The Holset VG TurbochargerA unique variable geometry system providing better vehicle response

with lower fuel consumption and reduced emissions

(HDLSET]

Performance wlthoutcompromise

We'realllooking forthesame things from a modernengine/turbocharger/transmissloncombb".ation .

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better accelera,ttona,ncJffilllo1ii:J'pull-away' torque,. parlicularly Íf1litbansituations .

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-.::} economy, better fueletonomywith lower emission levels..........

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:~,..,irtA1?rovecJtransient response over awir!erl'tingéóf speecJ ancJ 10acJ

rcoqcJttíons, wt~hout the neecJ forCOI1$;tElRft/oWljstJ,ifting .

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r...effectl~e'~ngine braking qhcJ'!imf"iro.vecJH ..dilllcl.t.1n.:. bing.p erformance..........

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A tough chaU.engei':butOjnéWh;i:~.h:i$'bé;ingmetbyHolsets unique VariableGeomefry (VG)Turbochargers.

Nozzle Ring andBlades Retracted

Air Inlet

FixedShroudPlate

Turbine

Compressor

PneumaticControl

~CYlinder

*= Control Air

The problem facing diesel engine designers today can be summarised as:

How can the performance of the vehicle be improved to satisfy the truck driver...............

How can vehicle operating costs be reduced to satisfy the truck owner...............

How can the engine be moditied to reduce emission levels without affecting the other needs..............

These conflicting objectives can be resolved by the use of the Holset Variable GeometryTurbocharger as part of a totally integrated fuel and air control system.

As the airflow needed by the engine varies directly according to speed, fuelinjected, atmospheric pressure and volumetric efficiency, the actual airflow foundin existing engines has been limited by the restrictions of fixed geometryturbochargers. Even Wastegate turbos present only a small improvement.Holset engineers have developed a simple way of managing the availableexhaust gases, effectively producing a turbo with an infinitelyvariable sized turbine to meet boost pressure demand over awide power and speed range.

Exhaust gases are directed on to the turbine wheel through agap between a fixed shroud plate and a sliding nozzle ringand blade assembly, the position of which is controlled by amechanical yoke and external pneumatic cylinder.

ln the insert to the illustration above, the nozzle ring andblades are retracted allowing exhaust gases to act on a largeturbine area, just the conditions necessary for high speed fueleconomyat low boost pressures.

When more power is needed the nozzle ring and blades areextended, reducing the gap and so the effective size of theturbine.This enables the availablegases to turn the compressorfaster and produce extra boost pressure without the usual

lag. When used in conjunction with today's advanced enginemanagement systems, the Variable Geometry design also providesa means of altitude compensation and enhanced engine braking.

Optimum Variable GeometryControl System

PressureSensor

TurbochargerSpeed Sensor

PneumaticActuator

IsolatorSwitch 1 Electrical Control LineVehicle Brake

AirTank

Engine SpeedEngine Control Unit (ECU)

Throttle Demand

Inlet ManifoldPressure &Temperature

Contains pre-set data on airflowrequírements for any fuel quantityínjectedat any engíne speed, with

built-in safety features for excessíveboost, smoke or turbo speed.Exhaust Manifold pressure

Fuel Injection Pump Information

. AmbientPressure ..

The Holset VG turbo provides such a wide range of airflowthat the engine designer mustoptimise the fuel pump and injector settings carefully, in order to achieve the greatest benefits.Consequently, many months of engine performance development are required to establish thefinal "data-set" used for production, to obtain better engine transient response and high torque atvery lowengine speeds.

The Holset VG turbo design has been developed over many years of research anddevelopment, to provide a simple operating mechanism that will function in all extremes ofengine firing and braking, without the need for periodic servicing. Special materials used in theoperating mechanism; coupled with a simple but rugged design, provide levels of reliability anddurability demanded by heavy duty truck engine manufacturers. This will also help to controlvehicle operating costs.

(HDLSET)for further information please contact:

Holset Engineering Co. Ltd St. Andrew's Road Huddersfield HD1 6RA England

tel: +44 (O) 1484422244 fax: +44 (O) 1484 452623

email:turbos@holset.co.uk http://www.holset.co.uk 3580712 2/98