Technical information

Engine

Volvo 850 GLT

Volvo 850 Engine

IntroductionThe demands on the car of the 90's arevery high in every respect. As vehiclemanufacturer one can no longer con-centrate only on a subset of all prop-erties. To gain success, excellence is re-quired in all areas.

Furthermore, the customer of the 90'swill not accept having to adapt himselfor herself to the vehicle. The vehiclemust instead be adapted to man. This

makes it necessary to study man-machine interactions when developinga new car.

These demands, coupled with themany properties affected by enginecharacteristics, create the need for aproperty oriented development processwhere the combination of all propertiesare taken into consideration from thevery beginning.

Development goalsEvery customer expects good comfort,good performance and fuel economyfrom their car. This in turn, places ademand for effective and efficienttechnical solutions; to choose, as Vol-vo sees it, the best solution for eachspecific purpose.

The challenge for Volvo con-sequently meant to combine a roomyinterior with a solid safety structure,compact exterior dimensions and ef-fective energy absorption with a pow-ertrain combining comfort, per-formance and energy efficiency.

A transverse installation of an in-line engine is today accepted as thebest technical and most space efficientsolution. This is a solution alreadychosen for the Volvo 400-series andwas on space, packaging and handlinggrounds also chosen for the Volvo 850GLT.

The development of the new engineis the second step of Volvo's newmodular engine family, the N-series.The first step was the in-line sixB6304F, which was introduced in theVolvo 960 in August 1990.

The modular engines have severalidentical components. The major com-ponents are machined in a commontransfer line, in a highly rational andmost cost-effective manufacturingprocess.

The normal order of priority for en-gine properties during design and de-velopment within Volvo Car Corpora-tion is the following:- Exhaust emissions- Fuel economy- Driving pleasure- Performance

The interactions between thesefour main properties are very strongand it is very difficult to alter onewithout affecting the others.

Since a lot of emphasis during thedevelopment of the Volvo 850 wasput on performance and drivingpleasure, this had its effect on the in-ternal relationships of the four prop-erties given priority. In order to meetthe performance requirements withmaintained fuel economy, a variableinduction system was introduced.This made it possible to combinehigh torque at low engine speeds withhigh power at high engine speeds,keeping fuel consumption optimized.

Big efforts have also been made toreduce noise and vibrations. There-fore the best ignition timing has notonly been determined by emissions,fuel consumption, performance anddriveability but also by its effect onnoise and vibrations. Comfort is aproperty that also has been givenhigh priority when developing the en-gine for the Volvo 850.

Another example of this is throb-bing and sawing powertrain motionsthat goes with a transverse engine in-stallation and front wheel drive. Suchmotions have been minimized byelectronic dashpot functions and oth-er features of the engine managementsystems.

The Volvo 850 engine conceptThe engine in the Volvo 850 GLT isan in-line 2.5 litre five-cylinder calledthe B5254F. Thanks to an extremelycompact design of the engine andtransmission (See Technical in-formation Transmission) it has beenpossible to install it transversely (fig-ure 1), still allowing for excellent han-dling properties and an extremelysmall turning circle (10.2 metres) for afront wheel drive car of this size. TheVolvo 850 GLT is the first passengercar that has an in-line five-cylinder en-gine installed transversely driving thefront wheels. Overall length of thecomplete powertrain, engine and trans-mission, is only 948 mm.The main characteristics of theB5254F are:- Five cylinders with four valves percylinder and a high compression ratio- High performance and good fueleconomy without negative influenceon driveability- Minimized engine vibrations thanks

to inherent engine and transmission ri-gidity, damped engine and suspensionsystem and a separate insulated sub-frame carrying the powertrain.- A variable induction system, the V-VIS (Volvo Variable Induction Sys-tem) and an extractor type exhaustmanifold. Since this is located be-tween the engine and the firewall, theposition of the catalyst could be closeto the engine which provides fasterwarming-up of the catalyst and thusl ow exhaust emissions.Among the basic development goalsfor the engine concept were a high de-gree of reliability and long servicelife; high energy efficiency; easymaintenance; rational manufacture;compactness in size; low weight andlow noise level.As for reliability and service life, theengine has a life span of more than 20years or a total driving distance ofmore than 200.000 without needingdisassembly and with all vital parts in

good working condition.Regarding high energy efficiency, thegas flow has been optimized with theaid of computer simulations and lasermeasurement technology in order toensure efficient use of energy.During the development of the en-gine, Volvo Car Corporation servicepersonnel have contributed with theirknow-how in order to achieve high re-liability with a minimum of main-tenance. A number of automatic func-tions minimize the need for manualadjustments:- Hydraulic tappets (no adjustment ofvalve clearance)- Automatic belt tensioners for cam-shaft and auxiliary drives- Adaptive functions of the controlsystems compensating for system tol-erances and wear, temperature andfuel variations ensuring optimum fuelmetering and ignition timing- Automatic idling speed adjustmentand air/fuel ratio

six which is installed longi-tudinally in the rear-wheel driven

Volvo 960. Both versions clearlyillustrates the rational and flexible

manufacture of a modular enginesystem.

The major components for the fiveand six cylinder engines are machinedin a common transfer line in the Vol-vo Skovde plant. This new plant ispart of the investments carried out byVolvo for the 90's and which also in-clude the complete Volvo 850 car.

A large number of the componentsare identical for both engine versions:pistons, rings, gudgeon pins, con rods,bearings, seals, valve guides, valveseats, valve springs, tappets, waterpump, camshaft drives and covers,auxiliary drive and brackets.

Components machined in common

Technical solutionsCylinder block and lowercrankcaseFigure 5The cylinder block and lower crank-case are manufactured of high-pressure die-cast aluminium. Based onFEM (Finite Element Method) analy-sis and simulation, the block has beendesigned to produce a compact andrigid engine, featuring extremely lownoise and vibration emissions. Thelower crankcase, with its integratedcast-in reinforcements in the mainbearing caps, and cylinder block to-gether form a very compact and rigidunit. Furthermore, the walls of bothsections have been given a reinforcedribbing structure in order to minimizepanel vibrations and the transmissionof noise.

The grey iron cylinder liners arecast-in during the high-pressure die-cast process of the cylinder block. Theliners offer high wear resistance andreduce the risk for leaks. The pro-duction process is also cost-effectiveand environmentally friendly.

The slots between the cylinders atthe upper edge of the block have beenspecially machined to minimize the

risk for ovality in the cylinders as aresult of thermal expansion.

The lower crankcase has re-inforcements of cast nodular iron inthe main bearing caps. This mini-mizes the increase of clearance in themain bearing that can be caused bythermal expansion.

During the manufacturing process,the main bearing bores are machinedwith the block and the lower crank-case bolted together as one unit. In or-der to ensure that the unit is tight andstable, a liquid gasket is applied be-t ween the two parts. They are thenjoined to each other with yield-pointtightened bolts during final assembly.

Oil channels and coolant ducts arecast in during the production of blockand lower crankcase. This obviatesthe need for subsequent drilling andmachining of the channels. This de-sign principle is very cost-effectiveand well suited for series production.

Cylinder head and cam-shaft bearing housingFigure 6The cylinder head is made of chill-cast aluminium to ensure a homog-

enous material. The combustionchambers is of the pent-roof type withfour valves per cylinder. The valvesare set at a relative angle of 58 de-grees and flank the centrally locatedspark plug (figure 7). By selectingthis valve angle it has been possible toobtain an extremely compact combus-tion chamber, allowing for coolantducts between the valves and thespark plug.

The camshaft bearing housing hasintegrated upper bearing halves andforms the top part of the cylinderhead. The lower bearing halves are in-tegrated in the cylinder head.

The camshaft bore is machinedwith the camshaft bearing housingand cylinder head assembled. In finalassembly, a liquid gasket is appliedbetween both parts in order to obtaina tight and stable joint. Oil and cool-ant ducts are produced in the sameway as with block and lower crank-case.

The double overhead camshaftsand cam profiles have been designedwith the aid of computer calculationsand simulations in order to minimizetorsional vibrations in the camshaftwhile at the same time retaining ex-cellent gas flow properties. The camsoffer maximum 8.45 mm lift. At 0.1mm lift the overlap is 24 crankshaftdegrees between the exhaust valveclosing and the inlet valve opening.

Valve diameters are 31 mm for in-let valves and 27 mm for exhaustvalves. The valve stems are chro-mium-plated and has a 7 mm dia-meter.

The valve guides are cast iron. Hy-draulic maintenance-free valve tap-pets are used.

The cylinder head is bolted to thecylinder block with yield-point tight-ened bolts and a head gasket which,like all other gaskets in the engine, isasbestos-free.

CrankshaftFigure 8

The rigid crankshaftruns in six main bear-

ings and has ten coun-terweights. It is made of forged va-nadium-steel and is precipitationhardened. The thrust bearing is placedat the fifth main bearing from the frontto minimize both engine overall lengthand crankshaft rear end movements.FEM analysis has been used to op-timize the crankshaft and the vibrationdamper in combination with the en-gine block under simulated dynamicconditions, thus giving long servicelife and good comfort.The main and big end bearing surfacesare induction hardened, with press-rolled fillet radii for maximum fatiguestrength. The crankshaft nose in-corporates two sets of splines, to drivethe oil pump and the vibration damperhub. Theses splines, and the endthread, are all rolled in a single opera-tion, thus combining high strengthwith cost-effective production. Thebearing surfaces are finally ground ina data controlled point measurementgrinding machine, which stops ma-chining automatically once the correctdimensions have been obtained.The main bearing shells are alumin-ium while big-end shells are lead-bronze.

Figure 10

Figure 9

Connecting rods andpistonsFigure 9The connecting rods are forged fromvandium alloy steel with an effectivelength of 139.5 mm. High strength isachieved through a precipitation hard-ening process. The rods have a 1$0degree thrust face against the crank-shaft by virtue of the fact that thebearing caps are 0.7 mm narrowerthan the big end of the rods.

To achieve exact radial control be-tween con rods and con rod caps,these parts have ground serrated jointsemploying yield-point tighteningbolts without nuts.

The connecting rod small and bigend weight is controlled and keptwithin very narrow tolerances bymeans of a special machining opera-tion in order to minimize engine vi-bration.

The pistons are made of aluminiumwith cast-in steel expansion control.The piston ring package consists oftwo compression rings and one oilscraper ring.

Camshaft drive Figure 10Camshafts and water pump are drivenby the vibration damper hub on thecrankshaft by a toothed belt. For op-timal engine performance it is nec-essary to ensure extreme accuracy incamshaft timing during assembly.This is achieved by fixing the crank-shaft and camshaft positions with spe-cial locking tools while the drive isfitted and adjusted. The belt is auto-matically tensioned by means of aspring-loaded piston assembly whichis hydraulically damped, to maintainconstant tension and compensate forwear and temperature variations.

Lubrication systemThe oil is circulated by a rotor oilpump of the crescent-type and has amaximum capacity of 70 litres perminute at 6000 rpm and 80° C oil tem-perature. The inner rotor of the pumpis driven directly by splines on thecrankshaft. The pump design permitsa compact installation, with the oilpump at the front end of the cylinderblock.

The oil sump (figure 11) is man-ufactured in high-pressure die-cast al-uminium and is equipped with castbaffle plates and a steel windage trayto ensure a constant oil supply and tominimize foaming when driving hard.

Cooling systemThe water pump is designed to meethigh demands for reliability and com-pactness. The housing is integrated inthe engine block and the pump isdriven by the crankshaft via the cam-shaft belt. It has a capacity of appr160 litres per minute at 6000 rpm.Shaft sealing is based on a ceramicring and a sintered carbon ring toeliminate leakage.

The cooling fan is electrically pow-ered with two speeds, regulated by theengine's control or climate system.

Auxiliary drive andinstallation Figure 12Auxiliary units such as alternator,power steering pump and air condi-tioning compressor, are grouped to-gether on the left side of the engine ina very compact and rigid installation.The left side was chosen in order toprotect the auxiliaries from the ex-haust heat. The compactness makes itpossible to use the same installationfor both transverse and longitudinalengine installations. Thanks to the ri-gidity of the system, high strength andlow noise is achieved.

Drive is by a six-groove Poly V-belt and tension is maintained at aconstant level by a friction dampedbelt tensioner. The installation is verycost-effective with one one tensionerand one idler. The same componentsare used for version with or withoutAC-compressor. The only differenceis additional belt length.

Figure 11

Air inlet systemInlet air is taken ahead of the radiatorand passes through the air filter and airmass meter of hot-fim type. The airtemperature is thermostatically regu-lated to a minimum of +10° C by mix-ing with warm air taken from the ex-haust manifold. The inlet air thenpasses through the throttle housing.

Air inlet manifoldFigure 14The geometry of the inlet manifoldwas designed with the aid of simulatedunsteady compressible air flow. Dy-namometer testing confirmed the com-puter models and the result is V-VIS

(Volvo Variable Induction System). V-VIS consists of a conventional plenumchamber with twin inlet ducts to eachcylinder, parallel but of differentlength. The compact "roll" shapeachieves good space and use of materi-al at minimum weight.

The shorter ducts are closed by a setof electro-pneumatically controlledvalves when the throttle is more than80 per cent open and with engine speedlying between 1500 and 4100 rpm. Atsmaller throttle opening, or at otherrevs, the valves remain open and formpart of the wall of the short ducts in or-der to minimize flow losses. Figure 15shows the calculated volumetric ef-ficiencies with open and closed controlvalves.

With closed control valves a negativewave, caused by the descending pistonand the inertia of the gas in the longerduct, accelerates the air column in theduct. At resonance rpm the inertiacauses the air to ram into the cylinderjust before the inlet valve closes. Thisresults in a considerable gain in vol-umetric efficiency and hence in-creased torque.

Figure 16 shows the calculated in-stantaneous pressure variation at theinlet valve antler full load and res-onant rpm with open and closed con-trol valve. The increase in pressure be-tween BDC and inlet valve closing isclearly visible.

The V-VIS system thus provides amajor increase in engine torque in themost used medium range of enginespeed during normal driving. The sys-tem requires an absolutely tight clo-sure of the valves to work effectively.This is achieved by using stainlesssteel valves with soft heat resistantrubber sealing lips. These form a tightseal against the cast wall of tine ducts,thus avoiding expensive internal ma-chining of the ducts.

Control information is fed from thethrottle potentiometer and the ignitionsystem to a solenoid valve which con-trols the vacuum driven servo unit tooperate the split valve spindles via atorque balanced beam. This also to aidtight valve closure (figure 17).

Max output for the B5254F is 170 hp(125 kW) at 6000 rpm. Max torque is220 Nm at 3300 rpm. Thanks to theV-VIS system, 90 per cent of themaximum torque is available between2000 and 6000 rpm.

Exhaust systemFigure 18The exhaust manifold is a welded ex-tractor design. Five separate pipes,each with appr 400 mm length, com-bines performance with low weightand short light-off time. The choice ofmaterials is a combination of ferriticand austenitic stainless steel qualities.The manifold is connected to the ex-

haust system by a flexible joint andspringloaded bolts. The system hasone main silencer and a combinedcatalytic converter and silencer. Thelocation of the main silencer is in themiddle of the exhaust system to en-sure good attenuation at low fre-quences. The silencer inside the cat-alytic converter is located behind thecatalytic area for the same reason.The entire system has been fine-tunedin order to retain an "appealing" en-gine sound which enhances the ex-perience of driving pleasure but sup-press noise. The tail pipe ending is oflarge diameter pipe and straight.

Figure 18

Engine control systemsThe B5254F-engine is controlled byt wo advanced electronic control sys-tems, the LH 3.2 fuel injection systemand the EZ 129K ignitlon system.These systems are further develop-ments of the well known systems usedin the current four-cylinder Volvocars.

The development goal has been toproduce a completely integrated sys-

tem, based on the current components,which is less expensive, more flexible,more reliable and more efficient. Anew cable harness concept is used,and the engine control units includethe functions of a number of elec-tronic relays to reduce the number ofcomponents (figure 19).

Fuel injection systemL H3.2The system has a new air mass meterof hot-film type. Together with an an-gular position throttle potentiometer,it gives an accurate air mass measureat low cost. It has a closed-loop lamb-da control and an idle speed control,both with adaptive functions.

Previously each system in the ve-hicle has had its own temperature sen-sor for coolant temperature. On thisengine, however, there is only onesensor of so-called NTC-type. Thissignal is used by the LH3.2 to form aperiod-time modulated signal to allother systems which need this in-formation.

While the electronic control unithas been moved from the passenger

compartment to the engine compart-ment, the fuel pump relay has for safe-

ty reasons been replaced by an elec-tronic type. It is kept triggered by thecontrol unit with a constant pulsetrain, instead of just a "high" or "low"signal. This is also for safety reasonsto avoid the possibility of petrol leak-age in the engine compartment causedby a broken fuel pipe and a runningfuel pump after a crash.

Ignition system EZ129KTo measure the engine speed and an-gular position, a flywheel speed sen-sor of inductive type and a camshaftposition sensor of Hall-effect type areused. The system has two knock-sensors for best performance of the ig-nition timing regulation of each cyl-inder, with adaptive functions. Theelectronic control unit also controlsthe V-VIS system plus the air condi-tioning compressor and the electriccooling fans.

the vehicle by carefully selecting theengine mounting system. The mount-ing system for the Volvo 850 hasbeen designed on the followinggrounds:

- The two main engine mounts(hydromounts) are located at the nodefor the vibrations. This means on aline through the centre of gravity forthe powertrain.

- By using soft support at the frontof the engine, the engine is kept inbalance while the main mounts do notcarry bending loads.

- By using two nonlinear reactionrods, extreme loads from the driveshafts are taken care of.

When designing the engine mount-ing system great attention was takento the engine vibration characteristics.The engine mounting consists of atwo-way insulation system, wheretwo main hydromounts, one supportmount and the lower torque reactionrod are mounted to a rubber insulated

subframe (figure 20). This gives anexcellent insulation of engine vibra-tions.

The main mounts and the torquereaction rods are located in positionswith low displacement amplitude ofvibration. The dynamic stiffness of themounts is low to give a good vibra-tion isolation for small displacementamplitudes. Large displacement am-plitudes from the chassis are dampedby the hydraulic system of the hydro-mounts, which is essential for a goodride comfort.

Due to the engine vibration char-acteristics, the displacement am-plitude of vibration is larger in the po-sition where the support mount islocated. Therefore it has progressivecharacteristics with a low initial dy-namic stiffness .

The main purpose of the torque re-action rods is to restrict the enginemotions due to the torque of the en-gine. Their characteristics are softlyprogressive with a low initial stiffness.

Engine vibration levelsThe firing order of the B5254F is1-2-4-5-3, with even firing interval of144 crank degrees.

Both theory and practical ex-perience show that there are primarilytwo vibration characteristics whichmust be considered when installingthe engine in a car. The engine is ex-cited by a first order of rotating inertiacouple with magnitude

From the principal vibration patterndue to these excitations, it is possibleto minimize the disturbance input to

The B5254F has been developed tomeet the high demands on engines ina car, typified by the Volvo 850 GLTby using modern CAE technology.The result is a compact and light-weight in-line five-cylinder engine,characterized by excellent per-formance and torque, good fuel econ-omy and a remarkable comfort level.

The manufacturing process, based onextremely high demands for accuracyand quality to guaranteed engine re-liability, is particularly cost-effectivesince both the five and six cylinder en-gines were designed and developed asa modular engine family with a con-siderable degree of integration.

Volvo 850 GLT Engine specifications

Type: Transverse 5-cylinder in-line

Displacement:

DOHC all-aluminiumV-VIS Volvo Variable InductionSystem2435 cc

Bore x stroke: 83 x 90 mmCR: 10.5:1Valves: 4 per cylinder, angled atMax output;

58 degrees170 hp (125 kW) at 6000 rpm

Max torque: 220 Nm at 3300 rpmFuel system: LH Jetronic 3.2Ignition system: EZ 129KEmission control: Three-way catalytic converter,

Electrical system:

electrically heated lambda-sond,vacuum controlled evaporationsystemAlternator 100 amp. Battery440/520 amp

Weight; 153 kgsFuel consumption: Sweden average 0.89 litre per

Top speed:

10 km with manual gearbox,0.91 litre per 10 km withautomatic transmissionEurope R15 12.4 litres per 100km with manual gearbox12.9 litres per 100 km with auto-matic transmission90 km/h 6.6 litres per 100 kmwith manual gearbox215 kph manual, 205 kph aut

Acceleration: 0-100 kph: 8.9 sec manual,9.6 sec aut