Fiat 1998 Marea Weekend, Service Manual

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Marea-Marea Weekend®™®™
Engine
99 range Fuel system
10.
EMISSION CONTROL DEVICES
4F025NJ01
CATALYTIC CONVERTER
The catalytic converter is a post-treatment device
for oxidizing the CO, the HC and the particulates,
transforming them into carbon dioxide (CO 2) and
water vapour (H20).
The catalyzer consists of a ceramic honeycomb
monolith (1), whose cells are impregnated with
platinum (2) which acts as a catalyst for the
oxidation reactions.
The exhaust gases passing through the cells heat
the catalyzer, triggering off the conversion of the
pollutants into inert compounds.
The chemical oxidation of the CO, HC and par-
ticulates, is effective at temperatures of between
200 °C and 350 °C.
Above 350 °C the sulphur contained in the die¬
sel fuel starts to oxidize producing sulphur di-
oxide.
This system makes it possible to send some of the exhaust gases to the inlet in certain engine operating
conditions.
This dilutes the fuel mixture with inert gases lowering the peak temperature in the combustion chamber;
this contains the formation of nitrogen oxides (NOx) producing a 30-50% reduction at the exhaust.
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