the new four-cylinder engine series from the cooperation between bmw and psa

6
You will find the figures mentioned in this article in the German issue of MTZ 07-08I2007 beginning on page 526. Die neue Vierzylinder-Motorenbaureihe aus der Kooperation von BMW/PSA-Kooperation The New Four-Cylinder Engine Series from the Cooperation between BMW and PSA Authors: Frank Kessler, Gerrit Kiesgen, Johann Schopp and Marcus Bollig With BMW providing leadership, the BMW Group and PSA have developed a new series of small petrol engines. For both partners, the new engines are a significant improvement in the task of reducing CO 2 emissions. A fully variable valve drive and the combination of direct injection with turbocharging by means of a twin scroll turbocharger are being used for the first time in this vehicle class. A volume-controlled oil pump, a mechanical on-demand water pump and consistent frictional power optimisation make a considerable contribution to- wards achieving a generous torque characteristic and good specific fuel consumption in all variants. 1 Introduction The new engine series was designed on a uniform basic concept with a displacement range from 1.4 litres to 1.6 litres. Four dif- ferent power output levels from 70 kW to 128 kW have been derived. A total of approximately one million en- gines per year will be used in the various vehicle platforms for both Mini and Peuge- ot Citroën cars. Two technological variants have been developed in order to achieve the shared goals of both partners in the cooperation, Tables 1 and 2. The two lower power output levels, 70 kW and 88 kW, are equipped with two cam- shaft phase adjusters (double Vanos) and fully variable valve lift. The two upper power output levels, 110 kW and 128 kW, have in- take Vanos, direct injection ( =1) with a side injector position and turbocharging (twin scroll). The 110 kW variant is only used in PSA vehicles. Development was the respon- sibility of BMW in the Research and Innova- tion Centre in Munich. The engines for the Peugeot Citroën ve- hicles are produced by the PSA engine plant Française de Mécanique in Douvrin (France). 2 MTZ 07-08I2007 Volume 68 2

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Page 1: The new four-cylinder engine series from the cooperation between BMW and PSA

You will find the figures mentioned in this article in the German issue of MTZ 07-08I2007 beginning on page 526.

Die neue Vierzylinder-Motorenbaureihe aus der

Kooperation von BMW/PSA-Kooperation

The New Four-Cylinder Engine

Series from the Cooperation

between BMW and PSA

Authors:Frank Kessler, Gerrit Kiesgen, Johann Schopp and Marcus Bollig

With BMW providing leadership, the BMW Group and PSA have developed a new series of small petrol engines. For both partners, the new engines are a significant improvement in the task of reducing CO2 emissions. A fully variable valve drive and the combination of direct injection with turbocharging by means of a twin scroll turbocharger are being used for the first time in this vehicle class. A volume-controlled oil pump, a mechanical on-demand water pump and consistent frictional power optimisation make a considerable contribution to-wards achieving a generous torque characteristic and good specific fuel consumption in all variants.

1 Introduction

The new engine series was designed on a uniform basic concept with a displacement range from 1.4 litres to 1.6 litres. Four dif-ferent power output levels from 70 kW to 128 kW have been derived.

A total of approximately one million en-gines per year will be used in the various vehicle platforms for both Mini and Peuge-ot Citroën cars.

Two technological variants have been developed in order to achieve the shared goals of both partners in the cooperation, Tables 1 and 2.

The two lower power output levels, 70 kW and 88 kW, are equipped with two cam-shaft phase adjusters (double Vanos) and fully variable valve lift. The two upper power output levels, 110 kW and 128 kW, have in-take Vanos, direct injection ( =1) with a side injector position and turbocharging (twin scroll). The 110 kW variant is only used in PSA vehicles. Development was the respon-sibility of BMW in the Research and Innova-tion Centre in Munich.

The engines for the Peugeot Citroën ve-hicles are produced by the PSA engine plant Française de Mécanique in Douvrin (France).

2 MTZ 07-08I2007 Volume 68 2

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The engines for the Mini vehicles are produced by BMW’s Hams Hall engine plant in Warwickshire (England).

The targets for the engine series were extremely ambitious: the engines were to set the standard in the automotive indus-try with regard to fuel consumption, torque characteristics and manufacturing costs.

In addition, the individual variants had to be designed to be compact enough to support installation in more than 60 differ-ent vehicles from the various platforms without changes.

The engine family has been developed for vehicles to be sold in all worldwide mar-kets, and in some cases additional meas-ures have been introduced to satisfy the le-gal requirements of some countries.

2 Technical Characteristics

The technical concept of the engine series includes features of modern engine manu-facturing that, in their totality, create an engine that is unique in this vehicle seg-ment, Figure 1.

Despite this variety of technologies and a broad range of output levels offered, an extensive common part concept has been maintained, Figure 2. This has been achieved without affecting the achievement of func-tional targets.

A reduction in the number of variants, both at the component level and also in complete engines, was an important issue for achieving the manufacturing cost ob-jectives.

3 Design

3.1 Crankcase with BedplateThe crankcase/bedplate unit was designed so that it can be machined with an inte-grated cast timing case on a shared produc-tion line with an existing 1.6-litre diesel engine.

The die cast crankcase is from the mate-rial AlSi9Cu3 with cast-in grey cast-iron lin-ers that extend to the upper edge of the crankcase, Figure 3. Positive engagement of the liners is achieved by means of specially developed grooving that ensures good heat dissipation and ensures a very small amount of deformation during running. Coolant flow is optimised for longitudinal flow.

The design satisfies all requirements with regard to efficient manufacturing (minimum wall thicknesses, no casting ac-cumulations, uncomplicated machining

capability, 100 % natural tightness), compo-nent loads during continuous running (al-so for future increases in power output), acoustics (extremely high stiffness) and en-gine friction (very low pump losses). The weight is 17 kg.

The bedplate is also made from AlSi9Cu3 and, together with the crankcase, forms a rigid basis for good acoustic properties. For turbocharged engines, sintered F60-U2-70 inserts are utilized. For VVT engines, no in-serts are utilized, however, so as to favour-ably influence oil management and the acoustic properties, the main crankshaft bearing shells are classified fivefold for all engines. The bedplate is secured to the crankcase by two dowels, and sealing is achieved by means of a liquid sealant.

3.2 Crank AssemblyDue to the rigid bedplate design, a GSB2 cast crankshaft is used for the VVT engines, whereas a forged 38MSV5 shaft was needed for the turbocharged engines. The load-suitable design for both shafts resulted in a reinforced crank pin / web connection on the flywheel-side crank and a special con-figuration of the balancing masses for each cylinder. A very low weight, and a main bearing diameter of only 45mm, has been achieved for all engine variants. The con-necting rod pin diameter for the 70 kW en-gine is 40 mm, whereas it is 45 mm for all other variants.

There are three connecting rod variants that are distinguished by their different lengths, connecting rod bearing diameters and piston pin diameters. The material XC 70 is used for the crack / fracture split tech-nology connecting rods with a conical pis-ton pin boss. The Ecoform pistons have been designed for minimum weight; the piston pin diameters are adapted on a load-specific basis: 18mm (VVT) and 20mm (TGDI). A good compromise was able to be made in the piston ring set between low engine friction and oil consumption / blow-by. The ring set is identical for all engines. The total tangential force for each ring package is 40 N.

3.3 Cylinder Head with Valve Drive and Chain Drive, Cylinder Head CoverProduction-optimised design was very im-portant in the design of the cylinder heads. This includes surface machining, accessibility during preassembly to valve drive components, clearance for all cylin-der head screws and uniform wall thick-nesses. The two engine technologies re-sulted in two different cylinder head con-cepts, Figure 4. Through parallel develop-

ment of the variants, an extensive com-mon part package was still achieved for the chain drive and valve drive compo-nents without neglecting the specific re-quirements (valve angle, port shape, etc.). Port machining and combustion chamber machining has been eliminated due to a high level of casting quality.

The VVT cylinder heads are manufac-tured using the lost foam casting method. So-called „masking“ has been used on the intake ports in the combustion chamber to improve the mixture formation. The cast-ing method facilitated additional guiding ribs in the water jacket for uniform cooling of the combustion chamber roof and cast channels between the exhaust valves.

The cylinder heads for the turbocharged engines are manufactured from AlSi-5Cu3Mg by low-pressure casting in a twin cavity die with specially coordinated heat treatment. Cooling, especially in the criti-cal web area, was designed in such a way that usage of a secondary alloy was possi-ble despite turbocharging. The intake port was selectively optimised as the sole meas-ure for generation of a tumble flow in the combustion chamber.

Despite the differing valve drive (fully-variable or conventional), a large number of the components are identical in both en-gine concepts. For the purpose of reducing mass, all valve stems are designed to be 5 mm in diameter. The TGDI exhaust valve is a hollow-stem valve with a sodium filling. Weight reduction was further improved by the use of sheet metal-formed follower and intermediate levers and also in the fabri-cated hollow camshaft and eccentric shaft. All moving points of contact in the valve utilize antifriction bearings to optimise friction.

The fully variable valve drive, Figure 5, with 70 °CA of crankshaft adjustment range on the intake side and 60 °CA on the exhaust side, facilitates the valve lift on the intake side of 0.2 to 9.5 mm and 9.0 mm on the exhaust side. The ratio of intake valve lift to diameter is 0.32. The Vanos adjusters and the Vanos solenoids are common for all engines. In order to achieve a compact package, the servomotor for eccentric ad-justment was integrated directly into the cylinder head.

The chain drive, with its 8 mm single roller chain, is designed for simple assem-bly. In pre-assembled form, it includes the assembly of the guide rail, crankcase sprocket, tensioner rail and timing chain. In order to reduce the number of variants, the guide for the oil dipstick is integrated into the chain guide rail.

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The cylinder head cover for all variants is made of plastic (PA6 – 35 % GF) with inte-grated oil separation. For the VVT engines, a labyrinth separator is used with a down-stream diffuser and pressure-regulated blow-by induction into the intake system. For the turbocharged engines, a centrifu-gal separator is used that also facilitates microfine oil separation. In the part load range, the blow-by is introduced into the intake system; under full-throttle it is in-troduced before the compressor of the tur-bocharger. Both outlets are provided with pressure control and non-return valves.

3.4 Oil Pump and Oil CirculationFor the first time in this vehicle category, the engine utilizes a flow-controlled oil pump that makes a significant contribu-tion to reducing fuel consumption. Regula-tion is continuously variable by adjusting the engagement of the external gear.

By consistently reducing oil demand in-ternally in the engine, the pump size was able to be minimized, which makes an ad-ditional contribution towards reducing fuel consumption.

The one-piece steel sheet oil sump is package-optimised with undercuts and is filled with 4.5 litres of 0W30 oil. Replace-ment intervals are set at a maximum of 30,000 km.

For the turbocharged engines, an oil/wa-ter heat exchanger is integrated into the aluminium die cast oil filter module with a plastic cap.

3.5 Engine Peripherals

3.5.1 Induction SystemThe challenge to create a very compact drive unit that can be installed in many ve-hicle platforms without creating an exces-sive number of variants was successfully achieved in that the complete induction modules with attached intake silencer are affixed to the engine, Figure 6.

Due to crash requirements, the plastic induction system of the VVT engine had to be designed to be extremely compact. With many optimised details, even on the induc-tion system, and a four-part design with an integrated resonator, the demanding torque curve could nevertheless still be achieved. For acoustic reasons, the three-part intake silencer also includes a „lamb-da quarter tube.“

The plenum volume of the TGDI was kept very small for optimum vehicle response.

In the case of the throttle valve with two non-contact-type sensors, both the two-piece housing and the valve itself are made

of plastic. The selected valve material (BMC) guarantees good roundness and very small tolerances despite fluctuating tempera-tures.

3.5.2 VVT Fuel SystemThe solenoid injectors (DK7) are screwed to the plastic rail directly in the cylinder head. The cylinder head has been designed in such a way that the rail is protected in a crash situation. The fuel system operates return-free with 3.5 bar of injection pressure.

3.5.3 TGDI Fuel SystemThe aluminium high-pressure axial piston pump supplies a maximum system pres-sure of 120 bar. The parts of the pump that convey fuel are coated to achieve compati-bility with ethanol. The integrated volume control valve is activated by the engine con-trol unit. Combined pressure (nearly no load and coasting) and volume regulation make a return line and fuel cooler unneces-sary in the high-pressure range.

The seven-hole multi-hole injectors are arranged to the side in the cylinder head and are supplied with fuel, fixed in place and held down by means of a shared stain-less steel pipe. Stratified operation of the engine is not planned.

3.5.4 VVT Exhaust SystemThe stainless steel fan-type manifold, with its accurate pipe lengths and diameters, makes a considerable contribution towards good torque characteristics. It is directly welded to the close-coupled catalytic con-verter.

3.5.5 TGDI Exhaust SystemIn order to achieve a similar vehicle re-sponse from a turbocharged engine to that of a naturally aspirated engine, a twin scroll system was chosen, Figure 7. The dual-branch NiResist (D5S) cast manifold com-bines cylinders 1 & 4 and 2 & 3. The separa-tion of exhaust gas is maintained in the turbocharger until just prior to the tur-bine. In order to ensure fatigue strength in the web area, the turbocharger housing is made of cast steel (A3N). The maximum ex-haust gas temperature before the turbine is limited to 950 °C. The maximum permit-ted turbine speed is 216,000 rpm. The max-imum charge pressure of the 110 kW vari-ant is 1.8 bar absolute. The 128 kW variant increases the charge pressure to 2.0 bar ab-solute in the boost mode.

The boost pressure is regulated by means of an underpressure-operated wastegate valve. Activation is map-controlled via an electromagnetic valve.

3.6 Modular Engine Ancillaries and Thermal ManagementThe engine ancillaries, which are designed for a minimum lifetime of 240,000 km, can be divided into two relatively independent function groups that have been specially adapted to the respective engines and vehi-cle variants.

Module 1, Figure 8, is driven by a 905 mm long, six-ribbed poly V-belt. This means that no additional deflection pulleys are re-quired up to an alternator output of 150 A. For engines without an air-conditioning compressor, the tensioner does not apply; the alternator is driven only by means of an elastic belt with a length of 648 mm.

In Module 2, a friction wheel acting as an intermediate wheel and driven by the back of the belt takes on the function of driving the water pump. In the case of the turbocharged engines, this friction wheel is permanently engaged; for naturally aspi-rated engines, it is disengaged during the warm-up phases by means of a newly devel-oped actuator and is thus actively involved in thermal management. Deactivation of the water pump results in faster heating of the engine oil and a reduction in engine friction.

The use of a torsion spring tensioner for the first time makes it possible to connect the alternator directly to the crankcase and thus to reduce the length of the engine.

The combination of an on-demand wa-ter pump and map-controlled cooling cre-ates continuous thermal management and is an absolute first in this engine segment. It makes an important contribution to-wards reducing fuel consumption and CO2 emissions.

The static and dynamic forces on the wa-ter pump are exponentially lower than for an all-around poly V-belt drive, resulting in the use of a plastic water pump housing and simple mounting of the water pump shaft. The necessary contact force is en-sured purely mechanically by means of an eccentric spring mechanism integrated in the actuator housing; the friction wheel is always engaged in the currentless state.

3.6 Engine FrictionSpecific engine friction targets were agreed for each engine subsystem. Detailed engine friction examinations were performed in all development prototype groups. Deviations from the targets were analysed and appro-priate actions taken. An outstandingly low overall friction level was achieved, despite the high level of technical complexity of the engines. This contributed considerably to-wards the achievement of fuel consumption

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targets. Details regarding this optimisation work are discussed in a separate article in this edition of MTZ worldwide (see page 34).

4 Results

The results achieved regarding dynamics, efficiency and emissions are presented in the following.

4.1 Engines with 70 kW and 88 kW Rated Output

4.1.1 DynamicsThe Mini has always been known for its agility, which comes about in association with the spontaneity and the revving abili-ty of its engines. The corresponding re-quirements were implemented through a series of technical measures for the two naturally aspirated engines.

Extensive dethrottling of the overall in-duction system begins with the careful de-sign of the front end of the vehicle in terms of low-loss flow to the tulip-shaped induc-tion tract and continues in optimisation of the raw air duct, air filter and clean air guide in terms of flow. The intake system, which satisfies the demanding package re-quirements, is equipped with a resonator, the details of which have been improved with regard to volume and connection to the plenum by means of 1D-3D-coupled gas exchange computations. The result is a fuller and more continuous torque charac-teristic at low engine speeds. The high level of surface quality of the lost foam cylinder head, in conjunction with intake ports that have designed for uncompromising filling, were an additional important prerequisite for achieving the performance objectives. The elaborate design of the ports had to en-sure not only excellent filling but also low emissions in cold-start and warm-up situa-tions.

The 300 mm individual pipe length of the steel pipe manifold makes a noticeable contribution towards torque at low engine speeds. The reduced-backpressure exhaust gas system with centre muffler, the vol-ume, structure and position of which have been finely optimised in terms of gas ex-change, also makes a considerable contri-bution towards the build-up of torque at low engine speeds and towards the achieve-ment of power output objectives. It simul-taneously offers a sound that is typical Mini and is aimed at supporting the dy-namic driving experience.

The sum of the individual measures taken form the basis for achieving the tar-

gets in terms of full-load performance. The 1.4-litre engine provides a maximum torque of 140 Nm at 4000 rpm and a maxi-mum power output of 70 kW at 6000 rpm. The 1.6-litre naturally aspirated engine de-velops 160 Nm at 4250 rpm and 88 kW at 6000 rpm, with140 Nm already being achieved at 2000 rpm. The specific torque of 100 Nm/litre for both variants sets a new standard for this vehicle class, Figure 9.

4.1.2 EfficiencyThe low fuel consumption of the new en-gines not only achieves a high level of cus-tomer satisfaction but also fulfils ecologi-cal and social responsibilities. The combus-tion process of the naturally aspirated en-gines is based on the very successful BMW Valvetronic engines.

A compression ratio of 11.0:1 forms the basis for good efficiency. The variable in-take valve lift without slow opening ramps during partial lift results in distinctly re-duced gas exchange work as compared to load control with a throttle valve. Double masking and phasing provide for very good residual gas compatibility and combustion stability, with the result that the engines can be operated in broad areas of part load with a large degree of valve overlap and high internal exhaust gas recirculation. Through the masking of the intake valves, a tumble flow is induced in the combus-tion chamber, while the phase-offset open-ing of the two valves of a cylinder where medium lift is concerned creates an addi-tional swirl component. The total result is a turbulence level at the ignition point that guarantees low ignition delay times and high combustion speeds. With regard to electrode geometry and durability, the spark plug technology has been specially adapted to the requirements of the com-bustion process. The friction-optimised ba-sic engine with controlled oil pump, map-controlled thermostat and on-demand wa-ter pump complete the overall package.

In the fuel consumption map for the engine at operating temperature, the new naturally aspirated engines achieve class-leading positions. Figure 10 shows the mini-mum fuel consumption of the 88 kW vari-ant in the range of variation and the effec-tive specific fuel consumption at a load level of n=2000 rpm, we=0.2 kJ/l. Lower fuel consumption levels are attained only by leanly operated direct-injection engines in a spray-type combustion process.

The fuel consumption of the Mini One in the European test cycle is 5.3 litres/100km; that of the Mini Cooper is 5.4 li-tres/100 km. This represents an improve-

ment of 22 % compared to the predecessor models. The technologies used, even in the entire map at higher load points, guaran-tee a comparable reduction in fuel con-sumption worldwide irrespective of the lo-cal fuel quality. All vehicle consumption data refer to the models from August 2007, which are equipped with an Auto-Start-Stop function, brake energy recuperation and gear shift indication.

4.1.3 EmissionsThe design of the new engines was carried out with all relevant worldwide exhaust gas legislation taken into account (EU 4, JLEV 2005, ULEV II). The interaction of en-gine-related actions to reduce engine-out emissions and to increase the exhaust gas temperatures during starting and warm-up were decisive for the efficient achievement of the targets in combination with rapid light-off and a high level of durability of the exhaust gas aftertreatment system.

The fully variable valve drive of the nat-urally aspirated engines, with short start-ing times due to improved filling in partial lift and excellent mixture preparation on the small valve gap, provide the best condi-tions for low engine-out emissions in the test cycle. The injectors have been precisely optimised with regard to spray quality and injection spray targeting. Double masking and phasing lead to a high level of combus-tion stability and the ability to achieve leaner mixtures, as well as high exhaust gas temperatures and mass flow rates. The combustion chamber geometry optimised for raw emissions completes the measures taken on the combustion side.

A steel pipe manifold with a low heat capacity, representing the best compromise in the stress field of full load characteris-tics and rapid light-off of the catalytic con-verter, is used on the exhaust gas side. When designing the manifold, considera-tion was paid to facilitating rapid starting of the continuous lambda probe after a cold start. The design of the manifold pipes and the inlet cone form the basis for a bal-anced signal characteristic of the probe and uniform utilization of the catalytic converter. The close-coupled catalytic con-verter is designed as a one-piece, high cell density substrate with a total volume of 1.34 litres. It is provided with a coating technology that is not sensitive to thermal ageing and has a low level of pressure loss. With respect to European and Japanese leg-islation, the total result is an efficient and very economical exhaust gas aftertreat-ment system that requires an extremely low level of precious metal loading.

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The stricter requirements of Californian legislation in terms of emissions limits and diagnosis require the use of an additional underfloor catalytic converter with a vol-ume of 0.95 litres for the ULEV II variant (88 kW only).

4.2. 128 kW Engine

4.2.1 DynamicsThe Mini Cooper S with a rated output of 128 kW at 5500 rpm currently represents the top power output variant. Despite a high specific power output of 80 kW/litre, the maximum torque of 240 Nm is achieved at 1600 rpm. The Cooper S has to be con-vincing with a high level of spontaneity and agility in the low engine speed range. This is intensified by the requirement for a sufficient altitude reserve that also ensures robustness in everyday operation when subjected to high outside temperatures or poor fuel quality.

Significant factors for the achievement of these targets are the use of a twin scroll turbocharger, short intake and exhaust con-trol times, a single Vanos in association with a positive scavenging strategy at low engine speeds and a robust combustion process that is not sensitive to knocking. The short exhaust control times, together with the dual-branch exhaust gas mass flow to the turbine wheel, result in increased turbine efficiency and make a significant contribu-tion towards engine responsiveness. The de-sign of the intake control times in associa-tion with group separation on the exhaust gas side result in a high basic torque for naturally aspirated engines that also accel-erates the start-up of the turbocharger. A positive scavenging slope via the cylinder at low engine speeds can be converted into a stoichiometric exhaust gas with the help of direct injection. The corresponding increase of the exhaust gas mass flow allows the tur-bocharger to build up a boost pressure even at low engine speeds and the maximum torque of 240 Nm is already achieved at 1600/min. In order to enhance the dynam-ics, an overboost function is available to the driver in an engine speed range of 1700 rpm to 5000 rpm that increases the torque, in the short term, by an additional 20 Nm. Fig-

ure 11 clearly shows the good position of the engine when compared to the competition, especially with regard to stationary torque at low engine speed.

4.2.2 EfficiencyIn the case of turbocharged engine con-cepts, engine operation in everyday use moves towards higher loads at lower en-

gine speeds as compared to a naturally as-pirated engine with the same power out-put. In combination with highly dynamic uses in the possession of the customer, not only excellent part load fuel consumption but also moderate full load fuel consump-tion have been included in the technical specification requirements.

A series of measures taken played a deci-sive role in part load. Due to the combus-tion process’s high resistance to knocking, a compression ratio of 10.5:1 could be ap-plied. The intake ports were provided with a separation edge at the lower side of the port and a diminishing volume at the top side of the port directly before the intake valves. The macroscopic charge motion cre-ated in this manner is placed in a turbulent state shortly before the moment of ignition and results in good mixture homogeneity and rapid combustion. The intake Vanos can be implemented accordingly in order to achieve a high internal exhaust gas recir-culation and to reduce the gas exchange work. The objective of the design of the combustion chamber was to minimize the volume of the combustion chamber roof so that superstructures could be avoided on the pistons.

Particular attention was also paid to the area around the tip of the injector, because wetting of the wall in the area of the spray discharge would have negative consequenc-es in terms of fuel consumption and emis-sions. The selection of spark plug technol-ogy was for a surface-air-gap plug with a thin centre electrode that represented an optimum in terms of the criteria of residu-al gas compatibility, sensitivity to knocking at full load and combustion stability in catalytic converter heating phases.

Under full load, the low fuel consump-tion level is determined primarily by the resistance of the combustion process to knocking, the minimization of residual gas by means of a positive scavenging slope at low engine speeds, relatively short control times on the intake and exhaust side, the selection of a turbine with low exhaust gas backpressure and the reduction of the pres-sure losses of peripheral components.

The turbocharged engine also benefited from measures taken on the basic engine and cooling system: minimizing friction on all components, a controlled oil pump and a map-controlled thermostat.

Figure 12 shows the minimum fuel con-sumption compared to competitor engines. The 128 kW engine marks the lower end of the range and is characterized by a wide operating range close to this fuel consump-tion level. Fuel consumption at n=2000

rpm and we=0.2 kJ/litre is at a very good level. Compared to competitors, it repre-sents the best value among the turbo-charged engines.

The fuel consumption of the Cooper S in the European test cycle is 6.2 litres/100 km. This represents an improvement of 28 % compared to the predecessor model, with significant improvements also being achieved over the entire map for this vari-ant.

4.2.3 EmissionsThe Cooper S is also offered on a worldwide basis and satisfies the requirements con-cerning emissions limits (EU 4, JLEV 2005, LEV II).

The key to achieving emission targets is homogenous split injection (HSP) during the catalytic converter heating phase in combination with suitable camshaft con-trol (earlier intake). In this regard, only 60 % of the injected volume is injected with an injection start at approximately 300° of the crankshaft before top dead centre (ho-mogenous injection) and the remaining 40 % approximately 70° of the crankshaft be-fore top dead centre in the normal intake phase. In association with a stoichiometric or slightly lean air/fuel ratio, an ignition timing of 15-20° after top dead centre and an idling speed of approximately 1100 rpm, this results in highly effective catalytic con-verter heating with extraordinarily low en-gine-out emissions.

The precondition for robust HSP capa-bility is optimisation of the spray and a cor-responding design of the piston geometry that deflects the injected spray via the pis-ton to the plug. The multi-hole injector has been optimised in such a way that, firstly, enough momentum is available at low loads to reliably move the fuel to the plug and, secondly, sufficient air is transported into the spray for rapid evaporation and homogenisation. The latter prevents high soot emissions in operating points at high-er loads and low engine speeds. Other im-portant factors for reducing soot formation are good homogenisation due to a high level of charge motion, optimal droplet size distribution in the primary spray, a low level of component wetting and a care-fully coordinated injection strategy. The low level of wetting of the cylinder wall likewise prevents oil thinning that puts the durability of the engine at risk.

The 128 kW engine has a staged catalytic converter at its disposal with a total vol-ume of 1.67 litres, which represents the optimal compromise between the light-off characteristic and a low backpressure. As

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in the case of the naturally aspirated en-gines, a linear lambda probe is implement-ed and an additional catalytic converter is installed in the underbody area for the U.S. model.

5 Electronics

A new generation of control units is used for the engine family that is equipped with powerful TriCore processors. The basic ar-chitecture facilitates use in a multitude of vehicle and country variants for both man-ufacturers for the two engine technolo-gies.

6 Summary

The new small four-cylinder engine series resulting from the cooperation between BMW and PSA sets new standards in the segment of small and compact vehicles. The two very different variants (naturally aspirated engine with fully variable valve drive and turbocharged power unit with direct fuel injection) are exemplary in their class, both from a technological standpoint and also with regard to dynamics, econom-ics and sustainability, Table 3.

By merging the competences of both partners in the cooperation project and the high unit quantities, it has become pos-sible to implement the technologies under very favourable economic conditions and to utilize them in the small vehicle seg-ment.

The engines developed under the leader-ship of BMW are marked by the mutual transfer of expertise by both manufactur-ers as the primary objective set by BMW with regard to “efficient dynamics” and al-so PSA’s principle of “design-to-cost” were able to be consistently implemented.

MTZ 07-08I2007 Volume 68 7

COVER STORYIMPRINT

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Chief-on-DutyKirsten Beckmann M. A. (kb) Tel. +49 611 7878-343 · Fax +49 611 7878-462 E-Mail: [email protected]

Editors Ruben Danisch (rd) Tel. +49 611 7878-393 · Fax +49 611 7878-462 E-Mail: [email protected]

Dipl.-Ing. (FH) Moritz-York von Hohenthal (mvh) Tel. +49 611 7878-278 · Fax +49 611 7878-462 E-Mail: [email protected]

Dipl.-Ing. Ulrich Knorra (kno) Tel. +49 611 78 78-314 · Fax +49 611 7878-462 E-Mail: [email protected]

Permanent Contributors Christian Bartsch (cb), Prof. Dr.-Ing. Peter Boy (bo), Prof. Dr.-Ing. Stefan Breuer (sb), Jens Büchling (jb), Jörg Christoffel (jc), Prof. Dr.-Ing. Manfred Feiler (fe), Jürgen Grandel (gl), Erich Hoepke (ho), Thomas Jungmann (tj), Prof. Dr.-Ing. Fred Schäfer (fs),Caterina Schröder (cs)

AssistantsEllen-Susanne Klabunde, Martina Schraad Tel. +49 611 7878-244 · Fax +49 611 7878-462 E-Mail: [email protected]

AddressPostfach 15 46, D-65173 Wiesbaden, Tel. +49 611 7878-244 · Fax +49 611 7878-462

MARKETING | OFFPRINTS

Product Management AutomediaSabrina Brokopp Tel. +49 611 7878-192 · Fax +49 611 7878-407 E-Mail: [email protected]

OffprintsMartin Leopold Tel. +49 228 6907-87 · Fax +49 228-6907-88E-Mail: [email protected]

ADVERTISING | GWV MEDIA

Ad Manager Nicole Kraus Tel. +49 611 7878-323 · Fax +49 611 7878-140 E-Mail: [email protected]

Key Account Manager Elisabeth Maßfeller Tel. +49 611 7878-399 · Fax +49 611 7878-140 E-Mail: [email protected]

Ad Sales Frank Nagel Tel. +49 611 7878-395 · Fax +49 611 7878-140 E-Mail: [email protected]

Display Ad Manager Susanne Bretschneider Tel. +49 611 7878-153 · Fax +49 611 7878-443 E-Mail: [email protected]

Ad PricesPrice List No. 50

SUBSCRIPTIONS

ServiceVVA-Zeitschriftenservice, Abt. D6 F6, MTZPostfach 77 77, 33310 GüterslohRenate ViesTel. +49 5241 80-1692 · Fax +49 5241 80-9620E-Mail: [email protected]

PRODUCTION | LAYOUTHeiko Köllner Tel. +49 611 7878-177 · Fax +49 611 7878-464E-Mail: [email protected]

PRINT | PROCESSINGImprimerie Centrale Luxemburg. Printed in Europe.

SUBSCRIPTION CONDITIONSThe journal MTZ appears 11 times a year (with at least 5 additional special editions) at an annual subscription rate of 209 €. The price for an annual subscription including the English text supplement MTZ Worldwide is 259 €. Special rate for students on proof of status in the form of current registration certificate 81 €. Special rate for students including the English text supplement MTZ Worldwide 120 €. Special rate for VDI/VKS members on proof of status in the form of current member certificate 153 €. Special rate for studying VDI/ÖVK members on proof of status in the form of current registration and member certificate 45 €. Price per copy 23 €. All prices exclude mailing (annual subscription: inland 21 €; foreign countries 35 €; AirMail 109 €; annual subscription including the English text supplement MTZ Worldwide: inland 22 €; foreign countries 44 €; AirMail 119 €. Cancellation of subscriptions in writing at least six weeks before the end of the subscription year.

© Friedr. Vieweg & Sohn Verlag | GWV Fachverlage GmbH, Wiesbaden 2007

The Vieweg Verlag is a company of Springer Science+Business Media.

The journal and all articles and figures are protected by copyright. Any utilisation beyond the strict limits of the copyright law without permission of the publisher is illegal. This applies particularly to duplications, translations, microfilming and storage and processing in electronic systems.

HINTS FOR AUTHORSAll manuscripts should be sent directly to the editors. By submitting photographs and drawings the sender releases the publishers from claims by third parties. Only works not yet published in Germany or abroad can generally be accepted for publication. The manuscripts must not be offered for publication to other journals simultaneously. In accepting the manuscript the publisher acquires the right to produce royalty-free offprints. The journal and all articles and figures are protected by copyright. Any utilisation beyond the strict limits of the copyright law without permission of the publisher is illegal. This applies particularly to duplications, translations, microfilming and storage and processing in electronic systems.