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SAE TECHNICALPAPER SERIES 1999-01-0327

Design Of SI Engines In Regard To VolumeProduction Beyond Year 2000

Ralf Marquard and Frank BesteAVL List GmbH

International Congress and ExpositionDetroit, Michigan

March 1-4, 1999

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1 1999-01-0327

Design Of SI Engines In Regard To Volume ProductionBeyond Year 2000

Ralf Marquard and Frank BesteAVL List GmbH

Copyright 1999 Society of Automotive Engineers, Inc.

ABSTRACT

The principal engine used in passenger cars is, and inthe foreseeable future will be, the SI Engine. This papersummarizes AVL's experience in developing SI Enginesfor these vehicles. Special attention is given to the newtargets of SI Engine development and the resultingdesign strategies during the concept phase of newengine families. The new modular concept of engine fam-ilies includes a broad range of different engine designslike three to five cylinder inline and six to ten cylinder V-block engines, direct injection or fully variable valve actu-ation. It is shown that the design of central engine com-ponents, for example, that of the cylinder head, can beadapted for the different SI valve-train concepts by simplyswitching specific modular components.This modular design approach for main engine compo-nents facilitates more flexible engine families and there-fore significantly decreases the time to market, the costsof development and production of new variants of oneengine family. A reduced time to market in combinationwith an exact definition of the engine specifications is oneprerequisite not only to fulfill future customer and marketrequirements but also to observe varying emission lawswith their different test procedures.

INTRODUCTION

The demands of the automobile have increased signifi-cantly in terms of ecological aspects and are generallyset to continue with regard to future transportation con-cepts. In anticipating this fact, answers need to be foundto the central question of fuel consumption, emissionsand recycling strategies.Today the prime mover used in passenger cars is the SIEngine with a worldwide market share of more than 90%.It faces a growing challenge by modern diesel technologyand alternative powertrain systems such as fuel cells in aserial hybrid configuration. Growing customer demandand new legal requirements induce a necessity forimprovements, which the SI Engine has to fulfill in thefuture.

New practical technologies like direct injection, fully vari-able valve actuation, downsizing and supercharging offerpossibilities which in combination with growing competi-tion from other powertrain concepts and continuing pres-sure of the legislature offer a unique chance forfundamental improvements.

TRADITIONAL TARGETS

Most of the requirements listed below are not fundamen-tally new and have been around since the beginning ofthe automotive age. They have been and in the foresee-able future will be the main guidelines for engine develop-ment.

low fuel consumption low emissions high power output and torque consumer satisfaction good drivability and comfort

low air and structure borne noise low cost of

development production maintenance

low weight short time-to-market intervals

The focus of engine design has shifted since the late1960s when the emphasis was placed on an increase ofpower output. Due to the limited fossil energy carrierresources and the significantly growing environmentalconsciousness since the start of the 70s, reducing fuelconsumption and exhaust-gas emissions became onemajor objective of the consumer as well as of the legisla-ture.

ACTUAL TARGETS

In compliance with this development legal requirementshave increasingly been tightened especially in the USA

2and in Europe. Tight regulations to improve fuel efficiencybecame the driving force behind enormous developmentefforts.

LEGAL REQUIREMENTS The future emission stan-dard Euro IV in Europe and the new SULEV (Supra-Ultra-Low Emission Vehicles) standard in the USA are notdirectly comparable because of different test cycles, butare equivalent in terms of their requirements. The ZeroEmission Vehicle (ZEV) requirement in California is stillbeing discussed and might be reviewed because ofSULEV. Also currently under discussion are a number ofadditional regulations [1]:

mandatory On-Board Diagnosis (OBD) for gasolineengines in 2000 and for diesels in 2003

a new emission test at low temperature (-7C) change of the evaporation test procedure optimization of the reference fuel specifications used

in the type approval tests capability of continued emissions compliance after

100000km or five years vehicle in use define at an early stage the eventual additional

changes after the year 2005Fuel consumption is defined by legal regulations in theUSA only. CO2 emissions are directly correlated to fuelconsumption. But in meeting a compromise of 140gCO2/km or less results in an average fuel consumption of 6l/100km for gasoline driven cars and of 4.8l/100km for die-sel powered cars (assumed market share 25% inEurope).

DEVELOPMENT AND PRODUCTION TARGETS Tosucceed in this manner innovations are necessary. Forthe last ten years all engine components affecting fuelconsumption and emissions have heavily been investi-gated. Figure 1 gives an overview of the different technol-

ogies available today. The major difficulty carmanufacturers are facing today is to identify the singletechnology or that combination of technologies which willensure the company's competitive position in the future.Today, modern planning tools are available to facilitatethe search for innovative future concepts at a very earlystage yielding a strategy of technologies [2]. The devel-oping targets requiring additional focus utilizing new tech-nologies can only be achieved through increased co-operation of the car manufacturers and suppliers indevelopment and production. With this in mind the newpoints of focus can be defined as:

definition of integrated sub-systems developed by thesupplier (outsourcing)

growing integration of new simulation technologies[3]

fewer development stages shorter time-to-market intervals decision about future production facilities and invest-

ments today stronger consideration of FMEA lower costs of development improved reliability longer service intervals Fahrvergngen (driving pleasure)

One central necessity to achieve these targets and toensure companies maintain their competitive position is ahigh flexibility of future concepts in regard to conceivablescenarios focusing on a variety of dominant targets. Eachscenario listed below is based on the assumption that acentral requirement by the customer or the legislationexists and that in comparison further conditions have lesspriority.

Figure 1. Fuel reduction technologies

3 fuel consumption exhaust gas emissions performance comfort costs

This paper describes AVL's new modular designapproach for the cylinder head assembly and otherengine components. It will be shown that this modularconcept utilizes integral subsystems to shorten time-to-market intervals of new engine variants and to reducecosts of component design and production.

NEW ENGINE FAMILY CONCEPT

Basic modular engines have existed for some time. Gen-eral inline units reduce design and production costs byusing the same cylinder dimensions across four, five andsix cylinder editions. However, the modular concept pro-posed in this paper takes the thinking a step further bymodularizing not just cylinders but all main engine com-ponents like valve train, fuel system, intake air/fuel sys-tem or entire cylinder heads.In this way a car manufacturer would be able to use differ-ent modules to obtain a broad variety of engine technol-ogy concepts with significantly lower investment thanwould have been required for units developed fromscratch. The basic elements for inline engines wouldyield in combination with a V-crankcase concept a widerange of potential V-format engines.Figure 3 shows the range of the engine family concept.The engine family discussed consists of three, four andfive cylinder inline engines and the corresponding V-blockengines (six, eight and ten cylinder engines). The generaldimensions are listed in Table 1. Bore and stroke are cho-sen as a long-stroke ratio yielding an average pistonspeed of cm = 18.3m/s at 6000rpm.The highest potential for a modularized design can defi-nitely be found in the cylinder head. Only three differentcylinder-head castings are used for the inline and the V-block engines while six different cylinder blocks arerequired.

CRANKCASE The targets for the development of thecrankcase can be summarized with:

performance engine life/durability low weight cost effectiveness

As a consequence Figure 2 shows the main guideline forthe design and production of engine families. The modu-lar concept requires constant dimensions for the cylinderhead bolts (C), the bore pitch (A) and the crankcaseheight (B).

Figure 2. Guidelines for design and production of engine families

For production of different crankcases on one facility it isalso important, that all crankcases are made of the samematerial. Figure 4 displays AVL's activities in light weightdesign of crankcases. Because of its high weight reduc-tion potentials aluminum can be viewed as the futurestandard material for gasoline as well as for dieselengines. In the interest of high specific outputs and highcylinder pressures the crankcase concept is designed ina closed deck configuration so that a diesel version canbe produced from it. This is not to say that an open deckblock cannot be developed to meet the desired targets.But it seems likely that an unconventional bolting systemcould be required for cylinder peak pressures of 160barand more.Extensive calculations and testing at AVL resulted in abedplate design to ensure a maximum structural stiffnessand strength. To obtain the best possible counterbalancequalities the V-block engines should be designed withtheir three optimum V-angles:

six cylinder60 eight cylinder90 ten cylinder72

Nevertheless, the engine package dimensions are highlyinfluenced by this parameter and may require a differentangle.The potential for modular cylinder blocks is limited to thecylinder dimensions and the integration of various sub-modules like an oil filter/pump module. During their lifecycle, today's engine crankcases are already adapted tothe shifting market demands by, for example, changingtheir displacement via cylinder dimensions and/or con-necting-rod length. The potential for design modificationsmust be considered in the crankcase concept from thevery beginning of the design process and in the manufac-turing facilities.

C

B

A

4Figure 3. Engine family concept

Figure 4. Activities in light weight design

Removing belt driven auxiliary units like the water pumpfrom the engine block and integrating a starter/alternatorunit between engine and transmission can eliminate thebelt drive from the engine and simplifies the front end ofthe crankcase. The camshafts are chain driven.

CYLINDER HEAD Modularizing the complete cylinderhead to utilize it for inline as well as for V-format enginessets some stringent restrictions for the cylinder-headdesign. The V-engine concept includes a single chaindrive of the camshafts with the potential for a continuouscamshaft-phasing system on each camshaft. Therefore,the cylinder-head casting needs to be symmetrical aboutthe center plane between cylinder two and three. Thefront face design ensures that the camshaft drive, thecamshaft phasing system and the cooling-water dis-

charge hose can be adapted on either side. The chainhousing is cast on both sides of the cylinder head andmust be cut away on the side not needed.Figure 5 displays the modular concept of the four valvecylinder-head assembly. The cylinder-head design yieldsa high flexibility. Different valve-train configurations aswell as various fuel-injection- and intake systems can beapplied.

Figure 5. Modular concept of the cylinder head assembly

VALVE TRAIN MODULE The entire intake-valve train ispre-assembled in a frame shaped support which is boltedto the cylinder head at the assembly line. The supportframe supports the camshaft, the different valve-traincomponents and ensures the oil supply of the movingparts. Its precise position in the cylinder head is ensuredby guide sleeves.

example for a typical engine family :

(35 cyl. inline and 6-10 cyl. V-format engines;Modular cylinder head and crankcase)

Weight

Crankcase Material

St-Comp.Al-Comp.

Al Mg

CGICI

5Possible valve-train concepts include conventional tappet or roller-finger-follower valve

trains variable valve actuation systems (VVA) cylinder deactivation systems valve deactivation systems miller circle

and are adapted to the cylinder head by modifying thesupport frame. The space required by VVA or variousdeactivation systems is mainly dependent on the systemapproach. Latest developments seem to favor mechani-cal or hydro-mechanical (lost-motion principle) systemsas the most promising [4-7]. Both approaches require acamshaft and can be delivered as pre-assembled sub-systems directly to the cylinder-head assembly line. Thenecessary control unit constitutes an additional modulewhich is not bolted to the support frame.

INTEGRATED AIR/FUEL MODULE The second maincomponent of this modular cylinder-head assembly is theintegrated air/fuel module. This is mounted via an inter-mediate flange between cylinder head and intake mani-fold (Figure 6). Functions integrated in this module canenvelope the following technologies:

exhaust gas re-circulation (EGR) including ERGcooling and control valve

multi point fuel injection (MPFI) including air-supported fuel injection

controlled burn rate (CBR) and intake-port deactiva-tion

fuel rail with integrated fuel injectors (gasoline directinjection engines (GDI))

The technologies listed above represent the entire rangeof possibilities. Depending on the fuel injection system(MPFI or GDI), different technologies can be combinedas desired. The MPFI system, for example, combinedwith an air-support for the injection, a CBR system andEGR integrated in one module is already used in variousapplications.Applying the air/fuel module to a GDI engine requires adifferent design. GDI air/fuel modules integrate the fuelrail, the intake-port deactivation for intake swirl controland an EGR system with EGR cooling and control valve.The injection valves of AVLs GDI swirl system are posi-tioned between the two intake valves close to the edge ofthe combustion chamber. They can optionally beclamped by the air/fuel module itself or by separatebrackets.

ADDITIONAL SUBSYSTEMS Various engine compo-nents have already been integrated to sub-systems.Examples include modern coil-ignition units, variableintake manifolds with integrated electronic throttle valvesand mass airflow sensors, EGR systems and fuel rails.

This successful development is carried on with AVLsmodular design approach.

Figure 6. Example of an integrated air/fuel module of a GDI engine

RANGE OF ENGINE VARIATIONS

The engine technologies strategies needed for the yearsbeyond 2000 are still unknown and strongly driven by thedifferent conceivable scenarios summarized above. Nev-ertheless, the investment planning for production machin-ery of the main engine components crankcase andcylinder head has to be done today. The availability of thelatest engine technologies which are well adapted to themarket needs and the legal requirements are dependenton short term decisions requiring a high flexibility of thecrankcase and cylinder-head design.The highest possible flexibility is obtained by the modularengine family concept. The different sub-systems devel-oped and supplied by external manufacturers can beintroduced in the existing cylinder head with significantlyless effort relative to conventional concepts.A wide variety of different engine technologies within onefamily concept becomes feasible supporting a growingproduct spectra of the car manufacturers. A supermarket concept for new assembly lines with a choice of modu-lar engine systems laying in the shelf is thinkable. Figure7 shows the selection of single and combined enginetechnologies which can be adapted within the modularengine family concept.

ENGINE PRODUCTION BENEFITS

The new factory for the modular design and productionconcept looks much different compared to current ones[8]. In high wage countries the engine factory of thefuture will include:

Design departments using advanced simulation toolslike the AVL software packages.

Fully flexible machining lines for cylinder block, cylin-der head and crankshaft subject to production vol-ume requirement. All components could be boughtout with only the assembly and test operations car-ried out in house. If components, such as cylinderblocks or cylinder heads are manufactured in housethen fully flexible machining lines would be used.

Assembly lines for engine assembly and final testing.

6Each production step with a high probability of designmodifications requires flexible CNC centers. Some exam-ples are the cylinder diameter, the connecting rod length,the valve-train support frame dimensions or the bracketlocations for subassemblies like pumps or alternator.Therefore the combined machining line has to be com-patible for each version of a specific engine component.In terms of factory performance the major benefits of themodular design and production approach can be summa-rized as

reduction of investment volume reduction of engine unit costs reduced time-to-market intervals

when observing the entire life circle of the product.

INVESTMENT VOLUME BENEFIT Today factory plan-ning is understood as a simultaneous engineering effort.It needs to consider all the usually expected modelchanges resulting from the engine life cycle review (anal-ysis of the future market development in regard to theconcerned product). Especially power train consultingcompanies like AVL List GmbH are in the perfect positionto have a broad view of future developments. Otherparameters to be considered are the prospected produc-tion volumes of the different versions of a product and thefive production-flexibility parameters listed below. F1. Flexibility covering the step-by-step increases of the

production volume after start of production (SOP). Animportant source is the appropriate machining toolcapacity.

F2. Incorporated flexibility of the production units guaran-teeing a variability of the concerned components atSOP. Additional investment volume for machiningtools relative to a conventional factory setup isrequired.

F3. Flexibility of the production units necessary to coverdimensional design changes starting at a certaintime after the SOP-stage. This is important to saveinterest costs on investments. Additional investmentswill be required later on.

F4. Flexibility covering dimensional variations by opera-tor setup effort. The economic decisions has to bemade whether increasing the number of operatorsand labor costs instead of additional investments inthe production line.

F5. Flexibility to organize the production time accordingto the actual work load.

Design flexibility is expensive and can not be compen-sated by a modular design approach and flexible manu-facturing equipment during the first year after SOP. Thefive flexibility parameters listed above give a rough viewof the complexity of a factory planning process.It is undisputed that the investment volume for two singleproduction lines is higher than it is for one combined line.An estimated figure for the saving of investment volumeis about 35%. This positive effect has not been consid-ered in this comparison of the benefits of fully flexibleagainst dedicated production lines since combinedmachining lines have already been well used for sometime.

Figure 7. Range of possible engine concepts

valvedeactivation

camshaftphasing CBR

EGRcylinderdeactivation

VVA GDIMPFI

Modular Engine Concept

7Table 2 shows that the higher investment costs for flexibil-ity as well as the depreciation costs are more than com-pensated by the saving benefits connected with designchanges and the shorter time intervals necessary forintroducing new product versions during the product lifecircle. The major contribution to the costs of designchanges is made by the cylinder head. For instance,introducing a four-valve design and/or an advancedintake system in the base cylinder head requires verycomplex changes in the production line. Because of thishigh complexity nearly all manufacturers had to installnew machining lines parallel to the original ones.

UNIT COST BENEFIT During their life circle, mass pro-duced car engines have to be adapted to the changingmarket needs by more or less far reaching designchanges. The conventional dedicated production lines donot allow major changes without stopping the production.The engine manufacturer had the choice to live with theso called "loss of turnover" and to be disadvantagedwhen compared with the competition or to install an addi-tional not fully loaded production line beside the first oneto produce the supplementary versions of the concernedcomponent.Some minor changes can be introduced by employingmore expensive man power. Nevertheless, the overall uti-lization degree of these lines would decrease to 60-70%or less after the changes yielding a dramatic rise in unitcosts. All of this can be avoided by fully flexible produc-tion lines. There is no need for any additional invest-ments, except for some minor cutting tools etc. or foradditional labor. Stable unit costs which can easily beestimated over the entire product life circle are a veryimportant aspect of fully flexible production lines and setthem apart from dedicated lines.The example in Table 3 shows that the mean unit costsare slightly decreasing when observing the total productlife circle. It is another benefit for the factory planning pro-cedure. The higher necessary investments for more flexi-bility in the production must be kept in reasonable boundsto avoid an increase in overall unit costs. Nevertheless,the planning and execution effort of simultaneous engi-neering has to be taken into account, too.

TIME-TO-MARKET BENEFIT One major advantage ofthe modular engine concept in conjunction with a fullyflexible production line is the shortened time interval forintroducing design changes after SOP benefiting rapidtime-to-market intervals. Until now at least one year formajor design changes had to be considered in the manu-facturing area. This overall concept facilitates consider-ably reduced time to market intervals.

CONCLUSIONS

A highly modularized SI Engine family concept has beendeveloped to meet the broad spectra of future marketdemands. In summary the following main conclusionscan be extracted form this work:

A wide variety of different engine technologies withinone family concept is feasible supporting the growingproduct spectra of car manufacturers.

Reduced time-to-market intervals by increased con-cept flexibilty. Short term adaptation of new enginetechnologies to existing engine families. Closer con-tact to actual market needs and legal requirements.

The different engine modules can be developed andsupplied as integral sub-systems by external manu-facturers.

Observing the life circle of an engine a reduction ofengine unit costs and investment volume for produc-tion machinery is possible when using fully flexiblemachining lines for in house production.

REFERENCES

1. Seiffert, U., "The future development of the gasolineengine", The 6th Global Automotive Conference Bruessel,7-8th December, 1998

2. Kollmann, K., Niefer, H., Schommers, J., Panten, D., Scher-enberg, D., "Strategische Technologieplanung in der Otto-motoren-Entwicklung (Strategic Technological Planning forGasoline Engines)", Aachen Colloquium Automobile andEngine Technology, 5-7th October, 1998, p. 179

3. Powers, P.W., "Informationsintegration in der Entwicklungvon Kraftfahrzeugen (Automotive Information IntegratedEngineering)", Aachen Colloquium Automobile and EngineTechnology, 5-7th October, 1998, p. 11

4. Klting, M., Flierl, R., Unger, H., Poggel, J., DrosselfreieLaststeuerung mit vollvariablen Ventilsteuerungen Ther-modynamik und Technologie (Throttlefree Load Controlthrough Fully Variable Valve Train Systems Thermody-namics and Technology), Aachen Colloquium Automobileand Engine Technology, 5-7th October, 1998, p. 973

5. Nakayama, Y., Maruya, T., Oikawa, T., Fujiwara, M.,Reduction of HC Emissions from VTEC Engine duringCold-Start Condition, SAE paper 940481

6. Schlechter, M.M., Levin, M.B., Camless Engine, SAEpaper 960581

7. Sandford, M.H., Allen, J., Tudor, R., Reduzierung vonKraftstoffverbrauch und Abgase durch Zylinderabschaltung(Reduced Fuel Consumption and Emissions through Cylin-der Deactivation), Aachen Colloquium Automobile andEngine Technology, 5-7th October, 1998, p. 1017

8. Mungenast, E., AVL Production Engineering Department,internal AVL documents, November 1998

8Table 1. General dimensions of the concept-engine family

3 cyl.inline

4 cyl.inline

5 cyl.inline

6 cyl.V-block

8 cylV-block

10 cyl.V-block

bore D, stroke S, S/D D = 83mm, S = 91.5mm, S/D = 1.10average piston speed cm(at n = 6000rpm)

Cm = 2xSxn = 18.3m/s

displacement [ l ] 1.5 2.0 2.5 3.0 3.5 4.0

Table 2. Comparison of factory data of fully flexible with dedicated production lines

Component Original InvestmentInvestment for

changes Operators Utilization degreededicated flexible dedicated flexible dedicated flexible dedicated flexible

crankcase, cylin-der head, crank-shaft, assembly and testing, add. investment & tooling changesRelations [%] 100 119 24* 1 100 108 70 75

* costs to change the dedicated production lines. The losses are higher but hard to estimate

Table 3. Comparison of unit costs of fully flexible with dedicated production lines

ComponentOriginal unit costs costs of unit changes mean of unit costs

dedicated flexible dedicated flexible dedicated flexiblecrankcase, cylin-der head, crank-shaft, assembly and testing, add. investment & tooling changesRelations [%] 100 109 23** 1 117 109

** half depreciation time, doubled depreciation costs