fuel OPEL ASTRA 1991 Electronic User Guide

Downloaded from www.Manualslib.com manuals search engine 4 SPECIFICATION
The following specification is applicable to DEFITA200 P/N:
A020-C ECU's unless otherwise stated:
4.1 Electrical
Operating voltage : 9 to 15 VDC continuous : 6 to 16 VDC limited functions : 24 VDC for 60 seconds maximum
Operating current : Less than 500 mA
Standby current : Less than 12 mA (>1 minute after
ignition off)
Timing accuracy : +/- 0.5 degrees
R.p.m. limit : 6,297
Reference signal : Negative edge from Distributor Y24
at 10ø BTDC
Base timing : 10ø BTDC r.p.m. < 450 or diagnostics initia- lised after starting
Mapped timing : r.p.m. > 450 and diagnostics dis-
abled
Selectable octane maps : 97 RON Factory fitted
: 93 RON
: 87 RON
: 87D RON (For fuel with octane
below 87 RON)
Selectable by interchanging octane plug on harness

Downloaded from www.Manualslib.com manuals search engine Fuel mixture adjustment : - 15% Leaner
: - 10% Leaner
: - 05% Leaner
: + 05% Richer
: + 10% Richer
: + 15% Richer
: + 20% Richer
: + 25% Richer
Selectable by installing optional
mixture selection plug.
Operation only possible in open
throttle position.
Air-conditioner shut-off : Throttle > 88% open OR
: TPS closed and speed < idle r.p.m.
Fuel injection timing : Synchronous with reference signal
Idle CO adjustment : +/- 15% of base fuel map by means
of CO potentiometer with closed
throttle
Coasting cut-out : 1228 r.p.m. - EWT > 78 øC
: 1755 r.p.m. - EWT = 0 øC
Idle speed : 910 r.p.m. - EWT > 78 øC
: 1300 r.p.m. - EWT = 0 øC
: 1050 r.p.m. - A/C ON (EWT > 78 øC)
: 1495 r.p.m. - A/C ON (EWT = 0 øC)
Idle speed control : By means of stepper motor control
of IACV (Idle Air Control Valve)
Wide Open Throttle (WOT) : Throttle > 72% open
Flood compensation : 0.6x base fuel maps in WOT mode
and r.p.m. < 450

Downloaded from www.Manualslib.com manuals search engine Fuel pump prime time : 2 +/- 0.2 seconds
Immobiliser arming : Automatic; de-arming after success-
ful communication with the ACUProtection : All input and output terminals are protectedagainst accidental shorts to ground or battery voltage exceptthe following :- diagnostic lamp to 12 volt - coil drive to 12 volt
Default mode selection : Automatic in the event of a
sensor failure
Diagnostics initialisation : Short line on ALDL plug to ground
before starting engine
Diagnostics : Tell tale lamp
: D-TEQ200 PC based intelligent system
: C-TEQ200 Component tester
4.2 Environmental
Operating temperature : -25ø to +85ø Celsius
Water resistance : Splash proof
4.3 Fuel delivery
Pump : AC Rochester pump fitted in the fuel tank. P/NFuel pressure : 100 kPa

Downloaded from www.Manualslib.com manuals search engine 01B - Phase 1D drive signal to stepper motor
terminal D
02B - Phase 1C drive signal to stepper motor
terminal C
03B - Phase 2B drive signal to stepper motor
terminal B
04B - Phase 2A drive signal to stepper motor
terminal A
05B - TPS input signal from terminal C
06B - Bypass signal to distributor terminal C
07B - Coil driver output signal to distributor
terminal A
08B - Reference signal input from distributor
terminal B
09B - 5V output to TPS terminal A
10B - A/C relay output signal
11B - Fuel pump relay output
12B - Power ground connection
13B - Injector drive output signal
14B - Sensor/signal ground connection
15B - MAP sensor signal input from terminal B
16B - EWT signal input
17B - MAT signal input
18B - Fuel map selection input
19B - Timing map selection input
20B - CO mixture adjust input signal
21B - Sensor/signal ground connection
22B - Ignition voltage input
23B - 5V output to CO adjustment potentiometer
24B - 5V output to MAP sensor terminal C
25B - Power ground connection
26B - Battery voltage input

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 6.3 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 FUEL INJECTION
It is the function of any fuel injection system to ensure
that the correct mass ratio of air and fuel is delivered to
the engine under all operating conditions. We will concen-
trate on TBi (Throttle Body Injection or alternatively
called single point fuel injection systems) in this docu-
ment.
The availability of powerful low cost microprocessors has
made it possible to fit FI (Fuel Injection) systems to a
larger percentage of vehicles. The ECU (Engine Control Unit)
evaluates input sensor data and calculates the required
output signals to control the engine. The most important
function of a FI system is to measure the air mass entering
the engine and calculate the injector opening duration to
ensure the correct A/F ratio under specific engine operating
conditions. The A/F ratio has a direct effect on the power
output of the engine, fuel consumption and exhaust gas
emissions. It is therefore necessary to exercise precise
control over the opening duration of the injector.
A number of operating conditions exist where the A/F ratio
is deliberately modified and forced to deviate from the
calculated ratio to ensure better drivability and smoother
engine operation. These deviations are classified as A/F
corrections and will later be examined in detail in this
document.

Downloaded from www.Manualslib.com manuals search engine 7.1 AIR MASS TO FUEL MASS RATIO
The theoretical air mass to fuel mass ratio required by an
internal-combustion engine for complete combustion is
14.7:1. This ratio is also called the stoichiometric ratio.
The A/F ratio determines the fuel consumption, maximum
engine power output and exhaust gas emission levels. Unfor-
tunately there is no single A/F ratio that optimises these
three requirements.
The ratio of actual air mass supplied to the engine divided
by the theoretical requirement is defined as lambda.
ë = Air mass supplied/theoretical requirement
Where ë = Lambda
ë = 1
The air mass supplied matches the theoretical amount.
ë < 1
A lack of air resulting in a rich mixture. Increased engine
power outputs are obtained for 0.85 < ë < 1.
0.75 < ë < 0.85
A rich mixture suitable for transient conditions where a
sudden load change is experienced.
ë > 1
An excess of air resulting in a lean mixture together with a
reduction in engine power output. Optimum fuel consumption
takes place with 1 < ë < 1.2.
ë > 1.3
Lean mixture making it impossible to achieve reliable igni-
tion.

Downloaded from www.Manualslib.com manuals search engine 7.2 AIR MASS MEASUREMENT
As we have seen previously the principle of fuel injection
is based on measuring the air mass entering the engine and
calculating the fuel mass required to obtain an A/F ratio of
14.7:1. A number of possible methods exist for measuring
the air mass, but only the speed-density method used for
this TBi system will be described in detail.
Some of the possible methods are:
a) Speed-density
b) Throttle butterfly angle
c) Flap or vane type
d) Hot-wire meter
e) Hot-film meter
f) K rm n vortex ultrasonic meter.

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.