Exhaust Gas Recirculation System (E.g.r.) - Fiat Bravo Service Manual

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EXHAUST G A S R E C I R C U L A T I O N S Y S T E M (E.G.R.))

This system directs a proportion of the exhaust gases to the intake under certain engine operating condi-

The process dilutes the fuel mixture with inert gases to lower the temperature peak in the combustion

chamber. This reduces the formation of nitrogen oxides to bring about a 30-50 % reduction in emissions.

Exhaust gas recirculation is allowed only at medium-low loads, when the air - fuel ratio is very high and

engine operation is not impaired by the presence of inert gases instead of air.

The recirculation system is controlled by electronic control unit ( 1 ) , which receives input signals from a

potentiometer on the accelerator lever (on the injection pump) and from the rpm and coolant tempera-

ture sensors. It produces an output signal which controls the Borg Warner modulator solenoid and

hence the E.G.R. ( 2 ) .

The E.G.R. is connected to the atmosphere through filter (3). According to an imput signal, the valve d i -

rects a higher or lower vacuum from the brake servo vacuum pump (4) to the Pierburg EGR valve ( 5 ) .

If the vacuum is sufficient, this valve opens to bring the exhaust manifold into communication w i t h the

intake manifold.

The amount of gas recirculated can therefore be altered by adjusting Pierburg E.G.R. valve opening con-

tinuously on the basis of maps saved in the ECU memory and the degree of opening, which is in turn de-

pendent on signals received.

1. Electronic control unit

2. Borg Warner modulator solenoid control-

3. Atmospheric intake filter

4. Vacuum pump for brake servo

5. E.G.R. valve.

A. Gas from the exhaust manifold

B. Gas sent to intake

Btavo-Brava 1 0 ™

Publication no. 506.670/06