charging AUDI S4 1998 B5 / 1.G Engine Manual
[x] Cancel search | Manufacturer: AUDI, Model Year: 1998, Model line: S4, Model: AUDI S4 1998 B5 / 1.GPages: 72, PDF Size: 3.25 MB
Page 3 of 72
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This Self-study Programme provides you with information
regarding design and function.
The Self-study Programme is not a Workshop Manual!
Please refer to the Service Literature for all the relevant
maintenance and repair instructions.
Page
Engine .........................................................
Technical data, crankshaft, cylinder head,
camshaft timing, cooling circuit, engine
lubrication, overview of components, air ducting,
charging, exhaust system, pneumatically
controlled systems, charge pressure control, air
divert control in overrun, ACF system, crankcase
breather
4
Motronic ME 7.1 ..........................................
Subfunctions, system overview
31
Subsystems of the Motronic .....................
Torque-oriented engine management, torque-
oriented functional structure, Electronic throttle,
exhaust gas temperature control
33
Sensors .......................................................
Additional sensors of the Motronic
49
Auxiliary signals/interfaces ...................... 57
Functional diagram ..................................... 62
Self-diagnosis .............................................
Vehicle diagnosis, test and information system
VAS 5051, test box V.A.G 1598/31
64
Transmission ..............................................
Self-adjusting clutch, gearbox
66
Contents
Important!/Note!
New!
Page 8 of 72
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Engine
The variable valve timing
The camshaft timing has been modified
compared to the 2.8-litre V6 engine to meet the
demands of turbocharging technology.
Variable valve timing with an adjustment angle
of 22° is used here for the first time in
turbocharged engines
.
Advantage:
•
A torque increase of approx. 10% is
achieved at the bottom and top ends of the
engine speed range.
•
Better emission levels and fuel
consumption figures.
The variable valve timing is activated by the
Motronic by means of camshaft adjustment
valves N205 and N208.The design and function of the
variable valve timing are already
described in Self-study Programmes
182 and 192.
Activation of the variable valve timing is
dependent on engine load and speed.
In the self-diagnosis, you can find out whether
the variable valve timing is active or not by
reading out the relevant measured value block
(refer to Workshop Manual).
0
0 1000 2000 3000 4000 5000 6000 7000
SSP 198/45
Diagram of variable valve timing
(shown using the 265 bhp engine as an
example)
Engine speed
Engine load in %
Variable valve timing active
= advance position
Full throttle
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SSP 198/32
Charging
Two
water-cooled exhaust gas turbochargers
with wastegate are used for charging.
The charge pressure of both exhaust gas
turbochargers is controlled via the common
charge pressure control valve N75.
Advantages of the biturbo technology:
•
The exhaust gas turbocharger is smaller,
which means better response due its
reduced mass.
•
Higher charge pressure at low engine
speeds.
•
The exhaust gas turbochargers are located
outside the V-angle due to the high
temperatures they reach. This advantage of
this arrangement is that the intake air is not
heated up additionally and the sub-
assemblies are not subjected to so much
thermal stress.
•
Since the turbochargers are flanged
directly onto the exhaust manifold, the
exhaust gases travel less distance and
there is less temperature loss.
•
As a result, the catalytic converters are able
to heat up more quickly and the efficiency
of the exhaust gas turbocharger is
improved by the favourable air-flow.
Intake side of exhaust
gas turbocharger
Charge press. side
of exh. gas turbo-
charger
Exhaust manifold
to exhaust system
Pressure unit for actuating
wastegate flap
Control pressure from
solenoid valve for
charge pressure
control
The turbochargers must be replaced
in pairs
To maintain a synchronous air-flow
through the two chargers, it is
important to observe this instruction
to account for manufacturing
tolerances.
Service personnel are
not
permitted
to adjust the linkage to the wastegate
flap.
Turbine housing
Compressor housing
Page 25 of 72
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SSP 198/08
Engine
Charge pressure control
The air mass required to develop a specific
level of torque is determined by means of an air
mass calculation and produced by controlling
the charge pressure as required.
For safety reasons, the engine in the biturbo
regulates the charge pressure, and not the air
mass as is the case with the 1.8-litre 4-cylinder
turbocharged engine.
The charge pressure is measured by charge
pressure sender G31.
The Motronic regulates the charge pressure of
both turbochargers via the solenoid valve for
charge pressure control G31.
If a defect occurs in one of the cylinder banks
(e.g. melting of the catalytic converter or
blockage of the exhaust system), a purely air
mass-oriented charging system would still try
to provide the computed air mass.
This would lead to an excessively high charge
pressure.
In any case, the charge pressure control
prevents an excessively high charge pressure
building up inside the intake system.
Charge pressure sender G31
Atmospheric pressure
Solenoid valve for charge
pressure control N75
Charge pressure
Control pressure
Page 33 of 72
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Subsystems of the Motronic
In comparison with previously known
systems, the ME 7.1 is not confined to the
output of torque variables to the networked
control units (ABS, automatic gearbox), it also
uses these physical variables to calculate
control variables.All - internal and external - torque demands
are combined, and a nominal torque is derived
from this.
To translate the nominal torque into actions,
the control variables are co-ordinated with
regard to consumption and emissions so as to
optimise torque control.
SSP 198/75
External and
internal
torque
requests
Calculation of
efficiency and
torque reference
variables
Prioritisation of
charging path
Prioritisation
of crankshaft-
synchronous
path
Conversion of
torque into
charge
Throttle valve
angle
Charge
pressure-
control
Calculation of
crankshaft-
synchronous
intervention
Calculation of
throttle valve
opening
Charge
pressure
(Wastegate)
Ignition angle
Injection cut-
out
Injection time
Nominal charging
moment
Nominal charge
Nominal intake
manifold
pressure
Nominal inner
torque
Actual charge
Torque-oriented
functional structure
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The control variable calculation is subdivided
into two paths
Path 1
The charging path regulates the control
variables which influence charging:
• Throttle valve angle
• Charge pressure
Path 2
All control actions which influence torque
regardless of charging are combined in the
crankshaft-synchronous path:
• Ignition angle
• Injection cut-out
• Injection time
The air mass necessary to develop a specific
torque is determined by means of a
“calculation model“ and is made available
along path
1
.
Path
2
is used to set the injection quantity or
cylinder cut-out necessary under the given
circumstances and the optimal ignition angle.
Prioritisation of
charging pathPrioritisation
of crankshaft-
synchronous
path
By and large, long-term torque requests are
fulfilled along path
1
.
Path 2
is particularly well suited to meeting
short-term torque requests, which usually
have a torque-reducing effect.