Fiat 1996 Brava Service Manual page 372

Bravo-Brava ^™
98 range
P4A23KJ01
EXHAUST GAS CIRCUIT
The engine exhaust gases flow through the manifold
idizing catalytic converter and then to the silencer.
Special protection limits the heat given off
EMISSION CONTROL DEVICES
P4A23KJ02
Engine
Fuel system
10.
TURBOCHARGER
It is basically made up of two impellers (1) fitted
on one shaft (2), which rotates on floating
bearings lubricated via a duct (3) from the en­
gine lubrication circuit.
The oil used discharges part of the large amount
of heat given off by the exhaust gases at the tur­
bine.
There is a waste-gate valve (4), operated by a
pneumatic actuator (5), on the turbocharger,
which shutters the flow of exhaust gases to the
turbine, according to the engine power/torque
request.
1. Impellers
2. Shaft
3. Lubrication
4. Waste-gate valve
5. Actuator
To the turbocharger and, through a pipe, to the ox-
the bodyshell.
CATALYTIC CONVERTER
The catalytic converter is a post-treatment de­
vice for oxidizing the CO, HC and particle mat­
ter, transforming them into carbon dioxide
(CO2) and water vapour (H2O).
The catalyzer consists of a ceramic honeycomb
structure (1), whose cells are impregnated with
platinum (2), which acts as a catlyst for the oxi­
dation reactions.
The exhaust gases which pass through the cells
heat the catalyzer, triggering off the conversion
of the pollutants into inert compounds.
The chemical reaction of the oxidation of the
CO, HC and particle matter is effective at tem-
peartures of between 200 °C and 350 °C.
Above'350 °C, the sulphur contained in the
diesel fuel starts to oxidize, producing sulphur
dioxide and sulphur trioxide.
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