Datsun 1980 200SX Service Manual page 100

AIR FLOW SYSTEM
AIR FLOW METER
Helical spring
From air
cleaner
EN GIN E FU E L
E FI System
Component
Parts
Construction
and Function
Damper plate
To intake
manifold
By
pass
port
Air temperature
sensor
The air flow
meter
measures
the
quantity of intake air and sends
a
signal
to the
control
unit
so
that the
base
pulse
width
can
be detennined
for
correct
fuel injection by the
injec
tor
The air flow meter is
provided
with
a
flap
in
the air
passage
As the
air
flows
through
the passage the
flap
rotates
and
its angle
of rotation is
electronically monitored
to count the
air flow
rate
More
specifically the angle
of
rota
tion of the
flap
is monitored
by
a
potentiometer
provided inside
as a
potential
difference V When the
flap
deflects
along
with
a
change
in the
intake air flow
rate
the terminal
@
mounted
to the
flap
shaft slides
on
the variable resistor R from RI to
R9
causing the
voltage
across
tenninals
@
and@tochange
A constant voltage VB battery
voltage is applied
across
terminals
@
and @ Then the air flow rate is
converted
into
the voltage ratio
signal
V
VB
which in turn is sent to the
Potentiometer
To
EFI harness
control
unit
for
computation
The
flap
is able
to rotate to
an
angle
where
an
equilibrium
between
the air flow pressure
and
the return
torque
of l h e
coil
spring
can
be
main
tained
The
damper
chamber
and
damper plate
are
provided
as a
damper
for the
flap
so
that the
flap will
not
be
disturbed
by pulsation
in manifold
vacuum
during operation
The
damper
plate
is interlinked
with
the
flap
and
as
the
flap rotates
the
compensating plate
rotates in the
damper
chamber keeping
a
very
small
clearance between the chamber wall
During idling
operation
when the
amount
of
intake air is
extremely
small the air flows
parallel
with
the
flap through the by
pass
port
so
that
the
specified
intake
air
flow
can
be
provided correctly
The air passage is
provided
with the
air
temperature sensor
and the by
pass
port
has the air
by
pass screw
which
regulates
the idle mixture
ratio
U
35
Ro
33
R
Potentiometer
32
R
IB
RJO
34
Air temperature sensor
25
Terminal number
fi
EF441A
AIR REGULATOR
Electric
terminal
Shutter
Sleeve
Air outlet
r
Heater
SEF101
The
air regulator bypasses
the
throttle valve
to
control the quantity
EF 13