Porsche 928 GT1991, Руководство пользователя

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How emission control works Oxygen sensor
When an automobile engine is running, it
uses energy generated through the combus-
tion of a mixture of air and fuel. Depending
on whether a car is driven fast or slowly or
whether the engine is cold or hot, some of
the fuel (hydrocarbons) may not be burned
completely but be discharged into the en-
gine crankcase or exhaust system. Addi-
tional hydrocarbons may enter the atmos-
phere through evaporation of fuel from the
fuel tank. These hydrocarbons (HC), when
released into the air, contribute to undesira-
ble pollution.
In addition, carbon monoxide (CO) and
oxides of nitrogen (NO*) contribute to engine
emissions. They, too, are formed during the
combustion process and discharged into
the exhaust system.
To reduce these pollutants, your Porsche is
equipped with a precisely calibrated fuel in-
jection system to assure a finely balanced
air/fuel mixture under all operating condi-
tions.
The oxygen sensor, installed in the exhaust
pipe continuously senses the oxygen con-
tent of the exhaust and signals the informa-
tion to an electronic control unit. The control
unit corrects the air/fuel ratio, so that the en-
gine always receives an accurately metered
air/fuel mixture.
Crankcase ventilation
Through crankcase ventilation undesirable
emissions from the engine crankcase are not
permitted to reach the outside atmosphere.
These emissions are recirculated from the
crankcase to the air intake system. From
here the emissions 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 vehicle. The catalytic converter burns the
undesirable pollutants in the exhaust gas be-
fore it is released into the atmosphere.
The exclusive use of unleaded fuel is crit-
ically important for the life of the catalytic
converter. Therefore, only unleaded
gasoline 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 vehi-
cle is moving or
• 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 conver-
ter. Federal law prohibits use of leaded
gasoline in this car.
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