Group
28
Ignition systems
Des
ign
and
fun
c
t
ion -
Speed
and
crankshaft position
i
nformat
ion
c
I
,
c
·
TOC
B
TOC
-
A
Flywh
eel/
c
a
rr
i
er plate pr
ofi
l
es
The
above
figures
show
the three
different
'
Ioothed
'
or drilled crankshaft/carrier plate
profiles which are used
.
(The
profiles
afe
shown
in section
.)
Unlike
the
starter motor ring gear, which
is
moun
t
ed on
the flywheel. the profile
used
for
signal generation is usually an integral part of the component.
Volvo
igni
tion
systems are supplied mainly by
two
manufacturers
-
Bosch of Germany and
Bendix
,
France
.
Among
other factors.
this
means
that
several different profiles must
be
used. while
the
method
whereby the
control unit
tects and processes
the
induc
tive
pick-up signals may also differ
.
The electronic circuit
(
which
may be likened
to
a
frequency
divider or
'mul
tiplier'
)
in
wh
ich
the
signal is
f
i
rst received
and processed, also varies in design
.
The frequency of
the
incoming
voltage pulses is
divided
by a certain
factor to
i
mprove
signal resolution.
Th
is,
in
t
urn, means
that the
cont
r
ol unil
can
regulate
t
he
t
iming
in
more precise
steps,
for
example,
when re-advancing
t
he
t
iming
afte
r
knock in a cylinder
has been
elimina
t
ed.
A
.
I
gnition systems
supplied by
B
endix employ
a
type
4412 toothed
profile. The
figure 44 means
t
ha
t the
flywheel
is
provided with
44 dr
illed
holes
,
and
t
he
figure
2
that
i
t
has two
'
long
'
teeth
,
each equal
leng
t
h
to
tw
o sho
rter
teeth.
In
o
th
er
w
ords,
the
profile
provided
with
40
(
44
-
2x2
)
sho
rt t
eeth
and
tw
o
l
ong
t
ee
th
.
T
he
angular pitch be-
tw
een
tw
o a
dja
cen
t
short
t
ee
th
(X
O
)
is 8.
18
°
(360
°
/
44
).
The two
long
teeth
com
pris
e
the
c
rank
s
haft
position
referen
ce
points
are
located
180
°
apart
(angle
a
).
The
con
tr
ol
unit identifies
TDC a
s
th
e
90
°
after
the
passage
o
f
a
l
ong tooth
.
Th
e
type
44/2
profile
is
used
on
A
e
nix
-F
and
R
e
x
-I sys
t
ems.
In
each case,
the
control
unit
applies a
factor
o
f 8
.
18 t
o
improve the
signal resolution. This
means
th
a
t
it
can
adjust
th
e
timing
in
steps
of
8
.
I
gni
ti
on systems supplied
by Bos
c
h for
Vo
l
vo
4-cylinder
engines
f
ea
ture
a
type 60/1
t
oothed p
r
o
f
i
le
.
This means
t
hat
th
e
profile
is
provided with
60
holes and with
one
'
long
'
t
ooth
of
tw
ice
the
length of a
's
hort'
t
oo
th
.
In
other words
,
the
pr
ofile is provided
wit
h 58 (60-
1x
2) short
teeth
and one long
tooth whi
c
h represents
t
he
crank-
shaft
posit
io
n reference
point
.
The
angular
p
i
t
ch
between two
adjacen
t
sho
rt t
ee
t
h
is
6
.
0"
Th
e con-
trol un
i
t
i
dentif
i
es TDC
as
the
point
after
the
passage of
the
long
t
oo
t
h.
The type
6011
t
oo
t
hed profile
is
used
on
the
EZ
-1
16K
system
.
This means
that the
con
trol
unit applies a
factor
of 16
to
improve
the
resolution
of
the pick-up
signal.
In effect
,
the
control unit can adjust
the t
iming
in steps of
C
.
The EZ-1 15K
igni
tion
system for B 280 engines
is
designed for a flywheel
with
a type 6013
toothed profile.
The
file
is provided
with
60
holes and 3
'long'
teeth
,
each of which
twice
the
length of a
'sho
rt
'
tooth
.
In
other
words
,
the profile
is
prov
ided
w
i
th
(60-3
x2
)
short
leeth
and 3
long
teeth as the
crankshaft position
reference
points
.
The
angular
p
i
t
ch
between
two
adjacent short
teeth
(Z
O
)
is
(360
°/
60).
The
t
hree
long
t
eeth are
located
12
0" apart
la
ngle
cl.
The
control unit
iden
tif
ies
TOC
as
the point
after
the
passage of a reference
tooth
.
Th
e
con
t
rol
un
i
t applies
a
f
actor of
16
t
o
im
prove
the
resolut
io
n
of
the
pick-up signa
l
.
I
n
o
th
er
words
,
the unit
adjus
t th
e
ti
ming in s
t
eps of 0.375
°
.
24
