Fiat 1996 Brava Service Manual page 373

Engine
Fuel system
10.
JTD
Bravo-Brava ^
98 range
EXHAUST GAS RECIRCULATION CIRCUIT (EGR • Exaust Gas Recirculation)
This system makes it possible to send part of the exhaust gases to the inlet in certain engine operating
conditions.
This dilutes the fuel mixture with the inert gases lowering the peak temperature in the combustion
chamber; this contains the formation of nitrogen oxides (NOx), giving a reduction of 30-50% at the ex­
haust.
The recirculation of exhaust gases is only allowed at medium-low loads, when the air/fuel ratio is very
high and the operation of the engine is not adversely affected by the presence of inert gases in place of
the air.
The recirculation is controlled by the injection control unit (1) which, basically according to the signals
from the accelerator pedal potentiometer, the rpm sensor and the engine coolant temperature sensor,
supplies an output signal for operating the modulating valve (2).
On the basis of the signal received, the latter, connected to the atmosphere by means of a small filter (3),
transmits a lesser or greater vacuum, coming from the brake servo vacuum pump (5), to the EGR valve
(4).
If the vacuum is sufficient, the valve (4) opens placing the exhaust manifold in contact with the inlet
manifold.
Diagram showing exhaust gas recirculation
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