gas type AUDI S4 1998 B5 / 1.G Engine Manual

24
SSP 198/33

Engine
A new generation of probes is used
in this engine.
The “planar lambda probe“ is an
improvement on the finger-type
lambda probe (refer to chapter on
“Sensors”).
Advantage:
•
Short warm-up time
•
Less heating energy demand
•
Long service life
•
More stable control
characteristic
Exhaust system
The exhaust manifolds are designed as pipe
elbows with insulated air gaps.
Advantage:
•
Less heat loss of the exhaust gas and less
heat radiation in the engine compartment
•
Weight saving
Located downstream of each exhaust gas
turbocharger is a primary catalytic converter
close to the engine (metal substrate) .
Advantage
•
The catalytic converters quickly reach a
state of readiness for operation after a cold
start
The large-surface area main catalytic
converters (ceramic substrate) are located
under the vehicle floor.
Lambda probe
Prim. catal. converterMain catalytic converter
Exhaust manifold
Wire mesh ring acting
as a spacer
Air-gap-insulated pipe elbow
Outer shell
Inner pipes

52
Sensors
Lambda probes G39 and G108
The planar lambda probe is a further
development of the finger-type lambda probe
and has a transient response at lambda = 1.
There is a single lambda probe in the exhaust
pipe running to each of the primary catalytic
converters.
To ensure that the exhaust gases are treated
efficiently, it is important that the lambda
probe should react quickly. The lambda probe
should therefore reach its operating
temperature within as short a space of time as
possible. Its planar (= flat, elongated) design
makes this possible.
The probe heater is integrated in the sensor
element. It quickly reaches its operating
temperature despite its lower heating capacity.
Note:
At an exhaust gas temperature as low as 150
°C, the probe heater generates the necessary
minimum temperature of 350 °C.
The lambda control is ready to operate approx.
10 seconds after engine start-up.
A porous, ceramic protective layer is sintered
onto the sensor element.
This layer prevents the sensor element being
damaged by residues in the exhaust gas.
It ensures that the sensor element will have a
long service life and meet the tough functional
demands.
Substitute function:
Controlled operation based on a characteristic
curve (cylinder bank-specific).A new generation of probes used in
the biturbo for stereo lambda
control.
Advantages:
• The warm-up period is short, which means
lower emissions during the warm-up phase
• Low heating power consumption
• More stable control characteristic
SSP 198/37
Section
Probe heater
Sensor element