C OVER STORY Innovativ e Driv e C oncepts
The New 1.5-l Fourcylinder TSI Engine from Volkswagen The new Volkswagen four-cylinder TSI evo is a direct injection, turbocharged gasoline engine. The first application of the new 1.5-l TSI will be in the Volkswagen Golf as of mid-2017, with two power variants of 96 kW and 110 kW. Miller-cycle combustion and turbocharging combined with optimised valve timing and thermal management as well as extensive friction reduction, have led to consumption savings of about 10 % compared to the predecessor model.
Since its introduction in 2005, TSI engines have been global technology pioneers in the field of direct-injection turbocharged petrol engines. In addition to high customer satisfaction, the engines are characterized by excellent ratings in the trade press worldwide. With the market introduction of the evo R4 1.5-l TSI, the Volks wagen group has made further advances in the field of direct injection, turbocharged
A U T H OR S
Dr. techn. Wolfgang Demmelbauer-Ebner is Director of Gasoline Engine Development at Volkswagen in Wolfsburg (Germany).
Dipl.-Ing. Kai Persigehl is Leader of Technical Project Management of EA211 Gasoline Engines at Volkswagen in Wolfsburg (Germany).
–– integration into the Volkswagen Group’s A0 to B class vehicles –– robust engine configuration for global application –– flexfuel and CNG capable –– basis for hybrid applications –– early torque build-up and superior transient response characteristics versus competition. The first application of the new 1.5-l TSI will be in the Volkswagen Golf as of mid2017, with two power variants of 96 kW and 110 kW, FIGURE 1. The key technical data is presented in TABLE 1. A fundamental benefit for efficient production worldwide in the Group’s engine plants is in the carefully planned modularity of the EA211 toolkit and a reduced number of variants. In future, the EA211 evo toolkit will have two displacements for the MPI and TSI engine: 1.0 l and 1.5 l, FIGURE 2. EA211 EVO CONCEPT
Dipl.-Ing. Michael Görke is Subdivision Leader for Turbocharger Construction at Volkswagen in Wolfsburg (Germany).
Dipl.-Ing. Eike Werstat is Project Manager Gasoline Engines for EA211 R4 1.5-l-TSI evo at Volkswagen in Wolfsburg (Germany).
engines. The new four-cylinder TSI evo is based on the EA211 toolkit. To meet the demands for a lightweight, compact, efficient and cost-optimised engine, and taking into account tightening emissions legislation worldwide, the following targets were defined in the technical specification and implemented through the use of technical solutions: –– class-leading figures in customer consumption and CO2 emissions –– minimal friction across the entire map MTZ worldwide 02|2017
The 1.5-l evo, FIGURE 3, is based on the modern and compact EA211 toolkit. The high degree of functional integration as well as further measures for reducing friction and consumption are typical EA211 genes which have been further developed in the new concept. Proven technology has been retained and further optimised, including: –– all-aluminium engine with four valves per cylinder –– cylinder head with integrated exhaust manifold –– all outward-acting shaft seals are friction optimised –– zero-maintenance, low-friction timing belts –– valve drive via roller cam followers with friction-optimised grooved ball bearings on the drive end of the camshafts –– ACT (cylinder deactivation). The displacement of the EA211 1.5-l TSI evo has been increased to 1498 cm3 by lengthening the stroke from 80.0 to 85.9 mm. The bore of 74.5 mm remained unchanged. The stroke/bore ratio of 1.15 thus offers the optimum combination of charge motion and piston speed. The 110 kW engine has conventional valve timing and an wastegate exhaust turbocharger. The 96 kW variant starts with a Miller combustion process and variable turbine geometry. Careful configuration as a λ=1 concept means that both power variants offer consumption benefits across the entire engine map.
Technology synergies between the variants come from ACT cylinder deactivation, friction-optimised drives for crankshaft and valves, innovative thermal management, map-controlled oil feed, more precise timing management, the new chargeair cooling and the injection system with a maximum pressure of 350 bar. Many aspects of the engine management have likewise been reconceived. One particular innovation is the new fill control via the adjustable intake camshaft. The new EA211 TSI evo can achieve consumption benefits of more than 10 % in customer-relevant operation compared with the previous 1.4-l TSI (92 kW). CRANKCASE
The crankcase design is based on further improvements to the EA211 engine. Part count has been reduced taking into account cost-effective manufacturing. Key design features are: –– open-deck design in pressure die-cast AlSi9Cu3 –– torque-plate honing of the cylinder barrels –– high functional integration of media feed (oil, cooling water), ventilation and incorporation of external assemblies (oil cooler, ancillaries). The 96 kW evo variant features the proven cast-in iron cylinder liners. In the 110 kW engine, the liners in the aluminium crankcase are coated using the APS process (atmospheric plasma spray). Designed for ignition pressures of up to 135 bar and with web bores between the cylinders, it is prepared for further power increments. The use of fine-grain spray powder combines with optimised honing to create tiny lubrication pockets that guarantee the piston rings glide with very little friction and low wear. Configured as partial-flow ventilation, crankcase ventilation takes place almost entirely inside the engine. The blow-by gases are protected from oil splash as they travel from the engine block into the preliminary oil separator mounted on the crankcase. The separated oil is fed back into the oil sump below the oil level. The pre-cleaned gas is directed via a riser cast into the crankcase to the fine oil separator integrated into the ACT valve-gear module. When the turbocharger is active, the blow-by gases are fed from there into the turbocharger.
C OVER STORY Innovativ e Driv e C oncepts
FIGURE 1 Power and torque (© Volkswagen)
In naturally aspirated mode, the blow-by gases travel through a connection from the fine oil separator via a branch bore integrated into the cylinder head to the intake port, where they enter the combustion chamber. To ensure condensate discharge, even during frequent short journeys, negative pressure in the crankcase sucks fresh air through the engine during naturally aspirated operation from the clean-air side of the air filter via a non-return valve in the fine oil separator. Condensate released during engine warm-up is captured by the fresh air stream and fed into the combustion system via the route described above.
barrels. The piston pins are DLC coated, which also reduces friction and minimises wear. The flat, rotationally symmetrical piston crowns and valve pockets were adapted to the new combustion chamber geometry and the high compression ratio of ε=12.5. The flat piston crown design reduces piston weight and improves temperature distribution. CYLINDER HEAD
The cylinder head was fundamentally re-engineered for the EA211 TSI evo. An optimised water jacket and combustion chambers designed for optimum combustion were necessary for efficient execution of the TSI evo combustion process.
Cooling above the combustion chambers uses the cross-flow layout with a horizontal split. The integrated exhaust gas manifold (iEGM) in the cylinder head has been redesigned and optimised versus the 1.4-l TSI in respect of heat dissipation and to dethrottle the cooling system. The modified valve angle and high geometric compression ratio of 12.5:1 made the combustion chamber more compact and, in addition to higher charge motion, facilitated a combustion chamber without crevices on the piston crown. The objective was, with the aid of a comprehensive 3-D computation process, to achieve an optimum relationship between volume and surface and, through its geometric
The process of lengthening the stroke also involved making changes to the crankshaft. The proven EA211 production processes, including radius hardening for increased strength, were retained. To reduce frictional losses, the surfaces of the bearing journals on the crankshaft have an exceptionally smooth finish. The main bearing of the first cylinder has been polymer coated to meet the increased demands imposed during start/stop operation. The conrods are designed without bushes, with a finish-forged small end and a reinforced shaft to securely accommodate the higher loads. The cast pistons are designed for a maximum ignition pressure of 135 bar and a ring carrier is cast into the first groove. In developing the rings, the focus was on low friction and reduced particulate emissions taking into account the APS and cast iron cylinder
– Engine layout Valves per cylinder
1.5-l TSI (96 kW)
1.5-l TSI (110 kW)
Bore / stroke [mm]
74.5 / 85.9
74.5 / 85.9
Cylinder spacing [mm] Stroke / bore ratio Compression ratio Rated power [kW at rpm] Specific power [kW/l] Max. torque [Nm at rpm] Specific torque [Nm/l] Fuel [ROZ] Engine control Emissions standard Transmission
96 / 5000-6000
110 / 5000-6000
200 / 1400-4000
250 / 1500-3500
DQ200-7F / MQ200-6F
DQ200-7F / MQ250-6F
TABLE 1 Base engine data with output and consumption figures (© Volkswagen)
FIGURE 2 Reduction of displacement classes in the EA211 evo range (© Volkswagen)
design, to optimise spherical flame propagation, FIGURE 4. The measures implemented for this are: –– reduction in valve angle to 18.9° and 13.0° (exhaust/intake resp.) –– slight withdrawal of the intake valve for optimum flow of fresh air into the combustion chamber –– expansion of the intake-camshaft adjustment range without significantly deepening the valve pockets in the piston head –– flow directed across tangential combustion chamber shoulders –– flat piston head with a slight recess to aid charge motion and mixture formation –– slightly off-centre spark-plug position with the spark plug mounted upright for more robust ignition ensuring the flame front reaches the areas close to the cylinder walls at the same speed and thus avoiding knock clusters. Due to the very high exhaust tem peratures in the 110 kW variant, the exhaust valves are filled with sodium for cooling purposes.
–– exhaust pulse-generator wheel produced together with fixed cams from a single rough part, resulting in high dimensional accuracy –– toothed shafts made from 16MnCrS5 enabling optimised production processes –– use of stream finish for cams and camshaft bearings for maximum surface quality and friction reduction –– laser hardened functional surfaces on the 42CrMoS4 cams guaranteeing
lower distortion with the deletion of one process step. The valve gear module differs between the two variants of the 1.5-l TSI only in the cam geometry on the intake side – as a result of the new TSI evo combustion cycle. The compact module also incorporates the interface for the actuators, high-pressure pump and fine oil separator, with its high degree of integration delivering low costs.
ACT VALVE GEAR MODULE
The ACT cylinder deactivation has been improved and is now entering high-volume production with the TSI evo. Under low to medium load, it closes the intake and exhaust valves on cylinders two and three, while deactivating injection. Optimisation of the ACT valve gear module has been successfully executed in the following areas: –– one-piece sliding cam pieces and cams mounted directly onto toothing MTZ worldwide 02|2017
FIGURE 3 Engine modules from the EA211 evo engine family (© Volkswagen)
C OVER STORY Innovativ e Driv e C oncepts
NEW VALVE TIMING MANAGEMENT
Precise fill logging plays a central role in the TSI evo combustion process. The reduction of geometric tolerances for valve timing was realised through a new, high-resolution 12+1 camshaft pulse-generator wheel, press fitted with zero play onto the toothing. Valve timing is also defined with zero play by means of a flat point on the intake and exhaust camshafts. The angle deviations of the camshafts and camshaft pulse-generator wheels on the ACT module are recorded against standard during the production process and laser-etched onto the cylinder head cover as a data matrix code (DMC). The corrective values calculated are entered into the control unit and taken into account during fill calculation. FIGURE 5 illustrates the determination of electrical and geo metric valve-timing deviations for combustion optimisation in individual engines with the aid of four measures. The intake camshaft is adjusted via a high-speed hydraulic camshaft actuator with a central control valve. The exhaust camshaft is configured hydraulically in the conventional manner with a decentral control valve. ENGINE COOLING
The combination of high-temperature and low-temperature circuits has been carried over from the EA211 toolkit. An electrical coolant pump with low
FIGURE 4 EA211 1.5-l TSI evo intake port and combustion chamber (© Volkswagen)
energy requirements delivers chargeair and EGT cooling on demand within the low-temperature circuit, even during run-on after the engine has been switched off. The core of the high-temperature circuit is the all-new map-based cooling module, FIGURE 6. The combination of a coolant pump driven mechanically via toothed belt by the camshaft and a modular, mechatronic coolant regulator delivers new scope for innovative thermal management in an extremely small package. The main new feature is the e-actuator positioned directly
on the housing, which provides direct and infinitely variable adjustment of the upper rotary valve on command from the engine control unit. This upper rotary valve drives the shut-off valve via a gear segment to achieve “standing water”. These kinematics and the associated configuration of the necessary intake and exhaust channels and ports thus enable sequential, fast, on-demand and accurate regulation of diverse coolant flows, leading to the following benefits: –– improved cold-start characteristics due to standing water
FIGURE 5 Measures for increasing valve timing accuracy (© Volkswagen)
–– friction reduction –– rapid heating of the vehicle interior –– temperature management for reduced knocking tendency. CHARGE-AIR COOLING
The cooler for indirect charge-air cooling is positioned between the pressure pipe and throttle valve. This layout reduces the temperature level at the throttle valve and sensors. Resizing the charge-air cooler and changing its location delivers increased cooler performance, while maintaining a very compact package. The chargeair temperature has been reduced to 15 K above ambient.
FIGURE 6 Map-based cooling module (© Volkswagen)
The 1.5-l TSI evo marks the first application of the generation 4.0 Volks wagen direct injection (DI) system. In view of the strong influence of rail pressure on the spray pattern, a hole-by-hole five-hole spray pattern was developed for optimum interaction of air and fuel. Mixture formation has been improved in combination with the increase in fuel pressure to 350 bar and the expansion of multiple injection to as many as five injections per combustion cycle. The generation 4.0 injection system features the following improvements: –– reduced droplet size –– increased injection pulse –– optimised volume spread with reduced tolerances –– precision minute-volume measurement for low load and multiple injection –– short injection duration for optimum mixture formation under full load and rated power.
THE TSI EVO COMBUSTION PROCESS
Four central development targets were consistently pursued for the TSI evo combustion process: –– increase in the geometric compression ratio for greater efficiency in customer-relevant operation –– reduction of final compression temperature through early intake valve closing (EIVC) and associated expansion cooling in the intake tract, FIGURE 7 –– optimisation of charge motion for rapid flame propagation to
reduce knocking tendency under high specific loads –– increased charge density through efficient exhaust gas turbocharging. CHARGE MOTION
Due to the shorter intake event in the Miller cycle and to achieve sufficient charge motion even at low revs, there is a need for the design of the intake port, combustion chamber masking and combustion chamber geometry to be optimised in detail and relative to one another. A high-tumble intake port was developed for the EA211 TSI evo. Combustion chamber masking is used to prevent tumble flow from breaking down when valve lift is small during early intake valve closing. A consistently high tumble motion is generated as of around just 1 mm valve lift, leading to very stable charge motion through to ignition top dead centre, FIGURE 8. TURBOCHARGING
FIGURE 7 Valve timing for the TSI evo combustion process (© Volkswagen) MTZ worldwide 02|2017
The 110 kW variant of the EA211 TSI evo is configured for conventional valve timing and a mono-scroll wastegate EGT, while the 96 kW variant of the TSI evo combustion process – a first in high-vol-
C OVER STORY Innovativ e Driv e C oncepts
FIGURE 8 Flow values for the EA211 TSI evo with (left) and without masking (right) (© Volkswagen)
ume petrol engines – was developed using variable turbine geometry (VTG), FIGURE 9. Around low-end torque, VTG enables high accumulation of exhaust gases even when exhaust mass flow is low. This means that maximum torque is already available as of 1400 rpm. The high charge-pressure requirement of up to 1.3 bar around rated power can be generated with moderate exhaust back pressure. This results in balanced or even positive scavenging across a broad load and rev range, which enables low residual gas content, early centre-of-gravity position and efficient engine operation, particularly in the customer-relevant operating range. The turbine and compressor have been optimised for low-end torque. The turbine’s moment of inertia was
FIGURE 9 Cut-away view of turbocharger with VTG (© Volkswagen)
also reduced by decreasing rotor diameter. In combination with a friction-optimised water-cooled bearing design, torque build-up at 1500 rpm was accelerated by 35 % compared with the 1.4-l TSI with 92 kW, FIGURE 9. The TSI evo combustion process permits an air ratio of λ =1 with a maximum exhaust gas temperature of 880 °C across the entire map. Despite the strong synergies with a diesel turbocharging concept, the VTG was systematically adapted to the fundamental requirements of a petrol engine. Thus, play and clearances were reconfigured and material adaptations made. The conventional EGT with wastegate and electrical actuator is conceived for exhaust gas temperatures of up to 1050 °C, enabling λ=1 operation at all times here, too.
With the EA211 TSI evo, Volkswagen is once again setting a milestone in direct-injection, turbocharged petrol engines. Through systematic imple mentation of the Miller combustion cycle in a TSI engine with VTG EGT and in combination with innovations in valve timing and thermal management as well as far-reaching friction reduction, the EA211 TSI evo achieves considerable consumption benefits in customer-relevant operation. At the same time, the engine delivers excellent responsiveness that provides classic TSI driving fun and is unique in its displacement class. REFERENCES  Eichler, F.; Demmelbauer-Ebner, W.; Theobald, J.; Stiebels, B.; Hoffmeyer, H.; Kreft, M.: The New EA211 TSI ® evo from Volkswagen. 37 th International Vienna Motor Symposium, 2016  Eichler, F.; Demmelbauer-Ebner, W.; Persigehl, K.; Wendt, W.: The 1,0l 3-cylinder TSI-engine in Volkswagen’s modular petrol engine system. In: MTZworldwide 75 (2014), No. 11, pp. 18-23  Demmelbauer-Ebner, W.; Middendorf, H.; Birkigt, A.; Ganzer, M.; Hagelstein, D.; Persigehl, K.: EA211 TSI ® evo – The New four-cylinder Petrol Engines from Volkswagen. 25 th Aachen Colloquium, 2016
THANKS The authors would like to thank Dr. Jörg Theobald, Dr. Dirk Hagelstein, Dipl.-Ing. Steffen Jüstel, Dr. Hendrik Hoffmeyer and Dipl.-Ing. Sven Birnbaum.
FIGURE 10 Comparison of torque build-up between EA211 and EA211 TSI evo (© Volkswagen)
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