Honda HR-V: VTEC System Description (KA/KC)

Overview

This system 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 VTEC system changes the cam profile (angle) at cruising speeds. (Cam angle is changed to obtain the EGR effect and reduce pumping loss.)

Valve Timing Operation Image

Construction

VTEC is composed of the VTEC camshaft, the VTEC rocker arm, and the rocker arm oil control valve.

VTEC Camshaft

The cam shaft is structured so that each cylinder has two hight lift cam lobe and a low lift cam lobe.

VTEC Rocker Arm

The rocker arm is divided to the primary rocker arm, the secondary rocker arms A and B. The inner side of the intake secondary rocker arms A and B have two VTEC switching piston and a return spring.

Rocker Arm Oil Control Valve

The rocker arm oil control valve are integrated with the cylinder head.The rocker arm oil control solenoid turns ON or OFF the solenoid depending on a signal from the PCM to switch the hydraulic pressure applied to the valve to subject the valve to an ON/OFF control. By switching the ON/OFF of the valve, the hydraulic pressure applied to the VTEC switching piston in the rocker arm is controlled.

Rocker Arm Oil Pressure Switch

The rocker arm oil pressure switch attached to the rocker arm oil control valve monitors the hydraulic pressure condition and the statuses of the rocker arm oil control spool valve.

Control

Based on the vehicle speed signal, engine speed signal, engine load signal, throttle aperture signal, and engine coolant signal sent from various sensors, the PCM controls the ON/OFF of the rocker arm oil control solenoid.

Operation

At high load

At high load, the rocker arm oil control solenoid is turned on by the PCM. Oil pressure from the rocker arm oil control solenoid enters into the intake primary rocker arm via the intake rocker shaft, and it moves the VTEC switching piston in the rocker arm. This causes the VTEC switching piston to slide into the intake secondary rocker arm B, locking the intake secondary arms A and B together. The intake primary rocker arm and the intake secondary rocker arm A are driven by the hight lift cam.

Rocker Arm Oil Control Solenoid ON

At engine start, and cruise

At engine start, and cruise, the rocker arm oil control solenoid is turned off by the PCM. Oil pressure from the rocker arm oil control valve does not enter the intake rocker shaft. The intake secondary rocker arms A and B are driven by the low lift cam, and the primary rocker arm is driven by the hight lift cam.

Rocker Arm Oil Control Solenoid OFF

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