Vienna_14_VW_1L_I3_TSI_Helbing_e

Dipl.-Ing. Friedrich Eichler, Dr.-Ing. Hermann Middendorf, Dipl.-Ing. Carsten Helbing, Dipl.-Ing. Lars Hentschel, Dipl.-Ing. Jörg Scherf, Dipl.-Ing. Wolfram WendtVolkswagen AG, WolfsburgThe New 1.0l 3-Cylinder TSI®AbstractWithin the scope of the systematic ongoing development of Volkswagen engines in respect of consumption, emissions and driving fun, the 3-cylinder TSI® engine is the next step in the evolution of the EA211 engine family to enter series production in A0 and A-class vehicles. The modular construction of the EA211 engine family delivers the conceptual basis for efficient and rapid implementation of the adaptations necessary for the I3 TSI®engine, thus enabling a short development time. The developments made in the charge cycle and injection components of the I3 TSI®compared with the 4-cylinder unit form the basis of a more efficient combustion process with faster energy conversion.Within the EA211 engine family, the new 3-cylinder TSI®with 1.0l displacement represents the next systematic step in downsizing. Like the well-known, highly efficient and dynamic 4-cylinder engines in this family, the 3-cylinder TSI® combines low exhaust emissions with low fuel consumption without any restriction in driving fun.1. IntroductionAt the end of 2011, Volkswagen introduced the first engine from the new EA211 range – the 3-cylinder MPI in the up!. With a displacement of 999cm3and power output spanning from 44 to 55 kW, the 1.0l MPI is the base unit of this modularly conceived engine family. It is notable for its low internal friction, light weight and compact dimensions.With the 1.0l TSI®, which will be used initially in the Polo and the Golf, Volkswagen is expanding its existing line-up of 3-cylinder MPI and 4-cylinder TSI®engines. With turbocharging and direct injection, the 3-cylinder delivers up to 85 kW and offers a maximum torque of up to 200 Nm. This enables the 1.0l TSI®to provide good performance combined with extremely low fuel consumption. The Polo BlueMotion and Golf BlueMotion, Volkswagen’s first BlueMotion models with spark-ignition engines, emit less than 100 grams of CO2 per kilometre.With the new EA211 1.0l TSI®, Volkswagen is consistently and continuously pushing forward with its downsizing strategy. By adopting the modular approach, its engineering concept enables cost-efficient production at the group’s factories worldwide. This is a major benefit, particularly in the face of growing global competition in the A0 and A-class vehicle segments.Fig. 1 Power classes and platforms2. The EA211Range of Spark-Ignition EnginesThe EA211 engine range encompasses power units with three and four cylinders, notable in particular for their lightweight and compact construction. Displacement spans from 1.0 to 1.6 litres. The common cylinder spacing of 82.0 mm is used for three different bores. The new 1.0l TSI®(fig.2) takes its bore of 74.5 mm and its stroke of 76.4 mm from the 1.0l MPI.The most important design commonalities among the EA211 engines are:- the crankcase made from pressure die-cast aluminium with cast-in grey-iron liners,- weight-reduced crankshaft, pistons and conrods,- optimised main and conrod bearing diameter for reduced friction,- dual-circuit cooling for crankcase and cylinder head,- exhaust manifold integrated into the cylinder head,- intake module with integrated intercooler,- valve-gear module for operating the four valves per cylinder,- oil-sump module with integrated ancillary mounts,- toothed-belt drive for the camshafts with phase adjusters- and compact layout of the ancillaries without separate mounts.Fig. 2 Exploded view of 1.0l TSI®3. Structural Design3.1 CrankcaseThe crankcase (fig. 3) features an “open-deck” construction and is made from aluminium using the pressure die-casting process. Its low weight of just 15 kg forms the basis for the low overall weight of the 1.0i TSI®. Its weight is thus ten kilograms less than that of a 4-cylinder engine with a comparable output.The crankcase incorporates three cast-in cylinder liners made from GJL 250 grey cast iron and fluid-blast-honed in four stages. A lens lapping process is used to avoid cylinder-bore distortion. The use of grey-cast liners ensures optimum heat transfer. It raises the surface area in contact with the surrounding aluminium, resulting in better clamping. This configuration assures engine operation over the life of the vehicle with all types of fuel available worldwide.Further technical features of the crankcase include the cast-in channels for compressed oil supply, oil return and ventilation. The oil cooler is supplied with coolant via dedicated channels in the crankcase. Its design permits cost-effective manufacturing due to a reduction in the number of individual parts and machining requirements. However, it calls for a very high standard of production quality in the raw casting.Fig. 3 CrankcaseCrankcase ventilation (fig. 4) is in the form of block ventilation and is integrated within the engine. The system is incredibly robust, as external hose connections and transfer points are avoided almost entirely.Blow-by gases are extracted inside the cylinder case, with one coarse and one fine separator removing the oil from the gas in the separation chamber. The oil is returned to the oil sump beneath the oil level. The gas passes via a continuous riser in the crankcase through the cylinder head and the cover module into the discharge point at the turbocharger, where the pressure regulating valve is located. This gas management inside the engine guarantees operational integrity, even at low ambienttemperatures and high blow-by rates. In naturally-aspirated operation, the blow-by gases travel via a hose from the separator casing via a non-return valve integrated into the intake manifold directly into the induction tract.To ensure removal of condensate, even in the case of frequent short-distance driving, the low relative pressure in the crankcase enables fresh air to be continuously sucked through the engine from the clean-air side of the air filter via a non-return valve in the cylinder-head cover. Crankcase gases that escape during engine warm-up are captured by the fresh-air flow and fed into the engine through the oil separator for combustion.Fig. 4 PCV system3.2 Crankshaft DriveThe crankshaft drive (fig. 5) is particularly notable for low moving masses and minimal friction. The forged conrods and aluminium pistons are so weight optimised that the 1.0 TSI® does not a require balancer shaft. Mass balancing stands at 100% for rotating masses and at 50% for oscillating masses. Weight-reducing bores in the crank pins reduce the weight of the crankshaft by around 6%. Four counterweights reduce internal forces in the crankshaft and therefore the load exerted on the main bearing.The piston crowns have shallow recesses. This design leads to low weight and homogenous temperatures at the piston crown. The arrangement of piston rings is friction optimised and adapted to the pressures in the TSI engine. In laying out the rings, particular attention was paid to their form-matching capability.For the first time at Volkswagen, the conrod small end was designed for the use of a DLC-coated piston pin and has no bushing. The surface of the small end is smoothed by a rolling process. The big end has a slim design due to the comparatively low forces exerted. The geometry, which serves to transmit the ignition pressures, has a more robust design.The small dimensions of the main and big-end bearings make a major contribution to the low friction of the 1.0l TSI®. The design of the crankshaft webs has been optimised for maximum stiffness, in combination with targeted transverse bracing at the torsional-vibration damper and the single-mass flywheel opposite it.Fig. 5 Crankshaft drive3.3 Cylinder HeadThe cylinder head (fig. 6) of the 1.0l TSI®is manufactured using the rollover die-casting process. The production process guarantees a particularly high structural quality featuring heat-treated AlSi10Mg(Cu) alloy. Four valves per cylinder are arranged at an angle of 21° (intake) and 22.4° (exhaust) and actuated via roller cam followers. The valve-stem diameter is 5 mm. The low mass increases the dynamics of the valve gear, while friction is reduced. The valve-seat angle is 90° on the intake side and 120° on the exhaust side. This improves wear resistance when running on alternative fuels.As for all engines in the EA211 range, the 1.0l TSI®, too, has the exhaust manifold integrated into the cylinder head, where it is surrounded by its own water jacket. This has the effect of significantly reducing the exhaust temperature under high loads and allows the mixture enrichment necessary with conventional manifold concepts to be reduced to a minimum.Compared with conventional external manifolds, the flow paths of the exhaust gases are considerably shorter in the integrated exhaust manifold (iEGM). This leads to very low transient heat loss through the walls. The integration of the exhaust manifold into the cylinder head also leads to faster warm-up of the coolant due to the additional heat input following cold start. This reduces engine friction during the warm-up phase and the vehicle interior heats up faster.Fig. 6 Cylinder head3.4 Integrated Valve-Gear ModuleThe cylinder-head cover with the integrated valve-gear module used in the 1.0l TSI®is a further module from the EA211 matrix (fig. 7). The cylinder-head cover is made from AlSi9Cu3 pressure-die-cast aluminium alloy and incorporates the camshaft bearing mounts. With a low weight, it enables a very stiff layout of the camshaft bearing mounts, which has a positive impact on the dynamics of the valve gear.The production process was developed in-house by Volkswagen. First, the finish-ground cams and the pulse-generator wheel are heated slightly and positioned inside the cover module. The shafts, which have been super-cooled in a bath of liquid nitrogen to shrink them, are then inserted through the bearing mounts in the cover and the warmed cams. In the same manufacturing step, the drive cam for the high-pressure fuel pump is mounted at the end of the intake camshaft and the toothed-belt pulley to the drive for the coolant pump. Once the temperatures have normalised, the two camshafts are permanently mounted in the valve-gear module.At the end of the module assembly process, two grooved ball bearings are pressed onto the control side. Thus, the highly loaded first camshaft bearing is designed forminimal friction, while also providing axial guidance for the shafts. The remaining camshaft bearings are plain bearings with a diameter of 24 mm. This bearing diameter is the same as the tube diameter of the camshafts and designed for minimum friction.Fig. 7 Integrated valve-gear module3.5 Drive for Timing Gear and AncillariesThe 1.0 TSI®is equipped with intake and exhaust camshaft adjustment using a hydraulic vane-type actuator. The adjustment range is 50° of crankshaft angle on the intake side and 40° on the exhaust side. This gives the 3-cylinder a broad timing spread and enables powerful torque build-up at low engine speeds, as well as high power output at high engine speeds.The camshafts are driven by the crankshaft via a 20 mm toothed belt. The toothed-belt drive generates around 30 percent less friction than a comparable chain drive. Designed to last the lifetime of the vehicle, the toothed belt runs on a permanent tensioner pulley. A cover protects the toothed-belt drive from dust and grime.In order to avoid the resonance typically generated by the timing-belt drive of a 3-cylinder engine, the drive gears of the two camshaft adjusters have a slightly trigonal shape. These local changes to the gear ratio eliminate almost entirely from the toothed-belt drive the force peaks and deviations in angle of rotation that are specific to 3-cylinder engines. This means that tensioning force can be decreased significantly, lowering span forces and reducing the load on the toothed-belt tensioner. The harmonised forces in the toothed-belt drive lead to less friction, lower fuel consumption and greater system stability.For packaging and weight reasons, the ancillary systems of the 1.0l TSI®are mounted directly onto the engine without any additional bracketry. The associatedthreaded fixing points are located on the crankcase, oil sump and front sealing flange. Both ancillary-drive variants – the “basic drive” and “air-conditioning drive” – are driven by a six-groove belt.3.6 Cooling CircuitCooling of the 1.0l TSI®(fig. 8) is via a high-temperature and a low-temperature circuit. The low-temperature circuit is driven by an electric coolant pump and can be controlled fully flexibly on demand. Incorporated into this circuit are the intercooler and the turbocharger. This enables circulation of coolant to be maintained after the engine is switched off when warm.The base engine is supplied via the high-temperature circuit by a mechanically driven pump integrated into the coolant-pump module with the coolant-temperature regulator. The pump/regulator module is mounted to the cylinder head on the transmission side. It incorporates two wax thermostats for cooling the crankcase and cylinder head in separate circuits. Drive for the coolant-pump module is via a short, 10 mm toothed belt from the exhaust camshaft. This toothed-belt drive, too, is designed to last the lifetime of the vehicle.The coolant temperature in the cylinder head is set via the thermostat to 87° C in order to achieve the best compromise between friction reduction and efficiency-optimising ignition or minimum knock tendency. The cylinder-head circuit also supplies the interior heating system. Inside the crankcase, the coolant remains stationary during the warm-up phase, until it reaches a temperature of 105° C. The thermal management system significantly shortens the warm-up phase, which is the phase with higher internal frictionOn leaving the water pump, the coolant flows through a connecting channel in the cylinder head into the water gallery in the crankcase. From there, part of the flow is directed through the head gasket into the cylinder head, where it provides cross-flow cooling of the combustion chambers. The water gallery in the integrated exhaust manifold is in the shape of a pair of glasses to provide optimum cooling around the manifold flange area. Both coolant sub-streams come together again upstream of the thermostat module and flow into the mixing chamber ahead of the main thermostat.In the cylinder casing, the depth of the water jacket for cooling the cylinder liners is an average of 40 mm. The floor of the water jacket has a wave design in order to spread so-called butterfly distortion across a larger area, thus dissipating it.Fig. 8 Cooling circuit3.7 Oil CircuitThe friction-optimised base engine permits a similarly reduced sizing of the oil circuit in the 1.0l TSI®. Consequently, the oil pump used has a lower feed rate and less internal friction. The vane pump is driven directly from the crankshaft, sucking the oil from the oil sump through a plastic snorkel.For the first time, Volkswagen is using an infinitely variable, map-controlled oil pump. An electrically controlled proportional valve sets the pressure, which can be anywhere between 1.4 and 4.5 bar depending on requirements. The necessary information is delivered by the oil sensor, which is located in the main oil gallery.Inside the crankcase, the compressed oil travels to the oil filter, which is fixed to the oil sump and, from there, to the main oil gallery. Here, it splits between the main and big-end bearings and, via a riser on the timing-gear side, into the cylinder head. Two galleries supply the roller cam followers with oil. The oil flows through side bores to the camshaft bearings and the camshaft-adjuster valves. Piston cooling is designed so that oil is sprayed onto the piston crown only at higher pressure levels. At lower pressures, the nozzles remain closed.The single-piece oil sump on the 1.0l TSI® is an aluminium pressure die casting and is both extremely lightweight and stiff. Carefully positioned ribs improve its acoustic characteristics. The supply lines to the plate-type oil cooler are fully integrated intothe crankcase.Fig. 9 Oil circuit3.8 TurbochargerIn developing the turbocharger (fig. 9) for the new 1.0l TSI®, the focus was on low-end torque and good transient characteristics with full torque curves. The turbocharger with its single-scroll turbine has been carefully adapted for the exhaust manifold integrated into the cylinder head with its reduced exhaust-gas enthalpy. The rotor is notable for its compact dimensions and resulting low moments of inertia paired with a high degree of efficiency.The 1.0l TSI® with 85 kW realises a maximum torque of 200 Nm, available between 2,000 and 3,500 rpm. The turbocharger casing is made from heat-resistant austenitic cast steel and enables exhaust-gas temperatures of up to 1,050° C. The turbine wheel is made from a nickel-based alloy.At 1.4 bar (relative), the charge pressure in the 1.0l TSI® is the highest so far in the EA211 engine family. Charge-pressure control is handled by a newly developed, electric waste-gate actuator, which can be actuated at any time regardless of the prevailing charge pressure. This means that, even at low revs, it is possible to guarantee closure of the waste gate and a smooth build up of torque. Under partial load, exhaust-gas back pressure can be lowered by fully opening the waste gate to reduce charge-cycle losses. Dual camshaft adjustment facilitates a charge cycle purged with fresh air and improves dynamics.Integrated into the intake tract on the intake side of the turbocharger are broadbandreduce pulsation sounds in the transition to trailing-throttle operation, known as trailing-throttle growl. Together with the electric waste-gate actuator and the acoustic optimisation of the air filter, there was no requirement for an overrun valve.Fig. 10 Turbocharger3.9 Charge-Air CoolingThe intake module (fig. 10) of the 1.0l TSI® is conceptually identical to the module on the well-known 4-cylinder TSI® engines of the EA211 range. It incorporates a water-cooled intercooler. Compared with familiar air-to-air concepts, the charge-air volume between the turbocharger and the combustion chambers can be reduced significantly, thereby greatly accelerating the build up of charge pressure.In designing the intake module, the focus was on the efficiency of cooling and a uniform distribution of cylinder fill. The module is designed to be extremely stiff, in order to guarantee unobtrusive acoustic characteristics. The intake manifold is made from injection-moulded polymer. Screwed into it and sealed all round is the aluminium intercooler fitted with an extremely stiff top plate in a sandwich construction. In combination with further optimised screw connections, it is designed to deal with the high pressure pulses exerted on it in addition to the vibration of the engine as a whole.Fig. 11 Intercooler integrated into the intake manifold3.10 Fuel SystemThe 1.0l TSI® is the first engine in the EA211 range to feature high-pressure injection (fig. 11) with a maximum injection pressure of 250 bar. Compared with the I4 TSI®, the high-pressure fuel pump has been adapted to handle the increased system pressure. The stainless steel rail has been optimised with a greater wall thicknessand reinforced bracing.Fig. 12 Fuel system4. Combustion Process4.1 Charge Motion and TumbleThe 3-cylinder TSI® features a further development of the TSI® tumble channel from the 1.4l TSI®. Based on the series-production channel from the 4-cylinder TSI®engines, the AMO (Automatic Model Optimization) development tool from Volkswagen Group Research facilitated a further increase in the rate of tumble with no significant detriment to the flow coefficient. Figure 12 shows the envelope of the calculated channel variants generated from the steady-state and unsteady-state CFD analysis. On the Pareto front are the base channel and the target channel for the I3 TSI®.Fig. 13 Envelope of channel variantsFigure 13 shows the increased flow rate of the new tumble channel. Particular attention was paid to the prevention of swirl elements not on the main tumble axis (omega tumble). This guarantees symmetrical spray capture by the in-flowing air, a higher degree of homogenisation and a high level of turbulent kinetic energy at ignition OT.Fig. 14 Tumble channel flow rate4.2 Mixture Formation and InjectionHigh-pressure injection occurs via 5-hole magnetic injectors. Using CFD, the spray target was optimised for the new tumble channel in respect of penetration, component wetting and homogenisation. Validation of the calculations was systematically assured on the complete engine and on the transparent engine with the support of optical measurement technology. The high injection pressure of up to 250 bar enables a balanced injection layout when it comes to micro-dosing and optimum injection duration at rated power. Through the use of multiple injections, with up to three injections under partial and full load, as well as catalyst heating, it was possible to further reduce emissions and fuel carry-over into the oil, while increasing combustion stability at the same time. The tolerances for these injection quantities are reduced to a minimum via special functions in the engine control unit.Fig. 15 High-pressure injection4.3 Combustion Chamber and CombustionThe compact combustion chamber design was carried over from the existing 1.4 TSI®platform. The edge-free pentroof combustion chamber and the lightly formed central piston recess create the basis for even flame propagation across the combustion chamber starting from a central plasma core. At 240° of crank angle, the ignition interval for the 3-cylinder TSI®demonstrates considerable benefits under full load compared with a 4-cylinder engine when it comes to interference of exhaust gas pulses. This enables the use of a broader range of opening times for the intake and exhaust camshafts, delivering improved charge cycling with minimum residual gas. Together with high charge motion and optimum mixture preparation, the specific timing layout of the 3-cylinder enables a compression ratio that is very high for a turbocharged engine at ε=10.5, while able to run on ROZ95 and with a power output of 85 kW/l.4.4 IgnitionThe single-spark ignition coils are located directly above the spark plugs and fixed to the cylinder-head cover. Increased magnetic efficiency of the plug-top coils raises their overall efficiency and also covers higher ignition voltages as required. The M12 spark plugs are precisely aligned. This was facilitated by the carefully balanced interaction between the thread chamfer in the cylinder head and the corresponding position of the side electrode, based on the thread of the spark plug. This positioning enables optimum excursion of the spark in the combustible mixture and the formation of a stable flame core. Furthermore, it achieves reliable cooling of the side electrode by the incoming fresh air during charge cycling. The reduced material temperature of the spark plug increases its robustness in the face of reaction mechanisms that can lead to combustion anomalies. A new ceramic material from NGK also raises impact resistance by around 15%. An extended isolator above the hexagon led to a further increase in arcing resistance, while retaining the same overall spark-plug length.5. Performance, Consumption and EmissionsThe new 3-cylinder engine from the EA211 range combines the typical TSI® virtues of efficiency and driving fun. In the Polo, it produces 81 kW and, in the Golf, 85 kW, with rated power available from 5,000 to 5,500 rpm in each. In both cases, the maximum torque is a constant 200 Nm between 2,000 and 3,500 rpm. 175 Nm are available as of just 1,500 Nm.Volkswagen will use the new 3-cylinder TSI® in vehicles from the A0 and A classes. Its high torque of 200 Nm enables a fuel-efficient, long layout of gear ratios, with a simultaneous increase in performance. In the Golf BlueMotion, the 1.0 TSI® will emit just 99 grams of CO2per kilometre, in the Polo BlueMotion just 92 grams of CO2. These two variants are the first Volkswagen BlueMotion models with petrol engines.Fig. 16 Performance data 1.0l TSI® in the Polo BlueMotion and Golf BlueMotionFig. 17 Competitor comparison of elasticity figures6. OutlookThe 3-cylinder TSI® with 1.0l displacement represents the new entry-level engine in Volkswagen’s TSI®family, and is conceived for use worldwide. Future applications for use in markets with lower fuel quality were taken into account during development. The necessary hardware modifications and components for running on ethanol and CNG are already incorporated into the concept for the new 3-cylinder TSI®. Consequently, the new 3-cylinder engine is already equipped with all the necessary technologies for a broad range of uses across the most diverse vehicle platforms and markets.Its compact construction and outstanding torque and power, combined with its exceptionally low CO2emissions figures represent another successful milestone in the further development of the EA211 engine family.Literature[1] Dr.-Ing. Jens Hadler, Dr.-Ing. Rüdiger Szengel, Dipl.-Ing. Uwe Kirsch, Dipl.-Ing. Norbert Becker, Dr.-Ing. Gerhard Eggers, Dipl.-Ing. Manfred Friese, Dipl.-Ing. Kai Persigehl, Volkswagen AG, Wolfsburg“The New 1.0l 3-Cylinder MPI Engine for the up!”, 20th Aachen ColloquiumVehicle and Engine Technology 2011[2] Prof. Dr.-Ing. Jens Hadler, Dr.-Ing. Heinz-Jakob Neußer, Dr.-Ing. RüdigerSzengel, Dr.-Ing. Hermann Middendorf, Dr.-Ing. Jörg Theobald, Dipl.-Ing. Niels Möller, Volkswagen AG, Wolfsburg“The New TSI”, 33rd International Vienna Engine Symposium 2012。