## Fuel and Emissions Systems

#### System Descriptions (cont'd)

11-21

VTC system

- The VTC system makes continuous intake valve timing changes corresponding to the operation conditions.
- It optimises 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, stabilises 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.

VTEC system

- The VTEC system changes the cam profile to correspond to the engine speed. It maximises 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 engine changes both the intake and exhaust camshaft. Only the intake camshaft side has a VTEC mechanism on the K20A3 engine.

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