fuel consumption AUDI S4 1998 B5 / 1.G Engine Manual

8
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

28
SSP 198/05

Engine
Divert air control in overrun
To avoid pumping the exhaust gas
turbochargers when a sudden transition from
high load to overrun is made, two divert air
valves are used.
The Motronic also activates the
two pneumatic divert air valves by
means of
an
electrical changeover
valve, the divert air valve for
turbocharger N249.
Advantage:
•
Controlled opening of the
divert air valves reduces the
noise level in the induction
tract and reduces fuel
consumption.
The divert air valve N249, in combination with
the vacuum reservoir, enables the divert air
valves to operate independently of the intake
manifold pressure.
The system is designed in such a way that the
pneumatic divert air valves continue to be
opened by the intake manifold pressure if the
electrically actuated divert air valve N249 fails.
Divert air valve for turbocharger N249
Vacuum reservoir (inside
wheelhousing on the left)
Divert air valve (pneumatic)
with flow
without flow
Non-return valve

46
SSP 198/26

Subsystems of the Motronic
Exhaust gas temperature control
A new feature of Audi automobiles
is a function which monitors
exhaust gas temperature over the
entire engine speed range.
For turbocharged engines, the maximum
permissible exhaust gas temperature is a key
design criterion.
To protect the exhaust gas turbocharger and
the exhaust manifold, the exhaust gas
temperature should not exceed 1000 °C for a
lengthy period of time.
Since many of the components which
influence the exhaust gas temperature have
tolerances, thermodynamic adaptation
previously took place at 950 °C for safety’s
sake.
This was achieved by enriching the air/fuel
mixture.
The exhaust gas temperature is recorded in a
cylinder-bank-specific manner by the two
exhaust gas temperature senders G235 and
G236.
The Motronic controls the exhaust gas
temperature to 980 °C by enriching the air/fuel
mixture .
It is therefore possible to largely dispense with
the prophylactic enrichment process that has
been standard practice until now.
The mixture is only enriched...
... when necessary and
... to the extent necessary.
This means that engine operation with lambda
= 1 is possible up to high load and engine
speed ranges.
Advantage:

• Improved efficiency and reduction of fuel
consumption as well as exhaust emissions.
Exhaust gas temperature sender
Engine control unit
Injectors
G235
G236

57
Additional signals/interfaces
Additional signals/interfaces to
Motronic ME 7.1
The Motronic receives a large number of
additional signals.
The following overview shows the signal
direction and meaning referred to the Motronic
control unit
Input
signalOutput
signalBidirec-
tionalSignal meaning
·CAN-high, data bus signal for automatic gearbox
·CAN-low, data bus signal for automatic gearbox
·CCS, “set/decelerate“ signal for cruise control system
·CCS, “Off“ signal for without cancellation cruise
control system
·CCS, “On/Off“ signal for with cancellation cruise
control system (master switch)
·CCS, “Resume/accelerate“ signal for cruise control
system
·Road speed signal
·Immobiliser/diagnosis signal
·Air conditioner compressor “On/Off“ signal
·Coolant temperature signal
·Engine speed signal
·Fuel consumption signal
The term “interfaces“ is used to
describe the control unit connections
and wiring connections of the various
control units.

61
The fuel consumption signal...
... is a data message which is conditioned by
the engine control unit. The sum total of the
high levels during a defined period of time
corresponds to the injected fuel quantity.... is required by the dash panel insert to
calculate fuel consumption and range.
The interfaces of the cruise control system (CCS) ...
... are linked to the controls on the steering
column switch.
Cruise control is executed by the
engine control unit by means of the
electronic accelerator function.
Road speed can be kept constant as
of approx. 25 kph.The CCS must be enabled or disabled using
the “login procedure“ function (as with TDI
engines).
When the control unit is enabled, a “G“
appears in the control unit identification (refer
to Workshop Manual).
SSP 198/68
Fuel consumption signal
Signal of Hall sender G40
Signal at idling speed in a time grid of
50 ms/div.

62
Functional diagram
Components:
F Brake light switch
F36 Clutch pedal switch
F47 Brake pedal switch
F96 Altitude sender (integrated in engine
control unit)
G2 Coolant temperature sender
G6 Fuel pump
G28 Engine speed sender
G31 Charge pressure sender
G39 Lambda probe (cylinder bank 1)
G40 Hall sender (cylinder bank 2)
G42 Intake air temperature sender
G 61 Knock sensor (cylinder bank 1)
G62 Coolant temperature sender
G66 Knock sensor (cylinder bank 2)
G70 Air mass meter
G79 Accelerator position sender 1
G108 Lambda probe (cylinder bank 2)
G163 Hall sender (cylinder bank 1)
G185 Accelerator position sender 2
G186 Throttle valve drive (electric throttle
control)
G187 Angle sender 1 for throttle valve drive
G188 Angle sender 2 for throttle valve drive
G235 Sender 1 for exhaust gas temperature
G236 Sender 2 for exhaust gas temperature
J17 Fuel pump relay
J220 Motronic control unit
J338 throttle valve control part
K132 Warning lamp for electric throttle
control
N Ignition coil, cylinder 1
N30 Injector, cylinder 1
N31 Injector, cylinder 2
N32 Injector, cylinder 3
N33 Injector , cylinder 4
N75 Solenoid valve for charge pressure
control
N80 Solenoid valve for activated charcoal
canister
N83 Injector, cylinder 5
N84 Injector, cylinder 6
N122 Output stage (cylinder bank 1)
N128 Ignition coil, cylinder 2
N158 Ignition coil, cylinder 3
N163 Ignition coil, cylinder 4
N164 Ignition coil, cylinder 5N189 Ignition coil, cylinder 6
N192 Output stage (cylinder bank 2)
N205 Camshaft adjustment valve 1 (cylinder
bank 1)
N208 Camshaft adjustment valve 2
(cylinder bank 2)
N249 Divert air valve for turbocharger
Z19 Heater for lambda probe
Z28 Heater for lambda probe 2
I To dash panel insert
II To dash panel insert (warning lamp)
Additional signals
1 CAN-high (automatic gearbox)
2 CAN-low (automatic gearbox)
3 „Set/decelerate“ signal for cruise
control system
4 “Off“ signal without cancellation for
cruise control system
5 “On/Off“ signal with cancellation for
cruise control system
6 Resume/accelerate“ signal for cruise
control system
7 Road speed signal
8 Immobiliser/diagnosis signal
9 Air conditioner compressor “On/Off“
signal
10 Coolant temperature signal
11 Engine speed signal
12 Fuel consumption signal
Colour codes:
Input signal
Output signal
Positive
Earth
Bidirectional