1991 OPEL ASTRA ABS

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 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 7.3 SPEED DENSITY CONCEPT
If we know the density of the air inside a container it is
possible to calculate the exact mass of the air inside the
container.
Am = Va*p Where Am = Air mass (g)
Va = Air volume (cc)
p = Air density (g/cc)
In an automotive FI application the quantity of fuel to be
injected can be calculated if the displacement volume of the
cylinder and the density of air within the cylinder at the
onset of the compression stroke are known.
The air density could be determined by measuring the abso-
lute pressure and absolute temperature of the air. In an
automotive application it is, however, not practical to
directly measure the air pressure and temperature inside the
cylinder. To overcome this limitation the air pressure and
temperature are measured in the inlet manifold. This leads
to certain pressure measurement errors for which corrections
have to be made.
To understand and correct these errors the engine is mo-
delled as an air pump. For the purpose of explaining these
problems one has to view the engine as a pump sucking air
from the inlet manifold through a restriction which is
formed by the inlet valve in the open position. The dynamic
properties of the air moving past the inlet valves are
engine speed dependent and to such an extent that the inlet
manifold pressure will tend to be slightly higher than the
in-cylinder pressure at the end of an inlet stroke. This
leads to higher than actual air mass measurements which
have
to be corrected. The air pumping efficiency is called the
volumetric efficiency of the engine.

Downloaded from www.Manualslib.com manuals search engine 9 IMMOBILISER OPERATION
The system contains an immobiliser function which prevents
hot-wiring. When the ignition is switched on the ECU will
wake up and prompt the ACU for its ID (Identification Code).
The ACU will respond by sending its ID to the ECU for com-
parison with an ID code stored in the ECU's ROM. Only if the
ACU's ID matches the ECU's ID normal engine
management
control will be allowed to take place.NO ENGINE CONTROL IS POSSIBLE IN THE ABSENCE OFTHE CORRECTACU ID.

Downloaded from www.Manualslib.com manuals search engine 11.2.5 CO potentiometer supply voltage: The voltage
between
terminal 23B and signal ground should be between 4.7 and
5.2 volt.
11.2.6 MAP sensor supply voltage: The voltage between
terminal
24B and signal ground should be between 4.7 and 5.2 volt.
11.2.7 MAP sensor signal voltage: The voltage between
terminal
15B and signal ground with ignition on should be:
MAP signal voltage Manifold absolute pressure
_____________________________________________________
___
1.00 20 kPa
2.00 40 kPa
3.00 60 kPa
4.00 80 kPa
4.50 90 kPa
5.00 100 kPa
A general tolerance of +/- 5% exists on the above voltages.