Porsche 912E 76 Instrucciones de funcionamiento e instalación
The
Porsc
he
912
E
..
.
The techni
ca
l
spec
ifications are
as
follows:
Capacity: 1971 cm3
Stroke:
71
mm
Bore:
91
mm
Horse power:
developed at:
Torque:
develo
ped
at:
86
hp/64
4900 rpm
98
Ibft/133
4000 rpm
.
..
is
equipped
with
..
.
... a 2
Itr
., 4 cylinder engine (similar to that in the
Type
This
motor
has
been
fitted
with
the electronically controlled AFC fuel injection thermal reactors
and
exhaust
gas
recirculation.
.
· . . a 5
speed
transmission
(based
on transmission
type
915)
with
modified transmission ratio
and a newly designed clutch operation mechanism.
·
..
a like the 911, a dual-circuit brake system,
disks brakes
without
"inner
ventilation"
.
·
bodywork
similar
to
the 911
but
with
permanently
fixed rear side windows aswe
ll
as
other
minor
changes.
2
10
ENGINE
CRANK
CASE,
CYLINDERS,
ENGINE
MOUNTS
The crank
case
and the cylinders
are
the
same
as
in the engine
type
914/2
.0 Itr.
The following
is
new:
The engine mount.
It
consists
of
a swung steel bar which
is
secured
to
the
motor
in the
same
way
as
in the 914.
The mounting points on the
chassis
were moved outwards
to
the wheel wells however.
Warning:
installing the
motor
mount, note that the casted in part number (arrow)
is
pointing toward
t
he
rear.
3
13
CRANK
SHAFT
DRIVE/PISTONS
All
parts
of
the crank shaft drive
are
the
same
as
in the basic motor.
An
additional fan-belt
pulley
is
fitted
to
drive the secondary air pump. It
IS
secured to the
front
of
the air intake housing
by
means
of
a
thr
ee-armed block and
is
driven by
means
of
a shaft
from
the center
of
the cooling fan.
19
COOLI
NG
The
eng
ine sh
ee
tmetal w
as
changed
to
conform
to
the
911
engine compartment configuration.
4
20
FUEL
SUPPL
V
The
912
E
is
fitted
with
an
80 Itr. (inc!. 8 Itr. reserve) fuel tank.
The fu
el
pump
is mounted on the
front
axle auxiliary mount.
The fuel
filter
is the
same
as
in the CIS injection
It
is
secured
to
the l
eft
-h
and wheel well in the
engine compartment
1
1.
) Fuel
tank
2.)
Fuel
pump
3.
) Fuel
filter
4.)
Pressure
regulator
5
.)
Injection
valv
es
6.)
Cold start
valve
5
24
EL
ECTRONIC
F
UEL
INJECTION
-
AFC
The Porsc
he
912 E
is
equipped
with
a
motor
that
has
aair
flow
controlled electronic fuel injection.
Before we describe this
unit
in detail, a few words about the accelerator cable.
The
accel
era
tor
cable
is
in
two
parts.The connector (arrow)
is
located
within
the engine compart-
ment behind the rear panel
and
is
accessible when the cover
to
the guide channel
is
removed.
Construction
and
funct
ion of the
ATC
injection
The component parts
1 Fuel Tank
2 Fuel Pump
3 Fuel Filter
4 Cold Start Valve
6 5 Fuel Injector
6
Pressure
Regulator
7
Auxiliary
Air
Regulator
8
Throttle
Switch
9
Air
Filter
10
Temperature
Sensor
II
11
Battery
12
Ignition Switch
A Int
ak
e-air
Sensor
B
Throttle
valve
C
Air
Sensor
Flap
o
Co
ntrol Unit
Principles
of
Operation
The amount
of
fuel
that
is
to
be
used
is
determined
by
the volume
of
intake air
and
the
speed
of
the
motor.
The injector sequence
is
determi
ne
d
by
th
e igni
tion
dis
tr
ibu
tor
breaker points.
The fuel required
for
cold starting
is
injected by the electro-magnetic cold start valve.
Warm-up
en
richment
of
t
he
fuel
mixture
is
via the
au
xiliary air regulator in conjunction
with
the
temperature s
ens
or I in the intake-air
Se
n
so
r housing and t
he
temperature sensor II in the cylinder
head.
Fuel mixture enrichme
nt
for
full
load conditio
ns
is
by
me
a
ns
of
a
throttle
switch.
6
2
.
24
ELECTRONIC
FUEL
INJECTION
-
AFC
Description
Intake-Air
Sensor
The intake-air sensor
is
located
in
the engine compartment at the right-hand side between the air
filter
and the
throttle
housing (L) .
Construction
Aluminum
housing (A)
with
Bye-pass channel (5)
and
Adjustment
screw (6)
Air
sensor flap (1)
with
Back pressure valve (8)
and Damping vane (2)
Damping chamber (7)
Return spring (9)
Potentiometer (B)
with
Pump contacts
(C)
Temp
era
ture sensor I (D)
Operation
The volume
of
air that the
motor
can
draw in
is
determined
by
the position
of
the thro
ttle
valve.
The resultant air
flow
causes
the sensor flap
to
deflect against the return spring. T
he
flap deflection
is
transmitted via a shaft
to
the potentiometer which supplies a specific voltage
to
the con
trol
unit. The
temperature sensor I
is
connected
to
the potentiometer and influences the control signal volta
ge.
The injector which
is
activated by the control
unit
injects
an
exact amount
of
fuel appropriate
to
the
volume
of
intake-air.
The damping vane
is
designed
to
minimize sensor flap hunting. The
function
is
as
follows:
with
deflection
of
the flap the damping vane
is
forced
into
the damping chamber. The resultant compressed
air
within
the chamber
can
escape
only
through the
release
slit
(S)
. Sudden movements
and
hunting
is
thereby reduced.
A fraction
of
the air intake
is
detoured around the sensor flap via the bye-pass channel. The fuel-air
mixture
for
idle
can
be
set
by
means
of
the adjusting screw (6).
A pump contact
is
located
within
the potentiometer.
When
the sensor flap
is
deflected open the pump
contact
is
closed and the fuel pump started.
Probl
em
condition:
Motor
does
not
start;starting
dif
ficulties;
low
efficiency.
Troubleshooting:
Remove the plug connected
to
the potentiometer on the intake-air sensor. Connect
an
ohm meter
between the contacts 6 and
9.
value: 200
to
400
Mea
sure between contacts 7
an
d 8.
Nominal value: 120
to
200 7
\
4
~
---
.
---.------.
"
-,
24
ELECTRONIC
FUEL
INJECTION
-
AFC
Throttle Switch
This switch provides the control
unit
with
necessary
information
for
mixture
enrichment and
full
load
cond itions.
It
is
not
necessary
to
adjust this switch.
Problem
condition:
Low
engine power
Troubleshooting:
Disconnect the wires
from
the switch and connect
an
ohm meter between contacts 3 and 18.
Slowly
open the
throttle
valve. The resistance must change
from
00
to
0
Ignition Distributor
The ignition
distributor
provides the control
unit
with
information
concerni
ng
the
speed
of
the
engine (rpm) and sequen
ce
for
activating the fuel injectors.
Operation
In addition
to
de
livering impulses
to
the ignition coil,
thecontact breaker points
also
supply impul
ses
to
th
econtrolunit.
Each
impulse (1)
is
converted
to
a
squ
are wa
ve
(2)
within
the
control
unit
. These
sq
uare wave impulses are then presented to a gate (3)
whichprovides asingle
pu
Ise
output
for
each
sequ
ence
of
four
input
pu
Ises
which are the
resu
It
of
t
wo
re
volutions
of
the
motor
crank shaft. That
is,
f
ollowi
ng
each
revolu
tion
of
thecrank shaft all
fo
ur
fuel injectors
hav
e received
an
ac
tivat
ing
impulse (5
).
Thus the fuel injectors inject a de
fin
ite
amount
of
fuel independent
from
the position
of
th
e air sensor flap. The injected fuel
is
always half
of
the amount necessary
for
the correct fuel
mix
ture. Si
nce
the crank shaft turns
tw
i
ce
for
each
cycle,
two
injector sequences
are
put
into
operation
thus
each
cylinder receives the
full
amount
of
fuel
for
each
firing stroke.
o
Zyl. 1
Zy
l.4
Zyl.3
Zyl.2
1 breaker
im
pulses
-
--t-
2 imp
ul
se
shaper
3 frequency
d
ivid
er
4 air
flow
senso
r
fla
p position
(pot
entiom
eter)
'5
injection i
mpul
(duration
of
injection)
su
ct
ion
compressi
on
ign
it
ion
exhaust
o crankshaft angle
360
7
20
·
I
:
control
unit
(e
lectronic)
8
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