Group
28
Ign
it
ion
systems
D
esign
and
function
-
Components
Output unit
D.
The
digital
information
supplied
by
the
microprocessor
is
fed
10
the
output
unit
(D)
for
conversion
in
to
the
ignition
pu
lses
fed
to
th
e
power
stage
.
(This
may
either
be
an
integral
part
of
t
he
control
unit
or
a
separate
uni
t .)
Depend
ing
on
th
e
program
selected
at
t
he
particular
instant,
t
he
con
trol
unit
de
t
ermines
the
p
oin
t
at
which
t
he
igni·
tion
pul
se
must
be
delivered
to
t
he
power
stage.
The
la
tt
er
con
t
rols
the
current
in
the
primary
winding
of
th
e
ignition
coi
l
in
re
sponse
to
the
signa
ls f
rom
th
e
output
unit.
Voltage stabilizer
The
con
trol
unit
is
powered
by
a 12 V
supply.
However
,
since
the
ba
he
ry
voltage
is
too
high
for
the
internal
integ
rat
ed
circuits
, a
vol
tag
e
stabilizer
is
used
to
produ
ce
a
stabilized
5 V
supply
for
these
.
• Engine
speed
limitation:
All
control
units
are
programmed
with
some type
of
speed
limiting
function.
On
Bend
ix
systems, the
conlrol
unit
normally
commands
the
power
stage
to
reduce
the
Ignition
coil
charging period.
producing
a
weaker
spark
which
limils
the
eng
i
ne
output
. On
EZ-K
systems,
Ihe
conlroi
unit
uses
Ihe
power
slage
10
interrupl
l
he
spark
10
every
second
plug.
The
speed
limiting
funct
ion
normally
inlervenes at
aboul
6200
r/min.
In the case of cars
equipped
with
Fengines,
the
speed
limiting
function
controlled
by
Ihe
ignition
syslem
control
unil
is
set
to
op-
erate
81
a
higher
level
than
thaI
controlled
by
its fuel system counlerpart. This prevents
unbu
rnl
fuel
from
reaching
Ihe
catal
yti
c
converter,
with
the a
nendant
risk
of
overheating.
•
The
control
unit
memory
is
programmed
with
a range
of
speed
and
load
values. The
unit
improves
the accuracy of
control
by
in-
terpolating
between Ihese values,
performing
up
to
about
1ססoo
compu
tation
s
per
minute
to
ensure that
optimum
l
imi
ng
is
maintained
under
all
conditions
.
As
many
as
4000
individual
settings
may
be
computed
as
required.
• Built
from
components
such as
integrated
circuits
, transistors,
diodes
and capacItOrs, electronic
componen
ts
like
the
control
unit
are
relatively
fragile. Since
the
electronics used in cars are exposed
to
such a
diversity
of
operating
conditions,
they
are subject
to
particularly
arduous
demands
. The
equipment
mUSI
be
designed
to
withstand
vibrations.
moisture,
w ide
temperature
fluctu
-
ati
ons
,
variable
voltages
and
other
sources
of
outside
interference (e.g.
from
rad
iosl
to
which
the electrical
system
is
unavoidably
exposed.
•
In
th
e case
of
certain
internal
fault
s,
the
control
unit regulates
the
ignition
in
accordance w ith a fixed.
pre-programmed
timing
curve.
•
In
Ih
e absence
of
a load signal,
Ihe
con
trol
unit
modifies
the
timing
on the basis of the speed signals
which
it
receives, and
ope
r-
ates in accordance
with
the
pre-programmed.
full
-load
timing
selling
when
the
idling
switch
has opened.
•
If
the knock
sensor
signal
is
lost. the
con
lrol
unit
com
putes the
timing
setting
on
Ihe
basis of a 'fail-safe' retardation
of
approx.
10".
• The
control
unil
electronics
must
not
be
exposed
to
excessively h
ig
h temperatures. For
example,
removal
of
the
unit
prior
to
the
completion
of
the
stoving
process
during
manufacture
may
result
in
its
destruction
. Because
of
its
sensitivity
to
temperature,
the
unit
is
normally
installed
in a location
well
protected
from
engine
heal.
15
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