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Special Functions – EGR

What is EGR valve and how it works?

Exhaust gas recirculation how works

EGR valve works by recirculating a small portion of an engine’s exhaust gas back to the engine’s combustion chambers through the intake manifold.

So, it is used to reduce the combustion temperatures and the nitrogen oxide emissions in petrol and diesel engine.

The EGR valve is normally closed. It connects the exhaust manifold to the intake manifold and control the flow of exhaust gas. Its function is to control the flow of exhaust gas recirculation depending on the engine load.

The EGR valve starts working when the engine is started and gradually regulates the flow of exhaust gases.

Dirty exhaust gas recirculation valve

The most frequent issue with EGR valve is sticking due to a build up of a carbon deposits.

In some cases, the valve and its passages can be completely locked preventing the gas recirculation process.

Closed EGR is the cause of black smoke on the car’s exhaust, increased fuel consumption and reduced performance and we have also the check engine light illuminated on the dashboard.

How EGR valve is managed from ECU?

exahust gas recirculation map table

Exploring old engine control unit Bosch EDC15, we can find one or more maps that manage EGR valve only.

Here you can see an example (Bosch EDC15C7 Fiat Alfa Romeo Lancia).

exahust gas recirculation map 3d

As you can see from table and 3D, values inside map are mg/Hub (milligram of air). Axis are RPM and mm^3 (millimeters of fuel).

At low RPM and low mm^3 of fuel, values of air (exhaust gas) are low. So the EGR valve is closed.

At high RPM and high mm^3 of fuel, values of air (exhaust gas) are high. So the EGR valve is partially opened.

What can we do with special function?

We are able to disable the EGR valve, so it will be always closed. In some cases it is also necessary to close manually the valve.

There will be no DTC on vehicle’s dashboard.

Where I can find this special function?

If the vehicle and engine control unit are supported with this deactivation, you will find the EGR mark in column “special functions”.

Click here below and look for your vehicle:

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