184000290 - 1080C EXHAUST GAS RECIRCULATION SYSTEM (E.G.R.)

CONSTRUCTION FEATURES

This system directs a proportion (5-15%) of the exhaust gases to the intake under certain service conditions.This lowers the temperature peak in the combustion chamber to reduce the formation of nitrogen oxides (NOx).

Components

The system consists of:

  • an EGR Pierburg solenoid valve (1) that is controlled by the engine management control unit;
  • the pipe coming from the exhaust manifold (2) from which the exhaust gases come;
  • an air/water heat exchanger (3) that lowers the temperature of the exhaust gases;
  • the pipe connected to the throttle casing (4) where the exhaust gases are introduced.

Operation

When coolant temperature is > 20C and engine speed is between 800 and 3000 rpm, the engine control unit governs the EGR solenoid by means of a square wave signal.

The change in this signal allows the EGR coil to move a plunger and thus adjust the flow of burnt gases from the exhaust manifold to the intake manifold; two results are thus obtained:

  • less air is introduced;
  • combustion temperature is reduced (due to the presence of inert gases) to reduce NOx (nitrogen oxide) production.
The engine management control unit is kept constantly informed of recirculated gas quantity by information from the flow meter. If the intake of a certain amount of air (Qam) rpm is required at a certain rpm and the amount sent by the flow meter (Qar) is less, the difference (Qgr) is the recirculated gas quantity.Qam - Qar = QgrQam = theoretical air quantity in memoryQar = true air quantityQgr = recirculated gas quantityThe atmospheric pressure signal is used when controllling the EGR valve to recognize when the car is driving at altitude and so reduce the quantity of recirculated gas and prevent the engine from producing fumes.

COMPONENT DESCRIPTION

EGR solenoid

Specifcations

The Pierburg EGR valve fitted to the intake manifold modulates the flow of exhaust gas to the intake according to a command received from the injection control unit.Modulation takes place via an internal solenoid controlled in PWM by the control unit, which operates the control rod from the internal valve.
1. EGR valve body2. Internal valve3. Gas inlet from exhaust manifold4. Gas outlet from exhaust manifold