Exhaust Gas Recirculation Valves

Reducing emissions is a priority for all vehicle manufacturers. Exhaust gas recirculation (EGR) valves are key to this reduction.

How they work

Types and characteristics

Installation and fault finding

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Exhaust Gas Recirculation Valves

How they work

Bringing fuel and air together is the basis of the combustion process. However, if the level of oxygen, and therefore the temperature, of combustion is too high, then harmful nitrogen oxide (NOx) emissions are produced. Exhaust gas recirculation (EGR) valves play a key part in controlling this oxygen density and therefore the production of NOx.

The EGR valve is located in a small gap between the intake and exhaust manifolds. Here, it adjusts the amount of exhaust gas that is recirculated back into the intake manifold. This means that when an engine is idling, the EGR valve remains closed until the engine is warm and working under load. As this load and the combustion temperature increases, the EGR valve opens and sends exhaust gas back into the intake manifold. This is then mixed with the intake air to reduce oxygen levels and combustion speed according to driving conditions. This process also lowers the amount of NOx emissions produced.

Features and benefits

Exhaust gas flow optimized to driving conditions.
Integrated position sensor for accurate exhaust gas control.
Accurate exhaust flow provides resistance to carbon corrosion.
Significant reduction in NOx emissions.

Accurate exhaust flow
Integrated sensors positioned between the exhaust and intake manifolds ensure more accurate measurement and control of the flow of exhaust gases.
Responsive performance
Alongside accurate measurement, the valve enables responsive control over exhaust gas flow depending on engine temperatures and driving conditions.
Fewer emissions
By optimizing the level of oxygen within the combustion process, EGR valves can improve engine performance, increase durability and reduce NOx emissions.

Types and characteristics

This innovative design enables greater control over exhaust gas flow and emission production for a range of different car models and types.

Exhaust Gas Recirculation Valves types

Step motor type

Step motors are angle motors, which means they move into a certain rotational position based on the input signal they receive. This motor drives the opening and closing of the EGR valve.

Solenoid type

These types of EGR valves are driven by an electromagnet. When a current is passed through the part, a magnetic field is produced that opens the valve.

DC motor type

As an electric current is passed through a DC motor, a set of gears are driven until the intended position or angle of the EGR valve is reached.

Characteristics

Whatever type of motor is used to drive the EGR valve, every product in DENSO’s range enables better engine performance and helps to reduce vehicle emissions.

Installation and fault finding

To get optimal performance from a DENSO EGR valve, it needs to be installed correctly and fixed quickly. Here are the most common questions asked about EGR valves.

Installation

Ensure your EGR valve is installed accurately.

Drain engine coolant, referring to the car maker’s instructions. Locate the EGR valve and disconnect its connector and water hose. Remove the mounting bolt(s) and nut(s). Remove the EGR valve and gasket(s)
Install the new EGR valve with new gasket(s) and the original mounting bolt(s) and nut(s). Torque the bolt(s) and nut(s) to the car maker’s specifications. Connect the EGR valve connector and water hose.
After the EGR Valve installation is completed, add engine coolant and check for engine coolant leakage, referring to the car maker’s instructions. Check for exhaust gas leakage.

Fault finding

Find and fix any EGR valves quickly and easily.

Electronically controlled EGR valves are used in engines with an EFI (Electronic Fuel Injection) system and cause the engine warning light to switch on when there is a malfunction.
The most common cause of EGR valve failure is clogging caused by deposits, causing the valve to stick or preventing it from opening or closing properly.

A faulty EGR valve carries no danger to life but may shorten the engine life, increase harmful emissions and cause drivability problems such as rough idling, start-up difficulty and stalling.
Poor drivability: hesitation during acceleration or abnormal knocking
Increased emissions: elevated NOx emissions and even elevated hydrocarbon (HC) emissions in the exhaust

There could be other causes of poor operation with electronically controlled EGR Valves. One cause can be a faulty intake air temperature sensor, which is located in the MAF sensor. This is one of the sensors that enables the ECU to determine the correct amount of EGR flow and adjust EGR Valve for precise control. Therefore, for a correct diagnosis always check the DTC codes for EGR Valve problems and refer to the car maker’s instructions for test procedures.
Cleaning the EGR valve of carbon deposits might be considered as a temporary solution, but it is not recommended. It is almost impossible to remove clogging completely, potentially allowing harmful contaminants to enter the engine. The right solution is therefore to replace the EGR valve with a new one that is calibrated to the same specifications as original one.