Spark OPEL ASTRA 1991 Electronic Workshop Manual

Downloaded from www.Manualslib.com manuals search engine Injection Systems
Multi PointSimultaneousInjectors receive pulses from E.C.U. twice per engine cycle.
( Corsa 13 NE, 16NE, Astra 14SE, 16SE, 18XE, 20SHE )
SequentialInjectors are pulsed by E.C.U. once per engine cycle as per spark
plug firing order. ( Astra 20XE )
GroupedInjectors pulsed in groups or banks, once or twice per cycle
depending on system design
Single PointThrottle BodySingle injector mounted on throttle body pulsed as per engine
requirement ( Astra 160 TBI )
Operation
Injectors on the Bosch Motronic engine management systems receive battery voltage and are
triggered by the E.C.U. depending on the signals received from the various sensors attached
to the engine. Fuel pressure is constant (M.P.F.I. – 250 to 300 Kpa).
Injector opening frequency (Hz) and duration (pulse width) determine the amount of fuel
being delivered to the combustion chamber. Variations in pulse width and frequency ensure
that adequate fuel is supplied for efficient engine operation.LONGER PULSE WIDTH= RICHER MIXTURESHORTER PULSE WIDTH= LEANER MIXTURE
Pulse rate and width will increase with increased engine rpm and load.
Duty Cycle
Duty cycle is the combination of pulse width and pulse rate, and is expressed as a percentage
of time “ON” and time “OFF” eg. If an injector was on for 10ms and closed for 90ms, the
duty cycle “ON” is 10% and the duty cycle “OFF” is 90%. The total on and off duty cycle
reading should be 100%.
CrankingInjector duration is longer during cranking (richer mixture) for easier startingand to promote warm-up.
IdlingInjector duration is longer at start-up if engine is cold, and graduallydecreases as engine warms up.
AccelerationInjector duration is longer at initial acceleration to prevent “flat spot”RunningInjection pulse is controlled by the E.C.U. depending on the signals receivedfrom the various engine sensors.

Downloaded from www.Manualslib.com manuals search engine DUPEC ELECTRONICS (PTY) LTD
DEFITA200
MICROCONTROLLER BASED
FUEL INJECTION AND
SPARK TIMING SYSTEM
AND INTERFACE
SPECIFICATION
TRAINING MANUAL
93/5

Downloaded from www.Manualslib.com manuals search engine CONTENTS
1.0 PRODUCT DESCRIPTION
2.0 FEATURES
3.0 PRODUCT IDENTIFICATION AND APPLICATION
4.0 SPECIFICATION
4.1 Electrical
4.2 Environmental
4.3 Fuel delivery
5.0 CONNECTIONS
6.0 SPARK TIMING
6.1 Distributor bypass operation
6.2 Engine speed and crankshaft
position measurement
6.3 Engine load measurement
6.4 Advance angle look-up
6.5 Ignition firing delay calculation
6.6 Dwell time calculation
6.7 Engine water temperature measurement
7.0 FUEL INJECTION
7.1 Air mass to fuel mass ratio
7.2 Air mass measurement
7.3 Speed density concept
7.4 Fuel metering
7.5 Continuous fuel flow rate
7.6 Injector opening and closing times
7.7 Injection timing
7.8 Injection duration
7.9 Correction factors
7.9.1 Injection hardware deficiencies
7.9.2 Engine operating conditions
7.9.3 Intake air temperature
7.9.4 Engine temperature
7.9.5 Cold starting conditions
7.9.6 Post-start and warm-up conditions
7.9.7 Acceleration conditions
7.9.8 Deceleration lean-out conditions

Downloaded from www.Manualslib.com manuals search engine 1 PRODUCT DESCRIPTION
The DEFITA200 range of ECU's (Engine Control Units) is
microcontroller based and controls the spark timing, fuel
injection and certain other functions of internal combustion
engines electronically, thus ensuring optimum operating
efficiency.
DEFITA200 is an abbreviation for Dupec Electronic Fuel
Injection and Timing Advance.
2 FEATURES
The DEFITA200 range of ECU's is designed, developed and
manufactured in the Republic of South Africa and offers the
following features:
Standard functions:
- Spark timing up to 7,810 r.p.m. on 4 cylinder engines
- Spark timing based on engine load, temperature
crankshaft position/speed and battery voltage
- Automatic altitude compensation by measurement of
manifold absolute pressure
- Fuel injection based on engine load, speed, tempera-
ture and manifold air temperature
- Coasting fuel cut-off
- Pre-programmed rev. limiting by fuel cut-off
- Active idle speed control

Downloaded from www.Manualslib.com manuals search engine - User selectable spark timing curves for different
fuel octane ratings
- User selectable fuel mixture maps for different
octane ratings
- Automatic default mode selection in the event of
sensor failure allows limp-home operation
- Air-conditioner shutdown control
- Self-diagnostics with fault storage
- Intelligent PC based diagnostics with logging
facility.
- Software immobiliser which prevents hot-wiring
- Repairability. THIS IS NOT A THROW-AWAY UNIT. IT CAN BE REPAIRED AT DUPEC FOR A MINIMAL CHARGE

Downloaded from www.Manualslib.com manuals search engine 6 SPARK TIMING
Spark timing and fuel injection for DEFITA200 ECU's is
calculated by a central processing unit and are based on:
I - MAP
II - EWT
III - Battery voltage
IV - Crankshaft position
V - Engine speed
VI - Throttle position
The optimum timing advance curves for a given engine are
determined by running the engine on an engine dynamometer
under any combination of the above-mentioned conditions.
This process is known as mapping the engine. The mapping is
further refined by extensive driving tests.
The mapped data regarding the engine is stored in a ROM
(Read Only Memory) within the ECU.
The following processes take place when calculating the
advance angle:
I - engine speed and crankshaft position measurement
II - engine load measurement
III - advance angle look-up
IV - ignition firing delay calculation

Downloaded from www.Manualslib.com manuals search engine 6.1 Distributor bypass operation
At engine speeds below 450 r.p.m. the ECU does not control
the firing angle. The ECU keeps the bypass line to terminal
C of the distributor low for engine speeds below 450 r.p.m.
The spark advance for the vehicle is set to 10ø BTDC by the
distributor, while the engine speed is below 450 r.p.m..
Above 450 r.p.m. the ECU takes the bypass line high (+5
volt) and takes over control of the spark advance as de-
scribed below.
6.2 Engine speed and crankshaft position measurement
Engine speed is calculated by measuring the period from one
negative edge to the next negative edge of the distributor
reference signal. The reference signals are separated by
180 degrees.
The distributor generates a signal as shown in the reference
and ignition waveform diagram. The time taken for the crank-
shaft to rotate from 10ø BTDC to the next 10ø BTDC marker
is measured. Knowing the time it takes the crankshaft to
rotate through 180ø it is possible to calculate the current
engine speed in degrees per second (ø/s). Crankshaft posi-
tion is obtained by sensing the falling edges of the refer-
ence signal.

Downloaded from www.Manualslib.com manuals search engine 6.3 Engine load measurement
Engine load is measured by an external MAP ( Manifold Abso-
lute Pressure) sensor. Absolute pressure measurement auto-
matically adjust spark timing for altitude changes. It is also
required to determine the air mass for fuel injection
applications.
6.4 Advance angle look-up
The optimum advance angle obtained by mapping the engine
is stored in a matrix (table) having 10 load and 62 r.p.m.
sites. There are thus 620 possible advance angles stored in
ROM for every RON number used. The CPU (Central
Processing Unit) compares the calculated engine speed and
measured load with the site indexes stored in ROM. If an exact
correspond-ing speed and load site are found it uses the
corresponding advance angle in the matrix. In cases where
exact corre- sponding load and r.p.m. sites are not found the
CPU uses linear interpolation to calculate the corresponding
advance angle to be used.

Downloaded from www.Manualslib.com manuals search engine 6.6 Dwell time calculation
Dwell time is the time during which the battery voltage must
be applied to the ignition coil's primary winding prior to
an ignition pulse. The correct dwell time is important to
ensure constant spark energy.
The correct dwell time depends on the battery voltage. A
look-up matrix contains dwell time versus battery voltage.
The prevailing battery voltage is measured and compared with
the voltages stored in the dwell look-up matrix. The corre-
sponding dwell time is used to energise the ignition coil.
6.7 Engine water temperature measurement
EWT measurement is accomplished by a NTC (Negative
Temperature Coefficient) sensor mounted on the engine block.
The base advance angles are increased with decreasing
engine temperatures. This is necessary because it takes
longer to reach maximum cylinder pressure after ignition
when an engine is cold. Typical additional advance required
for an engine at -20ø Celsius ranges from 3ø to 8ø with
respect to an engine operating at 100ø Celsius.

Downloaded from www.Manualslib.com manuals search engine 8 IDLE SPEED CONTROL
Idle speed is controlled by means of the IACV (Idle Air
Control Valve) mounted on the throttle body assembly. The
IACV is driven by the IACSM (Idle Air Control Stepper Motor)
which is controlled by the ECU.
The IACV maintains constant idle speed (temperature depend-
ent) under all engine loads.
The ECU makes use of closed loop control algorithms to
ensure the best idle conditions for warm and cold engines.
Whenever the ignition is first switched the ECU selects a
pre-set idle position which is temperature dependent, there-
after it operates in the closed loop control mode.
Idle speed control is only possible with the throttle in the
closed position.
Timing advance support is utilised in the idle range to
enhance idle speed control. Spark timing is advanced by up
to 10ø if the idle speed drops below the set point, result-
ing in increased engine torque to offset the drop in speed.
If the idle speed rises above the set point the timing will
be retarded up to 10ø to reduce engine torque.
Correct idle speed control is not possible when the battery
voltage is below 9 volt.