were Reflecting the potential benefits to reduce knock risk and improve also applied. for reducing fuel consumption and engine performance. improving engine performance, water injection has been investi- VCR has attracted many research and 4.6 WATER INJECTION gated extensively over the past few development efforts from both OEMs Apart from cooled EGR, water injec- years. However, significant prob- and suppliers for a long time. Vari- tion offers an alternative technology lems need to be resolved before ous approaches have been proposed, for reducing the risk of knocking, this technology can become widely

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Fuel efficiency / GHG reducing technologies

Percentages in () are fuel consumption/GHG emission reduction potential Arrow: estimated fuel consumption potential includes impact of other technologies

Figure 10 Advanced engine technology map for passenger cars in China adopted. From a cost-of-ownership 5 Summary China. The blue question mark for perspective, the most significant friction reduction technology indi- Figure 10 summarizes the key tech- obstacle is the rather large amount cates a lack of information on market nologies explored in this paper. The of on-board water required. Most penetration. Water injection is not adoption status of each technol- studies indicate an optimum water- included because the technology is ogy in the China market is indicated to-fuel ratio of 30%-50%, which still at an early stage of research and before the name of each technology. translates to 2.4- 3.9L/100 km of development. The pie charts reflect the latest mar- water consumption for a vehicle ket penetration of commercialized The percentages following each tech- with fuel efficiency of 7.8 L/100km. technologies in China. VVT, VVL, nology summarize its potential for This would require filling up a 10L GDI, and turbo-downsizing have reducing fuel consumption. In most water tank at roughly every other relatively higher penetration. The cases, the reduction potential is com- fuel stop. One option could be on- start signs represent emerging tech- pared with baseline vehicles without board recovery of water, which nologies that appear on a couple of only the technology under study. For researchers are investigating. Other models, such as conventional DEAC, some technologies, the impact on fuel considerations are the cost of addi- direct start, and Atkinson cycle. The consumption is provided in combi- tional hardware, pressure drop, size green flags represent underdevel- nation with other technologies that limitations, complexities for engine oped technologies that have been are difficult to isolate. In those cases, management, purity of water, and applied or researched in other coun- arrows indicate which technologies consumer acceptance. tries but still under development in are included in fuel-consumption

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reduction estimates. For example, the Table 2 Advanced engine technologies at different development stages in China application of Atkinson cycle is always Commercialized Emerging Underdeveloped combined with GDI, cooled EGR, VVT, technologies technologies technologies and high compression ratio, so its • GDI • Conventional cylinder • Cooled EGR (Turbo) impact on fuel consumption includes deactivation • Cooled EGR for (NA • Miller cycle the effect of all the included technolo- engine) • High compression • E-boost gies. The percentage ranges repre- ratio • Turbocharger (waste gate) • Dynamic cylinder sent the average impact. • Atkinson cycle (NA • VVT deactivation engine) Based on the application status of • VVL • HCCI/SPCCI • Direct starter advanced engine technologies in • Atkinson cycle (hybrid) • Variable compression ratio China, we group the technologies • Reinforced starter into three categories: • Friction reduction Commercialized technologies. Tech- nologies that are already adopted at or luxury vehicles targeting high-end on production passenger cars in the least on several production models users. near future. in China and could be applied widely through the fleet. Underdeveloped technologies. Table 2 lists the advanced engine Technologies that have been adopted technologies under each category Emerging technologies. Technolo- in other markets but currently are based on our definitions. This infor- gies that are available on passenger not available on cars produced in mation will be used for estimating cars sold in the Chinese market but China, or technologies that have been fuel-saving potential of all efficiency are available on only a couple of mod- announced by manufacturers or sup- technologies in the summary paper els, such as variants of flagship autos pliers and are likely to be adopted of this series of working papers.

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