Turbocharger; Exhaust Gas Circuit; Catalytic Converter - Fiat Bravo Service Manual

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E X H A U S T GAS C I R C U I T

The engine exhaust gases flow through the manifold To the turbocharger and, through a pipe, to the ox-

idizing catalytic converter and then to the silencer.

Special protection limits the heat given off towards the bodyshell.

E M I S S I O N CONTROL D E V I C E S

T U R B O C H A R G E R

It is basically made up of t w o impellers (1) fitted

on one shaft ( 2 ) , w h i c h rotates on floating

bearings lubricated via a duct (3) from the e n -

gine lubrication circuit.

The oil used discharges part of the large amount

of heat given off by the exhaust gases at the tur-

There is a waste-gate valve ( 4 ) , operated by a

pneumatic actuator ( 5 ) , on the turbocharger,

w h i c h shutters the f l o w of exhaust gases t o the

turbine, according t o the engine p o w e r / t o r q u e

1. Impellers

3. Lubrication

4. Waste-gate valve

C A T A L Y T I C C O N V E R T E R

The catalytic converter is a post-treatment de-

vice for oxidizing the CO, HC and particle mat-

ter, transforming them into carbon

and water vapour

The catalyzer consists of a ceramic honeycomb

structure ( 1 ) , whose cells are impregnated w i t h

platinum ( 2 ) , w h i c h acts as a catlyst for the o x i -

dation reactions.

The exhaust gases w h i c h 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 t e m -

peartures of between 200 °C and 350 °C.

A b o v e ' 3 5 0 °C, the sulphur contained in the

diesel fuel starts t o oxidize, producing sulphur

dioxide and sulphur trioxide.