Porsche 928 S 1986 Driver Manual page 67

Fuel canister
If the tank is filled up in good time and as the
tank has a large capacity plus a reserve of
approx. 8 litres, it is generally not necessary
to carry a fuel canister.
If a fuel canister is nevertheless carried in
the vehicle, this should be secured in a safe
place where it will not slip (e.g. behind rear
seat backrest). Incorrectly stowed canisters
may be damaged in an accident and split fuel
represents an additional fire risk.
Fuel may leak from canisters which do not
close securely and this may lead to unpleasant
odours and danger of explosion.
The Emission Control System
Your Porsche is equipped with an emission
control system which very effectively reduces
the pollutants in the exhaust gas.
The system consists of several components:
• the double catalytic converter
• the lambda sensor
• the LH-Jetronic control unit
• the tank ventilation system.
The first three components are required in or-
der to enable so-called three-way catalytic
converter operation.
In conjunction with the computerized LH-Jetro-
nic, the controlled three-way catalytic converter
represents the most effective emission control
system. The emission of hydrocarbons, car-
bon monoxide and oxides of nitrogen is re-
duced by more than 80 % in such a system.
The tank ventilation system prevents fuel va-
pours, i.e. unburned hydrocarbons, from es-
caping from the fuel tank into the atmosphere
in summer.
The operating principle of these two systems
is described in the following:
The catalytic converter is installed in place
of the primary silencer. It contains two mono-
liths. These are ceramic bodies which have
channels running through them in the longi-
tudinal direction (62 channels per square centi-
metre).
The surface of these channels is dramatically
increased by a special coating, the wash-coat.
The catalytically active noble metal is applied
to this coating. The catalytic reaction is a sur-
face reaction whose effectiveness is propor-
tional to the size of the surface area acces-
sible to the exhaust gas.
Your Porsche provides a surface area of some
15 football pitches on which 6.6 g of noble
metal (platinum and rhodium) are finely distri-
buted.
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