WORKING PAPER 2018-15 Fuel-efficiency technology trend assessment for LDVs in China: Transmission technology Authors: Zifei Yang, Yong Chen, Aaron Isenstadt Date: 17 September 2018 Keywords: transmission technology, fuel efficiency, passenger car 1 Background Fuel eciency Fuel-consumption standards drive technologies down China’s use of fuel by the on- road sector and encourage the uptake of advanced vehicle-efficiency tech- Advanced Vehicle Thermal Hybrids and Transmissions nologies. Understanding the need for engines technology management electrifction a policy roadmap and long-term strat- egies to provide certainty for long- Figure 1 Categorization of fuel efficiency technologies in the working papers term fuel consumption, technology advancement, and potential compli- This series of technical working papers This research relies on information ance costs for manufacturers, China is aims to provide a comprehensive from publicly available sources, third- looking ahead to advance post-2020 understanding of the current availability, party databases, and information standards for light-duty vehicles. effectiveness, and future market from the participating partners. Our In its “Made in China 2025” strategic penetration of key fuel-efficiency approach includes: initiative (MIIT, 2015), China set a 2025 technologies that manufacturers are • A detailed literature survey, fleet efficiency target of 4 L/100 km likely to use in China by 2030. This including both Chinese and for passenger cars, a 20% decrease information enables a more accurate, global regulatory documents, from the 2020 target of 5 L/100 km. In China-specific understanding of future official announcements, and the Technology Roadmap for Energy technology pathways. industry and academic reports. Saving and New Energy Vehicles We group technologies into sev- published by the Society of Automo- • Analysis of databases from Polk eral categories: advanced engine, tive Engineers of China (SAE China, and Segment Y. transmission, vehicle technologies, 2016), a 2030 fleet efficiency target thermal management, and hybrids and • Conversations with manufactur- of 3.2 L/100 km was set. To evaluate electrification (Figure 1). The specific ers, tier one suppliers, research whether and how these targets can be technologies we considered include entities, and domestic and inter- met, it is essential to understand what those that are available today and national experts. technologies will be available within others that are under development the 2020-2030 timeframe and what For each key technology, we discuss and expected to be in production in the costs of applying those technolo- how it reduces passenger-car fuel the next 5-10 years. gies in the Chinese market will be. consumption, its effectiveness in Acknowledgments: The authors thank the Energy Foundation China for sponsoring this series of studies. We greatly appreciate valuable comments from Hui He (the ICCT) and Ameya Joshi (Corning). © INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION, 2018 WWW.THEICCT.ORG FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: TRANSMISSION TECHNOLOGY Manual Automatic reducing fuel consumption, and its 100% current level of application or poten- tial application in the China market. 90% Wherever applicable, we compare 80% technology trends in China with those in the United States and the European 70% Union to reflect potential technology 60% pathways in the long term. 50% This working paper assesses tech- nology progress and new develop- 40% ments in transmissions. 30% 20% 2 Introduction 10% Because of lower costs and fuel consumption, manual transmis- 0% sions (MTs) have been the main- 2007 2008 2010 2011 2012 2013 2014 2015 2016 2017 stream technology for decades in Market penetration of manual and automatic transmissions in China, China. However, MTs’ leading market Figure 2 2007-2017 share has eroded in recent years as demand for automatic transmissions to its most efficient speeds more pairs of concentric cones, with grew in response to an expanding of the time. This significantly infinite variability between the vehicle population and increasing reduces the efficiency gap. maximum and minimum gear city congestion. The market share • Dual-clutch transmissions ratios. The efficiency of the of MTs has decreased from a peak (DCTs) consist of two separate transmission is reduced by fric- of more than 70% in 2009 to 39% manual transmissions with odd- tional losses related to clamp- in 2017 (Figure 2). Today, automatic numbered gears on one shaft ing forces on the belt/chain transmissions account for the major- and even-numbered gears on a as well as the need for high- ity of new vehicle sales. second shaft. Each shaft has its pressure hydraulics. However, the system produces an infinite The automatic transmission (AT) own clutch, and the gear on one number of engine/wheel speed market is split among several types shaft is disengaged at the same time that the gear on the other ratios, allowing the engine to in China: shaft is engaged. This design always run at optimal speed/ • Conventional ATs traditionally approaches the efficiency of an load points, thus maximizing use a torque converter and a MT and offers the potential for engine efficiency. set of planetary gear sets. Shift- smooth and quick shifts without • Automated Manual Transmis- ing gear ratios is accomplished torque interruption. Because a sions (AMTs) are manual trans- through the hydraulic selection vehicle with a DCT must start missions that employ an electro- of a specific planetary gear set. moving while engaging one mechanical clutch actuator to Although the efficiency of an MT clutch, manufacturers use either automatically complete the shift. is generally higher than that of a a wet hydraulic clutch (wet DCT) AMTs combine the efficiency of hydraulic AT, advances in torque or an accumulator and high- MTs with the convenience of ATs converter lockup and hydraulics pressure hydraulic (dry DCT) to as the gears shift automatically. have improved the efficiency of improve launch performance. AMTs have been widely used on ATs. As the number of gear ratios • Continuously variable transmis- commercial vehicles in Europe. increases to six or more, ATs sions (CVTs) conventionally use Unlike DCTs, AMTs use a single allow an engine to operate closer a belt or a chain to connect two gear shaft. 2 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION WORKING PAPER 2018-15 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: TRANSMISSION TECHNOLOGY Table 1 shows fuel-consumption Table 1 Projected benefits and costs of considered transmission technologies benefits and costs for different Fuel-consumption Direct manufacturing transmission technologies based on reduction cost (CNY*) estimates by the U.S. National High- U.S. U.S. China China way Traffic Safety Administration estimate estimatea estimateb estimateb (NHTSA), Environmental Protection (2025)a Relative to Agency (EPA), and the China Auto- 6-speed MT 2.0%–2.5% 2.0% 1107 1800 5-speed MT motive Technology and Research 5-speed AT 1.1%-1.6% 448 4-speed AT Center (CATARC). It includes estima- 6-speed AT 1.7%–2.2% -70 4-speed AT tions of different types of transmis- 8-speed AT 6.4%–7.8% 5.74% 231 5500 4-speed AT sions, aggressive shift logic, early -1126 (dry) torque converter lockup, and high- 6-speed DCT** 5.7%–8.1% 4-speed AT efficiency gearbox. -794 (wet) 4% 1700 -154 (dry) As Table 1 shows, DCTs tend to 8-speed DCT** 9.7%–12.6% 4-speed AT -179 (wet) exhibit higher cost-effectiveness CVT 6.0%–8.7% 3.75% — 1200 4-speed AT in both U.S. and Chinese estimates Aggressive shift as they generate significant benefit 5.1%–7.0% 141 No ASL logic(ASL) while costing less than a conventional Early torque No early torque 4-speed AT (4AT). MTs consume less 0.4%–0.5% 128 converter lockup converter lockup energy than automatics, but ATs High-efficiency No high-efficiency 4.3%–5.7% 1043 select the optimum gear ratio at all gearbox gerabox times. So switching from a manual to an automatic with more gear ratios— * Exchange rate between USD and CNY is 1:6.4 ** Fuel consumption reduction estimation includes impact of AMT particularly a DCT—can offset the a U.S. EPA and NHTSA, 2012 advantage of a conventional MT and b CATARC, 2017 lead to greater fuel efficiency overall. Others MT AT 3 Current status 2% 4AT 3% Most ATs and CVTs today have adopted torque converter lockup AT to reduce fuel consumption by low- 8AT 3% MT 33% ering the loss of power transfer 39% 5AT 9AT through the fluid inside the torque 6AT 25% 1% 1% converter and from slippage during CVT DCT rapid acceleration. Despite differ- DCT ent transmission control strategies, CVT 12% 5MT 33% 14% the lockup is usually triggered at 7DCT 9% higher speeds. At lower vehicle 6MT 6% CVT 14% 6DCT 2.3% speeds, torsional energy is harder to dampen, and it can create shak- Figure 3 Market penetration of transmission by type among passenger cars in 2017 ing or shuddering as it passes through the vehicle. Thus, early Atenza is mated with a 6-speed According to Table 1, ATs with torque converter lockup requires automatic transmission (6AT) with aggressive shift logic (ASL) could upgraded materials to withstand early torque converter lockup. This also significantly improve fuel effi- higher loads (Isenstadt, German, expands the lockup range from ciency compared with conventional Burd, and Greif, 2016). Only a few 64% on current 5ATs to 89% over ATs without ASL. ASL increases models enable lockup at lower the New European Drive Cycle efficiency through downspeeding, speeds. For example, the Mazda (NEDC) (Mazda, 2018). which enables earlier upshift—at WORKING PAPER 2018-15 INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION 3 FUEL-EFFICIENCY TECHNOLOGY TREND ASSESSMENT FOR LDVS IN CHINA: TRANSMISSION TECHNOLOGY lower rpm during acceleration—and Others AT DCT CVT MT Others shift optimization. This requires con- 2% 100% stant monitoring of all gear options and selecting the gear that puts the AT 80% 15% engine in the most efficient operat- 60% ing zone.