DService BulletinVolvo Trucks North AmericaGreensboro, NC USA

Date Group No. Page

12.2006 254 60 1(5)

Trucks

EGR SystemDesign and Function

D13F

EGR System, Design and Function

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This information covers design and function of the Exhaust Gas Recirculation (EGR)System on the Volvo D13F engine.

Contents• “Exhaust Gas Recirculation System” page 2

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

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Service Bulletin 12.2006 254 60 2(5)

Design and FunctionExhaust Gas Recirculation System

Overview

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1 EGR Valve2 Hot Pipe3 EGR Cooler4 Differential Pressure Sensor5 Venturi Tube6 Crossover Pipe7 EGR Mixer

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1 EGR Mixer2 Crossover Pipe

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Service Bulletin 12.2006 254 60 3(5)

Nitrous oxide (NOx) emission levels increase withcombustion temperature. The primary function of theExhaust Gas Recirculation (EGR) system is to coolexhaust gas and send it back to the combustion chamberto lower the combustion temperature, thereby reducingNOx.

A portion of the exhaust gas is redirected by an EGR valve(1) from the exhaust manifold into the EGR cooler (2).

Cooled EGR gases flow into the mixing chamber (7),where they mix with intake air that has been cooledthrough the charge air cooler. From the mixing chamber,the combined EGR gases and intake air flow into theintake manifold.

The amount of recirculated EGR gases is controlled bythe EGR valve and depends on differential pressuremeasured at the EGR venturi tube, engine RPM, engineload and coolant temperature. Maximum EGR flow isused under high engine speed and load conditions.

System Components

EGR ValveThe engine uses one EGR valve to control the amountof gases being recirculated. This valve is a poppet-typevalve, operated by hydraulic pressure from the engineoil system which meters exhaust gas from the exhaustmanifold into the EGR circuit. The hydraulic pressure iscontrolled by a solenoid within the valve assembly reactingto signals from the engine EECU. An internal spool valvediverts hydraulic fluid, applying pressure to preciselyposition the EGR poppet valve for control of the exhaustgas circulated through the engine. The poppet valve hastwo sealing surfaces on a common shaft to draw gasesfrom the exhaust manifold EGR port simultaneously.The EGR valve is cooled by the engine oil lubricationsystem and has a position sensor to indicate its preciseposition.

The EGR valve is located on the rear section of theexhaust manifold for reliable response. This location alsoprotects the EGR cooler from exhaust pulses at highpressure, e.g., during engine braking.

Corrosion occurs in the inlet manifold if exhaust gases areallowed to condense in the manifold. This condensationcan produce both internal and external damage. Toeliminate this corrosion, the EECU compares engineRPM, torque load, ambient temperature, inlet manifoldtemperature and EGR demand to calculate the dew pointin the inlet manifold. It then adjusts the EGR opening tostay above the dew point. Additionally, surfaces withinthe inlet manifold and the mixing chamber are treated toresist corrosion.

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Service Bulletin 12.2006 254 60 4(5)

EGR Crossover TubeThe EGR crossover tube along with the venturi outlet andmixer inlet pipes, routes the exhaust gas from the rightside of the engine to the EGR mixer on the left side nearthe inlet manifold. The EGR crossover tube is connectedto the outlet end of the EGR cooler by a hose and clamp.

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EGR CoolerThe EGR cooler is cooled by engine coolant and containsa series of internal pipes with vanes that allow the EGRgases to cool before they reach the mixing chamber.These vanes cause the gases to swirl, creating a highercooling efficiency while reducing deposits. The swirlingaction also reduces the formation of undesirable solids inthe exhaust gas.

Temperature SensorThe EGR temperature sensor is mounted in the venturitube. The temperature sensor provides exhaust gastemperature information to the EECU. The EECUactuates the EGR valve to prevent cooler exhaust gascondensation which can be corrosive in the inlet manifoldor mixing chamber.

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EGR MixerThe EGR mixer is the meeting point for cooled,recirculating exhaust gas and outside air from the chargeair cooler. At this point, the combined gases pass into theinlet manifold and on to the combustion chambers.

EGR DiagnosticsThe EECU commands the EGR valve position andmonitors electric current consumed by the EGR valve.An abnormally high reading indicates a jammed EGRvalve. The EECU verifies that its command was sentand that the valve position reflects the command. If thevalve is jammed, or its position doesn’t change whencommanded, the EECU sets fault codes.

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Service Bulletin 12.2006 254 60 5(5)

EGR Venturi TubeThe EGR venturi tube conducts cooled exhaust gas to theEGR mixer where it combines with fresh air coming fromthe charge air cooler. The flow sensors mount here.

The venturi tube acts along with the differential pressuresensor to determine the amount and temperature of theexhaust gas. The differential pressure sensor providesa signal to the EECU which actuates the EGR valve toincrease or reduce flow.

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