AUDI Self Study Program 105 – V8 Engine SSP-105-V8-Engine

V.A.G Service

V8 Engine

Design and Function

Self-Study Program Nr. 105

V8 Engine

The aim of the Audi engineers was to develop an engine with a large displacement and thus effort­less power delivery, with minimum weight and compact dimensions for the new Audi V8.
The concept of an eight-cylinder engine in V-arrangement of the cylinders allows for the ideal con­ditions for installation in vehicles with a compact engine compartment.
With a multitude of technological innovations, Audi has driven the development of the V8 engine
substantially. The new V8 engine represents the latest technology for high-tech engines.
With an output of 184 kW (250 hp) from a displacement of 3.6 liters and a maximum torque of 350
Nm at 4000 rpm, this engine has high power reserves, elasticity and smoothness which are ex­ceeded by only a few limousine engines worldwide.

Contents

V8 engine with 4-valve technology

V8 engine

Cylinder crankcase and crank operation

Cylinder Head and Valve Train

Hydraulic tappets with labyrinth

belt drive for valve trains

The ancillary components

engine lubrication

Oil circuit

• viscous clutch fan

• newly developed air intake system

Motronic

Fuel system

Fuel vapor retaining system,

Injection with adaptive control function

Block Diagram

Sensors and Actuators

Motronic wiring diagram

• Self-diagnosis

The detailed inspection, adjustment and repair instructions
can be found in the Workshop Manual Audi V8 in 1989 in the volume
“8-cyl fuel injection engine” and the booklet “Motronic injection and igni­tion system.”

The new V8 engine with 4-valve technology is the most compact of all V8 engines built today. This
was achieved through a completely newly developed cylinder crankcase, short-designed crank­shaft, cleverly placed auxiliary power units and the compact design of the intake system. The 16­valve cylinder heads were redesigned for the V8 engine, with a portion of the existing production
line.

Engine Specications

Type: V8 with 90 V-angle
Displacement: 3.6 l
Bore / Stroke: 81.0 mm / 86.4 mm
Compression Ratio: 10.6 : 1
Cylinder spacing: 88.0 mm
Cylinder offset from right to left: 18.5 mm
Total length: 508 mm
Total weight: 215 kg
Mixture preparation and ignition: Motronic with knock control via two sensors
Emission: lambda control with two catalytic converters
Fuel: Premium unleaded / Regular unleaded with derating

Engine speed (RPM)

Power and torque

WIth a power output of 184 kW (250 hp) from a displacement of 3.6 liters and a
torque of 350 Nm at 4000 rpm, the V8 engine has high power reserves. In order to
achieve the high performance values on the one hand and a good torque in the low
speed range on the other hand, an intake system had to be developed with long
ram tubes and low air resistance. At the same time the new intake manifold design
provides good accessibility of the injectors and spark plugs provide for mainte­nance. A corresponding re-styling of the engine and the engine compartment was
demanded.

fuel pressure
regulator

fuel injector

intake

knock
sensor

Oil ducts

for piston
cooling

oil temperature
sender

oil pressure
switch

oil thermostat

Dynamic Oil Pres­sure Switch for
analog display

Air mass meter

spark plug

hydraulic tappets

knock sensor

Reference mark sensor

Speed controller

Oil pump with integrated
pressure relief valve

Idle stabiliza­tion valve

Throttle
switch and
potentiometer

water pump

Belt pulley
with vibration
damper

Air lter housing

Throttle actuator
shaft

converter drive
plate

crankshaft

To obtain good smoothness of the V8 engine, components of the highest quality are produced. By
using the same material (aluminum) and thus having equivalent expansion between the piston and
the cylinder block, very low thermal differential was achieved. In addition, the pistons are matched
to the the cylinder bores.

A tight clearance of the crankshaft main bearing is achieved by measuring the main bearing bore
and the main journals of the crankshaft and selecting the bearing shell by thickness.

cylinder crankcase

The crankcase is cast in a hypereutectic aluminum alloy, and tje cylinders are specially treated to
expose the hard silicon crystals as a wear-resistant running surface for the piston and piston rings.
Conventional cylinder liners are therefore not required. Through this weight-saving design, a low
engine weight is achieved.

Connecting rods and pistons

The connecting rods are designed to be lightweight and ade manufactured from aluminum. In
each case two connecting rods sit on a crankshaft journal.
The pistons have a Ferrostan reinforcement on the piston skirt, as a “running partner” to the alumi­num cylinder bore. The oil lubricating the connecting rod bearing is removed from the main bear-

ings of the crankshaft at the point at which the carrying capacity of the oil lm is not disturbed.
To ensure the oil ow to the connecting rod bearings, the large side carries oil pockets. This en-

sures that the oil can freely escape after it has lubricated the bearings.

Crankshaft

The crankshaft is designed as a classic V8 cross shaft with a hundred-percent mass balance. It is
made in the so-called twist technique. The shaft is forged in a plane and rotated in a warm condi-

tion to ensure optimal training of the counterweights. The ywheel or drive plate screw has been

optimized so that high output can be transmitted securely. At the forward end of the shaft, a vibra-

tion damper is tted.

An identical cylinder head with four-valve technology is installed on
each bank of cylinders of the V8 engine.

Distributor I

Drive for intake
camshaft

intake
camshaft

exhaust
camshaft

identication

Drive for ex­haust cam­shaft

The exhaust camshaft is driven by a toothed belt. The inlet camshafts are each driven by the
exhaust cam via a chain.
The timing of the camshafts had to be altered due to the ring order. The tappets were de­signed as a labyrinth ram. The two oil pressure holding valves for cylinder head oil supply in
connection with the labyrinth tappets ensure smooth valve train operation.

Distributor II

intake
camshaft

identication

Drive for ex-

haust cam­shaft

exhaust
camshaft

exhaust
valve

intake
valve

4-valve technology

4-valve technology, a sophisticated air intake and optimum exhaust manifold, has a signicant ef­fect on the spontaneous power delivery and high RPM ability of the V8 engine. The 4-valve design
permits a compact combustion chamber, and places the spark plug optimally between the valves.

This makes a higher compression possible, which improves the thermal efciency, and thus the

fuel economy.

The hydraulic tappets have been improved by a space maze in
the oil supply area. This results in a noise reduction in the cold
start phase.

Oil inlet bore

oil groove

Labyrinth

storage
space

Cylinder

check
valve

Piston

valve
spring

A hydraulic tappet consists essentially of two movable parts, the piston and the cylinder. These
parts are pressed apart by spring force until between camshaft and valve stem so that no play is

present. The check valve is used for lling and sealing the high-pressure chamber. The labyrinth-

like design of the oil supply prevents drain off of the oil after the engine has stopped.

high-pressure chamber

How it works

If the cam runs on the valve lifter, the check valve
closes and it builds up in the high-pressure chamber
a pressure. The trapped oil volume can not condense,
the tappet acts as a rigid element.

leakage gap

Start of valve stroke

The cam applies a force on the plunger, the pressure in
the high-pressure chamber rises. Some of the oil es­capes through the leakage gap from the high-pressure
chamber. Thus, the ram pushes while the valve lift to
max. 0.1 mm together. This is a construction necessary
so that the plunger also can adapt to a decreasing dis­tance between camshaft and valve.

valve play

Balancing valve clearance

After the closing of the valve, the cam does not press on
the plunger, and the pressure in the high-pressure cham­ber decreases. The compression spring pushes the cylin­der and piston apart only until no play is left between the
cam and tappet. The check valve opens, so that oil from

the reservoir can ow into the high pressure chamber. The
subsequently owing quantity is dependent on the valve

clearance.

The valve gear, oil pump and water pump are
driven via a 30 mm wide, specially designed belt

with Super Torque prole.

Drive
for
cam­shaft

Drive for
water
pump

deec­tion pul­ley

adjustment
roller

idler

crankshaft

Drive
for oil
pump

To meet the thermal expansion of the engine, an automatic tensioning
device was installed, which holds a spring-damper the timing belt at a
constant pressure. This is a prerequisite for reliability of the belt over the
lifetime of the motor. The belt length tolerance varies depending on the
manufacturer is different, so an eccentrically mounted adjustment roller
is used so that the automatic tensioning device must only compensate
for the thermal expansion, reducing belt stretch. The tensioner pulley
was positioned so that it most strongly secures the required wrap on the
crankshaft sprocket.

Automatic tensioning device

idler

setting
for stop

pressure
spring

center
hole

Vibration
damper

clamping

Crankshaft

How it works

Belt tension is transmitted by the compression spring via a lever mech­anism to the idler pulley. The effect of the damper prevents swinging
and uttering of the timing belt. The stop for the clamping lever pre­vents excessive loosening of the belt and thus skipping the reverse
rotation of the motor.

lever

The auxiliary units and the VISCO-fan are
driven by a V-ribbed serpentine belt with 6
ribs.

torsion
spring
(Tension
spring)

Vibration damper

The V-ribbed belt is required to exactly position the assembly
due to the low tolerances when meshing with the grooves of
the pulley. This is achieved by aligning the pulley discs of the
hydraulic pump by means of dowels. The small thickness com­pared with a conventional V-belt enables the use of small-diame­ter pulleys. A damped automatic tensioner keeps the belt tension
over its life almost constant, that is, belt length changes caused
by thermal expansion and belt wear are compensated for.

V-ribbed belt

Automatic tensioner

vibration
damper

tension
spring

idler

clamping
arm

How it works

The clamping force (tensile load) of the automatic tensioner is applied by a
strong torsion spring and transferred to the idler pulley on a tensioner arm.
The attenuation of the tensioner is via a hydraulic shock absorber with dif­ferent compression and rebound damping. It is not necessary to change
the V-ribbed belt over the lifetime of the motor.

Crankcase ventilation

The crankcase breather is positioned between the rows of cylinders.
An intermediate plate lets oil mist and oil splashes drip back to the
oil sump. The end cap is decorated inside like a labyrinth, which also

contributes to the deposition of ne oil mist droplets and prevents their

extraction by the motor.

vent
space

oil retention
valves

oil
pres­sure
switch

oil
pump
drive

oil pump

intermediate plate

The oil pump is a gear pump. It is driven via the
toothed belt at slightly higher than half the crank­shaft speed. The elastomeric oil intake will draw
even with a deformed oil pan -- the suction port is
fed without suppression.

Oil pressure
valve

End cover
with labyrinth

oil pan

The crankcase is closed from below by a two-piece oil
pan. The upper half is ade of die-cast aluminum and
simultaneously encloses the converter housing of the
automatic transmission. The lower half is ade of sheet
steel, so is deformable from the outside and crack-resist­ant during heat surges.
A newly developed oil honeycomb plastic is located in
the upper part of the oil pan. It aids in defoaming the oil

owing back and provides a bubble-free oil supply even

under extreme conditions.

oil

Elastic
rubber
intake

honey­comb

oil drain
plug

How it works

The required oil pressure to the bearings and for the double
spray nozzles in the crankcase is built up from the gear oil
pump. The double spray nozzles spray each a pair of pis­tons with oil cooling. A central valve ensures even oil pres­sure at all spray nozzles, and thus a uniform cooling effect
is achieved on all pistons. The oil retention valves at each
inlet channel of the cylinder heads prevent the oil from
returning from the bearings with the engine stopped. The
oil feed to the connecting rod bearing is located in the duct
to the crankshaft bearings. The oil thermostat opens the
passage to the oil cooler at approximately 100 ° C. The oil
cooler is disposed below the engine cooler and exchanges
to the air.

Oil Filter

Oil
cooler

oil
pres­sure
switch

dynamic
oil pres­sure
switch

The VISCO-fan operates temperature­dependent, ie, it only works when an
additional engine cooling is required.

How it works

The visco clutch substantially consists
of two chambers, the working chamber
of the drive pulley and the reservoir.
Silk spaces are connected via a valve

and with silicone oil lling.

With the valve open, the silicone oil
between two spaces circulates.

working

chamber

drive pul­ley

reservoir
silicone oil
fan housing

How it works

Engine cold

By rotation of the clutch via the oil guide
vanes is fully pumped into the reservoir. The
above bimetal controlled valve is closed, it

ows no oil in the working area. In oil-free
working chamber, there is no power ow

between the drive clutch and the housing
(with fan). The fan operates at a low speed in
driving.

Reed
valve

drive
pulley

switch pin

bimetallic
element

pump
body

Engine warm

The bimetal opens via the switching valve

spring pin the sheet. The silicone oil to ow

through the valve opening into the working
space. This creates a connection between the
drive pulley and fan housing.
The body is entrained with the fan-the fan
speed increases.

working chamber

valve

internal
bimetal

drive pulley

bimetallic
element

fan housing

Engine hot

The higher the ambient temperature of the
bimetallic element, the greater the stroke of
the valve spring. Through the valve open­ing a larger amount of silicone oil enters the
Arbeltsraum, thus the fan speed is increas­ing. In this operating state, the speed differ­ence is at its lowest between the drive and
the fan.
An internal bi protects the viscous fan clutch
from thermal overload, in which it coun­teracts at a certain temperature the valve
spring. The valve opening cross-section is
small, which causes a reduction in the sup­ply quantity Di into the working space. The
fan power is
limited, which has a thermal speed regula­tion for Falge

The entire intake system was developed for the lowest possible ow resistance. Specially

tuned ram tubes ensure maximum air supply, fast gas exchange and thus a high torque.

Hot-wire mass

air ow sensor

rectier

test sec­tion

Idle air
stabilization
valve

The suction tube is designed as a very compact structure and adapted to the shape of the V
engine. Beginning in the intake behind the throttle valve body t of the air collector. The intake
pipes go from the air collector each reciprocally to the inlet channels of the cylinder heads.
The hot-wire air mass meter was integrated into the intake manifold. For exact measure-

ment the test section is internally machined and tted with a calming rectier for air at the

entrance.
The entire intake pipe is coated with plastic on all sides for heat insulation, surface smooth­ing and corrosion protection.

rectier

Hot-wire mass

air ow sensor

test sec­tion

Throttle body

Idle air
stabilization
valve

plenum

How it works

If after the intake stroke the exhaust valves close, the gas masses travel by inertia in
the direction of the moving intake valve, where it is slightly compressed by colliding
against the inlet valves and swings back to the air manifold. At the point where the

extended cross-section, they are reected and swung back to the intake valves.

When the intake valves open again, the air is already moving towards the cylinder.

That is, it is under a certain pressure; The engine need not rst laboriously intake.

Complete engine control of the Audi V8 is handled by the digital electronic Motronic

engine control system. The operation of this system is based on the needs identied by

the various sensors data. The speed sensor and the amount of intake air can be continu­ously determined, for example.

The tasks of the Motronic are:

Ignition with knock control

•

Fuel injection, Lambda control

•

and fuel cut-off

Idle speed control

•

Tank ventilation control

•

transmission intervention

•

Fault diagnosis and fail-safe

•

fuel injec­tor

Igni­tion

air mass sensor

fuel pres­sure regu­lator

Hall sensor

intake air
temp sensor

Knock
sensor 1

Tempera­ture
sender

Throttle potenti-
ometer and idle
switch

Idle air
valve

O2 sensor

Knock sensor 2

Speed sensor

Ignition Coil II

clock valve

charcoal

lter

diagnostic con­nector

Control
Unit

An in-tank fuel pump pumps the fuel through the lter to the injectors. The return of

fuel from the injectors through the pressure regulator to the tank through the pres­sure regulator maintains the injection pressure at the injectors of about 4 bar differ­ential from intake manifold pressure.

Filter

Injector

Pump

of the in­jectors

full load

Tank

Intake manifold pressure

Membrane

Return to
tank

idle

pressure regulator

The intake manifold pressure affected by the pressure regulator the fuel pressure.
This means that, for example, at low intake manifold during idling, the fuel pressure also drops by
the return to the tank is opened more. Conversely, the process at the full load operation, by this
method it is ensured that the pressure difference between intake manifold and the fuel pressure
remains constant, and the uctuations in intake manifold pressure has no inuence on the injec­tion quantity.

Screen

magnet
wind-

Injector

As an injection valve, a magnetic valve is used. Jetro­nic the controller determines via the electromagnet in
the injector, the opening time of the needle valve. The
pressurized fuel in the injector is injected via a newly
developed two-stream nozzle. The wetting of the ridge
between the two intake valves is prevented and en­richment during the cold start and the warm up phase

signicantly reduced.

Two eroded* holes form an injection jet, which is direct­ed to a respective inlet valve.

* eroded:
Spark erosion process
of metals (EDM)

Fuel injector

Intake valves

Exhaust valves

Ignition and injection chart

cylinder

Reference
mark

Hall

ignition Coil I

ignition Coil
II

Injector 1, 5

Injector 4, 8

Injector 6,
3

Injector 7,
2

How it works

The ignition function is completely independent of the Hall signal, it only needs
the reference brand and speed information. The distributor is adjusted so that
each second tapped at the ywheel reference mark signal with its zero cross­ing comes to lie exactly in the middle of the tooth of the phase signal. Whenever

reference mark signal are in phase, that is before the ignition timing of the rst

cylinder. The zero crossing of the reference mark signal is 72 kW ° before TDC
of cylinder 1; the Hall signal is 40 ° wide kW; So the tooth-shaped Hall signal
between 92 ° and 52 ° kW is prior to the ignition of the GT 1 cylinder. Reverb is
particularly important point for determining the injection time it (pre-before open-

ing the inlet valve) and for the cylinder-specic knock control.

The V8 is provided with a fuel vapor retention system. The aim is to let go no fuel vapors
into the atmosphere.

suction pipe

Tank-venting
valve

activated
charcoal
canister

throttle

venting

control line

pneumatic reversing valve

How it works

Fuel vapors in the fuel tank of gasoline by heat­ing or by decreasing ambient pressure (height).
About a separate line be absorbed these va­pors like a sponge. While driving air is sucked
through the intake manifold pressure through the
charcoal canister, enriched with fuel vapor and
the motor via an electromagnetic tank vent style
valve (TEV) supplied. The activated charcoal
canister with the engine off again receptive. The
TEV is controlled by the Motronic control unit
and according to the current load state of the
engine with a duty cycle of 0 - msec opened or
closed 100% with a timing of 160 msec.
The TEV is followed by a pneumatic valve. At
idle, this valve is closed, the extraction is carried
out only through a choke. By a throttle valve at­tached to the low pressure control line, this valve
is opened in the part-load operation.

Tank

Example, duty cycle 40%

air

Basic fuel
amount
(Fixed)

actuator

exhaust

combustion

air

exhaust

combustion

O2 sensor

regulator

actuator

air

exhaust

combustion

O2 sensor

regulator

correction factor
(. tI ‘not 1 to 0.)

conventional injection

Previous injection systems are by tuning the system to the desired values
brought as close as possible under foreseeable operating conditions. Under different operat­ing conditions of the engine compromise solutions are necessary.
Cons:

Periodic inspection and adjustment he required

•

New basic fuel division

•

Disturbances lead to failure and requiring repairs (no 5eJbstheilung “)

•

Injection with control

A further development of the conventional injection is the addition of a control loop. With the
aid of a sensor (probe), a desired 1st comparison is performed. In case of deviations an ac­tuator (injector), the cold-start air-fuel ratio changes. However, this rule is only possible within
certain limits.
Cons:

Basic setting still “manually” necessary

•

“Self-healing” only within the range of the lambda control

•

Injection with adaptive control

The Motronic the V8 has been designed so that it constantly corrects deviations from toler­ances and “drifting” of the components. The fuel-air ratio always stays within the permissible
tolerance range. A deviation from the desired mixture composition (sl = 1.0) is detected by
the lambda probe. The controller will then change automatically the basic fuel division and it
eliminates a correction manually. The system has a very far-reaching “self-healing deep.”

Adaptive systems of V8 Motronic are:

Lambda control: To compensate for tolerances of the fuel cycle, air mass meter and

•

injectors

Fuel tank ventilation: prevents over-rich mixtures of raw Despite the purge rate of the

•

charcoal canister

Knock control: automatically adapts the power quality material, environmental condi-

•

tions and the engine state.

Freewheeling adaptation scheme: takes into account air pressure and temperature

•

inuence on the characteristic of the idle stabilizer valve and corrected the optimal operat­ing point.

Sensors (information provider)

Speed sensor
and
Reference mark

Air mass me­ter

Hall Sensor

throttle potentiometer
with idle switch

intake air temperature sen­sor

Engine temperature sender

Knock sensor I
and II

Lambda-sensor

Actuators (outputs)

tank vent
valve

Idle air stabilization valve

Injectors

Ignition Coil I
and II

Distributor I
and II

Relay

Fuel pump

Diagnostic connec­tor

Air mass meter

The hot-wire air mass meter plugged into the test
section of the suction tube and is sealed by O-rings
against air leakage. The actual hot wire is clamped
ARN lower end of the cylindrical neck of the double
V-shape and extends into the vicinity of the Saugro­hreinganges into the intake air. The double-V shape
Revealed from a particular Hitzdrahtläuge.

heating

RH = hot wire
RK = temperature sensor
(Compensation resistor)
R1 = resistance to high resistance
R2 = resistance to high resistance
R3 = resistance

amplier

signal volt­age
for
Air mass

ow rate

How it works

The hot-wire air mass meter (HLM) operates on the “constant over temperature” principle. Within

the test section, a thin platinum wire (0.07 mm diameter) is spanned. The current owing through
him heating current is controlled by the amplier. A lying in front of the hot wire temperature sen­sor of thin-lm platinum Informs the control unit, the intake air temperature. The heating current is

now measured from the scheme so that a hot wire temperature adjusts, the lBODe is above the
intake air temperature. This “trick” will depend on the heat transfer from the hot wire to the intake

air only from the air mass ow rate, no longer on the air temperature in the intake manifold.
Thus, the heating current is a direct measure of the air mass ow rate in the intake manifold, ie,

the cylinder charge, measured in kg / h
Since contamination of the hot wire surface can distort the output signal, the hot wire is about
one second electrically heated after each switching off the engine at about 10000e and freed
from impurities. The burn-off signal comes from the ECU.

note:

Removal of the HLM plug must only be carried out about 20 seconds after the engine has
stopped.

Idle stabilization valve

The idle stabilization valve controls the
air for the idle mode. Depending on the
control signal from the control unit it can
be more or less air to pass through the
bypass throttle valve. Thus, an adjust-

ment of the air ow rate is at closed

throttle to the current engine load is pos­sible.

How it works

The idle speed control essentially consists of a rotary slide valve which is connected to
an armature.
In normal operation, a pulsed voltage is applied to the anchor and thereby built up a
magnetic eld which causes a rotational direction against the spring tension of the con­trol unit. Lengthening or shortening of the electrical impulses lead to larger or smaller
opening cross-sections for the bypass air. Normally, the rotary valve is pressed by the

spring force against a stop, a xed air gap is maintained. In case of failure of the post by

the idle speed is guaranteed off.

off

on

off

on

off

on

off

Duty cycle: variable 5 - 95%

Example, duty cycle 70%

- valve 30% off

- valve 70% on

time

Coolant temperature encoder

The coolant temperature goes into very
many system functions as a correction fac­tor. To the injection time at

- start

- afterstart

- Warm-up

- The ignition angle

- The target idle speed control
In case of failure of the NTC coolant tel­temperaturgebers the control unit with an
emergency replacement value is greater?
designed. If the air temperature is less,?
Being pulled from the start for about 3
minutes, the intake air as a proxy, then is
switched to 80C.

intake air temperature sender

The information on the intake air for
an functioning knock control
necessary. She is also a proxy for a
possible failure of the engine coolant
temperature gauge.

knock sensor

To control the combustion process, the V8 engine
with two knock sensors (each cylinder bank one)
is equipped. The knock limit is in the engine com­bustion of fuel not a xed quantity, but it is de­pendent on various operating conditions. For the
optimal combustion process, it is important that
the actual knock limit ignition timing is detected
and the withdrawn accordingly.

Contact for
signal output

xing screw

The tightening torque is accurately
observed, as movement will cause
spurious readings.

Piezoelectric
element

piezoceramic

seismic mass

(Oscillating weight)

How it works
The piezoceramic converts mechanical energy into
electrical energy. Characterized in that it on the one
hand subjected to the vibrations of the crank and on
the other hand, an escape is not possible due to the
inertia of the seismic mass (vibration-resistant), the
crystal structure of piezoceramic is constantly chang­ing.
This change of the crystal structure causes a uctuat­ing rhythm at the same voltage.

The vibration intensity has a signicant inuence on

the level of the voltage.

voltmeter

When a mechanical force is ap­plied to the piezoceramic, there
is momentarily a voltage signal.

A lessening of the force
causes a voltage signal of op­posite polarity.

Throttle switch with potentiometer

The accelerator pedal position is mechani­cally transmitted via a cable to the throttling
lklappe. At the front end of the suction tube
is seated in the elongated valve shaft of the
throttle valve switches to idle and full throttle
and integrated potentiometer for switching
information for the automatic transmission.
Below 13 ° throttle ap opening angle in­cludes the idle contact, and above 72 ° throt­tle opening angle of the full-load contact.
.
From the perspective of the stationary vehi­cle, the idle switch is so designed as nor­mally closed, the full load switch as normally
open. The resistance of the throttle potenti­ometer varies linearly and continuously with
the throttle valve opening angle.

Reference marks and speed encoder

The reference marks and the speed sensor are
identical and sit in a common mount near the
starter crown gear. The rotary encoder number
the teeth of the starter ring samples it, the refer-

ence mark sensor one pressed into the ywheel

pin, which once again returns every 360 ° crank­shaft.

How it works

Donors are “active” and generation AC pulses ac­cording to the induction principle. The passing of
the donors or teeth, runs past the pin cause mag­netic changes within the donor winding.
Based on the reference marks and throttle signal is
oriented to the Motronic control unit on the Current,
exact angular position of the crankshaft and on the
current Motordrehzähl.
The engine can not be started if one of the donors.
Only in case of failure of the encoder reference
mark during ongoing engine If the engine runs with
the previously stored in the control unit value as a
reference mark considered further.

catalyst monitoring

The warning light KAT (catalyst) lights for function control
after the ignition is switched on and goes out after the en­gine starts.
If the light illuminates while driving, there is a danger of
overheating of the catalysts due to an engine malfunction
(for example, ignition system). To avoid further damage,
stop immediately. Stop engine and allow to cool.

Connection for CO measurement

Lambda
sensor

temperature sensor
for
Catalyst monitoring

Flat, three-way catalysts

lambda probe

The oxygen sensor monitors the combustion process and outputs a voltage signal with
a rich mixture of about 800 mV and with a lean mixture of about 100 mV to the Motron­ic control unit. The lambda probe is a prerequisite
for a regulated catalytic converter operation.
The lambda probe is electrically heated and speaks with a cold engine after 25 sec
at. The probe sits in a specially constructed for this purpose merging of exhaust gas
streams from the cylinder bank 1 and bank 2 cylinder the “l-lnsenrohr”

J 128 - Display unit with computer
J 153 - Control unit for r magnetic coupling
J 214 - Steuerge advises for Thermot ronic
J 217 - control rgerät for autom. transmission
J 218 - Combination processor in dash panel
insert
N - Ignition Coil
N 30 - Injector Cyl. 1
N 31 - Injector Cyl. 2
N 32 - Injector Cyl. 3
N 33 - Injector Cyl. 4
N 66 - control valve for idling speed
N 70 - Ignition system output stage 1 for
N 80 - solenoid valve 1 for activated charcoal

lter system

N 83 - Injector Cyl. 5
N 84 - Injector Cyl. 6
N 85 - Injector Cyl. 7
N 86 - Injector Cyl. 8
N 127 - power stage 2 for ignition system
N 128 - Ignition coil 2
O - Distributor
P - Spark plug connector
Q - Spark
S 5 - Lambda probe heating
S 13 - fuel pump
S 23 - injectors 1-8 hot wire air menger knife
S 24 - ACF valve, idle speed control
S 27 - Motronic control unit, diagnosis (sup­ply)
S 29 - Automatic Transmission
S 30 - Instrument Cluster: switch-board com­puter ...
Z 19 - Lambda probe heater

Self-diagnosis of the Motronic control unit monitors signals from the Motronic sensors and
actuators. If errors occur, they will be stored in the permanent memory and can be read. It
was created an interface that allows communication with the fault reader VAG 1551 (fast
data interface) and in the emergency case an information output on the test lamp VAG

1527.

Additional relay sta­tion in passenger-side
footwell

Diagnostic connector:
1 - Power supply for V.A.G 1551
2 - Fast data transfer
Motor-/Getriebeelektronik
3 - Dash panel insert
4 - Blinkeode for motor

Connector for self-diagnosis in additional relay

Lead V.A.G 1551/1
1 connector = L line
= K-line
2 = lamp cable plug
3 Connector = mass
= Plus

Fault reader V.A.G 1551

The possibilities of self-diagnosis can be best utilized through the use of fault
reader VAG 1551. It can be operated in the following modes:
1 Fast data transfer
2 Blink codes
3 self-test
4 Operating characteristics
After applying the leads is through the keyboard the system under test via an ad­dress word-number: for example - enter for motor e-Jetronic - 01. Now the corre­sponding function can be selected:

01 - Control unit version query
02 - Interrogate fault memory
03 - Final control diagnosis
04 - Initiate basic setting
05 - Clear fault memory ­06 - End of output
07 - Code control unit
08 - Read measured value
09 - Read individual measuring
value

Fault with the diode (VAG 1527)

After selecting the function, the
tester displays the detected error.An
error table in the repair guide helps
the user fault.

When the fault memory interrogation and at the nal control

diagnosis with blink code output the test lamp (VAG 1527)
should be connected. - First, plug - A - for mln. 4 seconds - B

- connect, then disconnect it.
Blink codes from the Motronic control unit at the test lamp
VAG 1527
Read and note.
An error table in the repair guide helps the user fault.