ELECTRONIC CONTROL SYSTEM
- HAC Sensor, Vapor
Pressure Sensor,
Turbocharging
Pressure Senso
r
HAC (HIGH-ALTITUDE
COMPENSATION) SENSO
R
The HAC sensor senses changes in the at-
mospheric pressure
. Its construction and opera-
tion are the same as those of the manifold
pressure sensor (See page 17)
.
This sensor can be mounted either in the Engine
ECU, or in the passenger compartment separately
from the Engine ECU
. Currently, the type
mounted in the Engine ECU is used the most
.
When driving at high altitudes, there is not only a
decrease in the atmospheric pressure, but also a
drop in the density of the intake air
. As a result,
the air-fuel ratio deviates toward the rich side in
engines with L-type EFI (excluding hot-wire type
air flow meters) . The HAC sensor corrects for
these deviations in the air-fuel ratio
.
ELECTRICAL CIRCUITR
Y
(type with sensor mounted separately
)
HAC sensor
Engine ECU
TURBOCHARGING PRESSURE
SENSO
R
The turbocharging
pressure sensor senses the
turbocharging pressure
(
intake manifold
pressure)
.
Its construction
and operation are the
same as those
of the manifold
pressure sensor
(See page 17)
.
If the
turbocharging pressure
becomes
abnormally high, the Engine ECU cuts off the
supply of fuel to protect
the engine
.
Silicon chi
p
f
intake
manifold pressure
OHP 3
8
(V)
5
4
3
t
Atmospheric pressure
OHP 3
8
VAPOR PRESSURE SENSO
R
Basic operation and construction is the same as
that of a manifold pressure sensor or turbocharg-
ing pressure sensor
. Output characteristics differ,
however, to enable the detection of small
changes in vapor pressure
.
(V
)
44
5
4
3
2
1
k
0
1
-3
.
5
(-26)
Atmospheric
pressur
e
0
+1
.5
(0) (+11)
Pressure
kP
a
(mmHg)
2
1
0 13 100 200 kPa
(100, 3
.9) (750, 29
.5) (1500, 59
.1) (mmHg, in
.Hg)
Turbocharging pressure (absolute pressure)
OHP 38
ELECTRICAL CIRCUITR
Y
Turbocharging
pressure sensor
Engine ECU
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