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Acura RSX Honda Integra. Manual - part 88

３７

VTEC/VTC

11-58

Fuel and Emissions Systems

System Description (cont’d)

HIGH

LOW

HIGH

ENGINE SPEED

ENGINE
LOAD

LOW SPEED CAM

HIGH SPEED CAM

TORQUE CURVE

• The i-VTEC has a VTC (Variable Valve Timing Control) mechanism on the intake camshaft in addition to the usual

VTEC.
This mechanism improves fuel efficiency and reduces exhaust emissions at all levels of engine speed, vehicle speed,
and engine load.

• The VTEC mechanism changes the valve lift and timing by using more than one cam profile.
• The VTC changes the phase of the intake camshaft via oil pressure. It changes the intake valve timing continuously.

Driving Condition

VTC Control

Description

At light-loaded running

Base Position

Cam angle is retarded to reduce the entry of exhaust
gas into the intake port and to achieve stable fuel
consumption during lean burn.

At medium/high-loaded

running

Advance Control

Cam angle is advanced for the EGR effect and to
reduce the pumping loss. The intake valve is closed
quickly. To help reduce the entry of air/fuel mixture
into the intake port and improve the charging effect.

At high speed running

Advance-Base Position

Cam phase angle is controlled for optimum valve
timing and maximum engine power.

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＊１３

３２

VTC System

VTEC System

11-59

MAXIMUM VTC ADVANCE 50 °

TDC

IN 1

IN 2

IN 1

MAXIMUM VTC ADVANCE 50 °

SHORT OVERLAP

LONG OVERLAP

LOW SPEED VALVE TIMING

HIGH SPEED VALVE TIMING

K20A3 engine

K20A2/K20Z1 engines

• The VTC system makes continuous intake valve timing changes corresponding to the operation conditions.
• It optimizes intake valve timing to allow the engine to produce maximum power.
• Cam angle is advanced to obtain the EGR effect and reduce the 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.

• Reduces the cam advance at idle, stabilizes combustion, and reduces engine speed. If a malfunction occurs, 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

speeds 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.
• The K20A2 and K20Z1 engines change both the intake and exhaust camshaft. Only the intake camshaft side has a

VTEC mechanism on the K20A3 engine.

(cont’d)

05/06/27 17:32:02 61S6M040_110_0059

＊１４

４１

VTEC/VTC

System Diagram

Camshaft Position (CMP) Sensor A

11-60

Fuel and Emissions Systems

System Description (cont’d)

From No. 4
ACG (10 A) fuse

VARIOUS
SENSORS

ECM/PCM

CMP SENSOR A

INTAKE
CAMSHAFT

VTC
ADVANCE
CHAMBER

VTC
RETARD
CHAMBER

ADVANCE

RETARD

HOUSING

VANE

VTC ACTUATOR

VANE

HOUSING

ROCKER ARMS

PISTON

ROCKER ARM
OIL CONTROL VALVE
(VTEC SPOOL VALVE)

ROCKER ARM
OIL CONTROL
SOLENOID
(VTEC SOLENOID
VALVE)

BLK

GRN/YEL

BLU/BLK

BLK/YEL

BLU/WHT

BLK/WHT (BLK*)

BRN/YEL

BRN/
YEL

*: 2005-2006 models

ROCKER ARM
OIL PRESSURE SWITCH
(VTEC OIL PRESSURE SWITCH)

TERMINAL

MAGNET

O-RING

DRAIN

From
OIL PUMP

VTC OIL CONTROL
SOLENOID VALVE

CMP sensor A detects camshaft angle position for VTC system.

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４２

−

Idle Control System

Fuel Supply System

Brake Pedal Position Switch

Idle Air Control (IAC) Valve

Power Steering Pressure (PSP) Switch

Fuel Cut-off Control

2002-2004 Models

Fuel Cut-off Control

2005-2006 Models

Fuel Pump Control

PGM-FI Main Relay 1 and 2

11-61

From AIR
CLEANER

To INTAKE
MANIFOLD

IAC VALVE

When the engine is cold, the A/C compressor is on, the
transmission is in gear, the brake pedal is pressed, the
power steering load is high, or the alternator is
charging, the ECM/PCM controls current to the Idle Air
Control (IAC) valve to maintain the correct idle speed.
Refer to the System Diagram to see the functional
layout of the system.

The brake pedal position switch signals the ECM/PCM
when the brake pedal is pressed.

To maintain the proper idle speed, the IAC valve
changes the amount of air bypassing the throttle body
in response to an electrical signal from the ECM/PCM.

The PSP switch signals the ECM/PCM when the power
steering load is high.

During deceleration with the throttle valve closed,
current to the injectors is cut off to improve fuel
economy at speeds over 930 rpm (1,100 rpm) . Fuel
cut-off action also occurs when engine speed exceeds
6,900 rpm (8,100 rpm) , regardless of the position of
the throttle valve, to protect the engine from over-
revving. When the vehicle is stopped, the ECM/PCM
cuts the fuel at engine speeds over 5,500 rpm.

1: K20A2 engine

During deceleration with the throttle valve closed,
current to the injectors is cut off to improve fuel
economy at speeds over 980 rpm (1,150 rpm) . Fuel
cut-off action also occurs when engine speed exceeds
6,500 rpm (7,800 rpm) , regardless of the position of
the throttle valve, to protect the engine from over-
revving. When the vehicle is stopped, the ECM/PCM
cuts the fuel at engine speeds over 3,500 rpm.

2: K20Z1 engine

When the ignition is turned on, the ECM/PCM grounds
the PGM-FI main relay which feeds current to the fuel
pump for 2 seconds to pressurize the fuel system. With
the engine running, the ECM/PCM grounds the PGM-FI
main relay and feeds current to the fuel pump. When
the engine is not running and the ignition is on, the
ECM/PCM cuts ground to the PGM-FI main relay which
cuts current to the fuel pump.

The PGM-FI relay consists of two separate relays. PGM-
FI main relay 1 (FI MAIN) is energized whenever the
ignition switch is ON (II) to supply battery voltage to the
ECM/PCM, power to the injectors, and power for PGM-
FI main relay 2 (FUEL PUMP). PGM-FI main relay 2
(FUEL PUMP) is energized to supply power to the fuel
pump for 2 seconds when the ignition switch is turned
ON (II), and when the engine is running.

(cont’d)

05/06/27 17:32:43 61S6M040_110_0061

Content .. 86 87 88 89 ..