## Fuel and Emissions Systems

#### System Descriptions (cont'd)

11-20

VTEC/VTC

- 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, change the intake valve timing continuously.

Driving Condition | VTC Control | Description
(1) 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.
(2) 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.
(3) At high speed running | Advance-Base Position | Cam phase angle is controlled for optimum valve timing and maximum engine power.

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