Porsche 912E 76 Operating and installation instructions

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

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-,
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