SsangYong Actyon Sports II. Instruction - page 58

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(9) EGR control

A. Overview

The EGR (Electric-Exhaust Gas Recirculation) valve reduces the NOx emission level by recirculating

some of the exhaust gas to the intake system.

To meet Euro-V regulation, the capacity and response rate of E-EGR valve in D20DTR engine have

been greatly improved. The EGR cooler with high capacity reduces the Nox, and the bypass valve

reduces the CO and HC due to EGR gas before warming up.

Also, the engine ECU adjusts the E-EGR opening by using the air mass signal through HFM sensor. If

the exhaust gas gets into the intake manifold when the EGR valve is open, the amount of fresh air

through HFM sensor should be decresed.

B. Components

E-EGR cooler

Accelerator pedal

module

D20DTR ECU

Coolant

temperature

sensor

Oxygen sensor

HFM (intake air

temperature)

Electric throttle

body

Crankshaft

position sensor

E-EGR valve

T-MAP sensor

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C. Input/Output of E-EGR system

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D. Bypass control for EGR cooler

Cooler temperature

When the coolant temperature is below 70℃, the exhaust gas is bypassed the EGR cooler.

Exhaust gas temperature

When the exhaust gas temperature is below 300℃, the exhaust gas is bypassed the EGR cooler.

Otherwise, PM could be increased due to too low exhaust gas temperature.

E. Control elements for EGR system

Accelerator pedal (engine load) - Indicates the driver's intention and engine load. If the load goes up,

the EGR ratio is decreased.

T-MAP (boost pressure map stored in ECU) - Compensates the difference in boost pressure by

adjusting EGR ratio.

Engine rpm - Used as the signal for determining EGR operating range.

Coolant temperature - When the coolant temperature is low, NOx is decreased but PM could be

increased. So, to reduce PM, decrease EGR ratio when the coolant temperature is low.

Intake air mass and temperature - HFM sensor measures the intake air mass to calculate the actual

EGR volume. If the air mass is larger than programmed value in map, EGR ratio will be higher.

EGR position sensor - Detects the actual opening angle of EGR valve and performs feedback

function according to PWM control by ECU.

Wide band oxygen sensor - Detects the oxygen volume in exhaust gas to check if the EGR ratio is

proper.

Electronic throttle body - Keeps EGR ratio to optimized level by controlling the throttle body in EGR

operating range (decreasing pressure in intake manifold).

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F. Features

As EGR ratio goes up, smoke volume will be

higher. But, this lowers the combustion

chamber temperature and accordingly the

concentration of NOx is decreased. The point

with highest NOx is immediately after TDC.

As EGR temperature goes up, the

concentration of NOx will be higher. Thus, it is

necessary to cool down the exhaust gas.

However, during engine cooled, it may cause

large amount of PM. To prevent this, the

exhaust gas is bypassed the EGR cooler.

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