Acura CSX. Manual — part 91
28
11
11
VTC System
VTEC System
K20Z2 engine
K20Z3 engine
11-38
Fuel and Emissions Systems
MAXIMUM VTC ADVANCE 25 °
TDC
EX
IN 1
IN 2
EX
IN 2
IN 1
MAXIMUM VTC ADVANCE 25 °
SHORT OVERLAP
LONG OVERLAP
LOW SPEED VALVE TIMING
HIGH SPEED VALVE TIMING
EX
IN
EX
IN
IN (LOW LIFT)
LOW SPEED VALVE TIMING
HIGH SPEED VALVE TIMING
EX
IN
EX
IN
• The VTC system makes continuous intake valve timing changes based on operating conditions.
• Intake valve timing is optimized to allow the engine to produce maximum power.
• Cam angle is advanced to obtain the EGR effect and reduce pumping loss. The intake valve is closed quickly to
reduce the entry of the air/fuel mixture into the intake port and improve the charging effect.
• The system reduces the cam advance at idle, stabilizes combustion, and reduces engine speed.
• If a malfunction occurs, the VTC system control is disabled and the valve timing is fixed at the fully retarded position.
• The VTEC system changes the cam profile to correspond to the engine speed. It maximizes torque at low engine
speed and output at high engine speed.
• The low lift cam is used at low engine speeds, and the high lift cam is used at high engine speeds.
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13
31
VTEC/VTC
System Diagram
Camshaft Position (CMP) Sensor A
11-39
VTC
RETARD
CHAMBER
From No. 3
ALTERNATOR
(10 A) FUSE
VARIOUS
SENSORS
ECM/PCM
CMP SENSOR A
INTAKE
CAMSHAFT
VTC
ADVANCE
CHAMBER
ADVANCE
RETARD
VANE
VTC ACTUATOR
VANE
HOUSING
From
OIL PUMP
VTC OIL CONTROL
SOLENOID VALVE
SPOOL
VALVE
ROCKER ARM
OIL CONTROL
SOLENOID
ROCKER
ARM OIL
PRESSURE
SWITCH
BLK
BLK
GRN/YEL
BLU/BLK
BLK/YEL
BLU/WHT
BLU/WHT
YEL
BRN/YEL
BLK
BRN/YEL
VTC STRAINER
O-RING
MAGNET
TERMINAL
DRAIN
DRAIN
CMP sensor A detects camshaft angle position for the VTC system.
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12
33
13
Intake Air System
Catalytic Converter System
Positive Crankcase Ventilation (PCV) System
Intake Air Bypass Control Thermal Valve
Three Way Catalytic Converter (TWC)
11-40
Fuel and Emissions Systems
OUT
IN
VALVE
WAX
ELEMENT
INJECTOR
INTAKE AIR
BYPASS CONTROL
THERMAL VALVE
FRONT OF
VEHICLE
HOUSING
THREE WAY
CATALYST
BREATHER PIPE
INTAKE
MANIFOLD
PCV HOSE
PCV VALVE
: BLOW-BY VAPOR
: FRESH AIR
This system supplies air for engine needs.
When the engine is cold, the intake air bypass control
thermal valve sends air to the injector.
The amount of air is regulated by engine coolant
temperature. Once the engine is hot, the intake air
bypass control thermal valve closes, stopping air to the
injector.
The TWC converts hydrocarbons (HC), carbon
monoxide (CO), and oxides of nitrogen (NOx) in the
exhaust gas to carbon dioxide (CO ), nitrogen (N ), and
water vapor.
The PCV valve prevents blow-by gasses from escaping
into the atmosphere by venting them into the intake
manifold.
2
2
* : This illustration shows K20Z2 engine
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35
36
37
Exhaust Gas Recirculation (EGR) System
(K20Z2 engine)
Evaporative Emission (EVAP) Control
System
EGR Valve
EVAP Canister
EVAP Canister Purge Valve
Fuel Tank Pressure (FTP) Sensor
EVAP Canister Vent Shut Valve
11-41
TERMINAL
COIL
OUT
IN
O-RING
TERMINAL
SENSOR UNIT
O-RING
VALVE
O-RING
TERMINAL
Refer to the system diagram to see a functional layout
of the system.
The EGR valve lowers peak combustion temperatures
and reduces oxides of nitrogen emissions (NOx) by
recirculating exhaust gas through the intake manifold
and into the combustion chambers.
Refer to the system diagram to see a functional layout
of the system.
The EVAP canister temporarily stores fuel vapor from
the fuel tank until it can be purged back into the engine
and burned.
When the engine coolant temperature is below 60 °C
(140 °F), the ECM/PCM turns off the EVAP canister
purge valve which cuts vacuum to the EVAP canister.
The FTP sensor converts fuel tank absolute pressure
into an electrical input to the ECM/PCM.
The EVAP canister vent shut valve is on the EVAP
canister.
The EVAP canister vent shut valve controls the venting
of the EVAP canister.
08/08/21 14:13:42 61SNR030_110_0041
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