Exhaust Gas Recirculation (EGR) Introduction - EGR
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Exhaust Gas Recirculation (EGR) Introduction

Waste gas recirculation (EGR for short) is to introduce a small part of the combustion waste gas from the exhaust pipe into the intake pipe and mix with fresh air, artificially increase the exhaust gas in the intake, the exhaust gas does not contain oxygen and cannot participate in combustion, thus reducing the combustion temperature of the engine and reducing the formation of NOx.

EGR control strategy:

* Increasing EGR rate can reduce nitrogen oxides (NOx) emissions, but at the same time, hydrocarbon (HC) and PM emissions increase, and fuel consumption increases.Therefore, the EGR rate used in various working conditions must be a comprehensive consideration of power performance, economy and emission performance.

* The test results show that: when the EGR rate is less than 10%, the fuel consumption is basically not increased; when the EGR rate is greater than 20%, the engine combustion is unstable, the work is rough, and the hydrocarbon (HC) emissions will increase by 10%. Therefore, it is generally appropriate to control the EGR rate within the range of 10%~20%.

1. Intake flow meter (MAF)

The ECU calculates the trip value according to the calibrated intake flow and the measured intake flow, and determines and observes the opening of EGR (the intake volume is the largest when it is closed, and the intake volume becomes smaller when it is opened;The ECU can see if the EGR is working by observing the intake flow.

The ECU can monitor the EGR rate through the intake flow. EGR rate directly affects NOx emissions, while the ECU indirectly calculates NOx emissions.

2. An EGR valve

EGR valves have different shapes, but the main function is the same. Most of the ECU is directly driven, but the country 6 system also has CAN line driven EGR valve.

Electric EGR valve is a combination of actuator and sensor.

* Execute the exhaust gas recycle instruction issued by the ECU, the motor works, and controls the EGR valve to open and close.

* The EGR position sensor detects the EGR opening position and transmits it to the ECU for EGR exhaust gas recirculation control.

If the EGR valve is suspected of failure, you can block the EGR valve directly to prevent it from importing exhaust into the intake system, and then try the test run to determine whether the EGR valve is faulty.

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