How emission control works
When an automobile engine is running, it uses
energy generated through the combustion of a
mixture of air and fuel. Depending on whether a
car is driven fast or slowly or whether the en-
gine is cold or hot, some of the fuel (hydrocar-
bons) may not be burned completely but be dis-
charged into the engine crankcase or exhaust
system. Additional hydrocarbons may enter the
atmosphere through evaporation of fuel from the
fuel tank. These hydrocarbons (HC), when re-
leased into the air, contribute to undesirable pol-
lution.
In addition, carbon monoxide (CO) and oxides of
nitrogen (NOx) contribute to engine emissions.
They, too, are formed during the combustion
process and discharged into the exhaust sys-
tem.
To reduce these pollutants, your Porsche is
equipped with a precisely calibrated fuel injection
system to assure a finely balanced air/fuel mix-
ture under all operating conditions.
Oxygen sensor
The oxygen sensor, installed in the exhaust pipe
continuously senses the oxygen content of the
exhaust and signals the information to an elec-
tronic control unit. The control unit corrects the
air/fuel ratio, so that the engine always receives
an accurately metered air/fuel mixture.
Crankcase ventilation
Through crankcase ventilation undesirable emis-
sions from the engine crankcase are not per-
mitted to reach the outside atmosphere. These
emissions are recirculated from the crankcase
to the air intake system. From here the emis-
sions mix with the intake air and are later
burned in the engine.
Catalytic converter
The catalytic converter is an efficient "clean-up"
device built into the exhaust system of the ve-
hicle. The catalytic converter burns the un-
desirable pollutants in the exhaust gas before it
is released into the atmosphere.
The exclusive use of unleaded fuel is criti-
cally important for the life of the catalytic
converter. Therefore, only unleaded gaso-
line without additives must be used.
The catalytic converter will be damaged by
• push or tow starting your vehicle
• misfiring of the engine
• turning off the ignition while the vehicle
is moving or
• driving until the fuel tank is completely
empty
• by other unusual operating conditions.
Do not continue to operate your vehicle
under these conditions, as otherwise fuel
can reach the catalytic converter. This
could result in overheating of the con-
verter. Federal law prohibits use of leaded
gasoline in this car.
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Содержание 928 GTS 1994
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