DService BulletinVolvo Trucks North AmericaGreensboro, NC USA

Date Group No. Page

1.2007 258 44 1(6)

Trucks

Exhaust After-Treatment SystemDesign and Function

D16F

Exhaust After-Treatment System

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This information covers design and function of the Exhaust After-Treatment System(EATS) on the Volvo D16F engine.

Contents• “Exhaust After-Treatment System, (EATS)” page 2

Note: Information is subject to change without notice.Illustrations are used for reference only and may differ slightly from the actual vehiclebeing serviced. However, key components addressed in this information are representedas accurately as possible.

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Service Bulletin 1.2007 258 44 2(6)

Design and FunctionExhaust After-Treatment System, (EATS)The Exhaust After-Treatment System (EATS) consistsof many engine and exhaust components and sensorsworking together to lower emissions to meet the stringent2007 emission requirements for the heavy truck industry.The following bulletin provides a brief description of eachof the main components and how these components

interact with each other to allow the EATS system to loweremissions and provide optimal fuel economy. This bulletinalso provides a list of the various modes of operationthat the emission system passes through during normalengine operation.

EATS Operational Modes DefinitionsNormal ModeThe engine is controlled by its normal calibration. Theengine exhaust forms Particulate Matter (PM) or soot,most of which gets trapped in the Diesel Particulate

Filter (DPF). Eventually the soot needs to be removedor oxidized.

In the normal mode no active regeneration is in progress,however passive regeneration may be occurring.

Passive RegenerationA continuous, slow oxidation (burning) process of sootdue to sufficient filter temperature and NOx/soot ratio. The

engine exhaust supplies the required heat under normalengine operating conditions.

Heat ModeAn engine control mode that allows the exhausttemperature to raise to a minimum temperature requiredto allow hydrocarbon (aftertreatment fuel) injection (active

regeneration mode). Heat mode is activated when anactive regeneration is required.

Active Regeneration ModeA hydrocarbon (aftertreatment fuel) injector is usedto inject fuel into the exhaust flow to raise the DPFfilter temperature to a controlled value, currently about575 C to 625 C (1067 F to 1157 F). The increasedtemperature is used to allow oxygen oxidation (burning)

of the soot to occur in the DPF. The active regenerationmode is used when the passive regeneration mode isinsufficient to allow the filter from reaching certain sootlevels.

Service ModeThe service mode is performed by a trained servicetechnician at the service center. The techniciandetermines whether the filter ash accumulation isexcessive and if the filter should be removed from theDPF and cleaned externally or exchanged. If the ashaccumulation is below the removal level, the servicetechnician could initiate a manual stationary regenerationthrough the use of the VCADS service tool.

CAUTION

The service technician must ensure that the truckis in a safe and suitable location to withstand thehigh temperatures that occur during the regenerationprocess. Equipment damage or personal injury mayoccur if combustibles are too close to the exhaust pipeor muffler.

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Service Bulletin 1.2007 258 44 3(6)

System Components

EGR SystemThe EGR system is designed to recirculate exhaust gasesinto the combustion chambers to reduce the nitrogenoxide (NOx) emissions.

The NOx content increases with higher combustiontemperatures. Recirculating cooled exhaust gasesreduces the temperature in the combustion chamber andlowers the level of NOx emissions. To be able to do this,the pressure must be higher in the exhaust side than inthe inlet side — this is controlled by the VGT turbo.

On the exhaust manifold an EGR valve (Exhaust GasRecirculation) is mounted. This valve is managed by theoil pressure and regulates recirculation of exhaust gases.

A portion of the exhaust gas is redirected from the exhaustmanifold into the exhaust gas (EGR) cooler, through theVenturi pipe, which measures the gas flow, and into theEGR mixing chamber. There the exhaust gas is mixedwith intake air cooled by the charge air cooler before it isled into the intake manifold.

The amount of recirculated exhaust gases is controlledby the engine Electronic Control Unit (ECU) and dependson engine load, coolant temperature and various otherfactors.

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Variable Geometry TurbochargerIn order to be able to quickly regulate the charge airpressure and drive the EGR, a new type of turbochargerunit with variable geometry has been introduced. Thisturbocharger contributes to lower emissions, providesoptimal fuel consumption and increases power output.The extent of turbocharger function can be varied bythe speed of the gases entering into the turbine. Thisis controlled by an electrically-operated actuator. Theturbocharger bearing housing and the actuator are bothcooled by engine coolant.

The variable geometry turbocharger (VGT) has a set ofvanes and a sliding nozzle ring that maintains sufficientbackpressure in the exhaust manifold for proper operationof the EGR system. A certain amount of backpressure isrequired to push the exhaust gases into the pressurizedintake air at the EGR mixer.

Additionally, the sliding nozzle ring of the turbochargercontrols exhaust backpressure not only for properoperation of the EGR system, but also for enhancedbraking. By fully closing the VG nozzle mechanism, theturbocharger performs as an exhaust brake.

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Service Bulletin 1.2007 258 44 4(6)

Particulate FilterThe Diesel Particulate Filter (DPF) with oxidation catalystand particulate trap greatly reduces the emission ofparticulate (soot), hydrocarbons (HC) and carbonmonoxide (CO).

The use of Ultra Low Sulphur Diesel (ULSD) meeting alimit of 15 parts per million sulphur is required to preventfouling of the DPF. Additionally, the maximum allowableblending of biodiesel is 5%.

In the DPF system, soot is trapped within a catalyzedceramic monolith, particulate filter with unique noblemetal coating. The particulate filter is regenerated eitherpassively, or actively by the means of a “hydrocarboninjector” that injects a small amount of diesel fuel toreburn the exhaust gases using catalytic reaction. Thiswill reduce the soot quantity and extend the function ofthe filter.

The DPF system has been designed to provide primarily“passive” regeneration in order to increase fuel economy.During passive regeneration, the soot is chemicallyremoved out of the monolith by an ongoing catalyticreaction process that uses no additional fuel.

If the duty cycle is more “stop-and-go”, it may beinsufficient to remove the soot passively, and “active”regeneration will sometimes occur. In this process,additional diesel fuel is introduced into the exhaust streamat the turbocharger outlet by a “hydrocarbon injector”. Thefuel travels to the precatalyst, where a chemical reactionoccurs which raises temperatures in the monolith to theoxidation level, and the soot is simply consumed. Activeregeneration takes about 20-30 minutes and consumesa liter or two of fuel. The driver will have the ability topostpone regeneration until later if one is not desired. Toincrease the exhaust temperature and to keep it duringregeneration, a Discharge Recirculation Valve (DRV) isconnected on the compressor side of the turbocharger. Itrecirculates a portion of warm charge air from the outlet tothe inlet of the turbo. The on/off of the DRV is controlledby a solenoid valve.

There are two variants of the muffler with particulate filter:the Compact DPF that is frame mounted behind the rightfront wheel, and the Vertical DPF that can be mountedbehind the cab for certain chassis configurations. TheVertical DPF includes the NOx sensor, while the CompactDPF has this sensor mounted on a separate pipe.

The particulate filter continuously oxidizes the trappedparticles in the filter module. A small amount of theparticulate trapped in the filter consists of inorganicmaterial (ash) that cannot be oxidized. If the filter is notserviced, this ash will eventually build up and block thefilter, causing exhaust gas back pressure. This leads toincreased fuel consumption and can also lead to de-rateand possibly excessive engine wear or damage and candamage the particulate filter itself.

Note: All gaskets must be replaced every time they areloosened.

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Service Bulletin 1.2007 258 44 5(6)

Discharge Recirculation Valve (DRV)Under some conditions the exhaust temperature is nothot enough for the Diesel Oxidation Catalyst (DOC) tooxidize, or burn, the hydrocarbons (fuel) that are beinginjected into the exhaust flow. Typically the conditionwhere more heat is needed is at lower torque levels. Heatmode is automatically activated as necessary duringactive regenerations.

One method of achieving higher exhaust temperaturesrequires reducing turbocharger effectiveness. This isdone by using the Discharge Recirculation Valve (DRV).The DRV allows boosted air to be re-circulated back intothe turbocharger compressor inlet. This function is usedto help elevate the exhaust temperature and maintainthe DOC temperature to a level which supports activeregeneration.

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Aftertreatment Fuel Injector (AFI)The aftertreatment fuel (hydrocarbon) injector is usedwith the DPF muffler systems to inject diesel fuel into theexhaust stream to increase the exhaust temperature tothe extent needed to allow active regeneration. Activeregeneration mode is used when the passive regenerationis insufficient to prevent the filter from reaching certainsoot levels. Active regeneration can be triggeredautomatically by the engine ECU or manually by a servicetechnician in a suitable location.

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Service Bulletin 1.2007 258 44 6(6)

Electronic Control Unit (ECU)The engine Electronic Control Unit (ECU) provides totalcontrol of the exhaust after-treatment system. Theengine ECU monitors lapsed time, distance traveled, fuelconsumption and soot accumulation, plus many othersensor signals to determine when conditions are right totrigger a DPF regeneration event.

The engine ECU is also responsible for monitoring all thevalves and components that are required to ensure thatDPF regeneration is controlled and successful. Thesewould include, but are not limited to control of the DRV,turbocharger actuator and EGR valve position. Control ofthese and many other components are all important to asuccessful DPF regeneration.

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Emission Control SensorsThe engine control unit could not provide the total controlof the emissions system without the feedback provided bythe many sensors throughout the EATS system. Theseinclude monitoring of the turbocharger, EGR system,engine coolant, engine position and the DPF muffler.Additionally, many chassis-mounted sensors are required,including the ambient air temperature and turbochargerwheel speed sensor. An example of some of the mainengine sensors are listed below. However, sensors willvary dependent upon the DPF system used.

1 Turbocharger

• Turbocharger Wheel Speed Sensor• VGT Position Sensor• Boost Pressure Sensor• Boost Temperature Sensor

2 Engine Position

• Camshaft Speed Sensor• Crankshaft Speed Sensor

3 Engine Coolant

• Coolant Temperature Sensor

4 Diesel Particulate Filter

• Pre-Oxidation Catalyst Temperature Sensor• Downstream Oxidation Catalyst Temperature

Sensor• Downstream DPF Temperature Sensor• Differential Pressure Sensor• NOx Sensor• AFI Pressure Sensor

5 EGR System

• EGR Temperature Sensor• EGR Flow Sensor (Differential Pressure Sensor)

6 Inlet Air Sensors

• Inlet Air Temperature Sensors• Inlet Air Humidity Sensors• Ambient Air Temperature Sensors• Ambient Air Pressure Sensors