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THE NEW BMW EFFICIENT DYNAMICS ENGINE FAMILY With its newly launched Efficient Dynamics engine family, BMW is for the first time applying the company’s modular powertrain concept to both gasoline and diesel engines. It covers a wide range of applications, from longitudinal and transverse engines and various engine displacements to different numbers of cylinders. The optimum overall package is achieved by differentiation in function-relevant design features.
AUTHORS
ING. FRITZ STEINPARZER is Head of the Diesel Engine Development Program of the BMW AG in Steyr (Austria).
DR. NIKOLAI ARDEY is Head of Design and Integration Powertrain of the BMW AG in Munich (Germany).
EXTEND MODULAR DESIGN APPROACH
The modular design approach for BMW drive systems evolved continuously across preceding engine generations; for in-line engines the degree of commonality had reached the high side of 60 %. “Horizontal modularity” was a keynote of this progression, focusing on one or other of the combustion concepts, gasoline or diesel. With boundary conditions continuing to evolve, a major target for development of the new engine generation was expansion toward “vertical modularity” offering considerably more cross-concept coverage for gasoline and diesel drive systems alike.
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DIPL.-ING. WOLFGANG MATTES is Head of the Department responsible for the Design of In-line Gasoline Engines in the Drive Development Unit of the BMW AG in Munich (Germany).
The production, development and purchasing divisions all deliver motivation for this progression as well as quality with high priority, ❶: : synergies for development and production stemming from standardised basic-engine platform for gasoline and diesel engines : production flexibility (gasoline/diesel, three, four and six cylinders) across multiple production locations : mastering increasing variant diversity : standardised interfaces to the vehicle : short reaction period for originating new derivatives : high quality level because of reduction in diversity, both concept-wise and for parts, accompanied by broader validation
DIPL.-ING. DETLEF HIEMESCH is Head of the Diesel Engine Design Program of the BMW AG in Steyr (Austria).
: economies of scale for purchasing and industrialisation : basis for current and future requirements relating to fuel consumption and emissions. As both premise and challenge for definition of the new BMW modular design drive system, maximum commonality had to go hand-in-hand with functionoptimised design for each combustion concept, safeguarding leadership vis-àvis the competition. MODULAR ARCHITECTURE
The new modular diesel and gasoline engine kit is geared toward three-, fourand six-cylinder units displacing 0.5 l per cylinder. Engine-displacement fig-
ures, therefore, multiply out to 1.5, 2.0 and 3.0 l. The new-generation engines are debuting in spring of 2014 with the three- and four-cylinder versions in the new Mini. Diesels and gasoline engines alike feature direct injection with centrally mounted injectors and turbocharging as the basis for a standardised engine architecture. Strictly in accord with the principle of “as much commonality as possible, as much differentiation as necessary”, this is the first time that BMW has opted for rigorous implementa-
❶ Objectives and motivation 05I2014
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tion of an end-to-end modular design approach embracing both diesel and gasoline engines. The all-aluminum engines share basic dimensions such as cylinder spacing, overall height of the crankcase, cylinder-head and main-bearing bolt spacing, plus the counterbalance-shaft concept and standardised interfaces to the vehicle. Commonality further extends to production and assembly on identical production lines. The main building block in this modular kit concept is the optimum cylinder
unit with a displacement of 0.5 l for diesel and gasoline engines, ❷. Cylinder center-to-center distance is a standardised 91 mm, with bore and stroke an uncompromising choice for the respective combustion process (gasoline: bore 82 mm, stroke 94.6 mm; diesel: bore 84 mm, stroke 90 mm), ❸. The new engine family allows for transverse and longitudinal installation of the threeand four-cylinder models in various vehicle architectures. The six-cylinder engines are for longitudinal installation only. There are many ways in which a displacement of 0.5 l per cylinder is ideal for the BMW vehicle portfolio. Broadly speaking, less per-cylinder displacement means less vibration and better acoustics, a higher figure means less friction and higher thermodynamic efficiency. When rpm bandwidth, test-cycle and real-life fuel consumption and emissions were all factored into the equation, the 0.5 l of per-cylinder displacement already featured by many BMW engines was reconfirmed as the optimum for both diesel and gasoline engines. The highest possible degree of commonality between diesel and gasoline engines was important in the brief for those components and systems that do not call for designs specific to the combustion concept. The timing gear, for example, is a two-part chain drive at the
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phase of product development. The requirements for components and systems have to be specified with a high degree of maturity already in the early phase and then be rigorously implemented along the entire process chain if the positive effects of the modular architecture are to be realised. Alongside the corresponding modular product kit, a gasoline/diesel modular process kit was simultaneously defined with the production departments and implemented endto-end for the very first time. MODULAR ENGINE DESCRIPTIONS ❷ Right-sizing for a wide range of applications (schematic view)
gearbox end of the engines, and the tandem pump for the oil and vacuum circuits is chain-driven and sits inside the oil sump. Diesel and gasoline engines share between 30 and 40 % common parts. The corresponding figure for parts of same concept is even considerably higher. The percentages of common parts for diesel engines and gasoline engines respectively are high of 60 %, ❹. The valve-gear components are identical within each branch, diesel and gasoline. A case in point as regards concept-adapted common parts is the chain drive, which utilises standardised points in relation to the engine interfaces, but features detail adaptations to the loads specific to the gasoline and diesel combustion concepts.
The standardised design of the vehicle interfaces of diesel and gasoline engines is a keynote, ❺. The two types of engine share the same installation position and angle. Including connection points for unfiltered air, cooling, vehicle wiring harness, engine mounts, transmission and the A/C lines, a total of ten interfaces for engine installation in the vehicle are defined and standardised via the modular family. This reduces the number of variants in the vehicle plants and permits a high degree of flexibility regarding the assembly. Implementing a modular design approach as extensive as this requires very intensive co-operation between the development, purchasing and production departments already during the early
❸ Cylinder slices, gasoline (left) and diesel engines (right)
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Along with the common parts, the shared modular drive system of the new BMW Efficient Dynamics engine family includes a multiplicity of components of same concept. Examples of systems and components in both these categories are outlined below. Common parts are e.g. cylinder crankcase, oil filter module, oil pan and angine front cover, ❻. Components of same concepts are tandem oil/ vacuum pump, belt drive, coolant pump and counterbalance shaft, ❼. CYLINDER CRANKCASE
Standardised concept features for the cylinder crankcase were defined as a baseline for the new BMW gasoline and diesel-engine family, the aim being to achieve a joint optimum of the concepts used to date by BMW. Technologies formerly the sole preserve of gasoline engine designs (e.g. coated cylinder liner) are accessed, along with others which, until now, featured only in diesel engines (e.g. high-strength alloy and heat treatment, deep-skirt and closed-deck design, integrated counterbalance shafts). The challenge of the modular cylinder crankcases was to utilise as many synergies as possible by having common interfaces for all engine versions (gasoline and diesel, longitudinal and transverse), while at the same time differentiating at the points where functional advantages occur. In the case of the three-cylinder engine this emerged as a common cast-aluminum blank for the gasoline and diesel versions, cast in a double mold, with no differentiation until the finish-machining stage is reached. Basic-engine medium routing, the interfaces to the oil module,
the anti-roll bar link to a transversely mounted engine (three- and four-cylinder versions) and connection of the front axle differential in all-wheel drive vehicle configurations. ENGINE FRONT COVER
The engine front cover for the new threecylinder gasoline and diesel engines is another common part. The plastic cover mounts on the end face of the engine to cover the counterbalance shaft gearwheel drive and it includes both the integrated crankshaft radial shaft seal and the static seals against crankcase and oil sump. The advantages of this design are low weight, the integrated seals and the preassembled connecting elements, which make for straightforward assembly. TANDEM OIL / VACUUM PUMP ❹ Commonalities of the new modular engine family
oil pump, coolant pump, transmission, engine mounts and starter motor are some of the common points of the design, along with the support concepts for production and assembly. This permits flexible production of gasoline and diesel versions on the same production lines. Points of differentiation include for example cylinder bore diameter, the diameter of the crankshaft main bearing tunnel and the bearing caps. OIL FILTER MODULE
The shared design features of the cylinder crankcase clear the way for use of a standardised oil filter module. The component is a common part for three- and four-cylinder gasoline and diesel engines for longitudinal installation and again for transverse installation. The compact plastic oil module combines oil filter and engine oil cooler in a single assembly. The modular sizing of the engine-oil/ coolant heat exchanger covers the different sets of cooling requirements.
ments of both gasoline and diesel engines standardised blanks could be used for each of the two engine types in the respective vehicle and drive system variants (front-wheel/rear-wheel/fourwheel drive) since the interfaces to the crankcase, engine mounts and gearbox are the same. The different requirements such as sensor integration, for example, can be taken into account when the blanks are finish machined. The oil pans of the modular engines are aluminum die-castings. This technology is necessary because the transmission is bolted to the oil pan, which acts as a bracing component for the engine/transmission combination. Further strength requirements come into play with connection of
The oil pump of the new BMW modular engines is combined with the vacuum pump. The interfaces to the engine are identical for gasoline and diesel drive systems, rendering it possible to implement a standardised oil/vacuum tandempump design concept. Flexibility for sizing the gearset in the pump enables to meet the different requirements regarding oil-pressure and volumeflow for gasoline and diesel-engine specifications. The common oil-pump concept means that it is possible to use standardised components such as oil intake tube, map-controlled control valve and mounting screws. The oil pump is of fully variable vane-type design, so the volume flow of oil can be adapted to demand by means of a map-controlled control valve. The vacuum pump is a component of same concept as well and sits behind the oil pump on the same drive shaft.
OIL PAN
The installed position in the vehicle is standardised for the new modular engines. With due provision for the require05I2014
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❺ Interfaces in the vehicle
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BELT DRIVE
One of the benefits resulting from the common concept for cylinder crankcase design is that the belt drive can be implemented as a modular kit across the
gasoline and diesel branches of the three-, four- and six-cylinder members of the family. On account of the package requirements specific in particular to transverse/longitudinal engines, there are only two belt layouts for the entire modular
family. The choice depends on vehicle requirements. Invariably, the ancillary components sit on the intake side of the engine, an arrangement that maximises space on the exhaust side for combustionprocess-specific turbocharging and exhaust aftertreatment. With standardised interfaces to alternator, coolant pump, air conditioning compressor and decoupled belt pulley on the crankshaft, the belt drive is ready for a wide range of different auxiliary units. The associated reduction in complexity creates synergies for the entire process chain of development, purchasing and production. The single-belt drive with preload force and belt routing optimised for low-friction operation is common to all the engines. The geometry of all the belt pulleys in the drive configuration is standardised for gasoline and diesel engines. Belt tensioner, idler, alternators and air conditioning compressor are all common parts. The belt and the coolant pump are synergy parts on account of optimum function. The belt-drive layout also makes provision for engine start by the alternator (starter motor/alternator system). COOLANT PUMP
❻ Examples of common parts in the new modular engine system
The mechanical coolant pump is a synergy part, a cross-engine design for the modular engines. In line with the two variants in belt-drive layout triggered by the differences in transverse/longitudinal engine installation, the coolant pump has only two different integration solutions for the entire modular engine family. The basic design achieved a high proportion of common parts despite the different cooling needs of diesel vis-à-vis gasoline engines. Casing parts, belt pulleys, bearings and supports are common to both variants, whereas the gasoline/dieselengine specifics are catered to by impeller variation and the design of the dynamic seal. The underlying design of the coolant pump makes due provision for mapping variable switchable coolant needs. For transversely mounted engines, thermostatic control of the cooling circuit is implemented in the pump unit. The thermostat can be either conventional or mapcontrolled, depending on the application. COUNTERBALANCE SHAF T
❼ Examples of components of same concept in the new modular engine system
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Layout and drive of the counterbalance shaft unit for gasoline and diesel engines
three-cylinder engines weigh in with high specific power and the corresponding potential. In series applications the engine covers an output range from 55 to 100 kW; the new BMW i8 is powered by a 170 kW variant of the gasoline engine. Uncompromising optimisation of the basic engines, sophisticated thermal management and the use of many consumption-cutting technologies such demand-controlled auxiliary components, volume-flow-controlled oil pumps with map control, low-friction oils and automatic engine start/stop function all contribute to extra-low CO2 levels. The new diesel and gasoline engines are compliant with the Euro 6 emission limits and, in combination with appropriate exhaust aftertreatment, they achieve the SULEV limit values. ❽ TwinPower Turbo modules
are based on the same concept. Integrated into the cylinder crankcase, the counterbalance shaft(s) of the three- and four-cylinder engines are gear-driven off the crankshaft. Differences specific to the combustion concept derive from the mass ratios necessary to counterbalance free mass moments/forces, but also as regards the details of gearwheel design in terms of decoupling and tensioning. These features make due provision for the different alternating torques specific to each combustion concept and ensure optimum acoustic performance of the gearset in each case. CO 2 TECHNOLOGY ELEMENTS
In accord with BMW’s Efficient Dynamics philosophy, the new-generation diesel and gasoline engines are designed for lowest possible friction losses and best possible thermodynamic efficiency. The gasoline engines use BMW’s highly effi-
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SUMMARY AND OUTLOOK
cient so-called TwinPower Turbo technology, a combination of direct injection, fully variable inlet-valve timing and twin-scroll exhaust turbocharging. The diesel engines TwinPower Turbo technology is characterised by common-rail direct injection and innovative turbocharger technology with variable turbine geometry, ❽. Another first, the three-cylinder diesel and gasoline engines with 1.5 l displacement achieve significant CO2 reduction potential. Better warm-up performance, lower friction losses and reduced displacement are major factors, as is the related shift of the operating point into the high-efficiency areas of the characteristic map. In their sector of the power bandwidth, these engines occupy the pole position in terms of fuel consumption. For example, the three-cylinder gasoline engine boasts a CO2 emissions level lower by 6.2 % than its four-cylinder 1.6-l predecessor. As regards dynamics, the
BMW has re-aligned its engine strategy, coming up with a completely new and modular product and process kit approach to the design of in-line engines. The high degree of commonality across the gasoline and diesel concepts and between three-, four- and six-cylinder engines creates high synergies in development, vehicle integration and production. The principles of the proven BMWspecific core technologies were taken over from existing engines and underwent further optimisation and refining in the course of complete new development. All the engines have direct injection with centrally mounted injectors and turbocharging. The new engines are another major contribution to the BMW Efficient Dynamics strategy, further helping to reduce BMW fleet consumption figures by a significant margin while at the same time boosting dynamics. In MTZ 6 a detailed article on the new gasoline engines will appear, and the new diesel engines will be presented in MTZ 7-8.
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