Exhaust gas recirculation - function - GF14.20-P-3000BK

ENGINE 113.967 in MODEL 219 

ENGINE 113.964 in MODEL 164.1 

ENGINE 113.971 in MODEL 251 

Right 

Fig 1: Identifying Compression Spring, Vacuum Reservoir, Diaphragm And Valve Seat

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Left 

Fig 2: Exhaust Gas Recirculation Function Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The EGR valve (89) is combined with an electric EGR vacuum transducer at the rear on the right cylinder head.

The EGR vacuum transducer stabilizes the sharply varying intake manifold vacuum and is actuated by the ME control unit by means of a PWM signal, frequency approx. 10 HZ, on/off ratio approx. 30 - 100%.

The EGR valve is opened to a varying extent as a result of this actuation with a vacuum of approx. 80 to 200 mbar and the quantity of exhaust gases which are recirculated is controlled in this way.

The exhaust gases are recirculated in line with the map stored in the ME control unit as soon as the following conditions are met:

• Coolant temperature between 60°C and 110°C
• Engine speed < 3500 RPM
• Partial load.

The map is designed to achieve optimum fuel consumption. In this case as much exhaust gas as possible is recirculated without impairing engine running or exhaust emissions.

Low-oxygen exhaust is inducted at the EGR valve, depending on the opening cross-section. As a result, the fuel-air mixture contains less oxygen. The combustion temperature drops and the formation of NO_X is reduced.

The inducted air mass is reduced by the quantity of exhaust gases which are recirculated. In line with this, the ME control unit meters less fuel.